ERMI Testing for Mold - What is it and do you need it?

ERMI Testing for Mold – What is it and do you need it?

If you’re concerned about mold in your home, you may have come across the term “ERMI testing.” But what is ERMI testing, and do you really need it? This is an interesting and often divisive topic in the industry. We’ll take a closer look in this article at ERMI testing to help you decide if it’s right for you.

What is ERMI Testing and where did it come from?

ERMI testing is a type of DNA-based testing that uses Environmental Relative Moldiness Index (ERMI) values to identify mold levels in a given area. Mold levels are measured by looking at the presence of 36 different mold species that are known to cause problems in homes. The test results are then compared to a database of known mold levels to determine whether or not the mold levels in your home are higher than average.

ERMI testing is often used in homes that have a history of mold problems, or in homes that are located in areas with high levels of mold. It’s also sometimes used in homes that have been flooded, as mold can often become a problem in these homes. ERMI testing is done via dust collection and analysis of that dust, so it is measuring spores that have settled onto the surfaces where the dust is being collected. This is different from air sampling, which is measuring airborne levels of spores.

Who Created ERMI Testing?

ERMI testing was developed by the Environmental Protection Agency (EPA).

The ERMI was developed by researchers at the EPA utilizing a DNA-based method for quantifying molds known as Mold Specific Quantitative PCR (MSQPCR). The ERMI was created as a result of the “application” of the MSQPCR technology.

EPA researchers used MSQPCR to quantify mold populations in more than 1,000 houses from across the United States as part of the American Healthy Homes Survey (AHHS) to assess mold contamination in homes, according to the Environmental Relative Moldiness Index (ERMI). The relative level of “moldiness” for each house was assessed using a standardized sample from each home and an analysis of 36 indicator molds in each sample.

This is important because the EPA identifies that ERMI is a research tool, and does not recommend its use except for that purpose.

Why is ERMI Testing Used?

While the EPA identifies ERMI as a research tool only, many companies and individuals in the mold industry have been using ERMI to evaluate homes for mold issues. In this case, ERMI testing is used to identify and quantify mold levels in a given area. This information can then be used to help determine if there is a potential for health problems related to mold exposure, or if there is a need for further investigation and remediation.

ERMI testing is often used in cases where there has been a previous history of mold problems, or in cases where there are high levels of mold present. It’s also sometimes used in homes that have been flooded, as mold can often become a problem in these homes.

ERMI testing is done via dust collection and analysis of that dust, so it is measuring spores that have settled onto the surfaces where the dust is collected. This is different from air sampling, where the test results indicate the level of airborne mold spores in a given area.

Do You Need ERMI Testing?

We have seen ERMI testing recommended for people who have chronic illnesses that may be exacerbated by exposure to mold, as well as for people who have had previous issues with mold in their homes. If you fall into one of these categories, ERMI testing may be a helpful tool in assessing the presence or absence of a mold issue in your home. While it can be helpful in certain situations, it is not a necessary test for most mold issues. 

What is an ERMI Score and how is it calculated?

An ERMI score is a numeric value that is calculated by looking at the presence of 36 different mold species in a given sample. These mold species are separated into different groups.

  • Group 1 – Water Damage Indicating Molds
  • Group 2 – Common Indoor Molds

To calculate the ERMI score the levels of the mold species found are log-transformed and the sum of logs in group 2 is subtracted from the sum of logs in group 1.

Water Damage Molds – Common Indoor Molds = ERMI Score

Are ERMI Tests Accurate?

ERMI tests are generally considered to be accurate, but it’s important to note that they can only test for the presence of mold, not for the amount of mold present. This means that ERMI tests can’t tell you how dangerous the mold in your home is. However, if ERMI testing reveals elevated levels of mold in your home, it’s a good idea to have the mold professionally assessed.

Is ERMI testing useful for Mold Remediation? How do you perform an ERMI test?

It really depends on how it is done. Typically, ERMI testing can give a “history” of the mold issues in the home, but may not provide the best context for active mold growth. In many cases, we see ERMI tests where the samples were gathered from all different areas of the home. While this practice is helpful in reducing the ERMI testing cost because only one sample is analyzed, it limits the usefulness of the results for remediation. Since the samples are not isolated to individual areas of the home, we cannot use the test results to inform where the mold is coming from.

ERMI test results can also help advise a mold remediator or mold inspector on what additional testing methods may be helpful to better understand the mold issues present in the home. However, it’s important to note that ERMI testing is not a cure-all for mold problems, and it should be just one part of a comprehensive approach to solving your mold problem.

What about ERMI testing after remediation? 

There are 2 reasons that homeowners should be very careful when using the ERMI test to evaluate the success of remediation or for Post Remediation Verification (PRV) Testing.

  1. The Environmental Relative Moldiness Index (ERMI) was created based on the EPA’s survey of more than 1,000 homes in normal living conditions. When a remediation project takes place, the air is moved all around the treated area, and the end result is very different from “normal living conditions”. 
  2. Above we outlined the formula for calculating the ERMI score, which is essentially a ratio of water damage molds to common indoor molds. When a remediation process takes place molds from both groups are removed, which will throw this ratio severely out of whack.

For these reasons, ERMI testing immediately after a project is not likely to provide the peace of mind that a homeowner is looking for. Even after a very successful remediation project the ERMI score could be basically anywhere and is not a reflection of the project or current environment. 

If you want to use ERMI post-remediation, it is important to wait approximately 6 months or more, to allow the indoor environment to settle back into normal living conditions. Additionally, if the goal of remediation is to lower a home’s ERMI score, specific remediation protocols may need to be implemented that are not always used in typical mold remediation projects. Complete dust removal of the entire home is necessary to ensure that the “history” of mold in the home is removed and you are starting from a clean slate. 

How do you perform an ERMI test?

ERMI testing is performed by collecting dust samples from your home and sending them to a laboratory for analysis. The laboratory will then compare these results to the Environmental Relative Moldiness Index (ERMI) values to identify a quantitative value of mold levels in your home.

Each laboratory that offers ERMI analysis may have different protocols for sample collection, so it is best to follow the process outlined by the laboratory that you will be using. In general, to collect dust samples for an ERMI test, you’ll need to use a dust collector that is specifically designed for ERMI testing. These dust collectors are available for purchase online and in some stores. Once you have a dust collector, you can follow these steps to collect the samples:

1. Choose an area of your home to sample. It’s best to choose an area that you suspect may have elevated mold levels.

2. Turn on the dust collector and place it in the chosen area.

3. Allow the dust collector to run for at least two minutes, or until it has collected a full sample.

4. Turn off the dust collector and remove the sample from the device.

5. Label the sample with your name, address, and the date it was collected.

6. Repeat this process in other areas of your home, if desired.

7. Send the samples to a laboratory for analysis.

Some labs are recommending that dust samples can be collected with a cloth, and that is not something that we recommend, as it is even further distanced from the original ERMI protocol.

Conclusion

If you’re concerned about mold in your home, ERMI testing may help provide a clearer picture of the mold history of your home. Depending on how it is done, ERMI testing can help identify areas of your home that have elevated mold levels, so you can take steps to remediate the problem and improve your indoor air quality. As nice as it would be for there to be one test that told us everything we need to know, unfortunately, that is simply not reality. All tests, sampling methods, and inspection practices have their benefits and limitations, so working with a team of qualified professionals is always a great idea. Every situation is at least a little different, so you need to find out what is best for YOU.

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