What is the difference between ERMI and HERTSMI-2?

ERMI (Environmental Relative Moldiness Index) analyzes 36 mold species from a settled dust sample and produces a score from roughly -10 to +25 by subtracting Group 2 (common outdoor) species from Group 1 (water-damage indicator) species. HERTSMI-2 (Health Effects Roster of Type-Specific Formers of Mycotoxins and Inflammagens - 2) analyzes only 5 species: Aspergillus penicillioides, Aspergillus versicolor, Chaetomium globosum, Stachybotrys chartarum, and Wallemia sebi. Both use MSQPCR analysis from the same dust sample and can often be run simultaneously.

How much does ERMI vs HERTSMI-2 testing cost?

ERMI analysis costs $200-$400 including lab fees at an AIHA-accredited laboratory. HERTSMI-2 analysis costs $100-$200. Many labs offer both tests from the same dust sample for $250-$450 combined. The dust collection kit and shipping add $15-$30. Professional collection (inspector visits property to collect sample) adds $100-$200.

What does an ERMI score mean?

ERMI score interpretation: negative scores (below 0) indicate the home is cleaner than the average US home in the EPA reference database. Scores of 0-5 represent moderate moldiness. Scores above 5 indicate elevated mold compared to the national reference. Scores above 12 are associated with adverse health effects in mold-susceptible individuals per Shoemaker CIRS research. The formula is: ERMI = log(Group 1 species sum) - log(Group 2 species sum).

What does a HERTSMI-2 score mean?

HERTSMI-2 scoring by Shoemaker protocol: scores below 11 indicate the home is likely safe for CIRS-susceptible individuals. Scores 11-15 indicate caution; some CIRS patients may react. Scores above 15 indicate the home is likely unsafe for CIRS-susceptible individuals and remediation should occur before re-occupancy. HERTSMI-2 is specifically designed for evaluating safety for people with Chronic Inflammatory Response Syndrome (CIRS).

Which test should I use: ERMI or HERTSMI-2?

Use ERMI for: general home mold assessment; screening a home before purchase; research and epidemiological purposes; getting a comprehensive picture of all 36 water-damage indicator and background species. Use HERTSMI-2 for: evaluating whether a home is safe for a CIRS patient per the Shoemaker protocol; post-remediation clearance for a CIRS patient; faster, lower-cost screening when CIRS safety is the specific concern. Run both when maximum information is needed from a single sample.

Are ERMI and HERTSMI-2 EPA-validated tests?

ERMI was developed by the EPA (researchers Vesper, McKinstry, et al.) and published in peer-reviewed literature. It is validated for research use and has an EPA reference database of 1,100 US homes. The EPA has not formally endorsed ERMI for regulatory or diagnostic use. HERTSMI-2 was developed by Dr. Ritchie Shoemaker for clinical CIRS evaluation and is not an EPA product. Both use MSQPCR analysis, which is the same validated molecular method.

ERMI vs HERTSMI-2 Mold Test Comparison (2026)

ERMI and HERTSMI-2 are the two primary settled-dust mold tests used in clinical and residential settings. Both analyze DNA from mold species in settled dust via MSQPCR, but they target different species sets, use different scoring systems, and serve different clinical purposes. This guide explains what each test measures, what the scores mean, and which test applies to your situation. For professional assessment contact Mold Remediation Hotline at (332) 220-0303.

36 vs 5 Species

ERMI analyzes 36 mold species from settled dust and compares to a national EPA reference database of 1,100 US homes. HERTSMI-2 analyzes 5 species specifically associated with mycotoxin production and CIRS (Chronic Inflammatory Response Syndrome). Both use MSQPCR analysis. Both can be run from the same single dust sample.

Side-by-Side Comparison: ERMI vs HERTSMI-2

Feature	ERMI	HERTSMI-2
Species analyzed	36 (26 Group 1 + 10 Group 2)	5 (subset of Group 1)
Analysis method	MSQPCR (DNA-based)	MSQPCR (DNA-based)
Sample type	Settled dust from carpet or floor	Same settled dust sample
Score range	Approx. −10 to +25	0–30+
Developer	EPA (Vesper et al., 2007)	Dr. Ritchie Shoemaker (CIRS protocol)
Reference database	1,100 US homes (EPA)	Shoemaker clinical population
Primary use	General mold assessment; research	CIRS safety evaluation; clinical use
Lab cost	$200–$400	$100–$200
Combined cost (both)	$250–$450 from one sample
EPA endorsed?	Developed by EPA; not regulatory standard	Not an EPA product

The 5 HERTSMI-2 Species vs ERMI’s 36

HERTSMI-2 Species (all 5)

Species	Why Clinically Significant	Scoring Weight
Aspergillus penicillioides	Mycotoxin producer; xerophilic (grows at low humidity)	4 points if ≥10 ERMI units
Aspergillus versicolor	Sterigmatocystin and aflatoxin precursor producer	4 points if ≥10 ERMI units
Chaetomium globosum	Strong water-damage indicator; immunotoxic	4 points if ≥10 ERMI units
Stachybotrys chartarum	Trichothecene mycotoxin producer; “black mold”	4 points if ≥10 ERMI units
Wallemia sebi	Xerophilic; associated with CIRS activation in susceptible individuals	4 points if ≥10 ERMI units

ERMI Group 1 Species (water-damage indicators, 26 species)

ERMI’s Group 1 includes all 5 HERTSMI-2 species plus 21 additional water-damage indicator species: Aspergillus flavus/oryzae, A. fumigatus, A. niger, A. ochraceus, A. sclerotiorum, A. sydowii, A. unguis, A. ustus, Aureobasisium pullulans, Cladosporium sphaerospermum, Eurotium (Aspergillus) amstelodami, Paecilomyces variotii, Penicillium brevicompactum, P. corylophilum, P. crustosum, P. purpurogenum, P. spinulosum, P. variabile, Scopulariopsis brevicaulis, S. chartarum, Trichoderma viride.

