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BackgroundHealthcare workers treating patients with SARS-CoV-2 are at risk of infection from patient-emitted virus-laden aerosols. We quantified the reduction of airborne infectious virus in a simulated hospital room when a ventilated patient isolation (McMonty) hood was in use. MethodsWe nebulised 109 plaque forming units (PFU) of bacteriophage PhiX174 virus into a 35.1m3 room with a hood active or inactive. The airborne concentration of infectious virus was measured by BioSpot-VIVAS and settle plates using plaque assay quantification on the bacterial host Escherichia coli C. The particle number concentration (PNC) was monitored continuously using an optical particle sizer. ResultsMedian airborne viral concentration in the room reached 1.41 x 105 PFU.m-3 with the hood inactive. Using the active hood as source containment reduced infectious virus concentration by 374-fold in air samples. This was associated with a 109-fold reduction in total airborne particle number escape rate. The deposition of infectious virus on the surface of settle plates was reduced by 87-fold. ConclusionsThe isolation hood significantly reduced airborne infectious virus exposure in a simulated hospital room. Our findings support the use of the hood to limit exposure of healthcare workers to airborne virus in clinical environments. Lay summaryCOVID-19 patients exhale aerosol particles which can potentially carry infectious viruses into the hospital environment, putting healthcare workers at risk of infection. This risk can be reduced by proper use of personal protective equipment (PPE) to protect workers from virus exposure. More effective strategies, however, aim to provide source control, reducing the amount of virus-contaminated air that is exhaled into the hospital room. The McMonty isolation hood has been developed to trap and decontaminate the air around an infected patient. We tested the efficacy of the hood using a live virus model to mimic a COVID-19 patient in a hospital room. Using the McMonty hood reduced the amount of exhaled air particles in the room by over 109-times. In our tests, people working in the room were exposed to 374-times less infectious virus in the air, and room surfaces were 87-times less contaminated. Our study supports using devices like the McMonty hood in combination with PPE to keep healthcare workers safe from virus exposure at work.
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ObjectiveTo assess the effectiveness of aerosol filtration by portable air cleaning devices with high efficiency particulate air (HEPA) filters used in addition to standard building heating ventilation and air-conditioning (HVAC). MethodsTest rooms, including a hospital single-patient room, were filled with test aerosol to simulate aerosol movement. Aerosol counts were measured over time with various portable air cleaning devices and room ventilation systems to quantify the aerosol concentration reduction rate and overall clearance rate. ResultsPortable air cleaners were very effective in removing aerosols, especially for the devices with high flow rate. In a small control room, the aerosols were cleared 4 to 5 times faster with portable air cleaners than the room with HVAC alone. A single bed hospital room equipped with an excellent ventilation rate ([~] 14 air changes per hour) can clear the aerosols in 20 minutes. However, with the addition of two air cleaners, the clearance time became 3 times faster (in 6 minutes and 30 seconds). ConclusionsPortable air cleaning devices with HEPA filtration were highly effective at removing aerosols. To clear aerosols (above 90% clearance) in under 10 minutes requires around 25 air changes per hour; readily feasible with air cleaners. Inexpensive portable air cleaning devices should be considered for small and enclosed spaces in health care settings such as inpatient rooms, personal protective equipment donning/doffing stations, and staff tea rooms. Portable air cleaners are particularly important where there is limited ability to reduce aerosol transmission with building HVAC ventilation.
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ObjectiveTo study the airflow, transmission and clearance of aerosols in the clinical spaces of a hospital ward that had been used to care for patients with COVID-19, and to examine the impact of portable air cleaners on aerosol clearance. DesignObservational study SettingA single ward of a tertiary public hospital in Melbourne Australia InterventionGlycerine-based aerosol was used as a surrogate for respiratory aerosols. The transmission of aerosols from a single patient room into corridors and a nurses station in the ward was measured. The rate of clearance of aerosols was measured over time from the patient room, nurses station and ward corridors with and without air cleaners (also called portable HEPA filters). ResultsAerosols rapidly travelled from the patient room into other parts of the ward. Air cleaners were effective in increasing the clearance of aerosols from the air in clinical spaces and reducing their spread to other areas. With two small domestic air cleaners in a single patient room of a hospital ward, 99% of aerosols could be cleared within 5.5 minutes. ConclusionAir cleaners may be useful in clinical spaces to help reduce the risk of healthcare acquired acquisition of respiratory viruses that are transmitted via aerosols. They are easy to deploy and are likely to be cost effective in a variety of healthcare settings
