A Low ERMI Score Does Not Mean Your Home Is Mold Free!
“Many indoor air quality (IAQ) professionals and numerous laypeople with an interest in mold have heard about a fungal sampling/analysis/interpretation method developed by the EPA called ERMI. Unfortunately, what many individuals do not appreciate with this precision analytical method is that sample collection and data interpretation controversies can place the unsophisticated user at great risk – particularly if ERMI samples are used following fungal clean-up efforts as post-remediation verification. (Should ERMI Be Used In Post Mold Remediation Verification?)”
The article, “Restorer’s Perspective: How to Lose Your Money, Sanity, and Credibility in One Mold Project“, discussed the difficulties with post remediation verification for restoration professionals working with mold sensitized individuals that rely on ERMI testing.
This article will explain what ERMI testing is and why it poses challenges.
What is ERMI?
ERMI stands for Environmental Relative Moldiness Index.
The ERMI process was developed by the EPA to “objectively describe(s) the home’s mold burden” using a specific settled dust sampling technique and analysis to evaluate fungal DNA.
ERMI samples determine the levels of 36 different types of mold. The key is the comparison of samples. 26 of the sample species, Group 1, are associated with water damaged homes; 10 of the sample species, Group 2, are not and are typically found out doors. Group 2 is subtracted from Group 1 to determine the ERMI score.
The comparison then assesses a number ranging from -10 to 20 or higher divided into four parts, called quartiles. The math is a bit complicated because it uses logarithms.
From a layman’s perspective, the lower the score for each quartile the better because it means the mold burden is low. Ideally, the score should be zero or less.
How ERMI is Tested?
“There is a risk the public may make inappropriate decisions regarding indoor mold based on the belief that the ERMI tool has been fully validated by the EPA for public use. (EPA’s Office of Inspector General)”
The goal of ERMI testing is to achieve a score of zero or less. Is it possible to achieve a score of zero or less?
Likely not because the testing process is inherently flawed in most remediation situations because the test must be done a specific way. If the test is not done properly, the results can give a false impression that the mold burden is less than it actually is.
“The related science provides another important tool for IAQ and mold professionals, but, just like any powerful tool, ERMI samples can be dangerous to those who do not understand how to use them properly.”
Michael states this because ERMI was developed by the EPA orginally as solely a research tool and not for public use. Despite this, some labs state in their advertisements that the ERMI sample analysis and interpretation process is “EPA approved”, even though the licensing of the technology to properly identify mold DNA does not mean that the EPA is endorsing the entire ERMI process.
When the EPA created the ERMI scale they used a standardized testing process. EPA samples for ERMI are collected with a filter device attached to a vacuum. Their instructions are very precise and systematic. For instance, if a composite sample is collected from the flooring of the living area and main bedroom of a home, in each location a 3-foot by 6-foot area is marked out and carefully vacuumed for exactly five minutes. All of the EPA’s comparison values are based on this process.
This has caused confusion in the market place, particularly for mold sensitized individuals who are trying to use ERMI testing to validate that their home is safe because they are using a flawed process perpetuated by labs that send them a “dust collection cloth” (aka Swiffer) to take ERMI samples. The lab instructs them to wipe the tops of door frames, baseboards, fan blades, dusty corners, etc. until the cloth is visibly dirty.
This process is flawed because it is not standardized. No emphasis is placed on recording specific locations where the cloth is wiped or carefully measuring the surface area being sampled. This process completely abandons the EPA recommended sampling process, meaning the outcome of the results to determine the ERMI score will also be wrong. As stated by the EPA Office of Inspector General:
“If mold samples are not collected in accordance with the sampling procedures used to develop the ERMI, the results would be of questionable value.”
From a layman’s perspective, if you want to use ERMI testing, then you need to compare apples to apples and not apples to oranges meaning the testing protocol must be done properly and follow the EPA guidelines exactly. As Michael Pinto states:
“The problem is obvious: individuals are collecting samples using one method and comparing the results to a table that was designed for samples collected using a different method. There may be a correlating factor, but no one has validated it yet—especially since the original sample collection method has not yet been validated!”
Simply put, do not rely on a Swiffer dust sample test to determine if your home is safe from mold.
What Is The Problem With ERMI Testing?
As stated by our founder, David Myrick:
“Clients want me to get them that low ERMI score. But I can’t for at least a month after remediation. Why? The cleaner I make a house, the worse the ERMI score gets.”
