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Cashins & Associates Blog

4 Things to Keep in Mind when Sampling for Mold.

Posted by Mike Cashins on Thu, Mar, 08, 2012 @ 14:03 PM

Mold Petri Dish

There are a lot of consultants out there that are happy to take your money for collecting a few air tests for mold and presenting you with the results.  However, there is a lot more to mold sampling than simply owning a pump and sampling cassettes. The following guidelines are presented here so that you as a consumer can help yourself get a proper mold evaluation performed when looking to hire a specialist to perform air sampling.


1. Pay attention to the number and location of samples

Many times, sampling methodologies are rather haphazard.  It is often the case that little to no thought went into the development of a sampling plan.  Thus, one of the first questions you should ask a consultant when presented with a proposal is “Why?”  “Why this number of samples and why in these locations?”

In order to obtain any meaningful data from spore trap testing, multiple samples must be taken at each location, preferably at different times of day.  One air sample at one location does not provide any real useful information.  Further, there should be a logic behind the sample locations – samples should be taken within the complaint area as well as from a non-complaint area.  Sometimes these “control” samples are taken from outside, sometimes they are not, such as in winter when there is snow on the ground.

2. Ask your consultant what the goal of sampling is

If you can see the mold, there is little you will gain by taking samples.  Unless it is an operating room, or the identity of the mold absolutely must be known, there is no need to sample if the growth is visible.  Just as I don’t need to ask you what color the wall is when I can see it clearly for myself, there is no need to sample the air for something that is right in front of me.

 3. Make sure the data is interpreted accurately

Consultants should not be comparing overall spore counts found outside with overall spore counts found in the complaint area.  It is almost always the case that outside spore concentrations will be much higher than indoors.  Rather, each individual type of mold found indoors should be compared to the concentration of that type found outdoors.  Sometimes there will be an amplification of one type of mold indoors, and the overall spore count will still be less. The validity of comparing of indoor and outdoor spore counts is under great debate amongst industrial hygienists and microbiologists. We believe this comparison can be a useful piece of data during an evaluation; however, this should not be the main determinator to conclude that a space has or does not have a mold issue. There are many companies that will make a determination solely using the indoor\outdoor spore ratios.  

4. Know the limitations of air sampling

It is important to note that spore trap testing and analysis offers only a snapshot of a portion of an indoor space over a short period of time.  Concentrations and types of mold spores change rapidly throughout the day, and depend on many variables, including relative humidity, air movement, housekeeping protocols, temperature, and the like.  The results do not prove or disprove the presence of mold growth, but may be useful in determining whether or not further assessment is warranted.

The short sampling times are problematic for obtaining accurate spore concentrations. This is why collecting many air samples is needed. The downside is that the cost of a proper evaluation can be significant. On the flip side, an inexpensive evaluation with statistically invalid data sets is a complete waste of money.

It is also important to keep in mind that spore trap air sampling may not identify the presence of hidden mold, or molds that are undisturbed or non-sporulating (do not produce spores).  These air samples give a brief glance at airborne spore levels during a relatively brief period of time.

If you have any questions about mold or indoor air quality we are here to help. Use our convenient web based request system and one of our experts will get back to you.

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Topics: health & safety, industrial hygiene, indoor air quality

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