The Pros and Cons of Using ERMI and EMMA Tests to Assess Mold Exposure Risk Inside a Home

By Catherine Fruechtenicht

It is likely that you are reading this article because you are exploring options for testing for mold in your home or perhaps in a home that you are intending to purchase or rent. Maybe you are looking to test because you know that you are mold sensitive and want to be careful, or maybe you want to test because someone in the home is experiencing health symptoms, and you suspect mold to be the causative factor. Whatever the reason, I realize that making heads or tails of testing options that assess the potential health risk that a home may pose is difficult, to put it mildly. And, while no single testing method is perfect, and nothing beats professional, extensive visual and mechanical inspections, I am a fan of not guessing when it comes to mold and mycotoxins. Thus, in this article, I am going to attempt to simplify, explain, and compare two of the most popular, analysis-based testing options for mold, the Environmental Relative Moldiness Index (ERMI), and the Environmental Mold and Mycotoxin Assessment (EMMA).

Before I get into the details of the ERMI and the EMMA, I think it is important to lay out the basics of why these two tests have risen in popularity in mold-aware circles. The main reason, in my opinion, is that both tests are designed to assess mold exposure risk from a HUMAN HEALTH perspective. But why should we care about our indoor mold exposure levels in the first place?

All Homes Have Mold . . . Obviously

Yes. All homes have mold. Outdoor mold enters constantly, and we carry mold in on our clothing, shoes, bags, pets, and on and on. But when mold actively begins growing on building materials or belongings and alters the biome of an indoor environment, something very dangerous can happen: the fungal load of the home will continue to increases exponentially (which means mold exposure is also increasing) and mycotoxins can become present in the occupants’ breathing air and living spaces. The toxic potential of some molds and their ability to produce these mycotoxins is why I assert to anyone listening, that you need to be concerned about mold levels in your home. You also need to know whether or not the molds present in your home are pathogenic (capable of causing disease) or toxigenic, producing mycotoxins which may have many deleterious effects on the human body, including being known to cause some cancers.

What Are Mycotoxins?

Mycotoxins are well-documented for their toxic effects on the human cell. Mycotoxin exposure causes problems in normal cell function and is associated with a wide variety of clinical symptoms and diseases. The World Health Organization (WHO) 2011 publication entitled “Mycotoxins. Children’s Health and the Environment” defines mycotoxins as follows:

  • A toxin is a naturally produced poison.
  • A mycotoxin is a natural byproduct produced by fungi (mold) that evokes a toxic response when introduced in low concentrations to Vertebrates (humans), by a natural route—inhalation, ingestion, or skin contact/absorption.

Thus far, we know, based on scientific study, exposure to mycotoxins produced by the following molds can cause health symptoms:

The one thing I cannot fully discuss here, in terms of mycotoxins, is what level of mycotoxins is an acceptable level for your home. That is because there is no established acceptable level. Yes, you heard me correctly. Even though inhalational exposure to mycotoxins is known to cause illness, disease, and cancer, there are no established parameters for what “safe” exposure levels are or should be. That is why you need to be your own advocate and to be aware of any health symptoms that seem to occur because of exposure to your home or any other indoor environments. YOU are the only one who can safeguard and protect your health when it comes to mold.

Indoor Mold/Fungal Burden

Quantifying a home’s mold or fungal burden is important, because the higher the burden, the higher the need for extensive remediation beyond single-area containment and removal of the mold source. In other words, the indoor fungal burden determines whether the mold issue is a small leak and simple fix or is systemic and distributed throughout the home requiring extensive deep cleaning to properly remediate. To date, the testing methods commonly employed for mold burden determination are Spore Count analysis (in some shape or form—you can read my in-depth discussion of that type of testing HERE), the ERMI (Environmental Relative Moldiness Index), and the EMMA (Environmental Mold and Mycotoxin Assessment).

