Mold Testing

Updated on January 20, 2016

Petri Dish Outdoor Molds Closeup 2

Step 1: Mold Testing – The First Step

I’m finally at a place where I feel like it’s time to delve into each of the first four steps in Dr. Shoemaker’s protocol more fully. As mentioned in other blogs, the first step to recovering from Biotoxin Illness, also called Chronic Inflammatory Response Syndrome (CIRS), is to dramatically limit your exposure to biotoxins and their related inflammagens. For most folks, this means limiting exposure to the types of molds typically found in water damaged buildings. For others, it means knocking out parasitic micro-organism like Lyme spirochetes, avoiding harmful algal blooms, and the like.

For those for whom mold is the issue, at a bare minimum, this means making sure your home and workplace have relatively low levels of the harmful toxins produced when mold grows. I also strongly recommend you read over the writings of mold experts Lisa Petrison and Eric Johnson. I’m going to cover all the ins-and-outs of mold testing in this blog but you also need to understand about “mold avoidance”. From my experience and many others, the more you get good at avoiding mold, the better off you’ll be both in terms of ease of treatment and symptoms.

I’m so thankful for Lisa and Eric’s work. They have lived and written extensively about “mold avoidance”. I’ve discussed the mainstay of what I do on my blog in the post Sleep Sanctuary. Graciously, on Lisa’s website Paradigm Change, there are free download links to their two mold avoidance books entitled “Back From The Edge” and “A Beginner’s Guide to Mold Avoidance” – see the right-hand sidebar. For those with the cash, please support their work by purchasing a copy from Amazon.

My contribution will be to dive deep into mold testing so you’ll know how to test for mold well. Now you might think that in our modern day world, mold testing should be easy. If you’ve been doing some reading, you’ve no doubt heard about a test that looks down at the DNA level to determine what molds are present called ERMI (Environmental Relative Moldiness Index). In addition, there’s air sampling, tape lifts, swabs, Petri dish cultures, and even mold-sniffing dogs. You’d think that with this arsenal of tests along with the expertise of a mold inspector that you could tell if a building is moldy or not. Unfortunately, sometimes it’s not always so straight forward.

My house is a perfect case in point. We’ve now spent over 2 years and $8,000 doing all of the above mentioned tests numerous times (7 ERMI, 40+ spore traps, a couple dozen Petri dishes, 2 VOC tests, and one mold-dog) in an effort to find out if the new home I built has mold issues. We’d do a round of tests. I’d tear into the house even more. Nothing would be found. I’d then go back and re-evaluate the test method before testing in another way. Round and round and round we went. None of the tests seemed definitive. Talking with four different professional inspectors often left me with more questions than answers.

Trinocular Compound Siedentopf Microscope

Due to the various test results, I’ve torn off sections of the roof and siding to convince myself that the very carefully thought out ventilation and flashing details were in fact working well (I’m a retired residential General Contractor). I’ve drilled over 20 holes in various walls, floors, and ceilings so that I could inspect them with a fiber optic camera. I’ve had two professional infrared inspections done on the whole house looking for variations in the home’s heat signature that would point to a leak. Later, I went out and purchased my own FLIR camera so I could do more inspections. I’ve stuck a moisture probe in any and every cavity I thought might have an issue. I even bought a microscope and spent months teaching myself how to read spore traps all in an effort to answer what seemed like a simple question; is my house moldy?

So with this introduction, I’m going to dive into each of these types of tests pointing out their pro and cons. I’m also going to point out the limitations of each type of test so you can better understand why no one test is the “be all and end all”. In the process, you’ll see why it’s important to hire a experienced mold expert whenever possible. When I’m done, hopefully you’ll see that it takes a combination of knowing how to read your own body, the expertise of seasoned and sensitive mold inspector, and often several mold tests to definitively determine if a building is relatively mold free. The more you learn about the ins-and-outs of mold testing, the better you’ll be able to interpret any given test result.

Common Misconceptions About Mold


Before we get started looking into the various tests, I wanted to take a minute to tackle a few common misconceptions about mold. First, when it comes to mold, all it takes is elevated moisture for a prolonged period before some sort of mold will start to grow. For example, a fairly unfriendly mold called Wallembia Sebi does just fine whenever the humidity gets above 65% – a level that is easily reached in cool, dark corners of a home when the overall indoor humidity gets above 50%. Depending on the temperature and humidity levels, it will start colonizing within a day to over three months later. You don’t need a leak or drops of condensation, although if you do, then mold will start growing within 24-48 hours. The reason for this is that there are mold spores (seeds) of all types lying around everywhere and given the wood and paper-backed drywall in most buildings, there is also plenty of food for mold to eat. All it takes is moisture.

A second common misconception is that if it doesn’t smell moldy, it can’t be moldy. Granted, when there is water damaged, mold and bacteria will be off gassing VOCs (Volatile Organic Compounds) as they chew their way through food sources. It’s the VOCs that we smell. When you go down into an old, damp basement, where mold has been growing for years with very little air movement, it’s the VOCs that create that musty smell.

However, not too long ago I went to a relatively new health clinic for a blood draw. It couldn’t have been more than 5 years old. The soil was well sloped away from the building; it had simple roof lines, a steeply pitched roof that included big overhangs with gutters, and the foundation was a slab-on-grade (no basement) that stood up out of the ground a good 8” before the siding and framing began. It was a model of good water management practices.

Nonetheless, the building was moldy. As I sat in an examination room while the phlebotomist prepared to draw some blood, the air-conditioning kicked on. Within a minute, the phlebotomist started sniffling. When I queried her, she commented that the A/C always gave her a runny nose.

There was no smell. It was a bright, new, clean building. Nevertheless, by the time I left the office, my head was already swooning from a mold hit. As I drove home, it got worse. It took days to recover using my mold protocol.

I’m guessing the condensate line on the A/C unit was plugged creating a pool of water around the evaporator core. Given that the debris in the air is more than enough food and that spores are everywhere, HVAC systems are quite frequently harbors of mold in spite of there metal ductwork. The bottom line is that you can not tell if a building is moldy without professional testing – unless you’re already better from Biotoxin Illness and have spent years refining your “mold radar” like mold gurus Erik Johnson and Lisa Petrison. If you suffer from any chronic illness, I strongly, strongly recommend you thoroughly look into if your home and work place are relatively mold free.

If you’ve got a chronic illness, I know your brain is probably foggy and that your life already is bad enough, but you have to look. Don’t stick your head in the sand thinking it’ll all go away. It won’t. Those toxins will continue to eat away at your body and mind until there is nothing left. Don’t let it get to the point that I reached where I prayed daily for Almighty God to come down and relieve me of this stay on planet Earth. Don’t wait; make sure your place is mold free!

My Story


So hopefully I’ve got you sitting up a bit and paying attention as we move toward looking at mold testing. I want to further peak your interest by giving you an outline of my personal experience with ERMI DNA mold testing. A couple years after we’d finished building our house that I oversaw every little detail on as the General Contractor, I was deathly sick with Biotoxin Illness. I’d been getting sicker and sicker for decades, but the “wheels came off” around the time we moved into our new house. After being left for dead by conventional medicine, my own research led me to see Dr. Shoemaker. As part of the first step to getting better, I had an inspector come and do an ERMI test (the current gold-standard of mold testing) on the carpeting leading into our finished basement to make sure I was living in a safe place.

The basement and first floors are concrete with in-floor heating so we couldn’t pull the typical ERMI sample from carpeting in the living and bedroom areas as was done in developing ERMI metrics. Nonetheless, I figured the basement stairwell carpeting was close enough as the stairs are open to all levels. The test came back a 3.8. With that score, I was in trouble because anything above a 2 for folks with my particularly multi-susceptible genes won’t be able to get better according to Dr. Shoemaker’s data. It meant he would not treat me until I got the ERMI below 2.

In talking with Dr. Shoemaker about the test results, I learned that because I hadn’t used Mycometrics for the ERMI that the test results may not be accurate. I also did some studying about ERMI on my own and realized that since we’d recently been working on a 100 year old barn and I hadn’t taken my boots off when traipsing into the basement for that odd tool, that I could have easily skewed the debris content of the carpeting we’d put in just months prior. I ordered another ERMI kit this time from Mycometrics and this time I did the test myself on the new carpeting on the second floor and the new couch in the living room. I felt confident my home was mold free.

Guess what? The second ERMI from Mycometrics came back at 23.25! Noooooo! How could the house I’d built with all the details already mentioned, a hand seamed metal roof, concrete siding over a plastic rainscreen mesh to make the walls breathable, 8” thick poured concrete walls with heavy dimple sheeting on the outside, and carefully selected breathable finishes on the inside be moldy?! As if Biotoxin Illness wasn’t bad enough, now I had to face the possibility that I couldn’t even build a house that was mold free. I was so heart-broken.

SamSung Moldy Drum

Well, I’ll unravel all the nuances to the rest of this story as this blog unfolds but for now I want to let you in on what we eventually found. First, our brand new front loading washing machine that was conveniently placed on the first floor was spewing out mountains of toxic mold. I’ll do a little blog on washing machines some day but for now take my advice and go to a store that sells reconditioned appliances and buy yourself a pre-digital, top-loading washing machine – the kind that uses timers and simple electrical switches. Do it today.

Second, we have a small crawlspace below the 8’x10’ entryway of the house. The rest of the basement is full height and finished. This crawlspace is essentially closed off from the house except for a small inter-connecting airway. Even though the floor below this crawlspace is covered with 4” of concrete over a plastic vapor barrier and the ceiling above is a concrete slab (the crawlspace is all concrete), the fact that it’s exposed to soil on three sides meant humidity levels got too high. Sawdust and a couple scraps of lumber left behind was more than enough food for Aspergillus and Penicillium mold to go to town. Given that this space had so little access to the house, it took a long time for levels to build to a point where this source could be found and addressed.


And finally, even though the soil is a well-draining sandy gravel, and I’d carefully protected the outside of the concrete walls of the basement with a heavy plastic dimple sheeting tied to detailed drainage, and I’d selected the XPS foam board, fiberglass insulation, drywall, and even the paint to make sure the finished basement walls could breath, testing showed moisture levels inside the walls exceeded 55% at times. Although I’ll never be certain about whether this was enough to promote substantial mold growth, we gutted and rebuilt those outside walls using a carefully thought out mold remediation protocol. I’ll talk about the remediation project and all about the ambiguity around if those walls were moldy in future posts.

So I hadn’t done anything wrong when I built the house. I didn’t screw up. I just didn’t have a deep enough appreciation for how tenacious mold is and how little it can take to make folks with Biotoxin Illness sick. The multitude of sources contributing in varying degrees over time made the problem exponentially harder to solve. Even though I’d done my research and had greatly exceeded all building practices, it still wasn’t enough. I’ve learned a lot since then and I hope to share a bit of that with you as I dig into the various types of mold testing.

Moldy Versus Bad for Your Health

Thinking Allowed

So I know, we’re a couple pages into the topic of mold testing and we still haven’t started talking about specific tests. Nonetheless, we’re laying important groundwork. You not only need to know the specifics related to testing but also understand various positions so called “experts” have taken around the subject so you don’t get side-tracked later on when these topics come up.

