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How to Interpret ERMI or HERTSMI Mold Test Results

The ERMI (Environmental Relative Moldiness Index) test is a dust sampling analysis offered by several labs to evaluate the health of a building. ERMI uses a DNA-based method for identifying 36 different species of mold.

Labs currently offering this test include:

A smaller version of this test, the HERTSMI (also called the HERTSMI-2), uses similar technology to identify and quantify five of the more common and toxic species of mold. This test is offered by EnviroBiomics ($130-$277) and Mycometrics ($155, also available through our momsAWARE Online Store).

All four labs offer vacuum canisters to collect the dust samples, while Mycometrics and EnviroBiomics also offer the option of using a Swiffer-type cloth to obtain the settled dust.

After sending your sample, the lab will email you an ERMI or HERTSMI report that looks something like the following (or like the reports excerpted later in this article):

ERMI Report Sample - click to enlarge

(Click on image to enlarge)

Keep the following points in mind as you seek to interpret the ERMI test results.

  1. Understand that all tests have limitations.

    While settled dust is one of the best ways to get a picture of the air you're breathing, there is no one test that can assess all areas of a given building. The indoor environment is a complex mixture of microbes and toxins, including:

    • MVOCs
    • 1,3-beta-glucans
    • endotoxins
    • pathogenic bacteria

    All of these have the potential to impact health adversely. For more on the complexity of the indoor environment, see The Biocontaminants and Complexity of Damp Indoor Spaces: More Than What Meets the Eyes.

    While air sampling, bulk sampling, and tape lifts all have their place, ERMI dust sampling remains one of the best first choices when evaluating the health of a building in regard to water damage.

  2. Consider the species of mold, not just the count.

    You will see spore counts of each of the 36 species of mold. When these counts are abnormally high, it may be assumed the building has the potential to harm health. Do not discount low counts of particularly hazardous molds, however. One spore of stachybotrys chartarum can indicate a serious mold situation. Species of mold that are particularly dangerous include those evaluated in the HERTSMI dust test:

    • Aspergillus penicillioides
    • Aspergillus versicolor
    • Chaetomium globosum
    • Stachybotrys chartarum
    • Wallemia sebi
  3. Use the HERTSMI scoring system.

    Even if you have the ERMI report, the HERTSMI scoring chart offered at Surviving Mold may help. The scoring system is designed to help those previously injured by water-damaged buildings, but can be very useful for beginners. Check your report for the five significant molds listed above.

    Follow the steps outlined on Surviving Mold's HERTSMI page. Your results can be tallied and compared with the following interpretation:

    • <11 Safe
    • 11-15 Borderline - clean and re-test
    • >15 Dangerous for those with CIRS (Chronic Inflammatory Response Syndrome) *

    * An acute and chronic, systemic inflammatory response syndrome acquired following exposure to the interior environment of a water-damaged building with resident toxigenic organisms, including but not limited to fungi, bacteria, actinomycetes, and mycobacteria as well as inflammagens such as endotoxins, beta glucans, hemolysins, proteinases, mannans and possibly spirocyclic drimanes; as well as volatile organic compounds (VOCs). See Surviving Mold's article What is Mold Illness? for additional information.

  4. Consider the health of the building's occupants.

    Are the building’s occupants experiencing health issues? Did these symptoms appear or escalate after moving into the home, school, or office? Are you or your family members experiencing sinus issues, fatigue, brain fog, food sensitivities, or digestive problems? (For a comprehensive list of symptoms, see Symptoms of Biotoxin Illness.)

    Evaluating the health of the family, yourself, or coworkers is critical when trying to assess the health of a building. If health issues are extreme, this must be taken into account when determining the safety of a building.

  5. Listen to your instincts.

    What is your gut feeling about the health of this building? Do you feel it's unsafe? Don't rule out the power of a gut instinct when trying to determine your next step.

