Los Angeles County · ERMI dust testing
ERMI and HERTSMI-2 Mold Testing in Los Angeles
ERMI and HERTSMI-2 are DNA-based dust tests that estimate which mold species have built up in a home. They can add useful history for mold-sensitive households, but they can’t find a leak, and the EPA says ERMI wasn’t built for routine home use. In Los Angeles, start with a moisture inspection.
- MethodPCR dust analysis
- CoverageAll of Los Angeles County
- First stepMoisture inspection
- PricingQuote before any work starts
- Call(213) 659-0672
The basics
What is an ERMI test?
ERMI stands for Environmental Relative Moldiness Index. A lab uses PCR, a DNA method, to measure 36 mold species in a dust sample from your home, then turns the result into a single score. EPA researchers developed it to compare homes in housing studies.
The 36 species fall into two groups: 26 linked with water damage and 10 common in homes without it. The score weighs the first group against the second, so a higher number means the dust leans toward water-damage molds. It’s a comparison with a set of U.S. homes, not a health limit.
What is HERTSMI-2?
HERTSMI-2 is a shorter score built on five species often tied to water-damaged buildings: Aspergillus penicillioides, Aspergillus versicolor, Chaetomium globosum, Stachybotrys chartarum and Wallemia sebi. It uses the same kind of PCR dust analysis, and many labs can report it from one sample alongside an ERMI panel.
It came out of clinical work with patients who report mold-related illness. Scores are often read as low at 10 or below, borderline from 11 to 15, and high above 15. Those bands are a working convention, not an official standard.
How do these tests compare with other mold tests?
| Test | What it measures | Best for | Can’t tell you |
|---|---|---|---|
| Moisture inspection | Wet materials, humidity, likely source | Finding the cause | Which species are present |
| Spore trap air sample | Spores in the air that day, compared with outdoors | Comparing rooms; checking recent conditions | What settled months ago |
| Tape lift or swab | What’s growing on one surface | Identifying visible growth | What’s in the rest of the home |
| ERMI | DNA of 36 species in settled dust | A long-term picture of the home | Where the mold is, or when it grew |
| HERTSMI-2 | DNA of 5 species in settled dust | A shorter screen for water-damage molds | Anything outside those 5 species |
The official view
What does the EPA say about ERMI?
The EPA says ERMI was developed for research and isn’t meant for routine use in homes. In plain terms, the agency whose scientists created the method doesn’t treat a score as a way to decide whether a home is safe or needs cleanup. There’s no EPA limit or pass mark for it.
The EPA and CDC focus on fixing moisture and cleaning up mold, not measuring it, and LA County Public Health says testing isn’t needed to understand health risk. For most homes, we agree. For a broader view, start with our Los Angeles mold inspection guide.
What are the limits of ERMI and HERTSMI-2?
These tests measure dust, and dust has a long memory. A score can suggest a history of water-damage molds, but it can’t say where they are, when they grew, or whether anything is growing now.
- It can’t find the source. A score won’t show a slab leak, a wet crawl space or a failed AC condensate line.
- Dust is history, not a snapshot. Old spores still count, and DNA can come from dead spores.
- Cleaning changes the result. New carpet or a deep clean can lower a score without changing the building.
- Scores can vary. Two samples from one home may not match, so a small change between tests means little.
- There’s no legal or health threshold. California never adopted numeric mold limits, and no agency sets a safe score.
Do you need it?
Who may want ERMI or HERTSMI-2 testing?
These tests make sense when a long-term picture of the dust would change a real decision, and the moisture checks are already done. That usually means a household with a health concern, or someone weighing a home before moving in. For most LA homes, they aren’t the first step.
| Your situation | Dust test? | What to do first |
|---|---|---|
| Your doctor suggested testing the home | Reasonable | Share the request with us and pair it with a moisture inspection |
| Someone in the home is mold-sensitive | Reasonable | Inspect for moisture so the score has context |
| Choosing a home for a sensitive household | Reasonable, with the owner’s permission | Check the home’s leak history, then sample |
| After remediation, for extra reassurance | Optional add-on | Pass a clearance test first |
| Musty smell, no visible source | Not first | Moisture inspection and air samples |
| Visible mold or a known leak | No | Fix the leak and remove the mold |
| A dispute with your landlord | No | Call LAHD at (866) 557-7368 in the City of LA for a free inspection |
Many people who ask for these tests work with a clinician or belong to mold-sensitive groups, and some have read about CIRS (chronic inflammatory response syndrome) or ISEAI, a professional group in this area. CIRS is a patient-community term, not settled science. Your concern deserves a careful answer, but we don’t diagnose. Talk to your doctor about symptoms.
The process
How is an ERMI dust sample collected?
