Mold Testing

Although mold testing can be incorporated in an attempt to find a mold problem and identify mold types present, it is expensive, often is unnecessary, has limitations, and requires specialized equipment and training. Mold testing generally is unnecessary if you know mold is present. The simplest approach is that if you can see or smell mold, you probably have a mold problem and should work to control it and clean it up.

The basic types of mold testing available are bulk sampling, surface sampling and air sampling. Samples for bulk testing are usually taken from visibly moldy areas by scraping or cutting materials with sterile tools and placing the sample into a sterilized sample container. Surface sampling is done by swabbing an area with a sterile swab or by using sterile adhesive tape to sample a surface. The samples from bulk or surface sampling usually are sent to a laboratory for analysis. Bulk and surface sampling can identify the existence of specific mold contaminants in a material and can be used as part of a medical evaluation.

Two forms of air sampling can be used: viable (culturable or living) and nonviable (non-cultureable or not living). In both forms, air samples are taken by drawing a measured amount of air through a sampling device. In viable air sampling, the sampled air is drawn into a sampling device that contains a nutrient agar petri dish. The particles in the sampled air impact the agar in the dish. The dish is then sent to a laboratory to be cultured. Viable mold spores will grow on the dish in colonies. In nonviable air sampling, the particles (mold spores, dust, etc.) are impacted onto a sticky surface. A laboratory analysis of the surface is then done.

Mold testing may result in "false negatives." The levels of airborne mold particles can fluctuate greatly depending on the weather (season), humidity, air movement, and other activities within the environment. Mold testing generally is done on a single day and presents only a "snapshot" in time. In addition, if mold samples are not taken in every room of a building, a room with a mold problem might not be sampled and a false negative result is possible. Even when mold testing is done correctly, there are no standards available for acceptable or not acceptable quantities of mold in a building. Typical indoor mold samples often are compared to outdoor samples taken on the same day to determine if there might be an indoor mold source.

Other Indoor Air Quality Web Resources - Mold Testing

Contact Information

  • Justin Otto - North Dakota Department of Health
  • Electronic mail address:
  • Office phone: 701.328.5188

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Page last revised: January 22, 2015