ERMI Basics

Updated on January 20, 2016

It’s come to my attention that the previous article Mold Testing may have been a bit too involved. I just wanted to make sure I covered the topic thoroughly. For those that aren’t interested in all the details, I thought it might be useful if I try to strip down what I covered to the basics in this article.

What Is ERMI?

ERMI Vacuum & Cannister

ERMI is a test that looks for the DNA of 36 molds from either a sample taken by vacuuming carpeting or by using a dust cloth. The vacuum sample is captured by attaching a small plastic tube with a filter inside to the end of a standard vacuum hose. The dust sample is captured by using a sterile cloth called a Swiffer Cloth that is swiped over surfaces. The plastic cartridge and Swiffer cloth are sent to a lab that does a mold DNA analysis and sends back an ERMI report.

The ERMI report lists 36 molds that have been divided into two groups, Group I and Group II. There are 26 molds in Group I and these are the molds typically found indoors especially in buildings that have water damage. There are 10 molds in Group II and these are the molds typically found outdoors. In addition to listing the counts for each of the 36 molds, the report also gives an overall ERMI score which is the difference of Group I molds minus Group II molds.


It may seem odd that I’m now going to take a minute to talk about fractions but in the next sections you’ll see why this is important. A fraction consists of the top number (numerator) over, or divided by, the bottom number (denominator). Fraction = numerator/denominator. If you look at the following examples, you’ll realize two truths about fractions. One is that the bigger the numerator, the bigger the overall value of the fraction. The second truth is that the bigger the denominator, the smaller the overall value of the fraction.

15/5=3; 25/5=5; The bigger the numerator (top), the bigger the overall value of the fraction
12/2=6; 12/3=4; The bigger the denominator (bottom), the smaller the overall value of the fraction

Spore E./mg

So now let’s take a closer look at the ERMI report. If you look at the top of the column listing the values for each of the 36 molds, you’ll see it is labeled “Spore E./mg”. It’s a fraction. The numerator (top) is Spore Equivalents and the denominator (bottom) is milligrams of dirt.

ERMI Sample Report

Looking at the numerator (top) first, remember that this is a DNA analysis. This test is very accurate. In other words, every little scrap of mold in the form of spores, chunks of the mold hyphae (fibers), and the like are all measured and counted. Now there’s no way to figure out what part of the total DNA found is from each of the parts of mold. So what they did was to figure out how much DNA you’d get from the average spore of each particular mold and then converted the total DNA found into an equivalent number of spores of that mold – Spore Equivalents.

The denominator (bottom) of this fraction is the milligrams of dirt. Typically what happens is that they sieve out 5 milligrams of the total amount of dirt that is sent in and do a DNA analysis of that 5mg. Once they get the spore equivalents for each of the 36 molds, they divide by 5 to get the number of Spore Equivalents in each milligram of dirt. If you happen to send in less than 5 milligrams, that’s OK too. Let’s say you only send in 3 milligrams. They just divide by 3 instead to come up with the same ratio of Spore Equivalents for each milligram of dirt.

So here comes the key point to this whole article on ERMI. Ready? The key point is that it’s essential to realize that ERMI is really a list of 36 molds showing the number of Spore Equivalents of mold found in relation to each milligram of dirt in the sample sent to the lab. In other words, the 36 values you see listed on an ERMI report are telling you the amount of each mold that was deposited in comparison to the amount of dirt that was deposited. It’s critical to realize that the amount of non-mold (dirt) in the sample influences the values listed on the report just as much as the amount of mold found. I call this the “dirt factor”.


So simply having counts for 36 molds found in each milligram of dirt regardless of the fact that they’ve been very accurately measured is meaningless without some way of knowing at what point the counts become too high – at what point people with CIRS and others get sick. Thankfully, Dr. Shoemaker has very kindly come up with the HERTSMI-2 scoring system. In this system, you simply assign a number to five of the 36 molds listed in ERMI and add them up to come up with your total HERTSMI-2 score. If your score is too high and you have CIRS, the building is not safe. Dr. Shoemaker developed this scoring system based upon thousands of ERMI scores from his patients. By looking at their scores and cross-referencing them against symptoms, he was able to determine that five molds in particular were of most importance and figured out at what levels they made people sick – very cool.

Is Your Home Average?

So let’s look at an example to see how this all plays out. Remember, the ERMI scores Dr. Shoemaker used represent an average of his patient’s ERMI scores. As a result, the more “average” your home is, the more “accurate” the ERMI values in the report will be.