A dust test is only as good as the sample. We start with the building, then collect dust the way the lab specifies, so the score means something when it comes back.
- Inspect first. We check for moisture with a meter, thermal camera and hygrometer, so the result has context.
- Plan the sample. We choose rooms with you, including where sensitive people spend the most time, and note recent cleaning or new carpet.
- Collect the dust. A measured area of floor or carpet is sampled with a clean collection filter or cloth, following the lab’s method.
- Ship it to the lab. The sample travels under chain of custody to an accredited lab for PCR analysis. Turnaround varies, so we’ll confirm it before you book.
- Explain the result. You get the score, the species counts and a plain written summary of what it does and doesn’t show.
Mail-in ERMI kits exist, and they differ from the petri dish kits in our guide to home mold test kits. The catch: you get a number with no moisture data and nobody to read it against the building.
Cost
How much does ERMI testing cost in Los Angeles?
In Los Angeles, the visit usually falls within normal inspection pricing: $250 to $500 for a visual and moisture inspection, or $400 to $800 with air samples. The ERMI or HERTSMI-2 lab fee is added on top and varies by lab, so we’ll confirm it in writing before you book.
| Service | Typical LA range |
|---|---|
| Visual inspection and moisture mapping | $250–$500 |
| Inspection with 2–3 air samples and outdoor control | $400–$800 |
| Each additional air or surface sample | $75–$150 |
| ERMI or HERTSMI-2 lab analysis | Varies by lab; confirmed in writing first |
| Post-remediation clearance test | $300–$600 |
Typical industry ranges for the Los Angeles area, not a quote. Your written quote depends on the size, access and materials involved.
Expect the PCR lab fee to run higher than a single spore trap sample. Our LA mold testing price guide breaks down the other line items.
If your budget stretches to only one thing, spend it on finding the moisture. A dust score you can’t act on isn’t a bargain.
Your results
What should you do with a high or low score?
A high score means your dust leans toward water-damage molds. It doesn’t prove a current problem or a health risk. A low score doesn’t prove a home is clear, either. Either way, the next step is to check the building for moisture, not to act on the number alone.
If the score is high
- Look for water. Check the roof, plumbing, windows, crawl space and attic.
- Check the HVAC. Dust can move through a system, so look at the air ducts and condensate line.
- Fix before you clean. Follow a documented process: moisture repair, containment, removal, then verification.
If the score is low but you’re still concerned
- Keep looking. A low score doesn’t rule out a damp wall, because fresh growth may not have reached the dust yet.
- Talk to your doctor. Symptoms have many possible causes, and a clinician should weigh them.
Reading a score in Los Angeles
The ERMI reference set is national, and LA homes aren’t typical: coastal marine layer humidity, Valley AC use, hillside crawl spaces. Read a score with someone who knows the building. If removal is needed, see our Los Angeles remediation overview.
Questions
ERMI testing questions we hear most
Is ERMI testing accurate?
The lab can identify species in a dust sample well, but that sample may not represent the whole home, and scores can differ between samples. The EPA says ERMI was developed for research, so treat it as one clue, not a verdict.
What is a good ERMI score?
There’s no official safe score. Scores commonly run from about -10 to 20, and lower means the dust looks less like a water-damaged home. No agency has set a limit, so any cutoff you see online is a convention, not a standard.
Should I do an ERMI test first?
Usually not. Mold-sensitive groups often suggest it, but a moisture inspection should come first, because a dust score can’t show where water is getting in. If your doctor asked for one, we can usually plan both for the same visit.
Can ERMI tell me if mold is making me sick?
No. ERMI and HERTSMI-2 measure dust, not your health, and no test of a home can show what caused your symptoms. Talk to your doctor, and bring the report if it helps the conversation.
Does ERMI test for mycotoxins?
No. It measures mold DNA, not mycotoxins, which are chemicals some molds can produce. If you’re considering other tests, ask your doctor whether the result would change your care.
Can ERMI be used as a clearance test?
It isn’t designed for that, because old dust can linger and there’s no pass mark. Clearance relies on a visual check, moisture readings and air samples compared with an outdoor control, ideally by someone independent of the remover.
Sources
- U.S. Environmental Protection Agency (EPA), mold resources: epa.gov/mold
- Centers for Disease Control and Prevention (CDC), mold: cdc.gov/mold
- LA County Department of Public Health, Environmental Health: publichealth.lacounty.gov
- ANSI/IICRC S520, Standard for Professional Mold Remediation
Last updated October 2026. Prices are typical Los Angeles ranges, not a quote. Health information is general; talk to your doctor about symptoms. Legal notes are not legal advice.
Not sure a dust test will help you?
Call (213) 659-0672, 24/7 across Los Angeles County. We’ll ask what you’re trying to decide, and tell you honestly whether ERMI is worth it.