Mold Sampling Considered
Visible Mold
In most cases, if visible mold is present, sampling is unnecessary. The most important sign of a mold problem is visible mold. If mold is found during a building investigation, the size and extent of the moldy area should be determined. Information on the water or moisture problems that allowed the mold to grow should be evaluated, in part because areas of hidden mold may surround the areas of visible mold.
Bulk samples can be examined using reflective light microscopes, such as stereo microscopes or this epi microscope.
Is sampling for mold needed? Usually, if the mold can be seen, sampling is unnecessary. After finding mold, the goal is to clean it up and fix the underlying water problem. Unless the results would or could make a change in your plans, you don’t need to sample. Under certain circumstances, such as when litigation is involved, the source of the mold is unclear, or health concerns are a problem, you may consider sampling as part of your site evaluation. However, routine sampling for mold is not recommended. Keep in mind that the goal of mold remediation is to find the source of the water problem, fix it and clean up the mold.
There are no EPA or other federal standards for airborne mold or mold spores, however, so sampling cannot be used to check a building’s compliance with federal mold standards because there are none.
Sampling may help locate the source of mold contamination, identify some of the mold species present and differentiate between mold and soot or dirt. Surface sampling may be useful in determining if an area has been adequately cleaned or remediated. After remediation, the types and concentrations of mold in indoor air samples should be similar to those in the local outdoor air.
Moisture meter, showing high moisture content in gypsum board behind tile.
Sampling for mold should be conducted by professionals who have specific experience in designing mold sampling protocols, sampling methods and interpreting the results. Several problems can occur when sampling, for example:
- There may be too few samples
- Sampling protocols may not be followed consistently
- Samples may become contaminated
- Outdoor control samples may be omitted
- Since sampling can be expensive, sufficient funds may not be available to sample and to fix the water/mold problem
Professional advice may be necessary to determine if the project budget will allow enough samples to be taken to characterize a problem. If sampling cannot be done properly and enough samples to answer the questions posed cannot be taken, then it is preferable not to sample at all. Inadequate sample plans may generate misleading, confusing and useless results.
Samples should be analyzed according to the analytical methods recommended by the American Industrial Hygiene Association, or AIHA, the American Conference of Governmental Industrial Hygienists, or ACGIH, or other professional guidelines.
Types of samples include:
- Air samples
- Surface samples
- Bulk samples (chunks of carpet, insulation, wall board, etc.)
- Water samples from condensate drain pans or cooling towers
Clear plastic tape can be used to collect a sample from a suspect site and then can be examined microscopically.
Keep in mind that air sampling for mold provides information only for the moment when the sampling took place. For someone without experience, sampling results will be difficult to interpret. Experience in interpreting results is essential.
Mold Versus Soot and Dirt
Not everything that looks like mold is mold. Paint on the backside of drywall or wood may look like mold growth. Alkaline crystals on soil or concrete walls may look like mold, but, unlike mold, they are usually water-soluble. Carpet stains also may look like mold.
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