Abstract View
Assessment of a Bioaerosol Test Platform for the Evaluation of Biothreat Sensor Performance in Identifying Live BSL-3 Threat Agents
LEAH CAROL, Benjamin Alvarez, Felix Sage, Thomas Pilholski, Elizabeth Corson, Brian Damit, Johns Hopkins University Applied Physics Laboratory
Abstract Number: 624
Working Group: Bioaerosols
Abstract
Robust evaluation of infectious bioaerosol sensors requires homogenous flow velocities and aerosol concentrations at sensor sampling locations. To support such testing, the Johns Hopkins Applied Physics Laboratory (JHU/APL) is currently designing and constructing a new Biological Safety Level (BSL-3) test platform for closed-circuit wind-tunnel exposures via inlet immersion of multiple instruments in series. A scaled-down prototype was described previously. The prototype includes 3D-printed honeycombs for flow straightening with minimal aerosol losses and a static mixer to promote aerosol mixing/uniformity. Results from the evaluation of the prototype system are reported here.
To evaluate velocity profiles and aerosol concentration uniformity, measurements were taken in a grid pattern at several points laterally along the flow path both upstream and downstream of the honeycombs. Coefficient of variation (COV) was calculated from these measurements and compared to industry standards provided by the Environmental Protection Agency (EPA) and American National Standards Institute (ANSI). For both velocity and aerosol concentration, EPA dictates COV no greater than 10% while ANSI allows COV up to 20%. Wind tunnel velocities of 1.5 m/s and 4 m/s were used to assess a typical condition and an extreme condition, respectively. Unobstructed flow as well as flow around a bluff body comprising 15% of the cross-sectional area were also examined. Use of the bluff body represented a worst-case scenario for perturbations.
Velocity COV met ANSI standards at all locations except the cross-section immediately following the bluff body (COV ~30%). Velocity COV also met EPA standards at most locations under unobstructed flow conditions. Meanwhile, aerosol COV met ANSI standards for all tested conditions and locations. When only the centermost grid points were examined, aerosol COV also met EPA standards. These results indicate the use of honeycombs and a static mixer can ensure homogenous flow velocities and aerosol concentrations at all sampling locations.