How to Test For Toxic Mold

By: Sara Elliott  | 
Luella Pinkney looks through a mold covered window as she gets her first look at her house in October 2005, more than a month after Hurricane Katrina.
Chris Graythen/Stringer/Getty Images

Key Takeaways

  • You can often detect mold in homes by smell, and its presence can lead to various health issues, particularly for individuals with respiratory conditions or allergies.
  • You can test for mold through DIY kits or professional services, though the accuracy and necessity of pre-removal testing can vary.
  • Effective mold management includes preventing moisture buildup by controlling humidity levels, repairing leaks and ensuring good ventilation to inhibit mold growth.

If you have mold in your home, your nose is one of the most inexpensive devises you can use to detect it. Mold smells, and chances are, you'll be able to detect the distinctive odor that taints the air around moldy walls, carpeting and other objects. The struggle is in understanding when mold is dangerous to your family or home.

The term toxic mold is a little confusing. Some molds, like Stachybotrys chartarum or black mold, produce mycotoxins, toxic substances that cause health problems in some people. There is no direct link yet between mold-produced toxins and serious conditions like idiopathic pulmonary hemorrhage in infants, but there are concerns that exposure to these toxins can exacerbate existing lung conditions and allergies, and possibly cause problems in otherwise healthy people. Common molds that aren't considered toxic also have the potential to cause reactions in some people, which makes it important to get rid of any type of mold you find in your home as soon as possible, particularly if you suspect that someone in your family is having a reaction to it. [source: CDC]


Mold can be scary. There are potential health implications for your family, and a mold outbreak can take a financial toll, too. Once established, mold can be very invasive, releasing millions of spores into your home. Many homeowners' insurance policies now exclude or limit coverage for mold related problems.

In the next few pages, we'll take a closer look at mold and evaluate some common methods of testing for it and dealing with it.

First up, let's learn a little more about household mold.


The Facts about Mold in Your Home

Mold is a fungus that reproduces by creating small spores that work like seeds. Every home has mold. Mold spores can be unwelcome guests floating in on the breeze through an open window or door, hitching a ride on clothing or hiding in plain sight on packaging materials like cardboard or paper. Once established, it will look like fuzzy spots or blotches that can be black, green, brown, yellow, and even orange or white.

There are nearly 1,000 types of household mold. A few common culprits are Alternaria, Aspergillus, Cladosporium and Penicillium. The dreaded black or toxic mold that you see in the headlines, Stachybotrys chartarum, also know as Stachybotrys atra, isn't a common mold, but it's not rare either. It will look dark green or black.


You can't keep mold out, but you can make it less welcome. Household mold needs hospitable conditions in which to thrive. One key ingredient in establishing and maintaining a mold colony is moisture. If you don't have a consistent source of moisture, mold won't be able to survive. [source: Consumer Reports]

This sounds pretty simple. All you have to do is keep the inside of your house dry, and you won't get mold. But keeping moisture out is harder than it may seem. There are the obvious sources of moisture you can watch out for, like leaks in the plumbing and the roof, but there are other ways moisture can get in that are harder to control. Steam from cooking and bathing can create conditions that will encourage mold, and condensation can be a big problem too. Warm air has the capacity to hold more moisture than cooler air. As this moisture-laden air starts to cool down, such as near the windows in summertime, it deposits water in the form of condensation. Condensation can accumulate on the insides of windowpanes and on pipes and walls, creating a great environment for mold, sometimes in spots you wouldn't expect. Mold is an equal-opportunity fungus. It can live in your walls, on wood, furniture and carpeting or on hard surfaces like tile, glass and metal -- practically anywhere.

In the next section, we'll take a look at ways to check for mold.


Do You Have a Mold Problem?