ERMI’s Group 2 (background/outdoor species, 10 species) includes: Acremonium strictum, Alternaria alternata, Aspergillus ustus, Cladosporium cladosporioides 1 and 2, Epicoccum nigrum, Mucor amphibiorum, Penicillium chrysogenum, Rhizopus stolonifer, Ulocladium chartarum.

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How to Interpret ERMI Scores

The ERMI formula: ERMI = log(sum of Group 1 species) − log(sum of Group 2 species). Score interpretation against the EPA 1,100-home reference database:

ERMI Score	Interpretation	Mold Burden vs National Average
Below −4	Very clean	Bottom quartile; very low water-damage mold
−4 to 0	Clean to average	Below to at national median
0 to 5	Moderate	Above national median; elevated water-damage indicators
5 to 12	Elevated	Top quartile; significantly above average
Above 12	High — action warranted	Associated with adverse health outcomes in susceptible individuals (Shoemaker research)

How to Interpret HERTSMI-2 Scores

HERTSMI-2 uses a weighted point system. Each of the 5 species receives a score based on its ERMI concentration value:

Score per species: 0 points if <2 ERMI units; 2 points if 2–10; 4 points if ≥10
Maximum score: 20 (all 5 species at highest level)

Clinical interpretation by Shoemaker protocol:

HERTSMI-2 Score	Clinical Interpretation
Below 11	Home likely safe for CIRS-susceptible individuals
11–15	Caution; some CIRS patients may react; remediation may be warranted
Above 15	Home likely unsafe for CIRS-susceptible individuals; remediation required before re-occupancy

Which Test Should I Use?

Use ERMI when: you want a comprehensive picture of all water-damage and background mold species; you are screening a home before purchase; you are conducting research or epidemiological assessment; you want comparison to the national EPA reference database.

Use HERTSMI-2 when: you or a family member has been diagnosed with CIRS and are evaluating whether a home is safe for re-occupancy per the Shoemaker protocol; you want lower-cost targeted screening; you are evaluating post-remediation safety for a CIRS patient.

Run both from one sample when: you want maximum information; you are dealing with health effects and want both the comprehensive ERMI picture and the clinical HERTSMI-2 safety assessment. Since both come from the same dust sample, the additional cost is only the extra lab analysis ($100–$200).

For professional mold assessment including ERMI and HERTSMI testing coordination, contact Mold Remediation Hotline at (332) 220-0303. See also our guides on DIY mold test kit accuracy and mold inspection cost by state.

Frequently Asked Questions

What is the difference between ERMI and HERTSMI-2?: ERMI analyzes 36 species via MSQPCR and scores against an EPA 1,100-home reference database. HERTSMI-2 analyzes 5 species (a subset) using a weighted point system specifically for CIRS safety evaluation per the Shoemaker protocol. Both use the same settled dust sample.
How much does ERMI vs HERTSMI-2 testing cost?: ERMI: $200–$400 including lab. HERTSMI-2: $100–$200. Combined (one sample): $250–$450. Professional collection adds $100–$200 to either test.
What does an ERMI score mean?: Below 0: cleaner than average US home. 0–5: moderate elevation. 5–12: significantly elevated. Above 12: associated with adverse health outcomes in susceptible individuals per Shoemaker research. Formula: log(Group 1) − log(Group 2).
What does a HERTSMI-2 score mean?: Below 11: likely safe for CIRS patients. 11–15: caution zone. Above 15: likely unsafe for CIRS patients; remediation required before re-occupancy per Shoemaker protocol.
Which test should I use: ERMI or HERTSMI-2?: ERMI for general comprehensive assessment and pre-purchase screening. HERTSMI-2 for CIRS safety evaluation per Shoemaker protocol. Both from one sample for maximum clinical information when health effects are a concern.
Are ERMI and HERTSMI-2 EPA-validated tests?: ERMI was developed by EPA researchers and is validated for research use with an EPA reference database. It is not an EPA regulatory standard. HERTSMI-2 was developed by Dr. Shoemaker for CIRS clinical use and is not an EPA product. Both use validated MSQPCR analysis.

Sources: Vesper SJ et al., "Development of an Environmental Relative Moldiness Index," Journal of Occupational and Environmental Medicine (2007); EPA ERMI research program documentation; Shoemaker RC, "Surviving Mold" HERTSMI-2 scoring methodology; AIHA EMPAT accreditation program. ERMI and HERTSMI-2 are research and clinical tools, not regulatory standards. Consult a physician for health-related mold exposure decisions.