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Mold Testing

Mold testing is the process of identifying the presence of mold through scientific measurement.

Mold testing is the process of identifying the presence of mold through scientific measurement. Additionally, mold testing techniques can be used to identify the species of mold in question. 

What type of mold testing is available?

  • Non-viable air sampling.  This is the most common type of laboratory mold testing used in the inspection process.  Air is drawn through a plastic cassette for a defined period of time, impacting mold spores and other particulates on a slide.  This slide is then placed under a microscope in a laboratory where a technician counts the number of spores and attempts to identify the species of mold.  The exact species of mold cannot always be determined with non-viable testing, as some spores appear identical until grown in laboratory conditions.
  • Viable, culture based air sampling.  Though less common, viable sampling provides additional information not available in other collection techniques.  The primary advantage is the ability to differentiate between mold species with similar appearances. This is essential for proper contrasting between mold spore counts in an outside control and the area of concern.  The mold testing technique also has disadvantages though.  Viable sampling is costly, time intensive and requires multiple types of media to ensure each species has the proper growing conditions.
  • Surface sampling.  Surface sampling is used to test a suspect material, both to determine if mold growth is present and to identify the species of mold.  This type of mold testing focuses primarily on qualitative rather than quantitative analysis.  Surface sampling techniques include:
    • Swab sampling
    • Tape lift
    • Settled dust sampling
    • Bulk material

    Is there a difference between professional mold testing and mold test kits available at hardware stores?

    DIY mold test kits available at home improvement stores rely on a Petri dish sampling technique, similar to the viable air sampling described above.  Professional sampling, however, uses a calibrated pump to draw a specific quantity of air across the Petri dish.  DIY kits are simply left in the open air for a period of hours or days, relying on gravity to pull spores onto the plate.  This technique is not quantifiable because the variables are not controlled.  For example, if a window is opened or a pet walks by and displaces mold spores, the sampling kit will show an artificially high count.  Additionally, even the cleanest home contains a background level of mold spores, which after contacting the Petri dish, will grow again providing a false positive.  

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