What Is HERTSMI-2
HERTSMI-2 is a condensed mold testing panel that measures DNA from five specific mold species using quantitative PCR (polymerase chain reaction). It targets Aspergillus penicillioides, Aspergillus niger, Stachybotrys chartarum, Wallemia sebi, and Fusarium species. These five species are most reliably associated with water-damaged buildings and documented health effects including respiratory inflammation, asthma exacerbation, and immune dysregulation.
The test uses dust or settled particulate samples collected from indoor surfaces, typically in bedrooms and living areas. The EPA and indoor environmental health practitioners developed this panel as a practical alternative to the full ERMI, which measures 36 mold species. HERTSMI-2 provides faster results (usually 5 to 10 business days) and lower cost, typically $300 to $600 per sample compared to $500 to $800 for full ERMI testing.
When to Use HERTSMI-2
HERTSMI-2 works best when you have a known or suspected water intrusion, visible mold growth, or moisture issues you want to verify with objective data. It's particularly useful after remediation to confirm that mold-related contamination has been adequately addressed. The test does not identify every mold species in your home, so it's not appropriate as a general baseline screening tool for homes with no known moisture problems.
If you're dealing with a basement flood, roof leak, or HVAC moisture accumulation, HERTSMI-2 gives you a quick assessment of whether the five highest-risk water-damage species are present at elevated levels. This information directly informs whether you need professional remediation or if standard moisture control measures will suffice.
Interpretation and Standards
HERTSMI-2 results are reported as DNA copies per milligram of dust. The American Academy of Environmental Medicine and some environmental consultants use a guideline of less than 1,000 total DNA copies per sample as a target for remediated spaces, though this is a reference value rather than an EPA-enforced standard. Individual species abundance matters more than total count. High levels of Stachybotrys chartarum or Aspergillus penicillioides, even in small amounts, warrant remediation investigation because these species correlate more strongly with water damage and health complaints.
Interpretation requires context. If your results show elevated levels, you need moisture source identification and control before remediation can succeed. If HERTSMI-2 detects these species but you have no visible mold or moisture problem, the source may be hidden in wall cavities, ductwork, or crawl spaces.
Comparison to Alternatives
- Visual inspection alone: Cannot detect mold behind walls or in HVAC systems. Does not provide objective documentation for insurance claims or litigation.
- Bulk sampling: Requires visible growth or material removal. Better for identifying what is actively growing, not overall contamination.
- Full ERMI testing: Measures 36 species instead of 5. More comprehensive but slower and more expensive. Useful if you suspect less common mold species or need detailed baseline documentation.
- PCR testing (general): HERTSMI-2 is one specific application of PCR. Other PCR panels target different species sets depending on your region or building type.
Before and After Remediation
Run HERTSMI-2 before starting remediation to establish baseline contamination and guide your contractor on scope. After remediation, test again (usually 2 to 4 weeks post-completion) to verify that mold-related species are no longer present at elevated levels. Successful remediation typically brings HERTSMI-2 results down to background levels matching outdoor samples or unaffected areas of the building.
Do not rely on HERTSMI-2 alone to declare a project complete. Moisture control verification is equally important. If humidity remains above 60% or moisture sources persist, mold will return regardless of testing results.
Common Questions
- Does HERTSMI-2 detect all mold in my home? No. It only measures five water-damage indicator species. Other molds present in your home will not be detected. If you need comprehensive documentation, ask your inspector whether full ERMI or visual combined with targeted sampling makes sense for your situation.
- What should I do if HERTSMI-2 results are elevated? First, locate and eliminate the moisture source. Have a qualified mold inspector or remediator identify where water is entering or accumulating. HERTSMI-2 alone does not tell you the source location. Remediation without moisture control always fails.
- Can I test my home myself? You can collect samples yourself following the lab's protocol, but interpretation requires environmental expertise. Many homeowners over-interpret normal background levels or miss critical context about moisture conditions. A professional inspection paired with testing gives you better decision-making data.
Related Concepts
- ERMI - the full 36-species mold panel that HERTSMI-2 simplifies
- PCR Testing - the laboratory method both HERTSMI-2 and ERMI use to detect mold DNA