As we begin to dive into the murky waters of mold testing, I want to start by bringing up a distinction that is often made between mold levels and health effects. Experts (many of them are ill-informed Mold Inspectors) often point out that even when testing clearly shows a building has high mold counts, this does not necessarily mean the building is unhealthy to its occupants. While this is technically correct, in practice this is a moot point. In fact, the inverse of this statement is much more accurate and helpful in that even when testing shows low mold counts, this does not necessarily mean the building is safe for occupants. Allow me to explain.

Let’s begin with the technically correct but impractical statement that a moldy building is not necessarily a health hazard. Literature abounds showing molds of all sorts like Aspergillus and Stachybotrys are indeed very unhealthy. Certainly those with CIRS are devastated by the mycotoxins these molds produce. Using a little common sense, is it so hard to imagine that even those that have strong immune systems are impacted? It may take decades or longer, but I don’t think anyone can rightly argue that continually taxing the immune system by breathing in known toxins is good for anyone’s long-term health. (Those with financial stakes tied to minimizing the impact of mold toxins will vehemently argue otherwise.).

Furthermore, while some molds are clearly more problematic, I found it interesting that in the article, Higher Environmental Relative Moldiness Index (ERMI) Values Measured in Homes of Asthmatic Children in Boston, Kansas City, and San Diego, molds that are commonly found outdoors (not in water-damaged buildings), and are not generally considered a health hazard, appeared to be associated with higher rates of asthma in children. The study itself showed that homes with asthmatic children had higher ERMI mold scores (we’ll get into ERMI later). No surprise there. However, in looking over the results, it was interesting to note that in dry places like San Diego, molds that are generally considered benign like Cladosporium and Aureobasidium Pullulans tended to be many time higher in the homes with asthmatic kids. Could these supposedly safe molds be contributing to asthma? It’s an interesting supposition that others with CIRS have suggested may in fact be the case. My take away from all this is that if a building has a high mold count regardless of the species, then it does not bode well for long-term health of its inhabitants.

We’ll switch gears now and take a look at how buildings with low mold counts are not necessarily safe – can be loaded with mold toxins (mycotoxins). To understand this, we need to make the distinction between mold and the toxins associated with mold growth. I go into mold toxins in detail in the blog What is Biotoxin Illness. Dr. Keith Berndtson summarizes it nicely when he says in Mold Toxicity – A Chronic Inflammatory Response Syndrome (slide 11) that besides mycotoxins there are additional “inflammagens including VOCs, endotoxins, actinomycetes, glucans, glycoproteins, and other noxious incitants” that create the toxic soup associated with fungal and bacterial growth on wetted building materials.

So get this. All of the current testing methods with the exception of the mold dog, VOC testing, and new mycotoxin testing are only capable of measuring the larger bits and pieces of the mold itself. They do not measure for mycotoxins let along any of the other inflammagens mentioned of which some are nano sized. To give you an understanding for why this distinction matters, take for example a home that has been remediated. Let’s say the contractor diligently partitions off the moldy area and creates negative pressure in this space by running a large HEPA filtered negative-air-machine (fan). The offending material is carefully removed and bagged. Later, the entire building is white-glove cleaned. The contractor continues to run large HEPA filters. There is not dust anywhere. And yet, the woman with CIRS that lives in the house gets sick 10 minutes after she re-enters her home. How can this be?

As you will learn later on in this post, the chemicals and gaseous particles that make up mold toxins are incredibly small. They get everywhere. Convection currents alone are enough to carry these super tiny particles through out the entire house – not to mention the forced-air systems in most buildings. Some of the toxins are so small the mere vibration of molecules of air keep them indefinitely suspended through “brownian motion”. If the mold problem wasn’t immediately addressed, those toxins will be everywhere through out the building.

So even though the entire building was cleaned of all dust, the contractor either had faulty HEPA filtration units (fairly common) or he didn’t take enough time “air washing” the space. Simply letting a blower sit on the floor and run isn’t enough. You need to continually agitate the entire body of air so all the micro particles eventually get caught up in the Jetstream of air created by the blower. Alternatively, you could use Greg Weatherman’s fogging method. Either way, the tiny toxins must go.

To further emphasize this point, in the real world, the equipment and protocols Remediators use are less than perfect. Furthermore, it is standard practice for many Remediators to have a “mold specialist” that has been trained in microscopy confirm that the remediation was done well. This person will take a tape sample from a horizontal surface and look at it under the microscope. If relatively few mold spores are found, the house is proclaimed safe. After what’s been said, it should be quite clear that simply having low counts of mold spores that are huge in comparison to the troublesome toxins is not necessarily indicative of a healthy environment. Not to mention the tiny sample area.

Don’t despair. This sort of misunderstanding is why I wrote this blog. I’ve brought up this discussion on mold counts versus health effects to both introduce some of the challenges related to testing and to make the point that to really know if a home is toxin free (safe to live in) requires careful consideration of all the facts. My advice to anyone with mold related health issues is to study this post and then consult with an expert like Martine Davis or Greg Weatherman.

Non-DNA Mold Testing

The Walk-Through


During typical home inspections, the Inspector walks through the home looking for issues. A recently painted ceiling, failed shower caulking, a musty smell, are some of the signs that suggests the building has had water issues resulting in a high mold count. The eyes, nose, and pointed questions directed at the current owners are the tools used in this type of “mold testing”.

Unfortunately, while this all sounds well and good, this method has serious limitations when it comes to finding mold. Even if the inspector also uses a moisture probe, the odds of detecting a problem are only slightly increased. Remember, we’re talking about really small particles. Furthermore, maybe the leak was years ago and was fixed but without proper protocols. The smell, high moisture, and sight of the mold is gone but the toxins remain. Mycotoxins (mold chemicals) alone can take years to break down.

Moisture Probe

Alternatively, maybe the problem is on-going like a dirty air-conditioning coil. Inspectors don’t tear into the main trunk on forced-air systems to inspect the A-coil. Recall my story about the health clinic above that looked perfect and yet was spewing toxins out of the ductwork. While the prospective Buyer may be well impressed by an Inspector that disassembles ductwork, the Realtor and Seller would have a fit. Better to leave any potential issues out of sight and out of mind.

To further substantiate this point, I refer you to the Correlation between ERMI Values and Other Moisture and Mold Assessments of Homes in the American Healthy Homes Survey. In this survey, occupants were questioned about water problems and the smell of mold. In addition, Inspectors went through the home looking for signs of mold visually and by smell. They also took dust samples for later DNA analysis.

Compared to the DNA mold analysis of the dust, occupants and Inspectors observations were off-base about half the time. I quote, “In the AHHS, the ERMI assessment was in agreement with the inspection and/or occupant’s answers about mold and moisture in 48% of fourth quartile homes. But neither of these human assessments indicated a moisture or mold problem in the other 52% of fourth quartile homes. Yet the population of the 26 water-damage indicator molds was statistically indistinguishable in any of these fourth quartile homes indicating that all of these fourth quartile homes had similar mold burdens. In these cases, the “walk-through” inspections and questionnaires missed hidden mold problems.”

I’m not saying that the walk-through isn’t important – see Good Inspectors & Labs below. It’s an important part of a good inspection. However, it should not be the only method used.

Tape Lifts & Swabs

Cannister & Plate & Tape & Swab

In essence, a tape lift consists of taking a piece of transparent tape, pressing it against the surface in question, and sending the sample off to a lab. A technician looks at the sample under a microscope and counts the number of mold spores that are present. A swab is essentially the same only instead of a piece of tape, a sterile swab on the end of a wooden stick contained in a plastic tube is rubbed over the surface being tested. When the swab arrives at the lab, part of the contents is transferred onto a microscope slide by rubbing the swab over the glass slide. As with a tape sample, the numbers of mold spores are counted by the technician under a microscope. How to Take a Tape Lift

When it comes to limitations, I’ve already discussed the problem of using tape lifts after a remediation project for establishing whether the home is safe for occupancy in the paragraphs above – low spore counts do not necessarily imply low toxin levels. Needless to say, the same holds true for swabs. Furthermore, I’ll leave out the discussion related to the inaccuracy of spore counting until later when I delve into spore traps but suffice it to say that this is another major limitation. In addition, there is no way of knowing if the sample taken was truly representative without taking lots of additional samples and then you might as well switch to a more reliable test. Finally, although technicians do try to quantify the amount of mold spores present, it’s a very rough approximation on a scale of 1 to 5. In the case of swabs, this carries even less weight as there is no standard related to the area to be wiped with the swab.

Even with these limitations, tape lifts and swabs are not worthless tools. For my point of view, they’re great for determining whether, and what type, of mold is growing on a surface. Let’s say you find mold inside the shower wall behind the hot-and-cold valve. If it were me, I’d want to know if this was Stachybotrys or some variant of Aspergillus/Penicillium. Not that the remediation protocol would be any different, but Stachybotrys is wicked bad. If I were doing the remediation, I’d want to know.

Alternatively, let’s say you tear into a wall that a mold-dog alerted on or that showed a high spore trap count. Visually, the drywall, studs, and insulation look fine. This is confusing. One way to double check for the presence of mold would be to do a tape lift, or a swab of some inner surfaces to gather more information as discussed in Mold Testing by Inspector. If the tape or swab came back moldy, you’d feel confident moving in the direction of the remediation. If it came back clean, then it’d be time to ask more questions and do more tests.

Culture Plates

Petri Dish Outdoor Molds

The yeast, bacteria, and mold that grows on culture plates looks cool. You can buy your own plastic Pre-poured Petri Dishes loaded with agar – a gooey food substance. Make sure to get Malt Extract agar as it’s meant for growing mold. You can buy kits too and send the dish off to a lab for analysis but I wouldn’t recommend it. Here’s why.

Just like with swabs and tape lifts, who’s to say that the spores that land on your dish are representative of what’s in the building – not to mention the whole issue around mold counts versus toxin levels? Maybe the water issue is in the bedroom closet but you mistakenly took the sample from the basement. The plate doesn’t grow much but it was taken in the wrong place.

Even if you took it from the right area, some molds like Stachybotrys are slimy and it’s rare to catch spores (mold babies) in the air. To top it off, molds grow at different rates and each likes different types of conditions so if you get one type of mold that happens to particularly like the light, moisture, and temperature in the dish, it will grow very fast and release mycotoxins to lay claim over the entire dish – mycotoxins prevent the growth of spores from different species.

For myself, I think the best way to use plates is for getting an overall sense of the mold burden in a building and in finding out the areas where it’s worse. For example, when I was trying to discover where the source of mold was coming from in our home, I took Petri dish samples from varying locations through out the house. I’d go into a room, bounce on the furniture, stomp on the throw rugs, and then take a sample. Because I wanted to take samples from the ductwork too, where the constant airflow could skew the results, I came up with another method besides simply leaving the plate uncovered for the typically recommended one hour time period.

What I did was to drill four small 1/8th inch diameter holes at opposite sides of a junk Petri dish cover. I then fitted this cover over clean agar and held the end of a vacuum hose near the holes at one end of the cover for exactly five minutes. My thinking was that by using this method, I’d have a much more uniform exposure in both the ductwork sample with moving air and the relatively still air in rooms. If you look at the pictures, you can see that there was a significant difference between the fairly high amount of Aspergillus/Penicillium mold that came from the HRV ductwork and the sample taken in the study.