ERMI (Environmental Relative Moldiness Index)

In short, the ERMI was created by the U.S. Environmental Protection Agency, Office of Research and Development to assess the water damage history of a home by analyzing dust for the presence of 36 different mold species. DNA from mold in the dust is then analyzed using a mold-specific quantitative polymerase chain reaction (MSQPCR) that quantifies the mold spores present to the species level. Dust is used for the analysis, because dust build-up around a home, such as the dust that builds in carpets or on top of the refrigerator, can be the perfect reservoir for mold (both new and old) and can give a wonderful picture of the mold levels in that home over time. The dust specimen for an ERMI can be collected via vacuum canister or Swiffer cloth.

The 36 mold species included on the ERMI are divided into two groups: Group I consists of 26 mold species most-commonly found in water-damaged homes, and Group II consists of 10 mold species that are considered outdoor molds—which is not something I totally agree with but will discuss more later. The results are then compared to the ERMI, an index or scale, which was developed for use in the U.S. to estimate the relative moldiness of a home. By comparing the counts of the two groups, an ERMI score is then determined which can be low to high—from -10 to 20. There are a lot of variables, but, in short, an ERMI score of three or more can be too much for mold-sensitive individuals.

(Note: The Health Effects Roster of Type-Specific Formers of Mycotoxins and Inflammagens – 2nd Version or HERTSMI-2 is another test very similar to the ERMI but less expensive and only tests a dust sample for 5 molds deemed most likely to cause health issues. The HERTSMI-2 scale is as follows: less than 11 is safe, 11 to 15 is borderline, and above 15 is dangerous. The HERSTMI-2 can be calculated from both the ERMI and EMMA test results.)

Pros and Cons of the ERMI

(Note: This is all based on my opinion. I am NOT an Indoor Environmental Professional (IEP), so please defer to a trusted IEP before making any decisions on the safety or remediation needs of your home.) 


  • The MSQPCR technology precise, and if a mold species is present in the sample, it is found and identified.


  • People like the idea that one test can determine the “moldiness” of a home or building.


  • The EPA continues to develop the testing; thus, it should become even more useful over time.


  • Gives a good picture of the history of a home, in terms of water damage and mold issues, so it is a good tool when looking for a safe home to purchase or rent.


  • Can use it to calculate the HERSTMI-2, which was designed specifically for the health assessment of indoor environments.


  • Tests for 36 different types of mold.


  • Because it was developed by the EPA it holds importance in legal cases where mold exposure is on the table.


  • Some environmental professionals report finding little to no correlation between the ERMI results and actual mold found on site. In other words, it is showing both historical and current mold species. Thus, there could be some mold species present in the sample that may not be a current problem in the home.


  • The cost (several hundred dollars). If remediation is needed additional testing will need to be done to pinpoint the source and cause of the mold problem, so things get expensive quickly.


  • The sample collection method is inconsistent and poorly defined, making accuracy an issue. For example, it was developed by the EPA using the vacuum canister method, but most specimens are now are collected using the cloth method.


  • Dust is taken from multiple sites, so results tell nothing about mold source location or severity.


  • Results are based on a scoring system rather than a sample analysis. Sample analysis is really where the power of the ERMI lies. Thus, to get the most out of it, non-professionals will need to pay or hire a qualified IEP to interpret the results to truly diagnose a home. For example, when an ERMI score is low, but Stachybotrys is present. Stachybotrys produces highly toxic macrocyclic trichothecenes. Because of the low ERMI, the occupant could feel that the home is safe and continue to live there and get sick from the hazardous mycotoxins. Additionally, and this is where the Group I and II distinction comes in that I don’t totally agree with, there low ERMI scores where Mucor and Rhizopus are detected. While considered outdoor molds, if present indoors and stirred up, both can cause a serious illness in immunocompromised individuals.


  • ERMI does not test for the presence of mycotoxins. In scientific literature thus far, mycotoxins are the number one indicator of potential health hazards in the home. Mycotoxins are also what doctors are measuring in a patient’s urine or blood when testing for mold toxicity and mold illness. Without specific information about mycotoxins in the home, it may be hard to tie the patient’s illness to the indoor environment.

EMMA (Environmental Mold and Mycotoxin Assessment)

EMMA uses dust from the home’s furnace/air handler filter to detect the presence of 10 toxigenic or pathogenic mold spores and assesses the mycotoxin levels in that dust. RealTime Labs developed the test based on their knowledge of and years of experience testing for 15 of the mycotoxins known to be dangerous to human health AND known to be the toxic byproducts of molds commonly found in water-damaged homes.