Roughly speaking, the average age of a home in the U.S. is 35 years, with a little over three occupants, and 50% have either a cat or a dog. Based upon my own experience, the carpeting is probably 10 years old, gets cleaned once a year, and although occupants do take off their shoes, they aren’t fanatical about it. You know, average.

So what if you’re a clean freak? Well, mold spores and fragments are everywhere. They’re so tiny, every time you open a window or walk through the door; they enter the building, drift about, and eventually settle to the floor or surface of some sort. That influx is more or less constant and inevitable.

Now let’s say there are two homes next door to each other. Both homes are identical track homes built at the same time and with the same materials. Neither home has an indoor mold problem. Let’s say that in the first house, a very neat retired woman lives. She never wears her shoes indoors. She replaces her carpeting every 5 years.

In the second house, let’s say there is a couple with three kids, a dog, and a cat. The kids are supposed to keep up with chores but the bottom line is it’s hard to keep the house clean. They can’t afford to replace the carpeting.

How will the ERMI scores compare? Remember, ERMI values for each of the molds are given in the number of Spore Equivalent for every milligram of dirt. If the amount of dirt being deposited is greater than average (the denominator is bigger), the each of the mold counts on the ERMI report will be smaller than what it should be. Likewise, if the amount of dirt being deposited is less than average (the denominator is smaller) the mold counts will be skewed higher.

So both homes do an ERMI. Not surprisingly, the home with the single woman comes back very high. The neighbor’s home comes back a little below average. Happily, the woman knows that ERMI results can sometimes be off and calls in a mold expert. The expert knows its important not to simply dismiss a high ERMI score even though he suspects the very clean home and newer carpeting skewed the results. Two side-by-side Swiffer Cloth samples are taken as I’ve described in the article Mold Testing, and the house is shown to be fine.

Does It Matter?

I can tell you from my own experience it matters a lot. My super clean home had an ERMI of roughly 23 and yet when I had inflammatory markers measured according to Dr. Shoemakers’ SAIIE protocol, I was not reacting to living in the house. This was at a time that I was not taking any binders or treatments. I’ve also inspected a dirty home that was an incredible toxic soup with roughly 12 feet by 12 feet of mold growth that had an ERMI less than zero – a very good score. So ERMI values can definitely be way off. If the overall ERMI score is off, then HERTSMI-2 mold counts are off.

Don’t just take my word for it. Talk to experienced mold inspectors – the ones that really care and understand the limitations of mold testing. They’ll tell you flat out that it’s quite common for ERMI to be significantly off. So yes, this does matter.

Is ERMI Useless?

So the temptation may be to simply dismiss ERMI and throw us all back to square zero where we’re left confused and disheartened. That’s not the point of these articles! ERMI is awesome; you just have to know how to use it well.

Furthermore, Dr. Shoemaker’s data doesn’t lie. I have no doubt that a very thorough all statistically analysis was done showing the relationship between ERMI spore counts and adverse health effects. Also, ERMI DNA analysis is stunningly accurate. With 99.7% accuracy, they can tell you exactly how many spore equivalents that they found for each of the 36 molds in every milligram of dirt sample you sent in. This is not a test to just throw up your hands and say it’s junk!

Swiffer Cloth

Swiffer Cloth

What about the Swiffer Cloth? The Swiffer Cloth method was not around when Dr. Shoemaker developed the HERTSMI-2 scoring system. As such, HERTSMI-2 was developed using carpet samples only. Almost certainly, the amount of dirt being deposited on top 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 the same.

I was 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 essentially the same provided that people did not “scrub” the horizontal surface with the Swiffer Cloth. This is a real conundrum. How can the amount of dirt being deposited on surfaces high up possibly be the same as on the carpeting?

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.

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. However, in some borderline cases, I would expect that some Swiffer reports may incorrectly indicate the home is unsafe when it isn’t. Said another way, if a Swiffer HERSTMI-2 score comes back OK, then a carpet HERTSMI-2 score would almost certainly be OK too – the building is almost certainly OK.

The Bottom Line

Petri Dish Outdoor Molds Closeup 1

So if you’ve had an ERMI DNA test done and your home is more-or-less average, then chances are very good that the test is accurate and the HERTSMI-2 score you calculate is meaningful. However, if you get an ERMI (or the less expensive HERTSMI) test done and it comes back OK even though you’re having all sorts of difficulty getting better in spite of following protocols, then take a step back and re-examine your ERMI.