Petri Dish Day 4 Study   Petri Dish Day 4 HRV Duct

Did this mean that the ductwork had mold issues as a result of condensation as is often the case? Not in our home. Instead, the mold counts outdoors are just really high as we live in woods. The solution was to have a custom filter box made out of sheet-metal to hold a MERV-13 pleated filter to clean the “fresh” air being drawn in from outdoors. Of course, we had the ductwork cleaned too.

So it can be instructive to take some culture plates. While you’re at it, you may want to take one or two from outdoors. However, don’t get upset in either case if you see mold growing because you will. If you can standardize the way you take the sample like I tried to, then you may be able to use cultures to help you find out the general area where the mold counts are highest and consequently where the water damage is. However, other than for very general observations, you’ll need more refined testing. Note: Mold counts at ground level are super high. If you want to get a sense for what’s in the outdoor air, take the sample a few feet off the ground.

Mold Dog


We hired a mold-dog. The dog was a sweet lab. We had to sit in a room away from where the dog was working so he wouldn’t get distracted – labs love attention from people. We had to move all the furniture away from the walls ahead of time so the handler could take the dog around the perimeter of all the rooms sniffing for mold.

I was told the dog had “alerted” in previous inspections on the slight amounts of mold that typically develop on wood, wall studs during construction when the building is still exposed to the weather. The studs had long ago dried out and the amounts were minuscule but the dog could still pick up on the scent many years later through the drywall and insulation. I was optimistic about using a dog.

When the inspection was done, the dog had “hit” on two areas in our finished basement and the refrigerator. I wasn’t surprised about the refrigerator as a lot of dust collects on the evaporator coil underneath. Who cleans their refrigerator evaporator coil with a HEPA vacuum exhausting to the outside? After the mold-dog, I do. 🙂 I tore into the two places in the basement walls and came up empty handed. I didn’t know about swabs at the time but visually, the walls looked pristine.

If you do a little research, you’ll see that just like all types of testing, mold-dogs have their limitations. Commonly mentioned drawbacks are the facts that they can only detect a handful of molds, need to be trained well, and can’t tell you if it’s really smelly (indicating a lot of mold growth) or just a faint whiff like the wall-studs mentioned. In addition, for me, the fact that the dog can’t sniff above a couple of feet off the floor is another shortcoming. Also, what if the building is just steeped in mold but the source is out of reach or covers a large area? How is the dog supposed to alert to this situation? He’d have to just lay down (alert) the entire time. And finally, as a former dog owner, I do worry about the health of these dogs. They can get sick just like us humans.

Nevertheless, I bet mold-dogs are quite good at finding localized sources. They’ve got incredible noses. Be advised that after a dog alerts to mold, the next step is to do some additional testing to make sure the dog was right. Mold dogs and the additional testing aren’t cheap but when a qualified mold inspector is having a hard time pinpointing the source of mold, in my estimation, the friendly canine may come to the rescue.

Spore Traps

Spore Trap Inside Wall

Spore traps are commonly used. In short, they consist of a vacuum pump that pulls air over a glass plate with a clear, sticky coating. The spores, mold fragments, pollen, dust, and whatever else is floating in the air strikes that sticky substance and gets trapped. The plate is sent off to a lab where a technician counts the number of spores of varying types under a microscope. Because the airflow rate and time the slide is exposed are carefully controlled, the test is much more standardized than tape lifts, swabs, cultures, and mold-dogs. The picture shows the configuration for pulling a spore trap from inside a wall cavity.

Spore Trap Parts

The technician is trained to identify the 17 different types of molds included on the report. All other spores are lumped into the “unspecified” category. According to the report, nine of the molds are considered “common allergens”, four are considered “water damage indicators” and the remaining four are considered benign outdoor molds. However, as you’ll learn later when I discuss ERMI mold testing, two of the common allergen molds listed on the report are often associated with water damage and increased health risk.

Spore Trap Sample Report

In general, the slide is prepared by the technician using a special stain like Lactophenol Cotton Blue to make the mold spores stand out. Ideally, the slide is examined under the microscope using oil-emersion and two different magnifications. The technician uses a special counter to keep track of the numbers of spores seen. To save time, only about 20% of the slide is examined and then using a standard algorithm along with knowing the time the slide was exposed along with the flow rate, the total number of each spore type per cubic meter of air is calculated and recorded on the report.

Now that you’ve got the basics, let’s look at some examples of how spore traps can be used. To begin, just like with tape lifts, swabs, and cultures, you need to carefully select where you’re going to sample the air. Maybe the owner reported water seeping from underneath a portion of a finished basement wall and even though there were no signs of mold under the baseboard molding, you suspect inside the wall is a different story. Time to drill a small 1/4″ hole through the drywall and insert a length of tubing that attaches to a spore trap.

On the other hand, let’s say you’re just trying to get a sense of what’s going on in the house. As such, you take a spore trap from outside and, after stomping around indoors disturbing dust on furniture and the like, you take a few samples from indoors. By comparing outdoor and indoor readings along with looking at the relative levels of the various molds, a good inspector can glean a lot of information.

Maybe the outdoor levels are just really high so even though the indoor levels are unhealthy, there may not be a water issue. Maybe one type of mold group Aspergillus/Penicillium is higher indoors compared to outside when all the other molds are much less. Even though the overall count may not be exceptionally high, the fact that it’s out of alignment with the other molds indicates a potential water problem. Maybe there are only a few Stachybotry spores indoors but a good inspector knows that even a few of these heavy spores that are rarely caught in a spore trap is not a good sign.

Microscopy – Spore Trap Overview

So what do you do if there is suspicion of a mold problem? Again, this is where a qualified mold inspector is invaluable. Based upon the types of molds found in any preliminary testing along with years of experience, they will have a good idea where to start looking. Maybe they’ll visually be able to find the mold. Just as often, they won’t see any mold and will have to rely on experience and additional spore traps to discern the location.

OK, let’s look at limitations of spore trapping. If the trap isn’t taken near the source or the flow of air through the house keeps most of the spores at a different elevation than the level of the trap, the results will come back clean even though the problem may have only been a little as a few feet away. In his article, Microbial Investigation & Remediation, Greg Weather says, “The World Health Organization has stated that if one wants to do air sampling, it should be done in multiple locations per room, at multiple times of the day, multiple days per week. In other words, air sampling done properly is too time consuming and cost prohibitive.”

Furthermore, not only are the numbers of molds species measured limited but it’s impossible to distinguish between Aspergillus and Penicillium spores under a microscope (not to mention several other small round mold spores like Trichoderma and Wallemia). As such, these two molds are lumped together when it fact it could be very helpful to not only be able to distinguish between these two species but also be able to identify the many sub-species of these molds. Not knowing whether high mold counts in the “Aspergillus/Penicillium” category are really from Aspergillus Niger that tends to be associated with water damage to flooring materials compared to Aspergillus Vericolor that is often associated with damage to wallboards, insulation, and textiles can make a big difference.

In addition, I’ve seen large discrepancies in spore traps results. One result will show exceptionally high Aspergillus/Penicillium in a wall cavity, and a subsequent test taken from the same location will come back clean. Maybe I unknowingly disturbed a portion of the insulation in the wall during one test that dislodged a bunch of spores. However, when you start to repeatedly see contradictory results like this, you may get to the point like I did and actually go out and buy a microscope, pump, and traps along with teaching yourself how to recognize spores. This is a long slog that I don’t recommend except when all else fails like it did in my situation.

Not surprisingly based upon my experience, in A Multi-Laboratory Comparative Study Of Spore Trap Analyses the authors stated, “The intent of this study was to assess the ability of analytical laboratories to recognize both spore genera and number of fungal spores with various spore trap methods. The data demonstrated that the seven AIHA-accredited laboratories were not able to reliably perform these analyses.” New technicians are typically given a two-week crash course before they start analyzing traps. This isn’t nearly enough time. I think Martine Davis is onto something when she uses a small lab with only two guys that have been evaluating traps and checking each others work for years. Even then, my impression is that spore traps are of limited use compared to the “new kid on the block”, DNA ERMI testing.

DNA Mold Testing

ERMI – Introduction


Before the advent of DNA testing, the only options folks had for trying to determine if their homes were moldy were the walk-through, swabs, tape lifts, culture plates, spore traps, and the occasional mold dog. Unfortunately, some molds hide out of sight and don’t create much smell. As discussed, these various types of test all have their limitations. Happily, the EPA got going on working out how to get really good (within 99.7% accuracy) at detecting the DNA of over 130 different species of mold and obtained a patent in 2002. They called the method Mold Specific Quantitive Polymerase Chain Reaction (MSQPCR) and started licensing their patented technique in 2006.

ERMI Vacuum & Cannister

That was all well and good but the EPA needed a whole bunch of dust samples taken from moldy and clean homes so they could analyze the DNA and determine what molds were of most importance and what levels were indicative of water-damage. They needed to create a scoring system for their new DNA technology. So they sat on their hands until around 2007 when they partnered up with the U.S. Department of Housing and Urban Development (HUD). You see, HUD was going around to homes and collecting data on lead, allergens, mold, pesticides, and arsenic in homes across the U.S. as part of the American Healthy Homes Survey.

ERMI Cannister

More specifically related to mold, the HUD surveyors went to 1,096 homes across the country and took a vacuum sample from the carpeting in the living room in combination with a child’s bedroom (or any bedroom in homes without kids). To be consistent, they measured out exactly 2 square meters (3 feet by 6 feet) in the two rooms and then vacuumed that entire area for precisely 5 minutes each using a single dust collection canister. Between 30 – 100 mg of dust was collected in the special canister (called a Mitest Dust Collector) attached to the end of the vacuum hose. The canister is fitted with a nylon mesh sleeve inside that captures the dust and dirt. You can read about how to take an ERMI test in HUD Vacuum Dust Sample Collection Protocol for Allergens.

When the samples arrived at the lab, they sieved the contents of the cartridge through a 300 micro-millimeter filter. Ideally, there was at least 5mg of dirt under 300 micro-millimeters in size (pet hair and really clean homes can be problematic). The technician then stirred this filtered dirt to achieve a homogenous mix. Out of the filtered dirt, 5mg was weighed out and analyzed using MSQPCR.

ERMI Sample Report

That was it. No questioning of the owners about mold problems and no walk-through inspections looking for mold – just dust samples. This makes sense because the whole point of DNA testing is to get away from having to rely on human senses to detect mold issues.

So the EPA scientists analyzed the DNA data and along with what is known about the types of conditions various molds thrive in. As a result, they figured out that by using the DNA values from 36 molds (out of the 82 molds they tested) that they could assign a value indicating how moldy a home was. They called this method of evaluation Environmental Relative Mold Index (ERMI). The range of the ERMI scores goes from minus 10 to positive 20 with a standard deviation of +/-3. The higher the ERMI score the greater the likelihood that there is, or has been, water damage that resulted in problematic mold growth. They knew they were on to something because a follow-up study showed that there was an 80% chance of finding a child with asthma in homes with an ERMI score of 1 or more. Note: Even though there are strong correlations between ERMI and health, technically ERMI is only a measure of specific molds – as discussed previously.