Knowing if, to what extent, and to which specific mycotoxins the occupants are being exposed to can inform BOTH remediation and medical treatment. This is because exposure to mycotoxins is the most well-documented and studied piece of the mold/health puzzle (in both animals and humans) thus far, so, in my opinion, it only makes sense to test the environment for them. (RealTime also offers a mycotoxin ONLY test that is less expensive.) Thus, an EMMA test, at a cost like ERMI, gives an indication of the actual health hazard of the home better than other tests currently being used.

The EMMA uses a quantitative PCR (qPCR) procedure for the detection of ten known pathogenic fungal species in the dust specimens. EMMA includes six analyses that were designed and used by the EPA and four analyses that were previously developed by Real Time Labs for mycotoxin-specific testing. The qPCR method used detects fungal DNA to the species level. The data generated for each specimen is plotted against a standard curve to calculate the amount of fungal DNA present in the specimen (nanograms of DNA per milliliter of dust). Controls are included to verify that the DNA extraction procedure was successful and accurate. For the mycotoxin assessment portion, testing is done using competitive enzyme-linked immunosorbent assay (ELISA), a sensitive, specific method for detection, using antibodies prepared against the mycotoxins to indicate their presence in the sample. Each analysis is specific for the mycotoxin identified and does not cross-react with any other mycotoxins in the same sample. In other words, it will only identify mycotoxins that are present and will not yield a false-positive result.

EMMA is based on finding clinically significant links between the molds in the home and the mycotoxins present in both the home and the occupants, so it takes into account intricacies in reporting the data, like filamentous fungi (like Aspergillus sp. or Penicillium sp.), which are branching and difficult to conduct actual spore counts on. The EMMA shows results as DNA ng/ml of fluid, rather than spores/mg of dust or spores/ml of solution, like the ERMI. This allows more precise reporting of how much fungal DNA is present in the sample. The reasoning goes, that once you know the detectable levels in your home and body, you can implement protocols to remove exposure and bring those levels down to where they are undetectable. Then, when you an acheive test results that show undetectable mold and mycotoxin levels in the home (and the body, of course), you know that remediation or treatment has been successful. This way of designing environmental testing, in theory, should make it easier for the occupant to monitor the health of the home and to quickly identify when an issue occurs or to associate a spike in health symptoms with similar spikes in the fungal load of their home.

Pros and Cons of the EMMA

(Note: This is all based on my opinion. I am NOT an Indoor Environmental Professional (IEP), so please defer to a trusted IEP before making any decisions on the safety or remediation needs of your home.) 


  • Only environmental test that tests specifically for the presence mycotoxins.


  • Developed for clinical significance. Molds are not included that do not have clinical research or known health significance.


  • Well-defined sample size and testing parameters.


  • Answers the two most-critical questions when deciding on remediation: Are the organisms found in the home toxigenic and/or pathogenic? What, if any mycotoxins are being produced and are present in the home?


  • Easy-to-read results. Not based on a score. Any presence on the test is significant.


  • Can be used to complement and compare with mycotoxin urine testing. In other words, what you are doing to assess your body complements what you are doing to assess your home.


  • Shows the current fungal burden of the home.


  • Can be used to calculate the HERSTMI-2.


  • Tests for the presence of Candida Auris, an emerging multidrug-resistant yeast causing invasive health care associated infection with high mortality.


  • Not as well-known or utilized by IEPs as the ERMI.


  • Does not pinpoint the mold source.


  • Does not include as many molds as the ERMI.


  • Can be expensive.

So, Which is Better?

There is obviously more than one way to skin a cat or to test for mold, as it were, but gathering as much data as possible that has significance when it come to your health is the name of the game. Mold often cannot be seen or smelled, so both the ERMI and EMMA can be used to find the problems that more traditional means of inspection can easily miss. And, despite what many people tell you, it is not always either/or, because if what you are after is the most data possible, so that you can fully remediate and make your home safe a combination of testing might actually be your best and wisest bet.

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