How to Test for Mold in Air

Mold isn’t always visible — see how to catch those spores.

Mold is a fungus that can grow indoors as well as outdoors. There are countless species of mold, some of which are more harmful than others. Mold grows in dark, damp and warm areas, such as bathrooms or basements.

However, not all mold is visible.

Sadly, if you have mold in one area of your home, there could be spores flying around. That’s right, mold spreads and reproduces through spores, which can survive severe environmental conditions (1). So, if your allergies are agitated, it might be due to mold spores flying around in the air.

How to Test for Mold in Air

In order to test your air for mold, you’ll need a viable mold test kit. These are widely available at any home improvement store and online at sites like Amazon and Home Depot.

Once mold is determined, call a professional to do additional tests to see what type of mold is present and how to remove it.

Keep In Mind

These test kits are designed to determine whether or not mold is present in the room where the test is done. You shouldn’t rely on these kits entirely. However, if you suspect mold, they can be helpful to point you in the right direction.

1. Prepare the Room

Start by closing all doors and windows in the room where the testing will be done. This should be done 24 hours before the test — check the directions before. Closing off the room enables mold spores to gather without being moved around by a draft.

2. Prepare the Test Kit

A test kit will generally consist of multiple disks that have been treated with a special substance called “microbial culture.” The treatment will promote the growth of mold spores, which will help you collect a significant amount if there are any present in the room. You should check the directions to know how long the kit should be left.

After taking out the test kit from its packaging, remove the lid from the dish. Place it with the open side up on a flat surface, such as a table. Avoid the floor as it will be too low — go for a surface that’s about the same height as a table.

3. Leave the Dish

Allow the dish 48 hours or more to gather samples — the dish should remain completely untouched during the time.

Try to keep the room closed off as much as possible — don’t allow too much traffic in and out. To remind family members not to enter the room, you can mark the door with some brightly colored tape.

4. Close the Disk

Once the time is up, put the lid back on the dish. Seal the lid onto the dish using tape to prevent any spores from escaping. You can use any type of tape for this, scotch or electric tape both work fine. Just avoid duct tape as it’s difficult to remove.

You should have gotten a sticky label with the kit. Here, you can write the date and even duration of dish exposure. Stick the label onto the bottom of the dish and place it in a dark spot, such as a closet, shelf or drawer.

5. Leave the Dish

The dish should remain closed in a dark spot for two days. After that time, check the dish for any signs of mold growth. During the two days, the spores would have begun growing and forming a mold that looks similar to what you’ll find on old food.

If you notice mold, you can send the dish to a lab recommended by the manufacturer. The lab will run tests to determine the type of mold and how to treat it. You can find many kits that come with an envelope ready to be mailed.

On the other hand, if you don’t notice any signs of mold within the dish, you can return it to the dark spot. Leave it for another few days and check daily for any signs of growth. If there’s still no signs of mold five days after the date on the label, there’s no mold in that room.

Take Note

If you still notice a certain musty odor in the room, it would be best to have a professional run a test. There might be mold hiding that the test kit couldn’t pick up.

6. Wait for the Results

After sending in your dish, you’ll have to wait three to eight weeks for the results. During this time, it would be a good idea to continue testing in other rooms and areas of the house.

How Mold Affects Your Health

Mold produces irritants and allergens that can cause various reactions when inhaled or touched. Reactions to mold are often allergic symptoms such as sneezing, red eyes, runny nose and skin rashes.

Sensitive individuals may experience immediate reactions when in contact with mold. Others, on the other hand, might have delayed symptoms (2).

Individuals with asthma may have an especially hard time when in a room with mold. Mold can trigger asthma attacks while irritating the throat, lungs, nose and eyes.

People who don’t suffer from allergies or asthma may also experience irritation in the eyes, nose, lungs and throat.

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One mold species, in particular, can be more hazardous than others — Stachybotrys chartarum. This species is generally referred to as “black mold” or “toxic mold.” Despite the name, this mold is actually more greenish in color and is gooier in texture compared to other species.