Getting into some more detail, what the EPA statistically concluded in looking at the DNA data is that there were 26 molds associated with water damage and 10 molds not typically found in wet buildings that were most telling. Why bother with molds not found in water-damaged buildings you may ask? The answer is that there are very large variations in background (outdoor) mold counts depending on where you live. Imagine comparing outdoor mold counts in the woods of Wisconsin with the dry land of Arizona. There is going to be a lot more mold of all sorts floating around and getting into the homes in Wisconsin. You need to be able account for this.

That’s why the ERMI scoring method adds up the logarithms for the DNA “spore equivalent” counts of the 26 problematic molds and subtracts off the sum of the logs for the 10 safer molds. (They used the logs of the mold count values instead of the actual values just to keep the numbers from getting too large – mold counts can easily go into the many thousands.) In effect, they’re accounting for the variability in overall background mold counts by making this subtraction. For an example, let’s say the 26 molds in Group I are really high. However, upon examination so are the 10 molds in Group II. As such, you know it’s quite likely that there is just a lot of mold around and that the home is not water damaged (more about this later).

As we finish up with this introduction into ERMI testing, you may have noticed that I used the term “spore equivalents” before. That’s because DNA testing measures the total amount of fungal fragments and this includes the mold spores, the hyphae, the fruiting heads, and so on. This total value is then equated to the number of whole spores that would have an equivalent DNA value. This total DNA value is then divided by the number of milligrams of sample used (usually 5mg) to come up with the number spore equivalents per milligram of dirt collected for each of the 36 molds measured. In other words, what you’re seeing for the individual molds on an ERMI report are the number of spore equivalents that were deposited relative to the amount of dirt deposited over a long period of time – the age of the carpeting.

What’s So Great About ERMI?


So you might be wondering where this is all headed. Why should you even bother learning about the different types of testing and what’s so great about ERMI. After all, can’t a person just call a mold inspector and be done with it? Well, in many cases, a single ERMI is enough. However, for those with moldy genes, getting away from mold is critical and the best way to do this is to educate yourself.

One of the really awesome aspects of ERMI testing is that you’re able get down to the DNA level with nearly perfect accuracy. Unlike spore traps, tape lifts and the rest that only allow you to identify a much more limited number of intact mold spores (because a technician identifies them under a microscope), ERMI gives you the total amount of spores and fragments of mold for more species down to a sub-species level. From a health standpoint, this definitely matters (e.g. HERTSMI-2) and it can even be helpful in trying to identify the source of a water problem.

Although I’ve made mention of the number of different types of toxins and their extremely small size, it will helpful at this point to talk a bit more on this subject. If you’ve spent anytime studying about Biotoxin Illness, also called Chronic Inflammatory Response Syndrome (CIRS), you know that fungi produces biotoxins – especially the mold that grows indoors. These biotoxins are much smaller and 1,000 times more prevalent than relatively large mold spores that range from around 2-100 microns in diameter – where a micron is 1/1000th of a millimeter. The range in size of the much smaller biotoxins extends from the toxic chemicals called mycotoxins that mold produces with a size about 0.1 microns down to the aerosolized Microbial Volatile Organic Compounds (MVOCs) that are responsible for the musty smell. Smaller yet are the exudate (guttate) water droplets that rise to the surface of mold and are then shed in nano sized particles – 1/1000th of a micron! I might mention that no filter exists to effectively capture mycotoxins let alone gaseous nano-sized toxins.

Toxic Bioaerosol Dispersal (slide #9)

So OK, enough about these tiny biotoxins for now, let’s finish the discussion on why being able to identify the total amount of mold DNA down to a sub-species level matters. When it comes to health, it may be entirely possible that a home at one time had a mold problem but now no longer has active mold growth. Even if the inspector manages to take a spore trap in the location of the past problem, there may be very few intact spores to catch still floating around in the air. Unlike the smaller biotoxins, mold spores will settle with time. Remember, technicians reading spore traps are only able to identify round, intact spores and not bits and pieces. As such, the spore trap may come back “clean” even though the carpeting is loaded with the moldy DNA fingerprint. This fingerprint is important because it points to a previous mold problem that still lingers in the air in the form of biotoxins (some mycotoxins persist for years) that almost certainly were produced by the mold and make the home unsafe for those with CIRS.

Then again, perhaps there is a leak in the form of condensation and it is on-going resulting in lots of Aspergillus/Penicillium spores that are then caught in the spore trap vacuum sampling of the air. Let’s say the inspector diligently pulls a sample from outside for comparison. However, since the home is in the woods and the sample was taken in September, (or maybe it’s next door to a foreclosure home with extensive water damage) the outdoor sample also shows high Aspergillus/Penicillium spores. Without being able to distinguish that the indoor mold is actually Aspergillus Niger while the outdoor mold is Aspergillus Flavus as is possible with ERMI testing, the inspector may incorrectly conclude that the contamination inside is coming from outdoors and not a water problem.

Moving on, another great feature of ERMI compared to other mold testing methods, is that it gives you the long term history of mold in a home. I suppose mold dogs might be able to do this too as from what I was told by a handler, the dog can smell both live and dead mold. Nonetheless, when it comes to ERMI, carpeting acts as a sponge soaking up tiny particles that then can be recovered for testing. If there was a problem in the past, or there is an on-going problem, a good part of the evidence you’ll need to draw this conclusion is buried in the carpeting. Sure you may vacuum and clean your carpets frequently but these particles are really small. Five minutes vacuuming a 3’x6’ area is actually quite a bit of time. Spore traps and culture plates are in-the-moment kinds of sampling and have no way of measuring what the mold types or numbers were in the air five minutes ago let alone last year.

ERMI & Politics

I’m going to take a short detour and briefly delving into mold politics. Surprisingly, in 2013 the Office of the Inspector General (OIG) came out with a report entitled, Public May Be Making Indoor Mold Cleanup Decisions Based on EPA Tool Developed Only for Research Applications. In the report, the OIG states that after all these years of use by the public to test for mold, ERMI is technically just for research purposes. What? Apparently, due to an “anonymous” complaint, the OIG went over to the EPA and grilled them about whether ERMI was meant for public use because surprise, surprise, the companies the EPA had licensed the ERMI technology to were using it for determining if homes were moldy. In addition, some like Dr. Shoemaker were collecting data and making connections between ERMI levels and measurable health parameters in individuals. Upon interrogation by the OIG, the EPA “ran for cover” and stated that ERMI technically should only be used for research.

Does this make any sense to you? After all, HUD and the EPA pair up to analyze over 1,000 dust samples from across the country for the explicit purpose of determining if a home is moldy and after completing this work they license the method to labs that do mold testing. Even the OIG in it’s report states, “…ERMI was developed using a nationally representative sampling of homes, the EPA and HUD researchers believed that one could compare any newly sampled home in the United States to ERMI, and assess the home’s mold burden…”. So why after developing this awesome DNA method is the government acting like this was just some sort of research project with no real world application?

Dr. Shoemaker does a great job discussing the politics but what it comes down to for me is that it’s all about money and power. Guess what, thanks to Dr. Shoemaker and others, ERMI is now being successfully used in the courts to show that buildings are moldy. Like always, Dr. Shoemaker meticulously collected ERMI data on his patients. Using this data he determined ERMI was good at predicting if a building would be safe for those with CIRS. Furthermore, he went on to develop a way of clearly showing a particular building was causing CIRS in patients that he calls the Sequential Activation of Innate Immune Elements (SAIIE) protocol. Basically, he gets folks better, they go back into the building in question, and if mold is present at harmful levels then in a very predictable pattern their inflammatory markers go haywire within days. Bingo. Case closed.

So ERMI in combination with SAIIE is a real threat to a lot of organizations. I’ve already written about this in my blog Finding A Mold Doctor. The powers that be are going to do everything they can to discredit the mold factor. If the mold genie gets out of the bottle, the impact is going to be huge. I’ve read estimates that approximately 40 million folks in the U.S. suffer from CIRS. Most go undiagnosed. Acknowledging the damage done from poorly built and maintained buildings will cause the insurance industry to implode. Oh yeah, not to mention the impact of all the civil cases like the ones being leveled against U.S. Military Housing in Norfolk, Virginia. See any connections? 😉

You know the saying, “We’re from the government and we’re here to help you”. OK, if that’s true, then why didn’t the EPA upon becoming aware of the issue around the validity of using ERMI take the 2,400 ERMI test results that Dr. Shoemaker analyzed and gave them in order to determine if ERMI really was as useful as it’s being made out to be. Alternatively, why didn’t they contact labs that are doing ERMI for the public and asked for their data so they could do their own analysis? Instead, nothing happened. It’s all about money and power. When you’re deathly sick from CIRS, who has the energy to put up a fight?

I’ll finish this bit on politics with a mention of a discussion I recently read between Mold Inspectors related to ERMI called What Are Your Thoughts About Using ERMI for Post Verification on Mold Remediation Projects. Some of these Inspectors quickly jumped on the OIG’s report as a justification for not using ERMI. Are you kidding me? You have a tool that can test down to a DNA level from a group of molds that have carefully been selected for the purposes of determining if a home is moldy and you can’t figure out this might be a useful tool for helping people? Take my advice; don’t hire these inspectors because for whatever reason they’re confused. If they were sick from CIRS, I can assure you they’d be using ERMI, spore traps, mold plates, and their Sunday horoscope to try and figure out if their home was moldy.

Well, I just wanted to make the point that ERMI is a very powerful tool in the right hands. Ignore the politics. Granted, ERMI definitely has its limitations but to simply dismiss the test in its entirety is wrong. To all those Nay-Sayers, we’re literally dying here; engage your brain and figure out how to use ERMI in new ways like Dr. Shoemaker and Greg Weatherman. Freaking help us!

ERMI & HERSTMI-2 Scoring

So what did Dr. Shoemaker find when he started correlating patient inflammatory markers against ERMI scores? It’s pretty simply.

Health Status Versus ERMI

  • CIRS people with MSH<35 and C4a<20,000 must have an ERMI ≤ 2
  • CIRS people with MSH<35 and C4a>20,000 must have an ERMI ≤ -1

That’s it. He found that when he tried to get those with CIRS better that had ERMI scores that were too high, he’d fail. For example, he may be able to take a patient all the way to the last step where VIP is employed. However, when ERMI levels were too high, TGF-beta1 would shoot up and create trouble. Furthermore, he learned with experience that even when patients were convinced that ERMI was wrong and emphatically claimed their homes were fine, more often than not, the patients were mistaken. In fact, after a time, he refused to treat patients beyond addressing MARCoNS until their ERMI scores were within range. I was one of those cases.

Later on, Dr. Shoemaker developed the HERTSMI-2 Scoring System. This scoring system is an improvement on the ERMI method when it comes to predicting if a home will be safe for those with CIRS. Basically, out of the 26 molds in Group I associated with water damage from ERMI, Dr. Shoemaker found that five of the 26 molds were particularly telling. The HERTSMI-2 score for a home is determined by using a scoring system that assigns points based upon the level of each of these five molds.

