ERMI Score in a Home With Allergy Symptoms

The ERMI is a dust-based index that compares the relative abundance of selected mold DNA markers in a sample with a reference population. A result above the 75th percentile suggests that the dust contains more of those markers than the reference, but it does not prove active mold growth, identify a source, measure exposure, or establish that mold is causing the family's symptoms. It also cannot distinguish current from past contamination, viable from nonviable material, or one room from another. Pets, outdoor dust, carpet, and sampling location can influence the result. The absence of visible mold means the finding should prompt a moisture and source assessment, not a fogging treatment. I would explain that ERMI is a screening tool with limitations and should not be used as a clearance test. The family's symptoms and the vacation improvement are important clinical information, but a medical evaluation is appropriate; the IAQ investigation should focus on moisture, ventilation, allergens, and combustion byproducts.

I would prioritize source control and ventilation over sampling. During the visit, check the bathroom exhaust and dryer vent, inspect under sinks and around the humidifier for leaks or condensation, and measure moisture in exterior walls and window frames. The whole-house humidifier at 45% may be excessive in cold weather and can raise indoor RH and condensation risk; recommend reducing it and verifying with a hygrometer. Test the gas stove for CO and CO2 with the monitor and recommend a range hood vented outdoors; a CO alarm is essential. Assess the HVAC filter and duct condition, recommend a compatible MERV 11–13 filter if the system can handle it, and suggest HEPA vacuuming and allergen encasements. Discuss reducing carpet in the child's bedroom, keeping pets out of bedrooms, washing bedding in hot water, and improving ventilation. A particle counter can show trends before and after filtration or cleaning, but it is not a mold test. Refer the family to an allergist for symptoms and explain that the ERMI should not be repeated as a clearance check.

I would decline to use ozone in an occupied home and explain why. Ozone is a respiratory irritant that can worsen asthma and airway inflammation; it is not a substitute for finding and correcting moisture or removing allergens. Fogging with an antimicrobial or 'mold treatment' is also not a remedy for a high ERMI when no source has been identified; it can leave residues, damage materials, and create a false sense of security. The better response is source control: manage humidity, ventilate combustion appliances, reduce allergen reservoirs, and fix any moisture defects found. If the family wants a treatment, I would offer cleaning and filtration measures with documented limitations, not a chemical fog. I would also explain that ERMI results can be influenced by dust and pets and are not a clearance standard. If they insist on ozone, I would document the recommendation against it and let them decide with full information, but I would not perform the treatment myself.