The Biotest APC Plus

Article excerpt

Only once before have we introduced a device that costs over $2000. Interestingly Number 2 is used for the same purpose as Number 1--to define indoor air pollutants. But before we tell you about today's featured instrument, the Airborne Particle Counter (APC) Plus from Biotest Diagnostics Corporation, [*] a bit of history is in order. Two years ago, we were asked to help adjudicate a rather problematic indoor air pollution event at a middle school. The school physician suspected a bioallergen; it was our job to find the source and, it was hoped, make some recommendations for amelioration. Never ones to turn down a challenge, we set about our task with determination and a "piece of cake" attitude. When we got to the building, though, our best inspection efforts turned up nothing. Intuition and introspection did not help either. There was no obvious source or sources, yet the situation was real; the several complainants did not have psychosomatic symptoms. The events seemed to be entirely without a discernible pattern. Our only clue was that we were looking for some particulate.

Through the generosity of a colleague who certifies biological safety cabinets, we were able to borrow a particle counter for a few days. Using this device, we took real-time measurements of the classrooms, hallways, special activity rooms, offices, and mechanical areas--with special emphasis on the ventilation system. Extramural air served as the control. Our sampling protocol was systematic rather than judgemental or random, and we started on the leeward side and progressed toward the windward side of the building. We took particulate measurements in two sizes: 1 micron ([micro]) and 5 [micro]. During the sampling, a weather front passed through the area. The timely change in wind direction and temperature provided an excellent opportunity to replicate our testing under different external conditions. When we plotted the results of both sampling events on a site plan, two particulate sources were revealed: one from an air intake, the other from the arts-and-vocational suite of rooms. Armed with this informa tion, we prescribed several remedial measures, including cleaning of the ductwork, and the problem was solved. To this day, the specific offending biological agent remains a mystery. Through particulate monitoring, however, we located possible sources and were able to make recommendations and suggestions to prevent future incidents. Had it not been for the particle counter, the situation might have progressed to expensive litigation.

This incident reinforced our conviction that a particle counter, although not used every day, is an invaluable tool for the sanitarian. We set about gathering as much information about these units as possible and finally settled on the APC Plus. Since then, we have had occasion to use our airborne-particle counter in conjunction with biological monitoring; for several indoor air pollution events; in two contamination control investigations in pharmaceutical and manufacturing clean rooms; and as a validation tool for a duct-cleaning firm. For some sanitarians, this may be a bit far afield. …