As usual, the answer is "it depends." Particle counters are becoming more and more sophisticated. Particle counts can be divided into relatively narrow ranges, and particles with special characteristics such as fluorescence can be detected. It would seem logical, since bioaerosols are particles that with all this technology they would be useful in mold investigations. The problems lie in the fact that bioaerosols are usually a relatively small fraction of the particles in their size range.

There are some cases where particle counters can be used. In research, of course, experiments can be set up where they are very useful. If you are doing a chamber study and want to monitor concentrations of a bioaerosols that is purposely released in high concentrations, particle counters can be very useful. This strategy could be used in a building where extensive growth is visible and you need to know whether or not specific activities create spore aerosols from this growth. In this case, you could identify the spores at least with respect to size range, then do a series of background measurements with the particle counter to establish baseline particle concentrations in that size range, then begin the aerosolization experiments.

A similar strategy could be used if the growth is composed of one or more fungi that fluoresce naturally. Specialized particle counters that stimulate and then detect this fluoresce can be used. Unfortunately, all fungal spores do not fluoresce, and those that do often do so irregularly.

I am often asked if particle counters can be used for bioaerosols clearance sampling. You can certainly monitor the fall of particle concentrations over time following remediation activities. However, these activities generate high non-biological aerosol concentrations in which the bioaerosols will be lost.

There are several studies in the literature that do report the successful use of particle counters in bioaerosols investigations. If you are lucky, you too can have this success. However, in my experience such cases are rare, and it is much safer to use more traditional methods for documenting air concentrations, at least of fungal spores.

This article originally appeared in the May 2011 issue of Indoor Environment Connections. Reprinted by permission.

About Dr. Harriet Burge Dr. Harriet Burge is EMlab P&K's Director of Aerobiology and Chair of EMLab P&K's Scientific Advisory Board. Widely considered the leading expert in indoor air quality (IAQ), Dr. Burge pioneered the field more than 30 years ago. She has served as a member of three National Academy of Sciences committees for IAQ, including as Vice-Chair of the Committee on the Health Effects of Indoor Allergens. View Dr. Burge's Curriculum Vitae. Read "Ask Dr. Burge" articles

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