An approach towards characterizing a reference sampler for culturable biological particle measurement

The first published account of a slit-to-agar sampler was of a system that used 10 cm petri plates. At some point after the 1950s samplers that collected biological aerosol particles on 15 cm plates appeared. More recently published patents describing slit samplers using 10 cm plates have cited economics as the prime motivation. Nonetheless, researchers have cautioned that the smaller plates can become saturated when heavy aerosol clouds are encountered, such as when a slit sampler is used as a reference collector when biological detectors are tested. This report describes how to determine the performance characteristics of slit samplers designed for either 10 or 15 cm plates. It also demonstrates the importance of controlled replicate measurements providing data suitable for rigorous statistical analysis. The results indicate that, for measuring biological clouds of between 5 and 30 agent containing particles per liter of air (ACPLA), the 15 cm plate sampler design is more efficient than those targeted for the smaller collection surface. A statistical method has been employed to test differences between regression slopes.