The Air-O-Cell cassette design allows for isokinetic sampling of aerosols in Heating, Ventilation and Air Conditioning (HVAC) Systems. Sampling can be conducted at the supply diffuser or inside most conventional ducts. The inlet of the cassette should always be facing into the flow stream. The inlet orifice has a cross-sectional area of approximately 11 mm x 15 mm (165.0 mm2) tapering to a slit with dimensions of 1.055 mm x 14.4 mm (15.19 mm2). The flow velocity can be increased up to 30 lpm with conventional sampling pumps, however, air flows exceeding 20 lpm may potentially damage some bioaerosols or cause “bounce off”. Isokinetic sampling can be conducted in most air duct system with flow rates of up to approximately 600 fpm. Approximate face velocities for the Air-O-Cell cassette are given below for both the entrance orifice and slit exit in Table 1
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