Air Quality Testing for Mold: Are Air Tests Important?

By: Licensed Mold Assessor Brad Fishbein

February 4, 2023

Air quality testing for mold involves using a negative air pump to collect mold spores on a cassette. A microbiologist then examines the cassette under a microscope to identify the type and amount of mold present in the air of a home.

The negative calibrated air pump is usually put on a tripod, table, or stand where it collects the mold inside a cassette (often called a spore trap) or microscopic slide.

There are many different air pumps for mold on the market today. Most of them are calibrated to collect 15, 75, or 150 liters of air into the cassette depending upon how long the pump is running.

The most common amount of time that air sampling for fungal spores is done is

  • 2 Minutes
  • 5 Minutes
  • 10 Minutes

The manufacturer of the pump and/or cassette will usually indicate how long sampling should be done.

Once the samples of air are collected, they are then sent to a laboratory to be analyzed under a microscope.

A lab report will then be issued indicating how much mold growth was found in the cassette as well as what type of mold.

There are hundreds of thousands of known species of mold that are known however only a handful are common to be found inside a home.

One of the most common methods of mold testing in a home after water damage is air quality testing for mold.

If you were to call a mold inspector to check your home, chances are they will do mold testing of your indoor air quality.

But is mold sampling the air even effective?

Answer: Yes and no. Air quality test for mold does have their place but it's not the only thing that needs to be done when determining if you have a mold problem in your home.

In this article you'll learn:

  • What is air quality testing for mold and how it's performed
  • What air samples can tell you about your home
  • When air quality testing for mold should be done
  • Who should do mold sampling
  • Where to air sample
  • Different types of air samples
  • Limitations of air sampling
  • Lab reports for mold samples
  • How Much Do Air Samples Cost


What Air Samples Can Tell Your About Your Home

As I stated earlier, indoor air quality sampling for mold is not the only way to tell if you have a mold problem in your home and should not be relied upon by itself.

A lab report will indicate how many mold spores are in the air, and that's it.

It will not always indicate if you have mold growth hidden in your walls or behind baseboards, although in certain cases it can.

You see:

Microbial growth is not always airborne. Sometimes it will stay localized in a water-damaged area of the home until removed. The disturbed mold will then become airborne.

That is why if you have water damage within your home, it's crucial for mold remediation to be done professionally to prevent aerosolization of the mold growth.

An air quality sample for mold will tell you if it is airborne prior to remediation because if it has traveled through your air conditioning system, the mold can affect other areas of the home.

This can also determine the correct remedy to remove the mold in the air.

When Indoor Air Quality Testing For Mold Should Be Done

Air quality sampling for mold should be performed when you suspect there has been mold exposure. If you are having any kind of symptoms such as:

  • Coughing
  • Itchy eyes and throat
  • Stuffy nose

It can certainly be mold growth but it also doesn't mean it can't be something else. Air sampling for mold can be a good way to at least rule out that mold is affecting you.

And if you are sicker just those minor symptoms it may even be Stachybotrys which is also referred to as the black mold or other types of indoor toxic molds that produce mycotoxins that is bothering you.

If it is indeed Stachybotrys there is more to worry about than just mold that is airborne to worry about, but more on that in a bit.

Water damage that has been neglected in a home can possibly produce mold in the air. So, if you have had a leak, it may be a good idea to do some collecting of air to be analyzed for microbial growth.


That's not to say you can't have a routine inspection where indoor air samples are done, but it's just not always necessary.

Many people decide they want to sample a home that they are purchasing or just for peace of mind and there is nothing wrong with that.

But again…

Spore trap sampling the air should not be the only thing relied upon. Determining if water damage is present in the home is also imperative.

Don't worry, I'll only say that one more time in this article but it's that important!

Who Should Do Mold Testing

Having an air test in your home is something that can be done by one of two people

  • You
  • A licensed mold professional

It's not something that is hard to complete. Realistically, you just need to put a cassette or slide on a pump and press a button.

But here's the thing:

A mold professional knows the ins and outs of where you should sample and why. They can develop a sampling plan and why it makes sense to sample in one area compared to another.

You are going to have to spend money anyways to get the pump so you might as well just hire somebody to do professional air quality testing because they know how to test for mold.

There are air quality testing kits on the market but your best bet is to hire a professional.

Where To Air Sample

Many people will hire mold inspectors for air testing and will often expect the professional to test every room in the house.

It doesn't hurt to do that, but often unnecessary.

