A two-stage cyclone using microcentrifuge tubes for personal bioaerosol sampling

Abstract

Personal aerosol samplers are widely used to monitor human exposure to airborne materials. For bioaerosols, interest is growing in analyzing samples using molecular and immunological techniques. This paper presents a personal sampler that uses a two-stage cyclone to collect bioaerosols into disposable 1.5 ml Eppendorf-type microcentrifuge tubes. Samples can be processed in the tubes for polymerase chain reaction (PCR) or immunoassays, and the use of multiple stages fractionates aerosol particles by aerodynamic diameter. The sampler was tested using fluorescent microspheres and aerosolized fungal spores. The sampler had first and second stage cut-off diameters of 2.6 μm and 1.6 μm at 2 l min⁻¹ (geometric standard deviation, GSD = 1.45 and 1.75), and 1.8 μm and 1 μm at 3.5 l min⁻¹ (GSD = 1.42 and 1.55). The sampler aspiration efficiency was ≥98% at both flow rates for particles with aerodynamic diameters of 3.1 μm or less. For 6.2 μm particles, the aspiration efficiency was 89% at 2 l min⁻¹ and 96% at 3.5 l min⁻¹. At 3.5 l min⁻¹, the sampler collected 92% of aerosolized Aspergillus versicolor and Penicillium chrysogenum spores inside the two microcentrifuge tubes, with less than 0.4% of the spores collecting on the back-up filter. The design and techniques given here are suitable for personal bioaerosol sampling, and could also be adapted to design larger aerosol samplers for longer-term atmospheric and indoor air quality sampling.