Norhtwoods subcontractor Doug Jollenbeck repairs mold damage in Sacramento, Calif.
Max Whittaker/Stringer/Getty Images

If you can smell mold in your home, you probably have a mold problem. If you can see mold on walls, in corners or on objects, you should get rid of it. The Centers for Disease Control and Prevention (CDC), a major operating component of the U.S. Department of Health and Human Services, has yet to establish guidelines for evaluating the health risks of specific mold concentrations or strains in buildings, but they have stated that the most prudent practice when discovering mold in your home is to remove it. All mold varieties should be considered the same when evaluating their potential risk to your family's health [source: CDC].

Health problems can sometimes be an indicator that there's mold present in your home. Sensitive individuals sometimes exhibit symptoms like sore throat, stuffy nose, eye irritation, wheezing and rashes. In more extreme cases, they might endure fever, shortness of breath, and mold-related lung infections when exposed to a mold-laden environment. But even if no one is sick at your house doesn't mean you don't have mold.


Checking for mold can be a little like playing hide-and-seek, but it's no game. Your efforts may even disturb mold colonies and release spores that can go on to contaminate other areas of your home. A good practice after checking easily examined areas like walls, ceilings, bathrooms, basements and inside cabinets is to consult a professional before pulling up carpeting or looking behind walls. This is especially true when you suspect there's a problem because of a moisture situation in the past, like a roof leak or flooding.

When conducting a hunt for mold, turn off your HVAC system and any fans that are running to reduce the chance of spreading spores to other locations. These are some popular hiding places where mold may be lurking:

  • Under carpets and carpet pads
  • Behind wall paper or draperies
  • Behind drywall, wallboard and wood
  • On pipes
  • Inside ductwork
  • Above ceiling tiles

The nose knows, and if you can't find any mold but the smell persists, there's probably mold hiding somewhere nearby.

In the next section, we'll discuss ways to get help dealing with mold in your home.


Mold Cleanup

The safest way to deal with any type of mold, not just toxic or black mold (Stachybotrys Chartarum), is to get rid of it and eliminate the conditions that caused a mold colony to thrive in the first place. Determining the type of mold you may have -- toxic mold or another variety -- is a secondary consideration. This is doubly important if you think someone in your family may be particularly susceptible.

The Environmental Protection Agency (EPA) recommends that a professional handle mold remediation for any area that covers 10 square feet (0.929 square meters) or more. If you're eyeballing a moldy spot smaller than three feet by three feet (91.44 centimeters by 91.44 centimeters), you can tackle it on your own. One exception is in areas where there may be contaminated water present. For more information about how to treat mold where there may be other health risks involved, contact your public health department.


Get prepared for the cleanup by making sure you have a respirator and goggles. N-95 respirators are available at most hardware and home improvement stores and will trap mold spores if worn properly. Goggles are easy to find, too; just make sure they don't have ventilation holes. Keep mold from coming in contact with your bare skin by wearing long sleeves and gloves. If you're using a biocide like bleach, make sure your gloves are natural rubber, PVC or neoprene.

There are things that are difficult or impossible to treat for mold. In the case of carpeting, upholstery, ceiling tiles and other porous materials, the best way to get rid of the smell and eliminate the risk of reintroducing mold into your environment is to pitch them.

Mold can also make you sick after it's dead, so be sure to do more than just treat moldy areas with a biocide. Clean everything completely and discard moldy materials.

The following do-it-yourself steps will help you deal with small mold problems in your home:

  1. Turn off the air conditioning or heating system in your home and stop all fans before you begin work.
  2. Lay plastic sheeting around the area where you will be removing mold.
  3. Discard porous materials like carpet, drywall and insulation by placing it in bags or wrapping it in plastic.
  4. Scrub all remaining surfaces with a solution of chlorine bleach and water (one cup bleach to one gallon of water), detergent and water, or commercial cleaning products.
  5. Vacuum the area with a wet-dry vacuum cleaner after removing mold, and scrub it thoroughly when you're done.
  6. Dry everything completely.
  7. Wash clothing in hot water.
  8. Discard plastic sheeting, masks and any other materials you used that cannot be thoroughly cleaned.