Dr. Shoemaker is not alone in showing high ERMI scores correlate with adverse health. I quote from an article by Stephen Vesper, the guy who developed ERMI. In the article, Traditional Mould Analysis Compared to a DNA-Based Method of Mould Analysis, he writes, “In four epidemiological studies, higher ERMI values in homes were associated with increased risk of asthma in children. Remediating the water-damage and mould in asthmatics homes resulted in a statistically significant improvement in the child’s health and a reduction in the need for hospitalizations and emergency room visits (Kercsmar et al., 2006).”

Five HERTSMI-2 Molds & Their Environments

  • Stachybotrys and Chaetomium: When present in significant numbers then materials have been saturated with water between 90-100% indicating there is most likely an active water leak.
  • Aspergillus Penicilloides and Aspergillus Versicolor: When present in significant numbers then materials have been saturated with water between 80-90% indicating there are most likely moisture condensation issues.
  • Wallemia : When present in significant numbers then materials have been saturated with water between 60-80% indicating there is most likely high humidity issues that must be found and corrected – check ductwork.

HERTSMI-2 Points Assignment

  • Stachybotrys Chartarum
    • Spore Equivalent Value over 125 = 10 points
    • Spore Equivalent Value of 26-125 = 6 points
    • Spore Equivalent Value of 5-25 = 4 points
    • Spore Equivalent Value less than 5 = 0 points
  • Chaetomium Globosum
    • Spore Equivalent Value over 125 = 10 points
    • Spore Equivalent Value of 26-125 = 6 points
    • Spore Equivalent Value of 5-25 = 4 points
    • Spore Equivalent Value less than 5 = 0 points
  • Aspergillus Penicilloides
    • Spore Equivalent Value over 500 = 10 points
    • Spore Equivalent Value of 101-500 = 6 points
    • Spore Equivalent Value of 10-100 = 4 points
    • Spore Equivalent Value less than 10 = 0 points
  • Aspergillus Versicolor
    • Spore Equivalent Value over 500 = 10 points
    • Spore Equivalent Value of 101-500 = 6 points
    • Spore Equivalent Value of 10-100 = 4 points
    • Spore Equivalent Value less than 10 = 0 points
  • Wallemia Sebe
    • Spore Equivalent Value over 2500 = 10 points
    • Spore Equivalent Value of 501-2500 = 6 points
    • Spore Equivalent Value of 100-500 = 4 points
    • Spore Equivalent Value less than 100 = 0 points

HERTSMI-2 Total Points Versus Health Risk

  • HERTSMI-2 Points Total > 15: This building is permanently off-limits to those with CIRS.
  • HERTSMI-2 Points Total 11 – 15: This building must be remediated before those with CIRS can enter.
  • If HERTSMI-2 Points Total < 11: This building is most likely safe for CIRS people.

HERTSMI-2 Calculator

You can check your results with this HERTSMI-2 Calculator.
Note: I have not tested this calculator for accuracy.

HERTSMI-2 Example Scoring

Spore Equivalents/mg
Stachybotrys Chartarum
Chaetomium Globosum
Aspergillus Penicilloides
Aspergillus Versicolor
Wallemia Sebe
HERTSMI-2 = 24

Tip: If you’ve already had a ERMI done that came back high, you may choose to have a “PCR10.X Panel” run by MycoMetrics instead of another ERMI or HERTSMI-2. With the PCR10.X Panel, you select the five mold species you want DNA tested. Using the results from the original high ERMI, you can hand-pick the worst offenders. As of early 2015, the PCR10.X Panel is the same price as HERTSMI-2.

ERMI Interpretation & Limitations

Lest you begin to think that ERMI is perfect, it’s not. Granted it tests for more molds down to a sub-species level using DNA analysis. Furthermore, unlike all other testing methods, through the work of Dr. Shoemaker, we have a way of correlating mold counts with health. This is awesome. For many, a single ERMI carpet sample is enough. And yet, ERMI does have limitations and these need to be understood both to give you greater peace of mind that your home and work are safe and to help you should your health fail to improve bringing into question the validity of the ERMI results.

Important: The following nuances related to ERMI mold testing are not meant to cause alarm. A single indoor ERMI test is very often accurate. It’s just that nothing is perfect and when CIRS is involved, it’s important to try to get it right. If your health doesn’t improve even though your ERMI is fine, then at a certain point it may make sense to further evaluate your ERMI score. Similarly, if your ERMI comes back high, in almost all cases, there is a mold problem – be very, very careful about using the limitations in ERMI to quickly explain away high molds counts. However, it’s good to know some details in the infrquent cases where it can be proven to have been skewed too high or low. Even with the information that follows, I strongly recommend you hire a professional mold expert like Martine Davis or Greg Weatherman as they will have a wealth of information beyond what is presented here.

I’ll begin with some basics. Remember that when HUD took their samples, it was from the living room and a bedroom. Clearly, if your sample is taken from different areas, who’s to say that your ERMI results are comparatively equal? Chances are they will be but technically there is a difference. Likewise, if you don’t take the sample exactly as described, or your vacuum is really tired or extra peppy, the results may not compare with the HUD results. What if you don’t have carpeting? We’ll get into the “Swiffer Cloth” dusting method later but clearly taking dust samples with a cloth is not at all the same as vacuuming carpeting. If you do have carpeting, my advice is to take the sample in an area that isn’t under furniture but is off the main walkways.

Looking a little deeper, consider these out of the norm examples. For starters, what if the building being tested is super clean or extra dirty? The results will be skewed. My house and a friend’s house are good cases in point. When I took my ERMI carpet samples, the home was nearly brand new. It can take years for the outdoor mold spores to build up to equilibrium levels in carpeting. Remember, ERMI is the result of subtracting the outdoor mold counts from indoor, water-damage mold counts. If the outdoor molds represented in the homes’ carpeting are quite low because the carpeting is new, the ERMI overall score will be skewed abnormally high.

To make maters worse, we live in woods and open windows for many hours each day to flush out the high VOC indoor air from all the new building materials that are still off-gassing. So we live in an environment with higher outdoor molds than the average HUD home used to develop ERMI and we leave our windows open more than most. This extra contamination from outdoors explained the higher than normal level of the mold Wallemia Sebi that was captured on the indoor ERMI report. (The reason I know this is because of a side-by-side outdoor ERMI test that was done at the same time as indoor ERMI testing – more about this later.) This examples shows how individual ERMI mold counts can be skewed too high.

To bolster this point, even with an ERMI supposedly over 23 in my house, my health was improving. All my inflammatory makers were down and were staying down without taking binders. I even went through testing of inflammatory markers in the Sequential Activation of Innate Immune Elements (SAIIE) protocol to prove to Dr. Shoemaker that the ERMI score was wrong. He didn’t budge. Apparently when he took another look at my ERMI values he didn’t believe the house was mold-free. In the end, we were both right. The values were skewed high because of the factors mentioned. However, once I’d learned enough about ERMI, it was clear that something was wrong and I eventually found the issues mentioned at the introduction to this post.

Let’s continue on with one more example of how ERMI can be incorrectly pushed too high. What if there was a minor but recent problem with mold? Maybe a little Aspergillus started to get a foothold before being noticed at the top corner of a shower in the master bedroom. Granted even small amounts of mold can make those with CIRS sick, but they can also skew ERMI results too high for an entire house.

To see why, let’s say the diligent owner carefully follows the directions and takes part of the ERMI sample as directed from that same master bedroom. Is it any wonder that Aspergillus will appear exceptionally high given the close proximity of the bathroom to the bedroom? In this example, even though the house may be essentially fine, with the exception of needing a good cleaning in and around the bedroom, the ERMI may come back high.

OK, enough of the examples of how ERMI can be skewed high. Let’s take a look at the flip side. What if you’re really sick from CIRS and consequently are finding it difficult to just take care of the basics let alone cleaning the house. You’ve got kids, a dog, and two cats. If you were healthy, the house would never have gotten so dirty.

In the case of my friend’s house, the ERMI came back minus (-)0.6. That’s less than zero. Based upon the test, the house should have been totally fine. And yet when I was driving home after a visit, I found myself inadvertently running stop-signs. My brain was so foggy from the mold-hit I took.

I went back later, suited up, and started looking. We found copious amounts of mold growing on items in the crawlspace (very nice crawlspace in a newer home with a concrete floor). We found mold behind the insulation in the band joists in the basement. We found a 6”X6” patch of Stachybatrys growing on the air-conditioning coil in the main trunk of the ductwork. We found over 60 square feet of blackened roof sheathing inside the attic due to an improperly vented bath fan. And finally, the cover on the ejector-pit for the basement toilet wasn’t even close to sealed from the last repair by a plumber. The house was a toxic soup and yet because it was so dirty, ERMI came back looking very good.

How can this be? Remember, individual ERMI mold values listed on the report are given in Spore Equivalents per milligram of dirt. If there is a lot of dirt because the home isn’t cleaned often, then the home is not like the average HUD home that was used to develop ERMI. The more dirt, the more the given number of mold spore become “diluted” when it comes to ERMI values. Said another way, think of ERMI mold counts as being the amount of mold being deposited in relation to the amount of dirt being deposited over a longer period of time (Spores/Dirt). If you like math, when the denominator (the bottom number in a fraction) gets bigger, the overall value of the fraction gets smaller.

So we’ve looked at what can happen when the “dirt factor” is abnormally low and when its unusually high. I’ll finish with one last scenario where the overall mold counts in both ERMI Groups are both high. In the article, A Quick Primer On The Perils Of Using Ermi Samples For Post-Remediation Verification For Mold Projects, the author rightly recounts a specific building wherein the Group I total mold count was 35,325 with a Log Sum of 35.88. The Group II total mold count was 96,553 with a Log Sum of 34.35. The ERMI for this building is then (35.88-34.35)= 1.53. This building technically is safe based upon Dr. Shoemaker’s work and yet there is no way I would ever want to go into a building with those super high counts. No way!

Swiffer Cloth

Swiffer Cloth

If you noticed, I deftly dodge the issue about what to do when your house doesn’t have carpeting until now. Clearly, taking a vacuum sample of a hard flooring surface isn’t going to compare at all with the carpeted HUD homes. As a result, the relatively new Swiffer Cloth Method has been released.

Note: The picture to the right shows the Swiffer cloth I used to take a 3-week dust sample. It contained 1mg of dust. Notice that the cloth is just slightly dirty. This was barely enough. Normally, the lab likes at least 5mg of dust.

Essentially, you call MycoMetrics and they send you a sterile cloth. Your job is to go around the building and in ten different places, wipe up the dust with the “swiffer cloth”. The cloth is then sent back to the lab in ziplock baggie and evaluated using the same methodology as all other ERMI tests.

If you’ve been paying attention, you’ll probably be a little perplexed when you learn that some consider ERMI results from Swiffer Cloth samples to be comparable to ERMI carpet samples. After all, ERMI was not developed using Swiffer Cloth samples. Besides the obvious differences in surfaces (carpeting versus cabinet tops), heights (ground level versus several feet or more up), and types of exposure (people don’t walk on their cabinets), when you read the Swiffer Cloth directions, there is no standardization regarding the total area to be dusted. Furthermore, Dr. Shoemaker’s work correlating ERMI and HERTSMI-2 scores were for carpet samples and not dust cloth samples. Why then would we possibly expect Swiffer Cloth and carpet samples to give the same results?

