Broadly speaking, most mold testing involves taking a sample of either the air or a surface. Essentially, a mold inspector “tests” the air or surface to find out what kind of mold exists and/or if the mold found is able to grow in the area tested.

Mold Testing: Air Samples

Air samples can be taken and analyzed in a variety of ways. The most common method uses a “spore trap” and is called a “spore trap sample.” Spore traps work by having a known volume of air pass impact a sticky surface as it passes through the spore trap sampling device. Most of the particles in the air also impact this sticky surface and consequently adhere to, and are captured on, this sticky surface. Mold spores comprise a subset of these ‘particles in the air’ and also are captured on the sticky medium inside the spore trap. When the spore trap is sent to the mold testing laboratory for analysis, the mold laboratory opens the spore trap, applies some stains to the sticky surface that the mold spores can absorb, and then identifies and quantifies the types of mold spores captured during the sampling process. There are other methods of mold sampling, including culturing or growing the mold spores captured from the air, but these are less commonly used.

Magnified under a microscope, mold spores captured on a Zefon Air-O-Cell™ spore trap. Source: EMLab P&K

Culturing or growing mold on a plate. Source: Environmental Protection Agency (EPA).

Mold Testing: Surface Samples

Surface samples can be taken in a variety of ways. The three most common methods are:

1. Bulk samples. A piece of the sampled area is physically removed and sent to the mold testing laboratory,
2. Swab samples. Something akin to a cotton swab is rubbed across the area being sampled, often a measured area, and subsequently sent to the mold testing laboratory, and
3. Tape samples. A piece of clear tape is pressed against and removed from the area being sampled, presumably picking up and removing part of any mold that was present on the surface, and then set to the mold testing laboratory for analysis.

After the mold samples arrive at the mold testing laboratory, there are many ways to analyze these mold samples. The most common methods involve transferring relevant sections (or all) of the submitted mold sample onto a glass microscope slide, adding a stain that mold spores can absorb, and then evaluating the sample for evidence of mold growth.