Likewise, if you get a super high ERMI, then consider facts like if you took the vacuum sample from new carpeting. If you did, then the Group II molds will be much smaller because they haven’t had the requisite years that it takes to build up to average levels. Remember that the overall ERMI score is calculated by taking the total of all the molds found indoors and subtracting off the total of all the molds found outdoors. Since you don’t have a lot of outdoor molds built up in your new carpeting, your overall ERMI will be way high. Note: You should be very cautious about dismissing high ERMI scores!

The bottom line is ERMI and the HERTSMI-2 scoring systems are awesome; you just have to be a little careful. I hear folks site their HERTSMI-2 scores as if they were “written in stone” and this simply is not the case. If you want a much more accurate way of knowing if a building is moldy, you can take two side-by-side Swiffer Cloth samples and compare them as I’ve outline in the in-depth Mold Testing article I wrote.

By using this improved method, you eliminate the “dirt factor” all together. In this method, you are simply comparing the amount of mold deposited over a given period of time inside the building relative to the amount being deposited outside the building. Although this method is more expensive and takes more time, it is much less prone to error.

I care about you all. I worry that the reason some folks with CIRS aren’t getting better is because they’re in a moldy home even though their HERSTMI-2 came back fine. Similarly, I’d hate to have someone leave their home and belongings without having really tested for mold properly. I’m trying to help. I’m not trying to scare people into thinking the ERMIs they had done are all bad. Most are just fine. However, there will be a few for which this information may prove very useful.

10 thoughts on “ERMI Basics

  1. Hi Greg,
    Again, another great article! Thank you for educating all of us!

    I’m wondering if I could get your opinion on the following situation:

    My husband has successfully remediated a 423 square foot portion of our main home which is totally sealed off the from main home, and all of which is on an agricultural setting. It’s our goal to move back soon.

    However, the water based sealant used on the wood sub floor, doors and trim is giving me grief as I currently have multiple chemical sensitivity. I am on the Shoemaker Protocol, but I’m not yet to the VIP medication portion. I understand that use of VIP may eliminate the chemical sensitivity.

    I’m a bit reluctant to open windows to let fresh air in and off gases out. I’m worried that I might increase the spore/mycotoxin level in the house thus affecting my health and increasing our HERTSMI-2 score, which is currently an 8.

    For the past few days we’ve been running a commercial HEPA air scrubber with a carbon filter. It seems to be helping as I can notice the improvement when first being in the area. However, after a prolonged time the MCS kicks in. As it all stands now, I would not be able to live in this area full time due the VOC’s.

    In light of your recent article on Mold Testing and indoor vs. outdoor mold levels, do you have any thoughts about your situation that you can share?

    Thanks much,


    • Hi Tina,

      You know, Dr. Shoemaker would say that the 26 “indoor” molds listed on ERMI when found outside aren’t a problem. The theory is that the weather along with competition from all the other micro-organisms prevents molds that grow outside from producing nearly the levels of toxins that well-fed and protected indoor molds do. To a degree, this is true. However, just from my own experience, when fall arrives and the fusarium counts shoot way up from all the surrounding cropland, my health definitely suffers. Likewise, if I spend more than 5 minutes in some of the low-lying areas along the river nearby, I’m toast. Lisa Petrison and Eric Johnson definitely talk about this and Lisa has her Locations Effect Board.

      Having said this, people in houses need fresh air. Remember you can check out the US Spore Map. I’m currently ordering materials to make up a filter that fits in a open window and consists of MERV 13 pleated fabric and activated charcoal. Currently, I have a MERV 13 pleated filter installed on the fresh air duct – most HVAC systems have a fresh air inlet pipe.

      That carbon filter will definitely help with VOCs. We’ve got a couple IQAirs running continuously. I’ve got my fingers crossed that VIP will fix up your MCS.