A plan should be developed based on what you are looking to accomplish. If you want to know how much and why type of mold is in every room and you won't be able to sleep without knowing?

Then by all means have spore trap samples done in every room.

But if you are just looking to determine if you have a mold problem in a home, a professional should develop a plan.

Here's an example for you:

Let's say there was a leak in your Kitchen and now there is mold. You can see it on and behind the cabinets. For something similar to this you want to take an air sample in the general area to determine if mold is in the air.


It may also make sense to take a sample in another area of the home to see if the mold spores were transported through the air conditioning system.

Ideally, you want to do it in a place that is in the same HVAC system if you have multiple air conditioning systems in the home.

An air sample should also be done on the exterior of the home to establish a baseline.

Different Types of Air Samples

So far we have only discussed one-way air sampling is done and it is the most traditional way. It can also be referred to as ambient air sampling or mold testing.

But there are a few other variants of air sampling that can be done:

Pat Sampling- Pat sampling for mold growth is done by basically patting something so spores become airborne and then running a negative air pump. This can be done on carpet, furniture, and inside an HVAC plenum. Etc.


Wall Cavity Sampling- Wall cavity mold sampling is done by either putting a hole with a hand tool in the wall (usually ¼ inch) or removing an electrical/cable outlet and sampling actually inside the wall. A tube can be used to attach to air sampling cassette.


Keep in mind that either way of sampling is not a good representative of the normal conditions in a room. Wall cavity samples can be controversial as it adds debris and can result in false positive readings.

Limitations of Air Samples

Ok, this is the last time I'm going to say it…

Indoor Air quality testing should not be the only thing relied upon when determining if a home has mold problems.

Air samples are just that…. Samples.

They only represent the conditions in the exact location they are taken at the exact time they are taken. You can take an air quality sample a day apart and get different results.

Heck, you can do a minute apart and even get different results.

There are also many things that can affect an air sampling cassette testing for mold.

Here's an example for you:

Let's say before you test the doors were open. And on the back patio is a beautiful wood chair with a cushion. You go to sit on in and what happens when you sit on something moldy?

It gets disturbed!

Now mold spores are everywhere and you will think you have a problem when really the mold growth was just in the outdoor furniture.

You see:

Indoor air quality testing is just one part of the equation. It will not always identify the amount of mold settled on a surface such as a floor or furniture. There also is no guarantee that it will pick up hidden mold inside the walls.

A visual mold inspection by a licensed professional including moisture mapping and checking the air conditioning system is just as important.

Another limitation is that mold spore traps are only collecting mold spores. There are certain types of mold that produce mycotoxins such as black toxic mold aka Stachybotrys. Toxic molds can off-gas which is not picked up on an air sample.

Mold Spores Lab Report

Another reason why you should get a mold inspection done by a professional is you may not know how to interpret the lab report.

A lab report will tell you different things that you may not understand. And every lab does its reports differently.

Some have advantages over the others.

The two things you will need to know above others is:

  • The Raw Count
  • The M3 Count


The raw count is the total amount of spores that are present. The M3 count for mold spores is per cubic meter.

But do you know how many mold spe is too much?

There are no government-set threshold limits so just because a number seems larger in one area it does not always mean it's considered too high.

Ideally in a perfect world, you would compare the indoor samples to the outdoor and if you have higher indoor spore counts in an area, it could indicate there is a problem.

Unfortunately, that is not always the case.

It's also not always how much mold is present but what species of mold is present. Mold fragments and clusters of mold spores also can indicate a mold colony is present.

The airborne fungal spore count reading can be very tricky and should be left to a professional to read it. Some laboratories offer a consult phone call if you decide to do the mold testing with an air pump on your own.

How Much Do Air Quality Samples For Mold Cost

The cost of mold samples varies because you may have multiple separate costs. The three main costs are:

In some instances, the cost of all three maybe combined into one. So it really depends and there is not a one size fits all.


Overall, indoor air quality testing for mold is an important tool for identifying and addressing indoor mold growth in homes and buildings.

But it's CERTAINLY not the only tool.

It should be used in conjunction with other types of sampling and inspection techniques.

Meet the author: Brad Fishbein is an ACAC council-certified Microbial Investigator. In the fall of 2012, he became a Licensed Mold Assessor in the State of Florida through the Department of Business & Professional Regulation. Brad has helped homeowners with over 5,000 successfully completed Mold Inspections since 2009.

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