Almost certainly, the amount of dirt being deposited on tops of cabinets and furniture is much less than the amount of dirt being trapped in carpeting. As such, I would anticipate Swiffer Cloth samples to be all skewed high – the denominator (mg of dirt) number is less for Swiffer samples while the numerator (Spore Equivalents) being deposited on both carpeting and furniture is essentially the same.

I’m a SurvivingMold Member and wrote in regarding this issue. I was told that when Swiffer samples were compared with vacuum samples, the ERMI scores were essential the same provided the people did not “scrub” the horizontal surface with the Swiffer Cloth. They wrote, “… we suggested that patients wipe one way, left to right or right to left, one time, using a Swiffer on at least 10 horizontal surfaces”. This is a surprising statement indeed given all that’s been explained here.

Update January 20, 2016 Note that in the Surviving Mold Swiffer Cloth Method, they no longer say that is important to wipe in one direction. In fact, according to mold remediation expert, Greg Weatherman, it’s best to wipe the area in various directions so as to pick up as much dust as possible. In fact, Swiffer clothes are designed to use electrostatic charge to collect dust. Using gentle back-and-forth motion in multiple directions helps this – don’t scrub the surface. Watch Mr. Weatherman’s video on How to Take an ERMI Sample for more information.

In attempt to understand what’s going on, let’s look more closely. We know that the vacuum and Swiffer samples are sieved through a 300 micro-millimeters (microns) screen when they arrive at the lab. Larger pieces are discarded. To give you a sense of scale, 300 microns is a bit larger than the diameter of a human hair, or about the size of the average piece of sawdust.

As such, we can explore a few possible explanations as to why the amount of dirt trapped in carpeting is comparable to the amount that lands on upper surfaces when it comes to HERTSMI-2 – that carpet and dust HERTSMI-2 scores are very often comparable. First, perhaps the size of the particles that get trapped on the bottom of shoes, are shed by dusty pets, and come off the knees of kids with dirty jeans are generally much larger 300 micro-millimeters. In which case, these larger sized dirt particles would be sieved out and not add to the denominator (dirt) in ERMI scores of carpet samples. This seems very unlikely especially given my experience with seeing really low ERMI mold scores from a dirty home that was loaded with mold.

Another possible explanation is that folks with CIRS tend to be “clean freaks”. I have a pair of dreaded genes meaning that my Mom has and my Dad had (RIP) Biotoxin Illness. They are both into clean and so am I. For folks like us, there isn’t that much extra dirt added to carpeting as shoes are always taken off at the door, kids are taught not to track in dirt, and so on. Again, it seems unlikely that this would be the norm for folks with CIRS but maybe.

The most likely explanation is that most homes that are water-damaged have a significant mold load. As such, regardless of whether the sample came from carpeting or dusting, the overall HERTSMI-2 score would indicate the building is unsafe – even though the dust samples no doubt tend to be higher. In either method, the home is unsafe for those with CIRS. Furthermore, remember that HERTSMI-2 scoring is based upon ranges of mold counts. It may be possible that variations in carpet versus Swiffer samples are often captured within those ranges.

Whatever the case, it is clear that a Swiffer dust sample will often be higher than a carpet sample because the sampling method is completely different. There is less “dirt” in a Swiffer sample and therefore the spores/dirt ratio is skewed higher. As such, in some cases, I would expect that some Swiffer reports may incorrectly indicate the home is unsafe when it isn’t. Along the same line, if a Swiffer HERSTMI-2 score comes back OK, then a carpet HERTSMI-2 score would almost certainly be OK too – the house is almost certainly OK.

Please note that Dr. Shoemaker does sanction calculating HERTSMI-2 from Swiffer Cloths and this is no doubt because the data supports this approach. Nonetheless, we know there are real difference in Swiffer versus carpet samples. As with all testing, it’s important to know a test’s weaknesses. When it comes to Swiffer samples, if your home comes back borderline high according to HERTSMI-2, I would be cautious to conclude the home is unsafe without further testing. In any event, keep in mind that HERTSMI-2 scoring is preferred over ERMI for determining if a home is safe for those with CIRS. Let’s see why.


I’ve already made the point that in my estimation, regardless of the mold species, if a home has high mold counts then it is a health risk. From Dr. Shoemaker’s work, we know what ERMI and HERTSMI-2 scores correlate to adverse health effects for those with CIRS. Let’s continue this discussion a bit by looking at the results for the original ERMI scores from the HUD homes that can be found in the Journal of Occupational and Environmental Medicine – Development of an Environmental Relative Moldiness Index for US Homes – August 2007.

It’s been suggested by uninformed inspectors that the values in this original report can be used to determine if one or more of the 36 ERMI molds is out of range in order to determine if a home has a mold issue – has high mold counts. This would be useful as there is no mention of what constitutes high levels for each of the individual mold in the final ERMI score. Remember, ERMI is a sort of “grand total” calculated by subtracting the sum of the logs of Group II molds from Group I molds.

Let’s say there’s a question about wheather the mold Aspergillus and Penicilloides values on a report are high. The owner found a small patch of mold in the laundry. The question is whether this small amount of growth was enough to contaminate the whole house. We can’t know just from the information in ERMI. We need a reference point.

That’s why I was initially excited about finding this data. Like some uninformed mold inspectors, I initially thought these values could be used as a baseline for establishing what’s safe. I’ve summarized the HERTSMI-2 molds from the article in the table below. In addition, I decided to add in the corresponding HERTSMI-2 values for the mold counts. When I did, I was surprised to see that the average HUD home is permanently off-limits to CIRS folks with a HERTSMI-2 score of 30! Yikes! What can we learn from this?

First off, if the average HUD home had a HERTSMI-2 of 30, we can not use the values in the original ERMI report sited for determining what safe levels are for each of the 36 molds. Second, we can be glad Dr. Shoemaker refined the inital scoring system that said most folks with CIRS would be OK in a home with an ERMI below 2. To see why, let’s look at a few facts.

ERMI Scale

We know that somewhere around an ERMI of zero is the score for the average HUD home based upon the chart that is presented with every ERMI report – shown right. However, now we lnow know that the HERTSMI-2 score for the average home is 30. If the average home with an ERMI of zero has a HERTSMI-2 of 30, then one with an ERMI of 2 must be even worse on average. It’s no wonder Dr. Shoemaker looked back through the data and developed the more refined HERTSMI-2 scoring method.

The third point I take away is that no scoring method for determining whether the 36 mold values on the ERMI report is full-proof. Granted, I’m sure Dr. Shoemaker has very good statistics showing that anyone with CIRS should definitely take a high HERTSMI-2 score very seriously. Perhaps some day other Physicians will develop an even better scoring system – one that is like HERTSMI-2 but considers more molds and/or is customized for each of the susceptible CIRS gene types.

Average HERTSMI-2 Mold Counts From 1096 AHHS Homes

Ave. Spore Equivalents/mg
Ave. Standard Deviation
HERTSMI-2 Points
Stachybotrys Chartarum
Chaetomium Globosum
Aspergillus Penicilloides
Aspergillus Versicolor
Wallemia Sebe
The HERTSMI-2 score is 30 for the average home across the U.S.!

Improved DNA Testing

A Better Way

Finally, we’re at the main reason I wrote this article. I was pleasantly surprised to read about the method I’m about to describe using Swiffer Cloths from Greg Weatherman who appears to have come up with the same approach around the same time as I was experimenting with it. Dr. Lin from MycoMetrics got me started thinking about this method given that we didn’t have carpeting, because I knew the outdoor mold counts were high, and all I’d learned about ERMI. I needed a way to account for the differences between my home and the typical HUD home. If the ERMI mold counts were skewed for any number of reasons, I needed a method that circumvented these limitations.

In the end, I essentially completely ignored the ERMI value in favor of comparing and contrasting individual ERMI mold counts from an indoor Swiffer Cloth sample against another from outdoors. I was careful to develop a method I felt took into consideration may factors including sample sizes, exposure times, type of exposures, sample weights, and the like. By learning about what were the most problematic molds in my area, along with comparing the Swiffer Cloth data, after two years I was finally able to figure out for myself that my home had a mold problem.

Note: Observe that Dr. Shoemaker’s HERTSMI-2 does not rely on the overall ERMI score. This is similar to the approach I’m about to describe related to determining if there is, or has been, active indoor mold growth. Certainly HERTSMI-2 molds can be skewed high or low for some of the same reasons ERMI can. However, in my estimation, it’s somewhat less likely.

So I needed to know if mold was growing in my house or if it was all coming from the woods and/or from the types of measuring errors I’ve discussed. If my home was moldy, I needed to find the problem, fix it, and then completely clean the house. If the mold was coming from outside, I needed to find better ways to filter the air and then completely clean the house. I needed a better test.

Improved Swiffer Cloth Method

So before I dive into the actual procedure, I wanted to take a minute or two to explain the reasoning behind the approach I’m suggesting. We’ve already discussed the various limitations of ERMI. For various reasons, the ratio of the number of spore equivalents to dirt can be thrown off. So what we’d like to do is try to circumvent many of those factors.

To understand why I’m suggesting the approach that follows, we need to look at the dust floating around in the air. Outside, this dust will consist of tiny particles of debris of varying sorts along with mold. The molds will primarily be from the Group II molds listed in ERMI – the kind that naturally occur outside. However, there will also be some Group I molds produced outside too and floating in the air from decaying tree and plant matter.

Given that no home is air tight, we can expect that a certain percentage of the dust floating around outside will end up inside depending on how leaky the building is and how much we opened windows and doors. Regardless of the amount that mold laden dust that got inside, if the building was perfectly clean and mold-free, the ratio of the spores of any given mold to the dust or dirt should be the same inside and out. If Aspergillus Penicilloides was at a ratio of 10:1 outside, then it will be the same inside because we’re assuming a theoretically super clean building that is not adding any dirt or mold from within.

Of course, we’d have to be careful to gather our samples at the same times. This is because the outdoor spore counts of the various species changes with the time of day, time of year, and the weather. Although it takes some time for the outdoor moldy dust to infiltrate the building, so long as the sampling times are over the course of several hours each day, we should get a relatively equal distribution between the outdoor and indoor mold to dirt ratios.

However, no building is perfectly clean. Debris from people, pets, furniture, fabrics, and the building are introduced into the air from various activities. If the building is completely mold-free, then additional dirt only will be added into dust floating in the air. In terms of ERMI, the ratio of mold per unit of dirt will become less. So for example, we might expect the ratio of ERMI mold counts comparing outside to inside to be 10:1 or even 5:1 on a mold-free home that has the windows open a lot. When the windows remain closed, the ratios may be closer to 20:1 – a lesser amount of mold from outside enters the building while the amount of additional dust/dirt added by the building itself remains the same. This will increase the ratio.

