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What Is ERMI?
ERMI stands for Environmental Relative Moldiness Index. It serves as a tool for researchers to gauge the levels and varieties of mold spores within a property.
It was developed by the U.S. Environmental Protection Agency (EPA) and HUD (U.S. Department of Housing and Urban Development).
The goal? To create a standardized way to measure mold levels indoors.
For more information, visit the EPA’s website:
Environmental Relative Moldiness Index fact sheet
How ERMI Works
ERMI testing uses a technology called Mold-Specific Quantitative Polymerase Chain Reaction (MSQPCR).
This is a type of DNA analysis.
It identifies and quantifies 36 mold species commonly found in homes.
These species are split into two groups:
- Group 1: Molds linked to water damage.
- Group 2: Common indoor molds not necessarily related to moisture.
The difference between the two group scores forms your ERMI score.
The ERMI scale ranges from a low of approximately -10 to a high of about 30.
Important Limitations
The EPA does NOT recommend ERMI for routine mold testing.
Why? Because:
- It was designed for research only, not for public use in homes, schools, or other buildings.
- The method requires specific sampling technique & expert interpretation.
- A high ERMI score doesn’t always mean a health risk or that mold growth is present.
- It doesn’t assess current air quality—only what mold spores were present in the dust.
In addition, according to the Inspector General from the EPA, “We substantiated the allegation that firms were using the mold index tool although the EPA had not validated the tool for public use. The EPA readily acknowledged that it had not validated or peer reviewed MSQPCR or ERMI for public use. The agency said it considers MSQPCR and ERMI to be research tools not intended for public use.”
This PDF document can be downloaded here:
EPA Inspector General on ERMI
Should You Use ERMI?
ERMI can provide helpful data, especially in complex or long-term mold cases.
However, it’s not a diagnostic tool for everyday indoor air quality concerns.
What’s a Better Option?
A professional visual inspection, performed by the Indoor Environmental Quality (IEQ) experts at American Metropolitan Environmental, Inc., combined with targeted air and/or surface sampling, is typically more useful for most homes or buildings.
Talk to an Expert
Not sure if you need ERMI or a different type of mold test?
Contact us today. We’ll help you find the most effective, science-backed solution for your space.