The core problem with ERMI is that it is a ratio between “good”, Group 2, mold spores and “bad”, Group 1, mold spores. This is a challenge because restorers use HEPA vacuums to remove both Group 1 and Group 2 mold spores. When this occurs, the ratio of Group 1 to Group 2 may not go down but actually get worse because a HEPA vacuum does not know the difference between either Group of spores.
In order to get a valid test, the home needs to gather regular dust (which contains Group 2 spores) for at least a month before the ERMI score will decrease.
The challenges with ERMI testing are demonstrated clearly in the table below, courtesy of Wonder Makers Environmental:
[table id=1 /]
This table is based on three ERMI reports and as you see the findings are quite interesting.
From the chart it would appear that Building 1 is the safest, mold free zone because the ERMI score is closest to zero and that Building 2 is not safe because it has the highest ERMI score. However, this is not the case.
Notice that Building 1 has a total spore count of 35,325 for Group 1. Group 1 spores include Stachybotrys, Chaetomium, and Fusarium. Even though the ERMI score seems to indicate that this building would be safer for a mold sensitized person, would it? Absolutely not. In fact, the Group 1 spore count of Building 1 is more than 200 times greater than Building 3 and more than 7 times the Group 1 spore count of Building 2.
It is also important to note that Building 1 has a total spore count of 96,553 for Group 2 spores which are common outdoors. Group 2 spores like Cladosporium can also cause health reactions.
Considering the spore counts of all of these buildings it is clear that Building 3 is the safest for a mold sensitized person and Building 1 is the least safe because it has such a high Group 1 and Group 2 spore count.
The table clearly shows why the ERMI score is a flawed method to determine whether a home is safe from mold.
Don’t Rely on ERMI Testing: Let Common Sense Prevail!
“The irony of the situation is clear. The cleaner a home is made through remediation, the more difficult it may be to achieve an acceptable ERMI score.”
In the chart above, Building 3 has the second highest ERMI score, yet when you review the spore counts of Group 1 and Group 2 they are nearly equal meaning the fungal ecology indoors is similar to outside. This building is the safest to occupy because the indoor and outdoor spore counts are nearly equal.
Clearly, ERMI is flawed.
As a consumer, what you need to understand is that mold grows everywhere and is nature’s recycler. It grows outdoors because it is designed to consume dead organic material. Mold only becomes a problem when it is growing indoors. When mold grows indoors, the spore count will increase. When the spore count indoors is dramatically higher than the spore count outdoors then you have a problem because some molds, like Stachybotrys, release toxins, also known as mycotoxins that can impact your health.
With this in mind, when you do find mold and call Valor Mold, our primary concern is to determine how high your indoor mold spore count is compared to the outdoor spore count. We accomplish this objective by working with third party indoor air quality specialists and industrial hygienists.
These individuals advise us on the following:
- Cause of the mold growth, ie. the source of moisture. It is imperative that the source of moisture, whether it be a leaky roof, leaky pipes, high humidity, etc. is fixed before any mold remediation begins.
- Identifying the species of mold through testing, which could include surface sampling or air quality tests that are then sent to labs for identification.
- Scope of work, which is the action plan that Valor Mold uses to meet the goals of achieving a healthy fungal ecology in the home.
- Finally, our work is verified through third party Post Remediation Verification (PRV).
Once we have our action plan, we will take precautions to prevent mold from spreading in your home. This is done with containment, decontamination chambers, and negative air. Then we remove all the porous contaminated materials and discard safely. The next step is to remove mold from semi-porous materials. Once all the mold is removed, we will scrub the air and HEPA vacuum the area to remove excessive spores in the air.
The final step before any reconstruction can begin is PRV. The purpose of PRV is to measure the level of spores inside of the home after the mold remediation. The mold spore count is always compared to an outside level as well so we have a control value to compare with.
Ultimately, the spore count should reduce dramatically and is the best measure of the success of a mold removal project.
Got Mold or ERMI Questions?
Valor Mold has been serving the Washington DC area since 2006. We are mold professionals that have worked on thousands of jobs, including many for mold sensitized individuals. If you have a question or even think you have mold, please give us a call, 571-210-2040, or send us an e-mail. Piece of mind is just a phone call away! 🙂
— Valor Mold (@ValorMold) October 19, 2016