To understand why, remember ERMI values are actually fractions or ratios of the spore equivalents to dust or dirt. If the building is perfectly sterile, the ratio of spores per unit dirt will be the same inside and out. There may be much less moldy dust inside, but the ratio of mold to dirt will be the same. For example, if Wallemia Sebe is at a ratio of 852 spore equivalents per milligram of dirt outside, a dust sample inside will be about the same. Even though there no doubt will be less overall dust inside, the ratio of Wallemia Sebe spores in each milligram of dust will be the same. However, no building is perfectly sterile so some additional “dirt” is always added by the building and the inhabitants and this lowers the spores per unit dirt ERMI values equally for all mold counts inside.

So here’s where the magic happens. What if the building is moldy? In this case, the building will be adding Group I molds into the mix. Remember from the previous discussion on the development of ERMI testing, Group I molds occur when there is water damage. If there is a very bad leaky, the building will likely be adding many more Stachybotrys Chartarum spores into the indoor air. If it’s a light water leak, it will probably be adding more Aspergillus Versicolor into the air. This will skew the ERMI values for these molds. If we take samples inside and outside as I’m suggesting below, we’ll be able to see those molds that are out of range.

So in the method below, we’re going to sample the outdoor and indoor air over at least a week so we get a longer term view of mold counts. If there is a problem in the building, this amount of time should allow sufficient levels of the offending indoor molds to build up to levels that can be detected. We will be careful to hold as many other variables constant so we get good results.

When the test is done, we will compare the ratios of the ratios. What I mean by this is that we will first establish a baseline by looking at the ratio of Group II molds. Since it would be very unusually for a water-damaged building to producing Group II molds from within, we know that whatever Group II molds show up inside the building must have come from outdoors. As discussed, this ratio will vary depending on how open the building is and indoor activity, but by and large the ratio of Group II ERMI mold counts when comparing outside to inside will be in the neighborhood of let’s say between 5:1 to 20:1.

Knowing the ratio of the Group II ERMI counts comparing outside to inside gives us a critical point of reference. With this ratio, we can then look at the Group I molds. If the building is not water-damaged, it should not be contributing any Group I molds. In other words, the ratio of Group I ERMI mold counts should be at the same ratio comparing outside to inside as the Group II molds.

In the example below, the ratio of outside to inside Group II ERMI counts was about 11:1. However, in looking at Group I molds, it can be seen that several Aspergillus and Penicillium molds were at ratios around 1:1. In other words, for every 11 molds spores from Group II, 1 would get inside. However, the ratios showed that every single one of some Group I molds were getting into the house. This just isn’t possible because most spores are relatively light and should all be entering the home in about the same ratio. So where did this extra mold come from if it’s not floating in from outside? The only explanation is that the building is moldy and spewing spores into the air from within. Let’s look at the specifics of how to do this testing.

Step 1: Plastic Bins

Plastic Bin

The first step is to get four larger plastic storage bins with lids. They should have a bottom at least a couple square feet in size. The height isn’t critical although shorter bins will be easier to work with. Wash and rinse them out well. They should not have been used to store chemicals. We’re going to use these bin to collect dust samples inside and outside over about a one week period.

One bin will be used exclusively to collect outdoor dust, and the three other bins will be used to collect indoor dust. Since the mold counts in each milligram of dust will essentially be the same, it doesn’t matter that the indoor sample area will be three times bigger. In fact, we need the extra area inside because it is much dustier outdoors.

When I did my comparative Swiffer test, I collected 15mg of dirt on a 3-day outdoor sample, and only 1mg on a 21-day indoor sample of the exact same size. This works out to over 100 times more dust/dirt outside. Now I live by a gravel drive and cropland so I’m sure this added to my outdoor deposit. Nonetheless, what we’re trying to do is ensure that by the end of the one week period that we will have ideally captured at least 5 milligrams of dust indoors as this is the preferred amount for ERMI testing. If it turns out to be a bit less, that’s OK too but more is better.

The outdoor bin should be at least 20 feet upwind of the house and at least 3 feet off the ground – there is a lot of fungi at ground level. We don’t want any spores being emitted from the house contaminating the outdoor sample. Also, place the bin away from gravel roads and cover it in rainy or windy weather. We want the dust exposure outside to be constant. If it’s by a gravel road, the amount of dust in the air will fluctuate significantly based upon traffic. Likewise, rain will ruin the sample and high winds will blow the sample away. Finally, you may want to place a rock or two that you washed off and put inside a zip-lock bag in the outdoor bin to keep it from blowing over.

Step 2: Collect Dust

When the windows are open or that exterior doors are being used, uncover the indoor and outdoor bins. If the outdoor bin is uncovered, the indoor bins should be uncovered too. Otherwise, close them all up. If it’s windy or raining, keep the bins closed and bring the covered outdoor bin inside temporarily to get it out of the weather. Close the bins at night and bring the covered outdoor bin inside temporarily to prevent issues with dew.

Essentially, we’re trapping the dust floating in the air both outside and inside when windows and doors are in use – when outdoor air is entering the building. We’re doing this over at least a one week period of time so we’re sure to get a longer term view of what’s in the air. In comparison, we know that spore traps sample a very small amount of air over a short period. Since there is variability in the amount of spores in the air at any given location depending on drafts and the source of mold, spore traps are often wrong. By sampling over a longer period, we’re given spores a chance to find there way into our capture bins.

Don’t take the separate Swiffer samples too soon and make sure to put them in separate, clean zip-lock bags. You need to collect enough dust such that the Swiffer cloth looks slightly dirty. If you can hardly see any dust inside your indoor bins after the first week, wait on taking the sample. As Dr. Shoemaker recommends, wipe up the dust with a single pass over any given area swiping in the same direction. I don’t know that you need to refold the cloth during the process to expose a clean portion, but I can’t see why it would hurt and it may help with collection. Just make sure to be very gentle about the entire dust collection process. You want to sweep up as much material as you can into the cloth.

As an aside, Greg Weatherman in the article A Condensed Remediation Plan for Small Micobial Particles, recommends taking the outdoor sample from a surface that is exposed to rain and wind like a sign or mailbox. Although this makes sense as you’re then only collecting relatively recent dust over a similar window of time as the indoor sample. However, I think we can get much better results using the bins. For example, what if it rains the night before you take the sample? The outdoor dust will be loaded with spores from molds that like to release during rain. If it had been dry otherwise, the mold that entered the building over the week prior may be significantly different.

Similarly, I’m sure there is some variability in spore counts at night versus the day. Since most folks close up their houses at night, the indoor samples will not contain the spores that released late in the day and early morning. Let alone the issue with dew on the outdoor bin. Now maybe some of these factors aren’t critical, but until someone proves otherwise, I want to try to eliminate as many of these types of variables as possible.

Incidentally, don’t do any cleaning, mow the lawn, have a big party, or the like when the samples are being taken. You want everything to be “average”. If you mow the lawn, you may spike up mold counts on the outdoor sample with the fungi in the grass and these molds may not have enough time to find there way inside. This will throw off the ratios of outdoor to indoor counts depending on what spores are most prevalent in the grass. Similarly, we don’t know what’s stored in your carpeting, but if you vacuum the carpets, you’ll be spiking up the indoor levels in unpredictable ways. We want to minimize variables. It goes without saying that if you knock a bin over, or one gets contaminated, start over.

Step 3: Compare the Results

The table below shows the results of dust collected from two large, new garbage bags that I cut open. I placed one inside our screened in gazebo so it would be out of the rain and high winds. The other went on top of the kitchen cabinets. I collected dust from the outdoor sample after 3 days. I waited three weeks to collect dust from the indoor bag – even then I only picked up a barely acceptable 1mg of dust.

Outdoor/Indoor Swiffer Cloth Comparison

3-days Outdoor
Outdoor per day
21-days Indoor
Indoor per day
Out/In Factor
Group I
Aspergillus flavus/oryzae
Aspergillus fumigatus
Aspergillus niger
Aspergillus ochraceus
Aspergillus penicillioides
Aspergillus restrictus
Aspergillus sclerotiorum
Aspergillus sydowii
Aspergillus unguis
Aspergillus versicolor
Aureobasidium pullulans
Chaetomium globosum
Cladosporium sphaero.
Eurotium amstelodami
Paecilomyces variotii
Penicillium brevicompac.
Penicillium corylophilum
Penicillium crustosum
Penicillium purpuro.
Penicillium spinulosum
Penicillium variabile
Scopulariopsis bre./fus.
Scopulariopsis chartarum
Stachybotrys chartarum
Trichoderma viride
Wallemia sebi
Sum of Group I Logs
Group II                                   .  
Acremonium strictum
Alternaria alternate
Aspergillus ustus
Cladosporium clado. 1
Cladosporium clado. 2
Cladosporium herbarum
Epicoccum nigrum
Mucor amphibiorum
Penicillium chrysogenum
Rhizopus stolonifer
Sum of Group II Logs
ERMI (Group I – Group II)

In the table, I’ve listed the ERMI mold counts for the 3-day outdoor and 21-day indoor Swiffer samples. Since the exposure times were different (it’s better if they’re taken over the same period of time), I’ve divided the 3-day values by 3 and the 21-day values by 21 to get the number of spore equivalents per milligram of dust being deposited on the plastic per day. Finally, I calculated what could be called the deposition factor by dividing the per day outdoor counts by the per day indoor counts.

Looking at the Group II molds, we see that there is roughly a factor of 11 between outdoor and indoor samples – 11 times more mold spore equivalents were being deposited on the outdoor plastic per day. This makes sense as the outdoor sample is not protected as in the house. A few of the Group II mold factors were considerably higher or lower than 11 but this could well have been due to the time of day the windows were open and the fact that the indoor and outdoor samples were not exposed the same amount of time. We don’t need perfection.

Since we can be fairly confident that the house was not growing any of these outdoor molds, we can use this factor of 11 to see if any indoor molds are out of range. Within the Aspergillus genus, Aspergillus fumigatus, Aspergillus niger, and Aspergillus sclerotiorum really stand out because they have factors less than one meaning there were significantly more of these spores being deposited inside than out (Aspergillus penicillioides and Aspergillus versicolor also are less than one but the daily counts are very low and nearly equal so this isn’t quite as telling). Certainly some of the Aspergillus is coming from outside. However, the only way the factors can be so different is from mold growth in the house. We don’t know if it’s active growth or residual debris but when I saw this data, I was convinced I had a problem.

By the way, you may be thinking to yourself that ERMI values are in spore equivalents per milligram of dirt so even bother to divide by the number of days. Just compare the ratios of outdoor and indoor ERMI values regardless of the number of days for each sample or the amount of dust collected. (In this example, there was a total of 14.8mg of dust on the outdoor sample and only 1mg on the indoor plastic – I called MycoMetrics for these values.) Well, you’d be mostly right; I did it because it seemed to make good intuitive sense even though I realized in playing with the numbers that it really doesn’t make any difference. Note: MycoMetrics now charges $25 for sample weight information and you must specify this on the Chain-of-Custody form.

