How to Test Your Home for Toxic Mold

It sounds like such a simple question: How do you test your home for toxic mold? I wish the answer could be as simple and direct as the question. The most difficult barriers in the world of biotoxic illness/Chronic Inflammatory Response Syndrome (CIRS) intersect around money, gender, and accessibility, and these obstacles are amplified by the lack of federal regulations in the field. This makes it difficult to know who to trust, what tests to invest in, and how to interpret the results.

Before we even look at the testing options, though, it’s important to talk about why testing is helpful to begin with. Testing can move you closer to getting some answers if you or a family member is sick and has some of the symptoms of CIRS, if you’ve found visible mold, or if you have signs of water damage or have a water event in your home. Testing can also give you the green flag on a new home or help you identify hidden red flags to keep you and your family safe.

There’s a lot to figure out when it comes to testing your home for mold when you suspect this nasty invader might be residing rent-free in your living space. Let’s go through some of the most common options here together, holding in mind that no test is perfect.

Environmental Relative Moldiness Index (ERMI)

The ERMI test analyzes a sample of the dust present in a building for the DNA of 36 mold varieties and rates the quantity of mold in the dust content within three categories: low, moderate, and high relative moldiness. 26 of the molds are associated with water damage and often produce mycotoxins, while the other 10 molds on the analysis are considered less concerning common household molds.

The sample is collected using a Swiffer cloth after you don gloves from surfaces that are least impacted by heat and water. After the cloth is covered in dust, it is placed in a ziplock bag, labeled, and mailed off to be processed by the lab.

The ERMI was created by the EPA to quantify the indoor mold burden on a building. It was designed by comparing homes that were “moldy,” being those with visible mold growth or a history of water damage, and those that were “reference” homes having no visible mold growth. Scores range between -10 and 20. A score of 0 is considered to be a home of average mold burden. 

Pros

• The ERMI is helpful in identifying the types of mold in a space historically
• It’s easy to DIY an ERMI with gloves and a Swiffer cloth
• The ERMI is more affordable than other testing options ($240-$435 depending on how fast you’d like the results)
• The ERMI collects DNA for mold that settles on surfaces as the more toxic mold fragments tend to do instead of floating in the air
• You can add on endotoxin and actinobacteria tests, as these two air quality concerns can cause just as much havoc as mold.

Cons

• The ERMI cannot pinpoint the source or location of the problem
• There has to be dust in a space to test (It cannot be used around construction dust)
• It’s not recognized as a reliable source by the unregulated world of mold since it can be DIYed
• Some people find the score calculation confusing, and there are some “mold consultants” who have high fees to interpret ERMI reports when it’s rather straightforward
• In the current housing market, you cannot get these results fast enough before making an offer on a home, nor can you include this as a contingency in the process

HERTSMI-2

HERTSMI-2 stands for Health Effects Roster of Type-Specific Formers of Mycotoxins and Inflammagens- 2nd version. I don’t recommend expending the brain power to memorize what the acronym stands for. The HERTSMI-2 is like a mini ERMI, as it focuses on the five most detrimental molds that accompany water damage: Aspergillus Penicilloides, Aspergillus Versicolor, Chaetomium Globosum, Stachybotrys Chartarum, and Wallemia Sebi. The purpose of the HERTSMI-2 is to determine if a build is safe or not from water damage.

Pros

• HERTSMI-2 is more affordable than the ERMI ($130-$277 depending on how quickly you’d like the results)
• You can add on endotoxin and actinobacteria tests
• It is a focused test used to determine the safety of a building

Cons

• The concerns within a building could be skewed without having the larger picture provided by the ERMI
• It cannot determine the source or location of the concern
• The current housing market does not allow for you to receive results before placing an offer or include this as a contingency in the process

Air Sampling

Air sampling is a common method used by mold inspectors; it appears to be the standard if you schedule an inspection with most of the run of the mill inspectors you can find in your local area. It consists of collecting a sample of air with a pump from the center of the room for about 5-10 minutes on an elevated stand. The sample is sent to a lab and viewed by a technician under a microscope where spores are counted and then reported in the results.

Utilizing air sampling in a general sense as described above can oftentimes mask significant indoor air quality problems. When used in a targeted way, however, it can be helpful in pinpointing the source of a problem. If toxic mold is suspected behind a wall, a small hole can be drilled in the wall to collect a source air sample, which can help to determine if the location is cause for concern.

Pros

• It’s easy to schedule an air sample tests
• It’s considered the standard for indoor air quality testing for mold at this time (even though the field is unregulated)
• Source air sampling can be helpful when used in wall cavities to pinpoint a source of mold

Cons

• The cost for air sampling varies
• The results are not reliable, even according to the CDC, and they have no set standards for mold indoors so that’s saying something
• Most fine particulates settle on surfaces around the room so they can be missed in an air sample test, giving a false sense of security
• There is room for human error since the samples are analyzed by eye under a microscope

Plate Testing

DIY mold test kits with petri dishes are about as easy and affordable as it gets when it comes to testing for mold. Unfortunately, you also get what you pay for. The plates are designed to catch spores and grow mold. You simply set them out on surfaces in the room you want to test and then come back later to cap them and let them grow in a dark place for 24 hours. Here’s the thing: every home has mold, meaning that you’re going to have mold growing in the plates, but you won’t know how much mold you’re dealing with in your environment or what kinds of mold are present from this method of testing.

Pros

• This is a simple, straightforward DIY method
• This is the most affordable method to test for mold at $34 for a set of 6 plates

Cons

• You won’t know how serious the concern for mold is because every home has mold
• It’s anxiety-provoking if you are hoping the plates to come back clear and don’t know that every home has mold
• You won’t know what kind of mold you’re dealing with unless you pay extra to send it off for further testing
• Most landlords won’t view this as a reliable source of information
• It doesn’t pinpoint the source or location of the problem

Hiring an Indoor Environmentalist

Hiring an indoor environmentalist is the most expensive and in-depth option when testing for mold. A set of highly trained professionals will come to your home to collect extensive history on past water events and any known damage, and then inspect your home from top to bottom and inside to outside to identify any areas where they would like to do further testing. They often use moisture meters and infrared cameras to help them identify sources of concern, taking photos to document areas with mold and water damage. Some of the testing they may do includes source air sampling, an ERMI, surface sampling, endotoxin testing, and actinobacteria testing. Then, they put all of the data together into a report detailing the specific concerns and the necessary procedures to remedy the concerns, which you can take to a high-level remediator to have them put the plan in action.

My Experience

I have utilized all of the testing methods in this post, and the ERMI and HERTSMI-2 reports I included photos of are actual reports I received from spaces I had tested. I rely heavily on the ERMI to help me narrow down safe places when it comes to choosing places where I spend the most time.

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