Establishment and application of test methodology demonstrating the functionality of air purification systems in reducing virus-loaded aerosol in indoor air.

BACKGROUND: The global COVID-19 pandemic has resulted in a greater interest in improving the ventilation of indoor environments in order to remove aerosolized virus and thus reduce transmission. Air purification systems have been proposed as a solution to improve aerosol removal. AIM: The aim was to determine the efficacy of air purification systems in reducing the viral load in the environmental air of a room. METHODS: A containment room equipped with HEPA filter on air intake and exhaust was constructed. It was connected via an inlet with the BSL-2 facility. From the BSL-2, Feline Coronavirus (FCoV)-loaded aerosols were released into the containment room. After nebulization, air sampling was performed to determine the viral load in air prior to assessing the clean air delivery rate of the air purification systems. The infectivity of the captured viruses was also examined. FINDINGS: The air purification systems realized a 97-99% reduction in viral load in air in 1 h. Captured infectious FCoV was reduced by 99.9%-99.99% by use of an ESP technology. CONCLUSIONS: The air purification systems, using ESP technology or HEPA filter, reduce the viral load in air. The ESP purifiers inactivate captured FCoV viruses. Therefore, air purification systems can be used as an adjunctive infection control measure.

Effective ultraviolet C light disinfection of respirators demonstrated in challenges with Geobacillus stearothermophilus spores and SARS-CoV-2 virus.

BACKGROUND: The global COVID-19 pandemic, accompanied by spikes in the number of patients in hospitals, required substantial amounts of respiratory protective devices (respirators), thereby causing shortages. Disinfection of used respirators by applying ultraviolet C (UVC) light may enable safe reuse, reducing shortages. AIM: To determine whether UVC disinfection is applicable to enable repeated safe reuse of respirators. METHODS: The UVC chamber, equipped with low-pressure mercury discharge lamps emitting at 254 nm, was used to determine the sporicidal and virucidal effects. Respirators challenged with spores and viruses were exposed to various UVC energy levels. Deactivation of the biological agents was studied as well as UVC effects on particle filtration properties and respirator fit. FINDINGS: A 5 log10 reduction of G. thermophilus spore viability by a UVC dose of 1.1 J/cm2 was observed. By simulating spores present in the middle of the respirators, a 5 log10 reduction was achieved at a UVC dose of 10 J/cm2. SARS-CoV-2 viruses were inactivated by 4 log10 upon exposure to 19.5 mJ/cm2 UVC. In case UVC must be transmitted through all layers of the respirators to reach the spores and virus, a reduction of >5 log10 was achieved using a UVC dose of 10 J/cm2. Exposure to a six-times higher UVC dose did not significantly affect the integrity of the fit nor aerosol filtering capacity of the respirator. CONCLUSION: UVC was shown to be a mild and effective way of respirator disinfection allowing for reuse of the UVC-treated respirators.