In the end, we’re only concerned with finding if there are any Group I molds wherein the ratio of outdoor to indoor ERMI values deviates considerably from the baseline established by the Group II molds. What’s the difference if we divide all the ERMI values by fixed constants (numbers) that represent the number of days for each sample and then multiply by the weight of each sample (I wiped the entire plastic clean on both pieces of equally sized plastic) to come up with the actual number of spores deposited on the plastic each day? The answer is none. If the baseline ratio for Group II molds comes out to be 11:1 or close to 1:1, it doesn’t matter. All that matters is if there are any Group I molds with a much smaller ratio.

Getting back to the example, within the Penicillium genus, Penicillium brevicompactum, Penicillium crustosum, and Penicillium variabile stand out in particular. Once again, there are distinctly greater indoor counts than outside. Having seen the issue with Aspergillus, it’s not surprising to me that Penicillium is also high as these two molds thrive under the same conditions and consequently tend to co-exist hand-in-hand. Other stand-outs are Scopulariopsis chartarum that enjoys drywall paper and Trichoderma viride that prefers wood. With a little research, its clear there is a condensation type of issue (wet but not sopping wet) in the house.

When looking at a mold like Stachybotrys chartarum, even though the factor was 3.3, the numbers in both indoor and outdoor samples were quite small and there was definitely more outdoors. Furthermore, Stachy spores are heavy and consequently aren’t frequently found in the air much. Hence, this mold isn’t an issue. Notice that the Sum of the Logs, and the ERMI scores don’t matter in this approach. The amount of dirt in relation to spores is inconsequential. We’re simply looking at the ratio of the number of spores deposited outside versus inside.

Granted this method isn’t perfect either. Still, by taking Swiffer Cloth samples from inside and out over the same time period on equally sized clean surfaces, we eliminate many of the factors mentioned that can skew ERMI results. Have a super clean or extra dirty house – no problem. Don’t have carpeting – no problem. Want to be sure that the source isn’t from outside or a very minor mold issue that has been addressed – no problem. Granted there is some added expense, especially if you take my advice and hire a mold professional to help you, but we’re talking about an illness that is truly horrible. You can spend thousands like I did and go around and around for two years trying to figure out what various tests (including the standard ERMI) are really telling you related to mold growth, or you can get a real good picture with two side-by-side ERMI tests. I know what I’d choose.

Good Inspectors & Labs

When it comes to DNA labs, the one recommended by Dr. Shoemaker and Greg Weatherman is Mycometrics. They do the standard ERMI, Swiffer Cloth, and HERTSMI-2 tests among others. The owner, Dr. King-Teh Lin, has a Ph.D. in Microbiology, helped refine ERMI testing methods, and is an Adjunct Instructor at a Medical School. He’s also a nice guy. I spoke to him a few times on the phone as we tried to sort through a very difficult to solve puzzle. Simply call the lab, order a kit, and then make sure to follow the instructions.

Note: Dr. Shoemaker’s website now also lists EnviroBiomics. They offer a range of testing options including ERMI, HERTSMI, Endotoxin, Actinomycetes, Beta-Glucans, and even Lyme.

When it comes to inspectors, Martine Davis has been in the business since before CIRS had a name. She’s a moldy herself and learned how to get better on her own – before Dr. Shoemaker’s work. She’s incredibly kind and helpful. When I was at a complete loss trying to discover the very difficult hidden mold sources in our home, she talked with me at length going over all the possibilities and then helped formulate a plan. Personally, I think she’s nuts to be in the business she’s in but that’s another matter.

Indoor Environmental Testing – Martine Davis

Healthy Home Expert – Nicole Bijlsma

Martine leap-frogged from spore traps, over ERMI, to Mycotoxin testing. In her case only, I can’t argue. Her internal mold-radar is so good that she doesn’t need ERMI to determine if mold is an issue. Years of experience has made her an excellent sleuth when it comes to pinpointing the mold source. Instead of HERTSMI-2, she currently likes to test for Mycotoxins for quantifying health risks. Even though I have a lot of respect for her work, my preference would be to use HERTSMI-2 given the supportive data. You can discuss this with her and I know she can help with ERMI sampling should you so desire.

The new kid on the block is Greg Weatherman. Well, not that new. He wrote the chapter “Testing & Remediation” in Dr. Shoemaker’s book “Surviving Mold” and continues to author articles available on Dr. Shoemaker’s website. I’m quite impressed with what I’ve read in terms of his in-depth understanding of mold, his development in the area of mold remediation (he’s got a cool way to fog the super tiny toxins out of the air), and his compassion for those with CIRS – he gets it. When it comes to mold, Mr. Weatherman is a total geek – in a good way.

SafeStart Analytics Safe Start Analytics – CIRS Knowledgeable Inspectors

EnviroBiomics EnviroBiomics – Mold Inspectors

Given the limitations in ERMI/HERTSMI testing, it’s important that whomever you chose as your inspector that they visually inspect every nook and cranny of the building. Be aware that finding mold visually is not easy. If the inspector you hire doesn’t visually inspect every inch of your home including crawling all around in the attic and crawlspace, moving boxes and shelving in the basement, emptying closets to see in the corners, and otherwise looking over all other hidden away places, you hired the wrong inspector! I’ll say that again. A good mold inspector gets their nose right up to the places they’re inspecting. That’s the only way to ever hope of visually finding mold as fungi is often the same color as the material it is feeding on and very fine in composition.

Furthermore, the inspector needs to be seasoned as finding mold visually is more of an art than a science. They should not rely on any one test exclusively and should visually pour over the building they’re inspecting. During the phone interview, query the prospective inspector about unusual places they’ve found mold and the subtleties involved. The stories should be numerous and full of nuances the Inspector learned over the years. Any suspect areas the Inspector finds should be swabbed and sent to a lab that will then identify it under a microscope.

(FYI, I do not have any type of financial affiliation with these Inspectors.)

Beyond DNA Testing

VOC - Prism Home Test Kit

There are a couple of additional types of mold testing that we haven’t covered yet. One is the VOC test I had done upon Martine’s advise. The moment Martine walked through the front door of our home, she commented on the high VOC levels she could smell. To confirm this, she did a spot VOC test and then instructed me on how to order a PRISM IAQ VOC test kit that included a small vacuum pump and a glass tube with a special medium inside.

You can order a VOCs, Hidden Mold & Formaldehyde Prism test kit from Home Air Check for $172 as of late 2015. To administer the test, you remove the caps on either end of the tube and insert it into the pump. For two hours, air is drawn through the tube with the VOCs being captured within the material inside. You can see a sample report below that includes a mold VOC level.

IAQ VOC Test 1of3   IAQ VOC Test 2of3   IAQ VOC Test 3of3

Mycotoxin testing is the last type of mold testing we haven’t covered yet. It is gaining some momentum and this makes sense given that none of the other mold tests actually measure any of the harmful toxins that cause CIRS – except for mold dogs and VOC testing. The labs that do this type of testing are Real Time Laboratories, US Bureau Veritas, Mycometrics, and EMSL. Currently, three of the most prevalent mycotoxins are measured. The cost is $300 from RealTime labs as of early 2015.

The three mycotoxins measured are Ochratoxin, Tricothecene, and Aflatoxin. All three are associated with the most common molds found in water-damaged buildings. Ochratoxin from Aspergillus and Penicillium is most commonly found. Next in line is Tricothecene primarily from Stachybotrys and Fusarium molds. Least common is Aflatoxin from other species of Aspergillus.

As discussed, mycotoxins are only a tiny fraction of the total toxic soup of inflammagens associated with CIRS. Additionally, there is some controversy around the accuracy of this testing. Furthermore, I do not know of anyone that has systematically collected mycotoxin testing and correlated it with CIRS inflammatory markers like Dr. Shoemaker has done with HERTSMI-2. Nonetheless, I do believe this type of testing holds out promise.

Meter Cases - Martine

Last but not least, when it comes to recovering your health, you need to look for more than just mold. Mold is critical but when your health suffers, it’s important to make sure you don’t have leaking gas fittings, that you’re not being inundated with EMF fields, that you’re not breathing in high VOCs, and the like. In addition to mold testing, Martine brings a trunk-load of other expensive equipment that includes a Carbon Monoxide Analyzer, Carbon Dioxide Monitor, RF EMF Analyzer, Combustible Gas Detector, Concrete Moisture Meter, Moisture Probe, Particle Counter, a VOC Spot Analyzer, and others. As a result of her inspection of our home, I changed out our phones to older 900Mhz models (high EMF), moved all chemicals out of the house (high VOC), and installed filters to subdue the high “stray voltage” on the house wiring.


Mold testing can have one or more of three goals. One goal would be to simply know if a building is safe to live in for someone with CIRS. A second goal would be to know if mold has grown, or is still growing, in a building. And a third goal would be to know where the mold is located. Depending on the goals, different approaches need to be taken.

Although there are many different types of mold tests, none of them test for the actual mold toxins that are at the heart of CIRS for so many. The exceptions are mold dogs, VOC, and mycotoxin testing. Nonetheless, given all the supportive data and accuracy of DNA testing, the best mold test to date for determining if a building is safe for those with CIRS is the less expensive HERTSMI-2 test. For determining if there is indoor mold growth, the best approach is the side-by-side Swiffer DNA analysis. Not only does this approach by-pass many of the issues with a single ERMI test but you can also calculate indoor and outdoor HERTSMI-2 values from the same results.

I do not recommend trying to determine if a building is moldy based upon a single indoor Swiffer test – you need indoor and outdoor Swiffer samples taken as I’ve outlined. However, if you’re on a tighter budget, then a single ERMI taken from the living and bedroom carpeting of an average home can be quite telling especially when interpreted by an experienced mold inspector. ERMI is really the only method that can be employed by a novice with any reasonable expectation of getting accurate results. Note: If you’ve already had an ERMI done, there is a very good chance the results are useable.

Unfortunately, if your home isn’t “average” or doesn’t have carpeting, you have no choice but the Swiffer Cloth ERMI method. I do not know of any data that supports the use of a single Swiffer for determining if a building has mold growth. As such, the best approach is to take side-by-side indoor and outdoor samples. Additionally, my understanding is that Dr. Shoemaker developed the HERTSMI-2 scale based upon the typical ERMI carpet sample – I don’t remember Swiffer being around at the time that HERTSMI-2 was introduced. Nonetheless, it does appear that he sanctions the calculation of HERTSMI-2 from a Swiffer ERMI. (Wouldn’t it be awesome if Dr. Lin from MycoMetrics in conjunction with one or more Physicians would collect data on Swiffer Cloth results along with the health status of CIRS folks so an improved Swiffer HERTSMI or Swiffer ERMI could be developed?)

Of course, if it turns out the building is moldy, the next step is to find the source. This is often easier said than done. In the home I mentioned with the numerous sources of mold, I only found half of them even though I’d studied about how to look. The less obvious sources were found by Martine. Figuring out where mold is growing is part science, part art, and a lot of experience. This is where you need a good inspector to help.

You can gauge the strength of an inspector by talking to them about the limitations of the various tests and asking them about how they go about determining if a building is moldy. Equally important, you should query them around what they know about Biotoxin Illness, also called Chronic Inflammatory Response Syndrome. If they give you a lukewarm response, look for someone else. You want someone that understands how devastating this illness can be and consequently knows how utterly critical it is that they get it right. Educate yourself and if possible, hire an experienced Mold Inspector.