Home Test Kits for Mold Contamination

At almost any box store, you can buy a home test kit if you want to know if there is mold contamination in your home. There are several kinds of kits you can buy. We will discuss the pros and cons of each. This will help you buy the one you need. 

One sample type is a viable sample method (you grow it in a petri dish). Another is a non-viable sample method (look under a microscope to see what is there). The third can be for either viable or non-viable lab analysis. All sampling methods require laboratory analysis by a mycologist if you want to know what is there. 

A common sample method that I see homeowners use is a petri dish. They follow the instructions on the package and either send it in for laboratory analysis or leave it on the table to let things grow in it. The following are a few considerations to think about when using this test method. What you see in the dish are only the viable spores that are in the air. 

Maybe only 10 or 30 percent of spores in the air can germinate so it always underrepresents what is in the environment. You cannot tell if what you see in the dish is a normal background or represents a problem. Four or five samples are normally needed for comparison to see patterns. If you don’t send it into a laboratory, you don’t know what the different colors of growth represent. 

If you send the sample to the lab for analysis, the growth conditions there will differ from your home. This will affect what germinates and how much it grows. Also, there is an ASTM standard for collecting and analyzing viable samples. It aims for accurate, repeatable results. To obtain accurate results from the laboratory, you place the petri dish in a sampling device that is made for this purpose. 

There is a funnel placed over the top of the dish, and then below the dish are 600 very small holes. You then attach this sampling device to a suction pump. You pull 28 liters of air through the sampling device for a period of only 3 minutes. You will see 600 very tiny holes that have been drilled into the sampling paste. 

The petri dish is then placed in a cooler and shipped overnight to the lab. There, they incubate it for 5 days at a constant temperature and humidity. Then they remove the sample and read the dish. This method requires you to hire an indoor air quality consultant. They have the equipment to collect the sample correctly. 

Also, there are many types of growing paste (called agar). Which type you use depends on your goals and your home's conditions. The consultant can help determine what to use. The next method of sampling is simply a microscope slide. It is made of flexible plastic that is sticky on one side. To sample some material, remove the cover from the sticky part. Then, gently press the slide against the surface. Finally, send it to the lab. 

There is no special handling of the sample, such as cooling or overnight shipping. The laboratory receives the sample, places it under a microscope, and sees the debris that is on the surface of your home. This is likely the most accurate method. The lab can give you a detailed report on both mold and allergens on the slide. And very important to any homeowner, it is easy to use! 

The third method is using a swab on a stick. It is the sampling method they use for COVID testing or for swabbing your throat. This method is versatile. It can transfer the collected material onto a petri dish for growing or a microscope slide for reading. Plus, you can collect a sample from hard-to-reach areas that you can’t with a slide. 

There are two kinds of swabs, wet and dry. The wet method has an ampule of distilled water that you break while the swab is still in the package, so the cotton on the swab gets wet. This is commonly used for viable analysis. Call the laboratory and ask if you need to ship the sample overnight; you could get growth on the swab if it takes a week to get to the laboratory. The dry swab is normally used for transfer to a microscope slide. The consideration with using a swab is that it requires two transfers of the material from the surface being sampled. 

Once onto the swab and then a second transfer onto the medium for analysis. This method focuses on what is there and not how much. In conclusion, the lab that sells the package in the store may not provide the best analysis interpretation. 

If you want to do this yourself, there are many laboratories in the country, and you can call to get advice on the best sampling method for what you need. 

They will send you sampling equipment and then they will analyze it for you. Look for a laboratory that is AIHA-LAP certified. They have been tested and meet the accuracy and redundancy standards in their quality control programs. Go to AIHA Laboratory Accreditation Programs and look up “find an accredited Laboratory” to help you.