Often the term mold testing is used in place of mold inspection or mold investigation. Strictly speaking mold testing is not the same as mold investigation or mold inspection. It refers to the testing of samples in the laboratory for the presence/absence of mold. Mold testing and a rarely used term mold analysis refer to the same thing. The samples are collected during a mold investigation or mold inspection.

Mold Investigation

While mold investigation and mold inspection are interchangeably used, mold investigation is a more detailed study of mold in the building. A mold inspection is more or less trying to find out if there is mold while a mold investigation goes a step further and tries to find out the causes of mold growth (i.e., moisture sources, etc).

Both mold investigation and mold inspection may involve taking a sample of either the air or a surface. Essentially, a mold inspector collects the air or surface sample to find out what kind of mold is present and/or if the mold found is able to grow in the area sampled.

Testing Air Samples for Mold

Air samples can be collected and analyzed in a variety of ways. The most common method involves impacting air on an inert sticky surface housed in a cartridge such as the Air-O-Cell cassettes, Allergenco cassettes and many others. These kind of samples are referred to as “non-viable” or “non-culturable” samples. These terms, however, incorrectly implies that all spores captured using this method are dead. You may also find some people calling these samples “spore trap samples” which is incorrect as we shall explain why below.

When the non-viable samples are sent to a mold testing laboratory for analysis, the mold laboratory opens the cartridge, 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.

The other method of capturing airborne fungal spores is to impact the air on agar medium in a petri-dish. The petri-dishes are then sent to the lab and incubated for a number of days. In this case the captured spores, if viable and if the growth medium used is suitable for their growth, develop into mold colonies which the laboratory can count and identify. These samples are referred to as “culturable samples”.

We mentioned that calling non-viable samples, “spore trap samples”, is incorrect because even the second sampling method involves spore trapping but using a petri-dish instead of a cartridge.

Testing Surface Samples for Mold

A number of surface samples can be collected during a mold inspection or mold investigation. These are:

1. Bulk samples. Bulk samples are pieces of moldy material sent to the mold testing laboratory. These include pieces of dry-wall, wallpaper, insulation, etc.
2. Swab samples. Swab samples are collect using cotton swabs by rubbing/rolling the swab on the area suspected of having mold growth.
3. Tape samples. Tape samples are collected using a piece of clear scotch tape. The tape is pressed against the surface suspected of having mold growth and then peeled gently, presumably picking up and removing part of any mold that was present on the surface.

Bulk, swab and tape samples are meant to confirm the presence of mold and to determine what type of mold is present.

You may be interested in our course Mold Inspection, Identification and Control.