Important: How to Find Mold in Your Home or Environment

Written By

Rhea Dali

Expert Reviewed By

Dr. Lauryn Lax, OTD, MS

Dr. Lauryn, OTD, MS is a doctor of occupational therapy, clinical nutritionists and functional medicine expert with 25 years of clinical and personal experience in healing from complex chronic health issues and helping others do the same.

Test Your Home For Mold Exposure

The tell-tell validation for mold exposure is actually finding remnants in your home, workplace or other environments you frequent. Note: It’s important to realize that many molds are not always seen with the naked eye, nor do they have to infest an entire wall, shower caulking or window sill to be hazardous.

Use “ERMI” Testing

To date, the best initial screening for mold is “surface” or “air PCR” (polymerase chain reaction) testing—also referred to as “ERMI testing.”

Woman Holding Blanket, Cleaning, Checking For Mold Exposure

The ERMI test was developed by the EPA as a means of determining the relative “moldiness” of a home compared to a group of reference homes that do not have mold. This type of testing involves collecting possible mold samples with a dust cloth kit on surfaces where you suspect mold may be present. The cloth is able to pick up mold DNA on the surfaces of walls, furniture and places it may be, as well as the air. After collection, you or the inspector send it back to the lab for testing and mold identification under a microscope.

Some people claim that mold plate testing can work too, but keep in mind, it is not very sensitive. Mold spores differ in weight, density, and air flow characteristics, so some types are more likely to settle on the plates than others. Sticky molds that often appear near water damage, like black molds, may end up evading the plates completely.


ERMI results will not tell you every single species, crevice or corner of your house that has it. Results are still limited since they only evaluate the areas where you take a sample.  Testing is best to give you an idea of patterns and what types of mold may be present.

There are two primary methods for using ERMI testing:

  • Hire (the right) professional
  • DIY

Method 1: Hire the Right Professional

Not all mold inspectors are created equal. Many mold inspectors do not use in-depth, accurate testing methods. If you call up a local mold inspector and ask him to come assess your property, he will probably do a visual inspection and take some air samples, but on their own, they are not enough. Air sampling does not allow identification of particular species.


To accurately assess your exposure, the best practice is to hire a mold inspector who is familiar with proper testing methods (ERMI with EPA validated methods). Do your research. Visit (ACAC is American Council for Accredited Certification) and look for “Certificants” in your area with one or more of the following certifications:

  • CCIEC, council-certified indoor environmental consultant;
  • CMI, council-certified microbial inspector;
  • CMC, consultant

A good mold inspector will walk your property and be aware that the inside and outside can be equally affected; they may ask you questions about your health or timeline of mold exposure; they will know what ERMI testing is; and they may have even heard about  Unfortunately, many specialists claim they test mold, but do not utilize this in depth type of testing—often missing the lingering root causes of toxic exposure.

Mold Testing Problems

Warning 1: NOT All Mold is Visible

Mold is sneaky and not always seen with the naked eye. Many average inspectors, unaware of the nuances of testing, will come to your house, look, and if they don’t see anything visually black on the wall, growing, they may feel you, “You don’t have a mold problem.” Buzz! It can still be present. Testing for spore counts can help you see beyond black splotches and green fuzz.

Mold Spore Count Test Guide

  • 0-50 spores 

These are only trace levels and are not an issue. Even Stachybotrys is not considered an issue at these levels if the sample does not also contain water markers like Chaetomium and Fusarium or high levels of Penicillium/Aspergillus.

  • 50-200 spores

These are still very low levels. The toxic mold species Stachybotrys and Memnoniella are just about the only species that are considered an issue at this level.

  • 200-500 spores

Up to this point, the most common species (Penicillium/Aspergillus, Cladosporium and Curvularia) are still not an issue and are in the normal range.

  • 500-1500 spores

Sometimes the Penicillium/Aspergillus & Cladosporium levels are in this range and there is not an issue that needs to be remediated. If no water intrusion or mold issue is found during the inspection, these levels can be caused by normal life in an enclosed environment.

  • 1500-3000 spores

This is where the grey area begins. When levels reach this point there may be an issue that needs to be addressed. Unless there is a corresponding number in the outdoor sample. If no water intrusion or mold issue is found during the inspection these levels can be achieved by a dusty home or A/C system.

  • 3000-10,000 spores

Unless there is a corresponding number in the outdoor sample, this is the point were some remediation may be necessary. If a mold spore source has been identified, then clean up of that area is needed. If there was no water intrusion or mold issue found, the home may need to be cleaned and the duct system should be evaluated.

  • 10,000-25,000 spores

Unless there is a corresponding number in the outdoor sample, a mold spore source has usually been identified and remediation of the area is needed. If there was no water intrusion or mold issue found, the duct system may need to be cleaned and/or a general “Spring Cleaning” of the home.

  • 25,000-75,000+ spores

When spore levels are at this point, a mold issue will be easy to identify. Clean up will be required and should be performed by a Professional Mold Remediator.

  • 75,000-1,000,000+ spores

When spore levels are at this point a mold issue will be evident. Remediation will be required and needs to be performed by a Professional Mold Remediator.

Warning 2: Mold Overgrowth Can Happen in New Buildings

Men Cleaning And Checking No Mold Overgrowth In A New Building

New construction is rarely suspected as a hotbed for mold, but don’t be fooled. Moldy drywall after new construction is particularly common. If you are a mold sensitized individual, consider purchasing an older home with plaster and lath walls instead of wallboard. If that’s not an option, consider mold resistant construction materials. They’re a little more expensive, but worth the price in prevention. Also, whether or not you’re a mold sensitized individual, remember mold can’t grow without water.

Therefore, get any problems with leaks, bursts or floods clean, dried and sanitized fast to prevent the problem from happening.

Warning 3: NOT All Mold Testing is Created Equal

The majority of companies and “mold professionals” use air sampling alone; however, air sampling is limited. Not all molds are the same—not all of them float in the air as much. Some are heavier and don’t linger in the air, others are lighter. Some settle out quicker, others slower. There are some which are dry, wet or sticky. When an inspector collects just an air sample and results are generated immediately (not the 8 hour+ process).  These tests only collect about 5 minutes worth of air, and many people are told “there is no problem”—yet still suffer from symptoms.

Warning 4: NOT All ERMI Testing is Created Equal (Go with a Reputable Company)

The quality of the lab that you use matters. The ERMI test alone is not the end all be all. Some labs try to cut costs by using lower quality primers and probes, leading to missed positives and lower counts of mold than what’s actually present.

Method 2: DIY Mold Test

If a professional is hard to come by, check out the company Mycometrics for the tools and information for a do-it-yourself mold test at home

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