Understanding ERMI and MSQPCR Mold Testing
ERMI, also known as MSQPCR, is one of the most recognized mold testing methods available today. Both methods use quantitative DNA qPCR technology to measure the concentration of individual mold species in a sample.
Useful as a starting point, but it should not replace a close review of the individual species listed in the report.
Shows species-specific results without adding an overall score, helping keep the focus on the detailed breakdown.
Why the species breakdown matters
Rather than relying only on the total ERMI score, the report should be interpreted by reviewing each mold species listed. This gives a clearer picture of the indoor environment and can help identify concerns related to water damage.
Start with the detailed findings
The ERMI score is a calculated number designed to simplify interpretation, but the individual species findings remain extremely important. Special attention should always be given to the Group 1 species, and added attention is often placed on the Big 5 species used in the HERTSMI-2 evaluation.
How the color ranges work
Quartile levels are used to highlight the concentration of each species. Any species in the red Q4 range is considered clearly elevated and should be investigated.
Lowest quartile range
Mildly elevated versus the lowest range
More elevated and worth closer attention
Clearly elevated and should be investigated
These quartile levels are based on data collected from 5,000 homes across the United States.
Water-damage-associated mold
Group 1 includes 26 mold species associated with water-damaged environments. These species are considered the most important part of the report when evaluating potential indoor mold problems.
Red boxes and star symbols
- Red boxes indicate elevated concern.
- 1 star (*) = 10 times normal.
- 2 stars (**) = 100 times normal.
- 3 stars (***) = 1,000 times normal.
What a stronger report looks like
- Most species in the green range.
- No species in the red range.
- Ideally only 2 to 3 species in the yellow range.
Context, targets, and next steps
Group 2 helps establish a baseline and calculate the ERMI score, but interpretation should still place the greatest emphasis on the individual species in Group 1.
Indoor control group
Group 2 serves as the indoor control group and is used primarily to establish a baseline and calculate the ERMI score. Even so, the overall ERMI number should not outweigh the detailed Group 1 species review.
Targets vary by sensitivity
- ERMI of 2 or lower is often recommended for individuals with mold sensitivity or Chronic Inflammatory Response Syndrome (CIRS).
- ERMI of 5 or lower is commonly considered acceptable for the general population.
Even when the score appears normal, individual species elevations can still act as warning signs.
AHHS2 and AHHS1
The ERMI and HERTSMI-2 report is based on AHHS2, which uses reference data from the EPA's 2021 housing survey for homes built after 1978. The EPA also published AHHS1 for homes built before 1978, and reference data for older homes is available separately.
Inspect the likely sources
- Beneath floating floors
- Behind air conditioning coils
- Areas with past or present water damage
- Crawl spaces
- Behind drywall in kitchens and bathrooms
Look beyond the total score
Some mold species should measure 1 or less based on the 2021 EPA home survey, so any elevation may be a warning sign even when the overall ERMI score appears normal.
EPA home survey summary tables
The source PDF defines GM as Geometric Mean and % Occur as Percentage of Occurrence. The tables below reproduce the numeric columns as presented in the PDF.
Showing all 36 species rows.
Note: the PDF shows two "% Occur" columns and two "GM" columns without additional column labels. That wording is preserved here.
| Species | % Occur | % Occur | GM | GM |
|---|---|---|---|---|
| Aspergillus flavus | 36 | 47 | 2 | 1 |
| Aspergillus fumigatus | 62 | 70 | 3 | 2 |
| Aspergillus niger | 69 | 97 | 4 | 18 |
| Aspergillus ochraceus | 27 | 74 | 2 | 3 |
| Aspergillus penicillioides | 90 | 99 | 91 | 140 |
| Aspergillus restrictus | 12 | 76 | 2 | 6 |
| Aspergillus sclerotiorum | 26 | 54 | 2 | 2 |
| Aspergillus sydowii | 29 | 6 | 3 | 6 |
| Aspergillus unguis | 20 | 36 | 2 | 1 |
| Aspergillus versicolor | 30 | 70 | 2 | 14 |
| Aureobasidium pullulans | 94 | 100 | 263 | 335 |
| Chaetomium globosum | 51 | 72 | 2 | 3 |
| Cladosporium sphaerospermum | 82 | 98 | 13 | 47 |
| Eurotium amstelodami | 98 | 100 | 155 | 71 |
| Paecilomyces variotii | 46 | 64 | 2 | 2 |
| Penicillium brevicompactum | 52 | 89 | 5 | 6 |
| Penicillium corylophilum | 17 | 68 | 2 | 4 |
| Penicillium crustosum | 8 | 63 | 1 | 6 |
| Penicillium purpurogenum | 15 | 25 | 1 | 1 |
| Penicillium spinulosum | 20 | 5 | 1 | 1 |
| Penicillium variabile | 50 | 87 | 3 | 6 |
| Scopulariopsis brevicaulis | 53 | 64 | 2 | 2 |
| Scopulariopsis chartarum | 38 | 75 | 2 | 3 |
| Stachybotrys chartarum | 35 | 38 | 2 | 1 |
| Trichoderma viride | 27 | 78 | 2 | 3 |
| Wallemia sebi | 75 | 100 | 18 | 155 |
Group 1 includes water-damage-associated molds and is the most important section when evaluating potential indoor mold problems.
| Species | % Occur | % Occur | GM | GM |
|---|---|---|---|---|
| Acremonium strictum | 57 | 82 | 4 | 7 |
| Alternaria alternata | 88 | 100 | 35 | 75 |
| Aspergillus ustus | 40 | 60 | 2 | 2 |
| Cladosporium cladosporioides 1 | 99 | 100 | 331 | 892 |
| Cladosporium cladosporioides 2 | 70 | 95 | 4 | 13 |
| Cladosporium herbarum | 84 | 99 | 31 | 180 |
| Epicoccum nigrum | 93 | 98 | 117 | 59 |
| Mucor amphibiorum | 92 | 97 | 15 | 17 |
| Penicillium chrysogenum | 66 | 95 | 5 | 24 |
| Rhizopus stolonifer | 29 | 52 | 1 | 2 |
Group 2 functions as the indoor control group used primarily for baseline comparison and ERMI score calculation.