Two ERMI reports compared:

ERMI Reports Compared - click to enlarge

(Click on image to enlarge)

The ERMI test on the left shows a home that has low levels of contaminants. What is not seen in the excerpt above is the presence of 6800 Spore E./mg of Epicoccum nigrum, an abnormally high number. Epicoccum nigrum is often associated with plant sources, so the homeowner removed all house plants and cleaned the air ducts, deciding to re-test in six months.

The ERMI test on the right shows a serious mold issue with high levels of critical species, as highlighted in yellow. This homeowner vacated the home, leaving everything behind due to the presence of stachybotrys and serious health issues. For more on decisions regarding possessions, see The Issue of Cross-Contamination.

While an ERMI dust sample is often a good first step, there is no one-size-fits-all approach to assessing the health of a building. Take it one step at a time and listen to your instincts as you seek a safe living environment.


"My daughter has had many blood samples taken to test for everything imaginable and her doctor just seems puzzled. Everything comes back normal."

– Anonymous

"I was skeptical at first that these (natural cleaning) products would work, but they work better than the stuff I buy at the store! We will soon be moving to the personal care products as well!"

– Jennifer

"I knew it was mold, but doctors kept telling me I had anxiety. I was sitting in my office and could not remember who I was talking to, or what we were talking about."

– Brenda

"The ERMI mold test as well as your helpful articles and Toxic Talk Tuesday programs have helped us avoid a terrible mistake in purchasing a new home."

– Angela

"My daughter started having digestive problems... heart palpitations... coughing episodes... muscle/joint pain... asthma/allergies... Her doctor finally advised me to check for mold in our home."

– Anonymous

"We all suffered from headaches, hormonal body temperature fluctuations, brain fog, fatigue, difficulty breathing, thrush, rashes, and yeast infections... we vacated our home two weeks ago."

– Anonymous

"My symptoms persisted and eventually turned into lethargy and depression. At the age of 26, I required a nap every evening after work."

– Jennifer

"We had some water leaks in our home... we never thought we needed to clean out and remove the floor, the ceiling, or the drywall... my two small children and I have remained constantly sick for years in this home."

– Mia

"I'm new at this, but today I cleaned my bathroom with baking soda and vinegar. It's much better not having those strong chemical smells afterwards."

– Anonymous

"I've been living in a mold-infested home for 13 months... I was going CRAZY! Finally figured it out... Just a few days of recovering in a mold-free home and I feel AMAZING!!!"

– Lauren

"In my moldy home if I left the wet clothes in the washer they would get musty very quickly and I'd have to re-wash... Sometimes I'd run a load, go to work, and they'd be musty when I returned that evening."

– Anonymous

"We were having a lot of health problems and had been to the doctor countless times... we had large circles of slimy greenish-black mold on the bathroom ceiling, where it had caved in a few months before."

– C.

"I had been struggling with headaches, head fog, breathing difficulties (unable to get a full breath), constant scalp tingling, migraines, nausea, feeling spacey/detached, and severe itchy skin."

– Anonymous

"Our family has been out of our home for 9 months due to mold... I am so scared and weak from all of this. We have lost friends; family members don't understand."

– Anonymous

"I have been sick for almost 6 months now and doctors were not able to figure out why. I finally put it all together after going away for vacation for a week and suddenly my symptoms were going away."

– Anonymous

"I started finding myself sitting on the floor in rooms of my house and not remembering how I got there, what I was doing before, or how long I had been there."

– Brenda

"The entire time we lived in our (mold-infested) house the kitchen sponge would get musty smelling within 3-4 days. It was so strange. I had to buy a pack of sponges nearly every week."

– Anonymous

"Both of my sons went downhill quickly and coughed for months... They both lost their ability to read, had profound vision disturbances, and had phenomenal gastric issues."

– Lee

" age 35 or 36 I started to become allergic to everything, and I got asthma at age 36... I went to doctor after doctor after doctor and was desperate for help, but nobody could help me."

– Mia

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