A new filter cassette for the direct microscopic examination of airborne fungal spores
Spurgeon, J.
2006 Aerosol Science and Technology, 40(11), November 2006, pp. 1025-1033
Spurgeon, J., (2006), "A new filter cassette for the direct microscopic examination of airborne fungal spores", Aerosol Science and Technology, 40(11), November 2006, pp. 1025-1033.
Abstract:
The study describes a 25-mm filter cassette constructed with a plastic masking disk covering the bottom of the cassette cowl, reducing the area of exposed filter by 95%. Two rectangular sample traces, each with a size of 1.7 mm กม 5.5 mm (9.35 mm 2 ) were produced. The traces were sufficiently small to be analyzed by direct microscopic examination without requiring a sample transfer step. Direct microscopy of fungal spores using the new Bi-Air (BA) filter cassette was compared to the Air-O-Cell (AOC) slit impaction cassette using Penicillium chrysogenum and Stachybotrys chartarum spores. The comparisons involved the collection of side-by-side samples in a quiescent settling chamber. The distribution of P. chrysogenum and S. chartarum spores between the duplicate BA sample traces was uniform. The deposition of spores across the sample traces was also similar for the BA and AOC, with a coefficient of variation (CV) between traverses of 27% for the BA and 29% for the AOC. The average retention of Penicillium spores was equivalent for mixed cellulose ester (MCE) filters with pore sizes of 1.2 um and 3 um. However, a 5 um pore size resulted in about a 20% reduction in the average retention for 3 um Penicillium spores. The average ratios of BA to AOC concentrations for P. chrysogenum spores were 2.0, 1.8, and 1.7 at airflow rates of 1 lpm, 2 lpm, and 3 lpm, respectively. The average ratio of BA to AOC concentrations for S. chartarum at the three airflow rates was 1.1. The edges of the BA sample trace were well defined and bounded, and the sample area did not vary between samples. The constant size of the BA sample trace allowed less than 100% of the sample to be analyzed without affecting the precision of the analysis.
