Portable air cleaners and residential exposure to SARS‐CoV‐2 aerosols: A real‐world study

Abstract

Individuals with COVID‐19 who do not require hospitalization are instructed to self‐isolate in their residences. Due to high secondary infection rates in household members, there is a need to understand airborne transmission of SARS‐CoV‐2 within residences. We report the first naturalistic intervention study suggesting a reduction of such transmission risk using portable air cleaners (PACs) with HEPA filters. Seventeen individuals with newly diagnosed COVID‐19 infection completed this single‐blind, crossover, randomized study. Total and size‐fractionated aerosol samples were collected simultaneously in the self‐isolation room with the PAC (primary) and another room (secondary) for two consecutive 24‐h periods, one period with HEPA filtration and the other with the filter removed (sham). Seven out of sixteen (44%) air samples in primary rooms were positive for SARS‐CoV‐2 RNA during the sham period. With the PAC operated at its lowest setting (clean air delivery rate [CADR] = 263 cfm) to minimize noise, positive aerosol samples decreased to four out of sixteen residences (25%; p = 0.229). A slight decrease in positive aerosol samples was also observed in the secondary room. As the world confronts both new variants and limited vaccination rates, our study supports this practical intervention to reduce the presence of viral aerosols in a real‐world setting.

Natural ventilation, low CO2 and air filtration are associated with reduced indoor air respiratory pathogens

“…Testing ambient air for bioaerosols of significance to human health has a long history in research 3,6,21,32 . While outdoor air sampling to detect respiratory pathogens is possible 26 , indoor air may be the more attractive alternative as humans spend over 90% of their time indoors, and as most respiratory transmission occurs there 5,8,9,34 . Dinoi et al (2022) combined data from 73 studies to show that the SARS-CoV-2 bioaerosol load is lowest in outdoor air, and higher in indoor air from hospitals than from community settings 31 .…”

“…Cuypers et al ( 2022) described the method for performing the Taqpath COVID-19 CE-IVD RT-PCR assay (Thermo Fisher Scientific, Waltham, MA, USA) on air samples 26 .…”

“…As for air filtration, portable filters were shown to speed up the clearance of airborne particles 24,25 . Two small studies also suggested a reduction in detection of SARS-CoV-2 in ambient air but the effect was not significant 26,27 , while Conway-Morris et al (2022) did see a significant reduction in the detection of SARS-CoV-2 and other respiratory pathogens 28 . No study has thus far controlled for other important variables when assessing the influence of either ventilation or portable air filters on the load of respiratory pathogen bioaerosols in real-life settings.…”

HEPA filters of portable air cleaners as a tool for the surveillance of SARS‐CoV ‐2

“… 16 Several experimental studies have provided evidence for the potential of portable HEPA purifiers to eliminate airborne SARS‐CoV‐2. 17 , 18 , 19 , 20 , 21 Rodriguez et al 20 analyzed the indoor air of positive patients in households before and after using a PAC. All the air samples collected (by using an MD8 Airport portable air collector with gelatin membrane filter) before using PACs were positive for SARS‐CoV‐2 while after switching on PACs, all samples except one were negative, but authors highlighted the fact that in the negative case the sampled room size was higher than recommended for the use of this device.…”

“…The analysis of dust collected on filters in central forced‐air heating, ventilation, and air conditioning (HVAC) or portable systems to determine the presence of biotic and abiotic contaminants in indoor air have been widely investigated and are collected in Haaland and Siegel's review 16 . Several experimental studies have provided evidence for the potential of portable HEPA purifiers to eliminate airborne SARS‐CoV‐2 17–21 . Rodriguez et al 20 analyzed the indoor air of positive patients in households before and after using a PAC.…”