On the next page, we'll explore your options for mold testing.


Getting a Mold Checkup

Getting rid of the mold in your home is your first priority. Since CDC (Centers for Disease Control and Prevention) guidelines don't distinguish between different types of mold and recommend the prompt removal of all mold in your home, testing beforehand isn't a priority if you've already decided you have a problem. Testing can be useful when you want to make sure your property is free of mold after a cleanup, though.

There are a couple of ways you can arrange for a test. You can purchase an in-home test kit, follow the directions and submit the resulting sample to a lab. The costs for this can vary quite a bit, anywhere from $40 to more than $200, and the results might not be reliable. Consumer Reports conducted an evaluation of home mold testing kits in 2006, and none of the four kits they looked at received a recommendation. The problems ranged from the kits having no expiration dates, potentially compromising the results, to being difficult to use [source: Consumer Reports].


Your second option is to hire a professional to evaluate your home for mold. Professional mold assessment and cleanup will typically involve equipment and detailed testing that you wouldn't have access to any other way. There are obvious advantages, but only if you are careful about the company you choose. Check with your state's contractor-licensing board to verify that the company you select is licensed for mold remediation. If there has been a water-related disaster in your area, like a hurricane or flood, you can also check with the Federal Emergency Management Agency or your public health department for more information on how to make an enlightened decision.

There is a third choice. After a cleanup, you can make periodic, careful evaluations of the infected area yourself and monitor your family's health to see if the problem recurs. The time and effort you take with the clean-up and the extent of the mold damage may have an impact on how comfortable you feel with this option. If a foul smell alerted you to a mold problem in the first place, using your nose to check the area periodically might be a good way to gauge the success of your cleanup efforts.

Proceed to the next page for a list of important steps you can take to can keep mold away from your home and family.


Keeping Mold Away

The best way to handle mold is to keep it from finding a place to grow in your home. Although it's impossible to make yourself completely safe, there are some precautions you can take to reduce your risk of mold contamination:

  • Keep your indoor relative humidity between 30 and 50 percent. Your air conditioning will help you control humidity, or you can purchase a dehumidifier. Test your relative humidity with an inexpensive humidity meter from your local hardware or home improvement store.
  • Use venting fans in your bathrooms and kitchen.
  • Insulate your home to help control condensation.
  • Repair leaks immediately.
  • Dry wet spots within 48 hours.
  • Grade landscaping to route water away from your home.
  • Keep gutters and downspouts clear of debris.
  • Promote good air circulation by periodically opening windows and interior doors to seldom used areas.
  • Clean the drip pans in your air conditioner regularly.

Don't leave yet. On the next page, you'll find lots more interesting information about mold and other related topics.


Frequently Asked Questions

What are the signs of toxic mold exposure in pets?
Signs of toxic mold exposure in pets can include respiratory distress, loss of appetite, lethargy and changes in behavior.
Can cleaning visible mold guarantee its complete removal?
Cleaning visible mold does not guarantee complete removal as spores can linger in the air or within materials, requiring professional assessment and remediation.

Lots More Information

Related HowStuffWorks Articles

  • CDC. " Facts About Stachybotrys Chartarum and Other Molds." Undated. 5/18/09.
  • Consumer Reports. " After the Storm: Cleaning up Mold." 10/08. 5/20/09.
  • Consumer Reports. " Gauging Mold's Harm." 10/08. 5/20/09.
  • Consumer Reports. "Finding a Pro." 10/08. 5/20/09.
  • Consumer Reports. "Getting Rid of Mold." 10/08. 5/20/09.
  • Consumer Reports. "Mold Test Kits." 10/08. 5/20/09.
  • U.S. EPA. "A Brief Guide to Mold and Moisture in Your Home." Undated 5/18/09.
  • U.S. EPA. "Mold Remediation in Schools and Commercial Buildings." Undated. 5/18/09.
  • U.S. EPA. "Mold Resources." Undated. 5/18/09.