ERMI, the Environmental Relative Moldiness Index, is a research method developed by EPA scientists that uses DNA-based (MSQPCR) analysis of settled house dust to measure 36 mold species and combine them into a single relative moldiness score.
What is ERMI?
ERMI was built from a national survey of US homes. A dust sample is analyzed by mold-specific quantitative PCR for 36 species split into two groups, group 1 (water-damage-associated) and group 2 (common indoor and outdoor), and the log-transformed counts are combined into one index value that ranks a home against the national distribution (EPA, ERMI research background). It is not an air sample and not a current-condition snapshot; dust integrates months of history. The EPA developed ERMI as a research tool and does not validate or recommend it for routine public use, a caveat that travels with every commercial ERMI report.
Why it matters to a mold inspection
ERMI answers "how does this home's accumulated dust compare to a national baseline," not "is there active amplification right now," so it does not replace a spore trap or the indoor-outdoor ratio. It cannot localize a source, and the EPA itself states ERMI is not validated for routine assessment, so reporting an ERMI number as a clearance pass or a diagnosis overstates it (EPA, Mold and Health). It is most defensible as one data point alongside visual findings and moisture mapping. The contrast with current-air methods is in ERMI vs air sampling and ERMI explained.
MoldMind can store an ERMI score and its 36-species breakdown as structured fields next to the air and surface results, so it is read in context, not as a standalone verdict.
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