Black mold can grow on surfaces high in cellulose and low in nitrogen. These include fiberboards, paper, dust and lint. This mold requires constant moisture in order to grow, so it’s commonly found near water damage, leaks and after floods.

While mold, in general, isn’t toxic or poisonous, some species such as black mold can produce toxic byproducts. One of these is called mycotoxins. However, little research is available as to how it affects people’s health (3).

Common Mold Hiding Places

All mold needs to grow is moisture, darkness and warmth, but where exactly should you look when you suspect a mold problem? Here are a few common places around the house where mold is likely to grow (4):

  • Behind appliances such as a refrigerator or dishwasher.
  • Behind drywalls where plumbing pipes are located.
  • Underneath cardboard or old newspapers.
  • Beneath sinks.
  • Inside ventilation ducts.
  • Under carpets, particularly in the padding.

Signs of Mold

It can be difficult to know if or where you have mold in your home. By knowing the signs, you can take a step in the right direction to get rid of the fungus problem (5).

  • Smell: Mold can cause a pungent odor to form; this can be described as musty or earthy. Moldy odors shouldn’t be ignored but should be further inspected.
  • Allergic symptoms: If you’re experiencing a runny nose, coughing or other hay fever-like symptoms, you might have mold. Some people might experience worse symptoms when at work or in other locations. This could mean there’s mold growing there.
  • Visible mold: This might be an obvious sign of mold, but you must take immediate action since it can spread rapidly.


How Can I Test for Toxic Mold?

If you suspect or fear toxic mold is growing in your home, you won’t need any special tests. A test such as the viable test kit we learned about above will detect all kinds of molds present. By sending your petri dish to a lab, you can get a better idea of which types of molds that are growing and then take the correct actions.

The next step should always be to consult a professional for further tests and investigations. Test kits are more of a guidance than something to fully rely on.

It’s also important to understand that simply because it’s called “toxic mold,” it doesn’t mean it’s toxic to you. As we mentioned above, molds that produce mycotoxins can affect some individuals, while others won’t be affected.

However, if you suspect that you have been exposed to toxic molds, your doctor can run a few tests. A blood test can help to determine if you’ve been poisoned by checking biotoxins in your blood (6).

How Much Does It Cost to Test Your House for Mold?

Getting your home professionally inspected for mold isn’t cheap. The average cost for an inspection is around $650. But, it can range between $250 and $1000 depending on the size and location of your house (7).

Many homeowners are enticed by the affordability of DIY test kits, usually available at around $40 or less. However, it’s crucial to get the house inspected by professionals if mold is detected or suspected.

How Can I Know If There’s Mold in My Carpet?

The plush fibers of a carpet can be a thriving spot for mold spores. It’s easy for the spores to stick to the surface and there’s often a significant amount of dirt, dust and bacteria. Once moisture is introduced, mold will likely begin to grow.

Mold can grow inside the carpet or underneath. The padding or backing of carpets is likely to have mold if exposed to moisture.

A tell-tale sign of mold in a carpet is a musty or even sour odor. However, the best way to know whether or not there’s mold growing in your carpet is to pull it up and inspect it.

If you do find mold, consider the severity of it and whether the carpet is worth trying to save or not. You can easily remove the area affected by mold and replace it with new carpeting. Adding additional waterproof padding underneath can help to keep mold and mildew at bay.

Getting to the Root of the Problem

Mold can affect your health in different ways; some people have severe reactions while others don’t experience any.

Common health effects of mold include hay fever-like symptoms such as a runny nose and red eyes. If you have allergies or asthma, you’ll likely experience more severe reactions such as asthma attacks or skin rashes.

Mold spreads and reproduces through spores in the air. You can buy DIY home test kits to help determine whether or not there’s mold present in your home. Yet, as popular as these tests are, you shouldn’t rely on them entirely. Always follow up with a professional inspection and treatment.

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About the Author

Matthew Sullivan

Matthew is a freelance writer with several years of experience in DIY and HVAC. For as long as he can remember, Matthew has always found great pleasure in taking things apart and learning how to put them back together.