Last Updated: May 4, 2026
By: Brian Karr · Co-Founder & Chief Inspection Officer, We Inspect
After getting a high ERMI score, your next step is to find out where the mold contamination is actually coming from inside your home. An elevated ERMI confirms that mold species are present in your dust at levels above the national average. But it does not tell you which wall, which floor, or which duct is the source. That distinction is everything.
The Environmental Relative Moldiness Index (ERMI) is a DNA-based dust analysis developed by EPA researchers. It measures 36 mold species and ranks your home’s mold burden on a scale from roughly −10 to 20+. Scores above 5 place your home in the upper quartile of contamination nationally. A high score confirms a problem exists but cannot pinpoint its location.
Key Takeaways
- A high ERMI score confirms elevated mold in your home’s dust but does not identify where the growth is or which areas are driving your exposure
- The critical next step is source-level sampling to locate hidden growth inside walls, floors, and HVAC systems
- ERMI measures mold species only. A separate mycotoxin dust test is needed to evaluate whether toxic compounds are accumulating in your living spaces
What a High ERMI Score Means for Your Health
A high ERMI score is not just a number on paper. A 2013 study in the Journal of Asthma found that asthmatic children in Boston, Kansas City, and San Diego were living in homes with average ERMI values of 8.73, compared to 3.87 in nationally representative control homes.1 A 2024 review in Critical Reviews in Microbiology confirmed that six independent epidemiological studies have now linked elevated ERMI values to both childhood and adult respiratory illness.2
I talk to families every week who have ERMI results in hand and no idea what to do next. A dad in Gilbert, Arizona called me last month with his daughter’s ERMI at 14. His allergist had never heard of the test. His pediatrician suggested replacing the HVAC filter. Nobody could tell him where the mold actually was.
That is the gap ERMI cannot close on its own. The score tells you the problem is real, but it cannot tell you which wall, which floor, or which duct is producing the contamination you are breathing.
Three Steps to Take After a High ERMI Result
Step one: get source-level sampling done. Exposure Mapping™ identifies exactly where mold growth is hidden and actively occurring, whether behind drywall, under flooring, or inside HVAC ductwork. This is where the ERMI leaves off and actionable data begins.
Step two: test for mycotoxins separately. ERMI measures mold species and relative abundance only. It does not measure mycotoxins. A separate mycotoxin dust test evaluates whether toxic compounds are accumulating in your living spaces. A 2013 study in Toxins found that 93% of chronic fatigue syndrome patients tested positive for at least one mycotoxin, and over 90% had a history of water-damaged building exposure.3 These are two entirely different tests, and most families need both.
Step three: get a contractor-ready remediation plan. Once you know where contamination is concentrated and what you are being exposed to, targeted remediation can address the actual sources. Families who skip source identification and jump straight to remediation frequently spend tens of thousands on fixes that do not reduce exposure. Recovery starts when the source is confirmed and eliminated.
For a detailed walkthrough of ERMI score interpretation and what each mold group means, see our ERMI interpretation guide.
Next Steps
If you want to know what your home is actually doing to your body, we can find out. We Inspect uncovers hidden mold contamination, ranks what truly drives your exposure, and delivers a contractor-ready Remediation Recovery Blueprint designed to meaningfully reduce exposure so your body can heal — without wasting tens of thousands on unnecessary fixes that won’t move the needle. Get My Free Exposure Consultation
Frequently Asked Questions
Is an ERMI score of 5 considered high?
Yes. An ERMI score of 5 or above places your home in the upper quartile of mold contamination compared to a nationally representative sample of U.S. homes. Scores above 5 were consistently associated with respiratory illness in EPA-funded studies. The higher the score, the greater the mold burden in your settled dust.
Can I do ERMI testing myself or do I need a professional?
You can collect an ERMI dust sample yourself using a kit from an accredited lab. The sample involves vacuuming a measured area of settled dust and mailing it in. However, interpreting the results and determining next steps typically requires professional guidance, because the score alone does not tell you where growth is occurring.
Does a high ERMI score mean my family needs to leave the home?
Not necessarily. A high score means elevated mold species are present in your dust, but the health impact depends on which species are present, where the growth is, and your family’s individual sensitivity. The priority is identifying and eliminating the source. Most families can stay in their home while targeted remediation addresses the contamination.
References
- Vesper SJ, McKinstry C, Haugland RA, et al. Higher Environmental Relative Moldiness Index (ERMI) values measured in homes of asthmatic children in Boston, Kansas City, and San Diego. Journal of Asthma. 2013;50(2):155-161. doi:10.3109/02770903.2012.740122
- Vesper SJ. The development and application of the Environmental Relative Moldiness Index (ERMI). Critical Reviews in Microbiology. 2024. doi:10.1080/1040841X.2024.2344112
- Brewer JH, Thrasher JD, Straus DC, Madison RA, Hooper D. Detection of mycotoxins in patients with chronic fatigue syndrome. Toxins. 2013;5(4):605-617. doi:10.3390/toxins5040605
This article is for informational purposes only and does not constitute professional medical advice. If you believe mold or other environmental hazards may be affecting your health, consult your healthcare provider.