Aerosol-to-Hydrosol Transfer Stages for use in bioaerosol sampling

Abstract

Single-Jet and Multi-Jet Aerosol to Hydrosol Transfer Stages (AHTS) with cutpoints of 2 and 0.8 []m AD, respectively, were designed and evaluated. Both devices operate at nominal air sampling flow rate of 1 L/min, 0.1% Tween®20, and 0.3 mL/min. collection liquid flow rate. Both systems have an ideal air power consumption of 1.4 mW and 4.5 mW, respectively. The total electrical power consumption, including that needed to heat the airstream and a sampling enclosure, is approximately 55 W at -23°C (-10°F) outside air temperature. The AHTSs were tested using polystyrene solid and oleic acid liquid aerosol particles to determine the collection efficiencies. The effectiveness of the fractional collection efficiency for the Single-Jet and Multi-Jet are 91% over the size range of 2 to 10 []m AD, and 90% over the size range of 1 to 10 []m AD, respectively. The hydrosol collection efficiency of the Multi-Jet is 95% over the size of 1 to 3 []m AD. The influence of a cleaning solution that was comprised of distilled water and 0.1% Tween®20 yielded an average collection efficiency of above 90% for the Single-Jet and 98% for the Multi-Jet. When the liquid flow rate is equal to or greater than 0.3 mL/min, the hydrosol collection efficiency is constant at 90%. The time responses for Single-Jet and Multi-Jet are 1.4 and 0.75 minutes, respectively. Preliminary results of bioaerosol testing with 0.7 []m AD single spores of Bacillus globigii var. niger show efficiencies over 100%. These discrepancies are probably due to the testing procedures at the U.S. Army Research Office, Chemical Biological Center, Edgewood, MD, facilities.