Generation and biological collection efficiency of MS2 bioaerosol for the evaluation of aerosol filtration devices

Exposure to bioaerosol in indoor environments is associated with adverse health effects. There is need to develop control devices to separate bioaerosols from gas streams in heating and ventilation systems to protect human health and enhance national security. The goal of this research is to develop an experimental setup to evaluate the virus removal efficiency of an electrothermally regenerated activated carbon fiber cloth (ACFC) filter. MS2 bacteriophage was used as a model virus. Three tasks were conducted. The first task involved the development of a modified Liquid Sparging Aerosolizer (LSA) generator, which was fabricated to produce a stable supply of tested bioaerosol. The second task involved the determination of the biological collection efficiency of the SKC BioSampler for bacteriophage MS2. The BioSampler is used to characterize the biological removal efficiency of the ACFC filter by capturing the bioaerosol in a liquid medium before and after the ACFC filter. The biological collection efficiency of the BioSampler was calculated based on the results of infectivity assay. A 100 kDalton membrane was used to collect aerosolized MS2 particles at the inlet of the BioSampler. Infectivity assay was used to determine the infectious MS2 particles on the membrane filter and in the collection media of the BioSampler. Under 1 slpm (standard liter per minute) (20 °C, 1 atm) flow rate of the filter, 6 slpm (20 °C, 1 atm) flow rate of the BioSampler, and 50% relative humidity (RH), the biological collection efficiency calculated based on the results of the infectivity assays was 7.9 ± 0.42% based on three independent tests. The third task was to determine the ACFC’s ability to physically remove nanometer diameter particles. ACFC was tested with 40 nm and 95 nm diameter PSL beads. A particle physical removal of 97 ± 0.07% of the particles was measured based on the difference of the outlet and inlet particle number concentrations. This research comprises the preparatory steps into the development of an indoor airfiltering device. A stable bioaerosol generator was built and tested; the physical removal efficiency of the filter and the biological collection efficiency of the BioSampler were quantified. The low biological bioaerosol collection efficiencies found in this research provide an opportunity for future research, which should involve the evaluation of the biological collection efficiency under variable conditions of RH, flow rate, and viral concentration for different nanodiameter sized viruses. Based on these results, a more accurate testing of the ACFC’s removal efficiency for viral particles should be conducted. Finally, electrothermal heating experiments must be performed, which will incorporate the evaluation of the amount of electrical power applied to the ACFC filter and the effect of increased electrical power on the infectivity of collected bioaerosols. All these experiments will test the ACFC’s capability to remove bioaerosols from airstreams and thus become a potential filter device for air conditioning and ventilation (HVAC) systems