AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
An Aerosol Dry Deposition System for Quantifying the Retention of Bacillus Spores on HVAC Filters
ANNE MARIE ERLER, Staci Kane, Matthias Frank, George R. Farquar, Lewis Wogan, Lawrence Livermore National Laboratory
Abstract Number: 368 Working Group: Homeland Security
Abstract Following a biological incident, surface samples will be taken to characterize the scope of the public health risk. Although many strategies exist for sample collection, interest has grown to utilize Heating Ventilation and Air Conditioning (HVAC) filters as a sample type due to the filter’s ability to concentrate aerosolized particles on its impact surface. Typical HVAC filter media installed in public ventilation systems are rated by the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) for the capture of only crude debris greater than 3 microns in diameter. Little testing has occurred on this filter media to confirm whether it could be utilized to recover smaller particles that may be present after a biological event. The initial physical state of a surface-deposited material (e.g. wet vs. dry) will impact the surface adhesion and re-aerosolization properties of the materials. To more accurately simulate real-world deposition for spore-forming agents, Lawrence Livermore National Laboratory (LLNL) has developed a flow-through Dry Deposition System (DDS) that was used to deposit aerosolized spores onto sectioned HVAC filters. One of the advantages of the LLNL DDS is the ability to provide highly accurate, absolute numbers for spore deposition since quantitative particle measurements are taken upstream and downstream of the filter using two cross-calibrated Aerodynamic Particle Sizer (APS) instruments. Additionally, the LLNL DDS utilizes low aerosol flow rate to deposit spores on the filter’s impact surface and can produce aerosolized spores at a wide range of desired concentrations. Low-level spore deposition was tested by depositing Bacillus spores on two different types of HVAC filters. The spores were directly extracted from the HVAC materials and recoveries were determined by culture analyses. Recoveries were also compared to filters inoculated by air-dried liquid deposition in order to determine if differences existed between the two deposition methods.
This work was sponsored by the U.S. Department of Homeland Security, Office of Health Affairs and performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-652306