Can an Air Purifier Deactivate Aerosolized SARS-CoV2?
Anyone working in enclosed spaces, such as health care personnel, first responders, and general populations worldwide are susceptible to the severe threat of COVID-19 infection and high rate of transmission. As a result, the pandemic has brought about a need for rapid development of effective methods for removal of SARS-CoV-2 from the air in these environments, coupled with testing to validate efficacy of equipment for doing so.
For an industry-leading customer and as part of our broad consumer product testing and evaluation expertise, we tested a personal air purification (PAP) device for its efficiency in collecting aerosolized SARS-CoV-2 from the environment to provide purified breathable air to the user. The device is pocket sized and incorporates replaceable filters, built in fan flow, and a rechargeable power supply. The device fan supplies a continuous air flow from the environment that is filtered for the removal of airborne contaminants. As air is pulled into the device, the filtered air exits the device through a supplied flow tube for delivery to a face mask that is wearable by the user. The PAP is designed to provide fresh purified air flow to the face mask at a rate sufficient to replenish breathing air and reduce potential transmission of airborne biological pathogens to the user in populated or contaminated areas.
To evaluate the efficacy of the PAP device in removal of aerosolized SARS-CoV-2 from the air, we fabricated a single-pass aerosol test system. This system consisted of an aerosol flow tube with nebulizer adaptation, aerosol dilution air regulation and control, exhaust flow regulation, system pressure monitoring, and aerosol samplers. System flow rates were monitored using calibrated digital mass flow meters and controllers with HEPA filter conditioned supply air. This testing was conducted in a Biological Class III safety cabinet in one of our high containment Biosafety Level 3 (BSL-3) laboratories, with bio-aerosols sampled simultaneously both upstream and downstream of the device throughout the entirety of each test and assayed to quantify its efficacy.
For each test, bio-aerosol challenge flows were continuously maintained at 39.5 to 40 L/min for ten minutes. This flow rate range provided adequate volumetric flow to satisfy the device operation requirements as well as additional aerosol sample flow rates. Supply flows and exhaust flows of the test system were controlled and equilibrated in the range of –0.1 to +0.1 inches of water column for each test. This near-ambient pressure operating condition ensured operation that closely replicates a personal use environment.
Following each test, samples collected upstream and downstream were analyzed by the Tissue Culture Infectious Dose (TCID50) assay to determine viral concentration. The efficacy of the PAP device to collect/remove SARS-CoV-2 aerosols was calculated by subtracting the recovered dose of virus (downstream sample) from the delivered dose of virus (upstream sample).
The results of the experiment showed that the PAP device was able to reduce viable airborne virus by 99.65 percent, particle counts by 91.84 percent, and particle mass concentration by 97.59 percent. The efficacy observed in testing indicates that this device or others like it could be a valuable addition to the landscape of consumer PPE.
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