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What is ERMI?
ERMI (Environmental Relative Moldiness Index) is a DNA-based dust test developed by the U.S. EPA as a research tool. It analyzes settled dust for specific mold species and produces a score intended for comparing groups of homes in studies, not diagnosing individual buildings.
What ERMI Measures
ERMI measures mold DNA in dust. That means it detects both living and dead mold and may reflect past conditions rather than current active growth. It does not identify the moisture source or explain why mold is present. The test can detect a wide range of species, including common indoor molds and water-damage indicators like Stachybotrys and Chaetomium.
What ERMI Detects
- 36 different mold species via DNA
- Both living and dead mold spores
- Historical contamination in dust
- Water-damage indicator species
What ERMI Cannot Do
- Identify the moisture source
- Distinguish current vs. past contamination
- Measure airborne exposure levels
- Provide a definitive health risk assessment
What is HERTSMI-2?
HERTSMI-2 is a private, non-EPA scoring system derived from results for five water-damage molds. It is not a health standard, does not diagnose illness, and has not been validated by EPA for deciding whether a home is safe or whether remediation succeeded.
- Focuses on 5 specific water-damage molds
- Does not establish health risk or diagnose symptoms
- Not an EPA-endorsed standard
- Should not replace visual and moisture inspection
Important Limitations
EPA says ERMI has been peer reviewed for research purposes but has not been validated for non-research use. Dust samples vary based on where and how they are collected, and scores can change with cleaning, seasonal conditions, and occupant behavior. There are no federal exposure limits that turn an ERMI score into a health or safety finding. Be wary of anyone using a score to push unnecessary services.
What to Do Instead
Start with a visual and moisture inspection. If a contract, claim, or dispute calls for sampling, use a qualified independent professional and define in advance what decision the result will support. Health symptoms belong with a healthcare provider, not an ERMI score.
- Find and correct active leaks, condensation, or excess humidity
- Document visible growth, staining, odors, and damaged materials
- Size the affected area and choose an appropriate cleanup plan
- Use testing only when a clearly defined result will change the plan
If a Research Protocol Requires a Sample
Follow the research team or laboratory's written collection, handling, and shipping protocol exactly. Dust methods are not interchangeable, and changing the location, surface area, cleaning interval, or collection device can make results incomparable.