Department of Homeland Security Research Description:
A recent research project involved bioaerosol sampling by means of filtration to determine normal background concentrations of selected bacteria and virus aerosols in large public buildings in the United States at selected locations.? Ventilation filters were removed from four air handling units within each building to be analyzed for collected bioaerosols.? Figure 1 shows a typical air handling unit for a commercial building.? The filters were basically being used as passive high volume air samplers for bioaerosol particles.? These data are time integrated over 3 month periods, as we were sampling for each season out of the year.? After the filters had been removed, samples were cut from each filter and then eluted to remove any captured bacteria and/or viruses from the filter media.? The bacteria were cultured on growth plates or identified by Polymerase Chain Reaction (PCR) methods.? The viruses were analyzed using PCR methods or egg inoculation methods to see if they are viable.
After the bacteria and viruses have been identified, comparisons will be made between building locations and seasons of the year.? The virus and bacteria detection and identification is performed by researchers in the Department of Environmental Health and the Veterinary Diagnostics Laboratory in St. Paul.
Figure 1: Schematic of a Typical Air Handling Unit for a Commercial Building
Center for Filtration Research Project Description:
A current research project involves measuring total lung deposited particle surface area with two aerosol instruments to generate a new ˇ°Health Indexˇ± filter efficiency. ?This method of aerosol sampling can also be used to determine the effectiveness of the Nanoparticle Surface Area Monitor (NSAM) compared to a Scanning Mobility Particle Sizer (SMPS).? The NSAM directly measures the total amount of particle surface area deposited into certain regions of the human lung.? The SMPS is able to measure particle concentrations of different sizes within a defined size range, but the SMPS measurements need to be manually integrated to correspond with the NSAM results.? This integration includes correcting the SMPS measurements for the specific region of the lung using deposition curves for a reference worker, as outlined by ACGIH.? These curves can be seen below in Figure 2. ?The two regions of the lung being observed are the Alveolar and Tracheobronchial regions and are illustrated in Figure 3 below.
An ASHRAE 52.2-1999 Classified windtunnel (see Figure 4) is used as the test facility for the injected aerosols.? The fan speed can be adjusted to control the aerosol concentration.? Three fan speeds were used to produce three different air flow rates of 500, 1000, and 2000 cfm.? A Constant Output Atomizer (COA) is used to produce a polydisperse aerosol, which is injected into the windtunnel.? Different solutions of NaCl are used to produce different concentrations of particles to be sampled.? Silver nanoparticles, produced by a furnace; and a DOS solution, aerosolized with the COA, will also be used to test this setup.? Sampling is made upstream and downstream of the filter being tested.? These upstream and downstream concentrations are then used to determine an efficiency of the test filter based on the lung deposited surface area.
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Figure 2:? Deposition Curves for a reference worker (ACGIH) |
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Figure 3: Various regions of the human lung (NSAM Spec Sheet; TSI) |
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Figure 4:? ASHRAE 52.2 ¨C 1999 Classified Windtunnel, located in room ME 357 |