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How to Test for Mold in 7 Easy Steps

Knowing how to test for mold in households with people susceptible to allergies, respiratory conditions, and other health concerns may mean the difference between continued good health and poor quality of life.

Read on to learn how to test for mold in house and keep your property as mold- and mildew-free as possible. 

How to Test for Mold in Houses?

Although most homeowners leave mold removal to professionals, they recognize the importance of testing the presence of mold and mildew. 

That way, it’s easier to tell if the mold requires a professional to successfully remove it.

How do you detect mold in your house? Here’s how to spot mold in your home. 

1. Learn what mold looks like

Get an idea of what the common types of mold are and what they look like, and it’s guaranteed to be a lot easier to deal with. 

As they say, know thy enemy. 

Here’s four of the most common types of mold. 

  • Aspergillus species – A very common fungal spore that causes aspergillosis, a respiratory infection. The fungus may start out white before turning  a yellowish, blackish, brownish, or greenish color with a velvety texture.
  • Cladosporium species – With at least 500 species, identifying this allergenic microorganism can be challenging. They appear blackish, brownish, or greenish specks on carpets, window sills, and wallpapers.
  • Stachybotrys chartarum – Also called “black mold,” this allergenic, black pepper-like microorganism is most prevalent in cardboard, wood, and wallpaper surfaces. It might be hard to spot on black colored surfaces, so you might want a black mold test kit for this.
  • Penicillium – We owe a lot to this mold, which shares its name with the antibiotic, but it’ll cause a flare up in respiratory problems like asthma. It has a plush texture that’s blue-green in color. It develops on aged fruit and veg, but also water damaged structures.
mold in the corner of the window
Black mold surrounds the edges of a window.

2. Perform a diluted bleach test on suspected mold

Combine 16 tablespoons of water and a tablespoon of bleach to make a home mold test kit. Get a cotton swab, dip it into the bleach-water solution, and dab it on suspected mold-infested sections.

Assume the presence of mold if the area changes color immediately after dabbing it with diluted bleach. Alternatively, the area returns to its original color (black or greenish-black) after blotting.

This method isn’t as sophisticated as professional mold testing. However, it gives you a head’s up whether you have a mold infestation in your home.

3. Buy a test kit

If unsure about the results of the DIY diluted bleach-based mold test kit, purchase a black mold test package.

Mold and mildew testing packages come in two forms: test-only and test-with-species-identification. 

The former is cheaper and only serves to confirm mold presence in the home. Testing kits with species identification are suitable for those curious about the specific mold.

When mold isn’t obvious, testing can be useful to determine if it is present. However, a faster means of gauging if mold is present is to simply listen to the body. Feeling unwell? These are the 10 most common symptoms of black mold.

Credit: Crawl Space Ninja

4. Follow the test kit’s instructions

Mold detection kits include step-by-step instructions on growing a suitable medium for promoting mold growth. We recommend reading this to get accurate results.

Most testing packages come with Petri dishes and other tools for collecting and managing the sample. 

5. Collect mold as sample

Specimen collection depends on what part of the house you want to mold test. 

Leave the Petri dish for as long as instructed, then cover it to grow the mold. 

This method is perfect for checking mold in ventilation systems and similar technologies that aren’t easily accessed, or if you’re unsure about mold being present at all.

6. Assess the test kit for mold growth signs

Check the Petri dish after 48 hours or as instructed for the telltale signs of mold. Assess the sample again after another 24 hours if you didn’t see mold signs in the first 48.

If after another 24 hours the  instant mold test produced negative results, it’s safe to say there’s no mold.

7. Send the specimen to the laboratory for mold species identification

Sending the specimen to a lab isn’t necessary, but might be considered if testing public spaces like shops and restaurants.

It shouldn’t be an issue if using a testing package with species identification, but a quick Google for “mold testing near me” should reveal labs nearby.

What are the Most Common Places to Find Mold in a Home?

  • Test for mold in walls – Look for telltale signs of mold on walls. Probe wall surfaces with a screwdriver. Wooden walls tend to soften, rot, and crumble with mold infestation. If it does, it needs completely replacing.
  • Test for mold in the air Mold is everywhere. Leave a mold testing kit Petri dish open for an hour to capture as many mold organisms as possible for culture.
  • Test for mold in air vents – Air vents are warm and humid, a favorable environment for mold and other microorganisms.
  • Test for mold in carpet – Poor or low-quality carpets are more susceptible to mold growth than high-quality options, especially when exposed to too much moisture. A mold detector should help identify mold presence on carpet if it’s not obvious just from looking.
  • Test for mold in basement – Condensation and leaks are prevalent in basements, creating a hospitable environment for mold.
  • Test for mold in attic – Poor ventilation and humidity make attics prone to mold growth.


How can I tell if there is mold in my home?

Your eyes and nose are the most important mold detector tools at your disposal. Mold produces a characteristic musty scent as the first sign of a moldy problem. You can also see slimy and fuzzy discolorations on surfaces. These “unusual” patches grow over time. 

Can I test for mold myself, or do I need to hire a professional?

Yes, you can test for mold yourself. However, a commercially available mold detector might produce inaccurate results compared to professional testing and lab work, which are necessary for mold in workplaces, shops, and restaurants. 

What should I do if mold is found in my home?

The CDC recommends removing the mold with a bleach solution comprising a gallon of water and a cup of ordinary bleach. A soapy solution and other cleaning products can also work.

Do air purifiers help with mold?

Yes, air purifiers help with removing mold by capturing spores floating in the air, preventing mold reproduction and spread.


Learning how to test for mold is as easy as using your senses to detect the telltale signs of a mold infestation. And if you spot it, you can always test them with a commercially available kit to confirm. 

Otherwise, skip straight to mold removal and help protect household inhabitants from mold-related health problems.