Whether you are buying a new home or living in your current one, mold is an issue worth paying attention to. It can develop quietly, out of sight, until a renovation, an inspection, or a change in the home brings it to light.
Discovering mold after moving in can be overwhelming. Remediation can become lengthy, stressful, and costly, and it may take months to fully restore your home. The good news — there is a simple, proactive step you can take to get a clearer picture early: the ERMI test.
What is ERMI
ERMI stands for Environmental Relative Moldiness Index. This index was developed by the Environmental Protection Agency (EPA) to estimate levels of mold contamination in homes. Any ERMI result is best reviewed together with a certified indoor environmental professional or mold inspector, rather than on its own.
What does the ERMI test measure
The ERMI test measures a total of 36 types of molds in your home: • 26 molds linked to water damage or damp environments • 10 common indoor molds that can trigger allergies, respiratory symptoms, and general health issues This test gives a general picture of your home's mold and moisture history and state — before you move in or while living there.
How to read your ERMI score
The ERMI scale ranges from -10 to +30: • -10 to 0: Lower relative mold levels • 0 to +5: Borderline — further investigation may be worthwhile • +5 to +10: Elevated — often associated with possible water damage, a professional check is advisable • +10 and up: Higher relative mold levels — typically recommended to bring in a professional for further evaluation These are general reference ranges used in the field, not official EPA thresholds — EPA has not published health-based cutoffs for ERMI scores.
Why completing an ERMI test matters
Running this simple test, whether before buying or in your existing home, gives you valuable insight into what may be present in your indoor environment. It allows you to: • Gain a clearer picture of your home's mold and moisture history and state • Make more informed decisions about your home • Reduce the likelihood of costly surprises and drawn-out remediation later on
The main takeaway is that it's worth considering the ERMI test, whether you're buying a home or want a clearer picture of mold in your current one, as a starting point rather than a final answer. It is a small, proactive step that can offer more clarity and help you plan ahead before costly surprises arise.