  2. I thought this article was very helpful and provided a broader perspective on how to interpret results. Thank you.

  3. Hello,

    First, thank you for your informative blog, it’s very helpful. I was recently diagnosed with Toxic Mold Illness completely by accident. I went to my doctor for routine bloodwork of my Thyroid and Antibodies(I have Hashimotos) and he accidentally check off the C4A test on the Quest Labs form. My C4a results were over 9000 which seems pretty high. He did another test(not sure what its called) and it showed that I tested high for Penicillium Notatum and Aspergillu Fumigatus. I also failed the VCS (visual test?). My doctor put me on cholestyramine and honestly, I don’t feel a difference. To be frank, I didn’t feel that bad before finding out I was moldy. Maybe I’m used to feeling a bit “hypothyroid” because I’ve been living this way for so many years. The symptoms for Hashimotos and toxic Mold Illness overlap. Now that you know some of my history, I’ll get to the point…..I’m a bit overwhelmed because I’m not sure how/where I was exposed to mold. I hired a mold expert to test my home and the results were negative for mold. Also, I work from home so it was the only place I thought to test. I still need to test my car as its 15 years old so maybe that is the culprit. I was thinking of ordering an ERMI test for my car but I was wondering if that test allows me to take more than one sample as I would like to test my car and test my house again. Would one ERMI test be enough to check both my house and car or do I need to purchase 2? Your help with this would be GREATLY appreciated!

    Wishing you good health!

    • Hi Tmszion,

      Simply having high C4a does not mean you have Chronic Inflammatory Response Syndrome (CIRS) – also called Biotoxin Illness. Infections, pregnancy, vasculitis, and adult insulin dependent diabetes can also cause high C4a. Granted it sounds like you’re symptomatic, have a fairly high C4a, and failed the VCS test, but additional testing is required – like HLA DR, MMP9, TGF-beta1, VEGF, MSH, VIP, and the like. I’m not sure what mold test was done showing Penicillium and Aspergillus but it is not part of making a proper diagnosis of CIRS.

      You’ll need more labs and a knowledgeable doctor to diagnosis CIRS properly. The reason I’m recommending this is because having CIRS is life changing. You want to be sure.

      Check out my Mold Testing article. There are all kinds of so-called mold experts. If this “expert” didn’t do an ERMI, then I’d say there is a very good chance he/she doesn’t understand CIRS and how to test properly. Of course, you don’t want to dive into expensive testing before you’re sure you have CIRS.

      You could sample from both your house and car with a single ERMI but if it comes back high, you won’t know which one (or both) are a problem. If you’re on a budget, there is the HERTSMI-2 test for half the price of an ERMI. If HERTSMI-2 comes back high, personally I would then take an inside and an outside Swiffer ERMI as discussed in the Mold Testing article. If a problem is still indicated, I’d then hire an expert to help find the source of the mold. This person should know all about ERMI testing, what types of molds are found under various conditions, and have years of experience tracking down hidden mold.

      In terms of exposure, you could have been exposed many years ago. Unlike an allergic reaction, once people with CIRS are exposed to biotoxins, their immune systems become permanently activated until proper treated.

  4. Hi Greg,

    I’m trying to recover from Biotoxin Illness. I’m at a new place, which has no known history of water damage or visible mold growth, nor does it have the right conditions for mold. I’ve been on treatment for two months and have been making a recovery, although certain symptoms aren’t getting better.

    I decided to do an ERMI of my room just to be sure my living environment was safe, and low-and-behold, it came in at a whopping 14. The HERTSMI-2 would be a 26. I was completely shocked. Stachybotrys showed up at 17 spore equivalents, and Chaetomium came in at 1000 spore equivalents. Oddly enough though, a lot of the more common water-damage molds did not show up at all.

    The only thing which makes sense to me is that cross contamination occurred (I did get rid of most of my belongings, but there were a handful of things that I had brought here initially, before throwing them out). A specialist suggested that, based on my ERMI, it looked like there was no active mold growth but that rather spores had been tracked in from outside, possibly due to construction which had been occurring on my street.

    I’m at a bit of a loss as to what I should do. Based on this score, what would you suggest is the best course of action? Are any of my possessions salvageable? Should I leave everything behind and move? If the home doesn’t have an “official” mold problem, per se, does that change how I should approach this?

    I’m planning on doing a few other ERMIs, including an outdoor one, to figure out why my score is so unbelievably high.

    • Donald,

      Not sure how much I can help but I do have a few questions before I attempt a reply.

      Was it a Swiffer or carpet sample and where was it taken?
      How big is the space you have in the new home and what do you mean by the “right conditions for mold”?
      What items did you bring with you and how long were they in the new place?
      How far away is the construction? Is it new or a remodel? How long has it been going on relative to when ERMI was done?
      Do you walk by the construction and then leave your shoes on in the house?
      What other molds on the ERMI were high?
      It sounds like your previous residence was moldy? Did you do an ERMI there?

      • Hey Greg, thanks for the help.

        It was a swiffer sample that I took. I took it from my room, running it along bookshelves, the top of electronics, a mantle and along the headboard of my bed. The space of the room is maybe 12×9 feet, but the house is much bigger. There is no moisture in the house; the humidity is very low.

