A rapid review of Supplementary air filtration systems in health service settings. September 2022.

The aerosol spread of SARS-CoV-2 has been a major challenge for healthcare facilities and there has been increased use of supplementary air filtration to mitigate SARS-CoV-2 transmission. Appropriately sized supplementary room air filtration systems could greatly reduce aerosol levels throughout ward spaces. Portable air filtration systems, such as those combining high efficiency particulate air (HEPA) filters and ultraviolet (UVC) light sterilisation, may be a scalable solution for removing respiratory viruses such as SARS-CoV-2. This rapid review aimed to assess the effectiveness of supplementary air cleaning devices in health service settings such as hospitals and dental clinics (including, but not limited to HEPA filtration, UVC light and mobile UVC light devices) to reduce the transmission of SARS-CoV-2. One systematic review (Daga et al. 2021), three observational studies (Conway Morris et al. 2022, Thuresson et al. 2022, Sloof et al. 2022), one modelling study, (Buchan et al. 2020) and two experimental studies (Barnewall & Bischoff 2021, Snelling et al. 2022) were found. Outcome measures included symptom scores, presence of SARS-CoV-2 RNA in sample counts, general particulate matter counts, viral counts, and relative risk of SARS-CoV-2 exposure. From real world settings, the systematic review assessed the effectiveness of HEPA filtration in dental clinics (Daga et al. 2021), two additional observational studies assessed HEPA and UV light in UK hospital settings (Conway Morris et al. 2022, Sloof et al. 2022) and one observational study included mobile HEPA-filtration units in Swedish hospitals (Thuresson et al. 2022). Studies were published from 2020 onwards. Real world evidence suggests supplementary air systems have the potential to reduce SARS-CoV-2 in the air and subsequently reduce transmission or infection rates but further research, with study designs having lower risk of bias, is required. HEPA filters alongside UVC light could provide the most notable reductions in SARS-CoV-2 counts, although the supporting evidence relates to HEPA/UVC filtration, and this review does not provide evidence on the effectiveness of other potential supplementary air filtration systems that could be used. Evidence is limited on the optimum air changes per hour needed and the positioning of air filtration units in rooms. Funding statementThe Wales Centre for Evidence Based Care was funded for this work by the Wales COVID-19 Evidence Centre, itself funded by Health & Care Research Wales on behalf of Welsh Government.