The impact of heating, ventilation, and air conditioning design features on the transmission of viruses, including the 2019 novel coronavirus: a systematic review of filtration

Fleck, B. A.; Thornton, G. M.; Zhong, L.; Hartling, L. A.; Dandnayak, D.; Kroeker, E.; Fleck, N. J.

Historically, viruses have demonstrated airborne transmission. Emerging evidence suggests the novel coronavirus (SARS-CoV-2) that causes COVID-19 may also spread by airborne transmission. This is more likely in indoor environments, particularly with poor ventilation. In the context of potential airborne transmission, a vital mitigation strategy for the built environment is heating, ventilation, and air conditioning (HVAC) systems. HVAC features could modify virus transmission potential. A systematic review following international standards was conducted to comprehensively identify and synthesize research examining the effectiveness of filters within HVAC systems in reducing virus transmission. Twenty-three relevant studies showed that: filtration was associated with decreased transmission; filters removed viruses from the air; increasing filter efficiency (efficiency of particle removal) was associated with decreased transmission, decreased infection risk, and increased viral filtration efficiency (efficiency of virus removal); increasing filter efficiency above MERV 13 was associated with limited benefit in further reduction of virus concentration and infection risk; and filters with the same efficiency rating from different companies showed variable performance. Increasing filter efficiency may mitigate virus transmission; however, improvement may be limited above MERV 13. Adapting HVAC systems to mitigate virus transmission requires a multi-factorial approach and filtration is one factor offering demonstrated potential for decreased transmission.