UPDATED 2021

The Mold Test Guide

The Mold Test Summary
What: Mold tests check for potentially dangerous mold growths in homes and businesses.
Who: It is estimated 40 percent of U.S. households have some form of mold problems.
Where: Mold growths usually occur in humid, poorly ventilated areas of homes or businesses.
When: A test can be conducted by professionals year round.
How: Home test kits can be used for exploratory or minimal mold problems. Professional testers and cleaners should be called in for serious problems.
Type: Air samples can be taken for non-visible mold spores. Surface swabs can be taken to check a specific area for mold growth.
Why: Inhalation or consumption of mold spores can lead to allergic reaction or serious health problems.
Time: Professional testers usually need a few hours to conduct their analyses, but the time may vary depending upon the size of the building. Home tests take about 48 hours for results.
Language: Varies.
Preparation: No special preparation is needed.
Cost: Professional testing can range $200-$900 depending on the size of the area to be tested. Home kits can cost as little as $5-$10, but offer only superficial results. Extra costs may be incurred to have the area professionally cleaned.

Two out of every five homes in the US have a mold problem, according to the Journal of Occupational and Environmental Hygiene. Although mold spores are commonly found in household and workplace dust, large concentrations pose a very real health risk to humans. For people who are allergic to mold spores, reactions can include irritation of the eyes, nose, and throat and severe respiratory problems. Fortunately, mold concentrations are easily controlled once they are identified. The most efficient way to identify if a home or office contains unsafe levels of mold is to have the building tested.

Why Test for Mold?

In addition to allergenic irritations of the lungs and sinuses, mold spores can produce very dangerous liquid or gaseous compounds called mycotoxins. These toxic particles are then carried via mold fragments to the surfaces they grow upon. Contact with humans can lead to a variety of symptoms, including asthmatic episodes, lung and skin infections and weakened immune function. In extreme cases, toxic molds have been known to lead to death. Not all mold growths can be easily spotted or give off a discernible odor, yet 40 percent of homes are believed to have mold problems. If left untreated, growths tend to spread.

When is a Mold Test needed?

If a mold growth is suspected, a test may be needed to confirm the presence of excessive mold. Signs of a mold problem include unusual odors and visible discoloration of walls or ceilings, although sometimes a mold problem exists with none of these signs. Certain areas of a building are more prone to mold growth, such as spots where there is little ventilation or sunlight, high humidity, or water vapor present.

Moisture is almost always a primary cause of mold growth, and the first step in treating any mold problem is identifying the location of the mold and its source of moisture. Testing is not generally recommended unless there is a clear visible sign of mold or someone in the area is symptomatic. However, if this is the case, testing may be necessary to check for airborne spores or to map the extent of the problem.

Who Should Conduct Mold Tests?

Because inhaling or coming into contact with mold spores can be dangerous, organizations such as the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA) recommend calling in professionals with proper disposal training. Groups such as the American Industrial Hygiene Association (AIHA) provide regularly updated lists of accredited laboratories in different areas.

Home test kits can be purchased at home improvement stores or online and completed by swabbing the suspected area and allowing the sample to grow for 48 hours. Any sample growth might indicate a positive result, in which case the sample should be sent away for further analysis. However, due to the potentially dangerous nature of a mold problem, groups like the EPA and AIHA recommend professional testers.

How Does a Mold Test Work?

A thorough mold test requires proper sampling techniques and an interpretation of the sample, which is why it is highly recommended that only professionals with proper safety training conduct such tests. Test samples are used to determine the spore concentration in a given area or check for the presence of specific mold species.

The three most common methods of mold testing are through air, surface and bulk samples. Air sampling is the most common procedure and can check for non-visible mold contaminations. It is conducted by taking a control sample of air outside (presumably in a non-contaminated area) and checking the level of mold against an air sample of the contaminated area. Surface samples are taken with swabs or tape to determine the level of mold spore deposits. Bulk samples can be taken from objects within the contaminated area. Because all three methods have their individual limitations, the AIHA suggests conducting all three to provide comprehensive results.

A professional mold test usually charges depending upon the size of the area to be inspected. An average sized home (2,000-2,500 square feet) inspection can run $200-$600, and larger homes (upwards of 5,000 square feet) can cost $600-$900. In cases where mold growth is extensive, walls may need to be cut open or other invasive procedures performed, which may add additional costs to the inspection.

The test can last a few hours depending on the size of the area to be inspected. Lab results can usually be expected within two to seven business days. If any significant amount of mold is found, the contaminated area should be closed off as best possible. Any potential sources of water vapor or humidity should be eliminated, but only a trained professional should come in contact with the mold spores.

Home test kits can be acquired for $5 to $100. Usually these kits can be sent away to a lab for further analysis of specific mold types, and after extra shipping and lab costs, total expenses can cost an extra $30 to $150 per report.

Interested in finding mold test providers or resources? Visit our Mold Test Directory for more information. To learn more about mold tests, read our interview with mold test expert John Jones.