        Initially, I brought some clothes that I was trying to clean with ammonia and hydrogen peroxide, a book, a CD, my shoes, and my wallet. All of these were disposed of after about a week, except I kept my ID and credit cards, and tried to clean them. My previous place was exceptionally moldy – no ERMI, but I did an air test. There were 200 stachybotrys spores airborne per cubic meter. Aspergillus and Penicillum were double what they were outdoors.

        At my current place, one strain of Aspergillius was slightly elevated. Stachybotrys was fairly high, chaetonium was very high and Wallembia Sebe was moderately high. Everything else was fairly low.

        Road construction has occurred directly in front of the house, maybe about a year or two ago. Its a busy road, so there’s work being done frequently.

        I usually take my shoes off and leave them by the door. Never wore them in the room before.

        • Donald,

          Given a HERTSMI-2 of 26 with Stachybotrys Chartarum contributing 4 points and Chaetomium Globosum contributing 10 points this must mean the other 12 points are coming from Wallemia Sebe and Aspergillus based upon what you’ve said. I’m just trying to double check your math here. Did you see the section on HERTSMI-2 scoring?

          Both Stachybotrys and Chaetomium love really wet environments. As such, it doesn’t surprise me to find Aspergillus and Wallemia Sebe too even though they don’t like as much water as certainly the perimeter of the drenched material is less wet. I’d say that you’re looking at a significant leak somewhere in the building or the items in the building came from a building with significant water damage. Of course there are ways ERMI can be skewed high like having a super clean space or infiltration from an outdoor source. However, I think this is quite unlikely especially since Stachybotrys and Chaetomium produce larger, heavier spores that don’t get around easily and the fact that some molds are very high while others aren’t.

          Regarding having cross-contaminated your space by bringing along some belongings, I doubt it. It sounds like you washed your clothes and used ammonia and hydrogen peroxide. Washing is quite good at removing biotoxins. Borax is the recommended cleaner for this. Your shoes and the book could have easily carried in spores. Shoes can be cleaned if they have a smooth finish by wiping them with Windex, 409, Fantastic, or some other quaternary ammonium product. Non-porous items like plastic cards can be wiped down with quat too. Books can not be cleaned. However, those are big numbers and a book isn’t going to come anywhere near to contributing that amount of DNA – unless it was covered in thick, sticky mold!

          Regarding road construction, I don’t see it as being a source of these molds. You took a dust sample so the mold would have to have drifted in through open windows and doors. Furthermore, the HERTSMI-2 molds come from the decay of cellulose based items like wood and paper along with other organic substances. Tearing up asphalt and concrete isn’t going to produce these molds. The small amount of lumber used isn’t either. It would have to be a major source like a decaying building upwind from your room.

          I know there are some that say you have to get rid of everything. After all, there are molds that eat jet fuel and rubber. Personally, I just think it very extreme to discard all of ones belongings based upon the loose evidence that there is supporting the “ditch it all” approach. Proper cleaning of non-porous items with quat and washing clothes is what Dr. Shoemaker recommends. He’s worked with over 10,000 patients. I’m just saying that I think it’s awesome you’re willing to do what it takes to get better but don’t know you have to go to that level of extreme. I’d recommend paying the small fee and buying his FAQs.

          Given that it doesn’t sound like you own the home, I don’t know that I’d spend the money for further testing. I’m really sorry for the bad news but that’s the way I see it. Well, on the bright side it sounds like you’re traveling light these days so hopefully moving won’t be too much trouble. Maybe do a HERTSMI-2 of the new place you’re considering before moving?

          • Thanks, Greg, this is a big help.

            The aspergillius and wallemia do make up the remaining 12, unfortunately.

            That does mesh up with what other people have told me — the numbers seem way too high to be solely from cross-contamination. I did come from an apartment with an extreme amount of airborne toxic mold, and I did bring my items for a bit, but not that many.

            Unfortunately, the home is a family member’s, so I do want to figure out what’s going on for their sake too. I’ll probably have to leave either way. I’m going to take a couple HERTSMI’s just to see if I can confirm where its coming from, and then leave it up to them to decide what they should do for their own health.

            I’ll buy the FAQs and look through them. I do want to save my items…I just really don’t want to have to go through this another time. I’d drop everything to just save the trouble of never having to deal with this again. I already got rid of everything from my last apartment, and it was terrible.

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