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

Abstract

Respiratory viruses are capable of transmitting via an aerosol route. Emerging evidence suggests that SARS-CoV-2 which causes COVID-19 can be spread through airborne transmission, particularly in indoor environments with poor ventilation. Heating, ventilation, and air conditioning (HVAC) systems can play a role in mitigating airborne virus transmission. We conducted a systematic review of the scientific literature examining the effectiveness of HVAC design features in reducing virus transmission; here we report results for ultraviolet (UV) radiation. Following international standards for systematic reviews, we conducted a comprehensive search and synthesized findings from 32 relevant studies published between 1936 and 2020. Research demonstrates that: viruses and bacteriophages are inactivated by UV radiation; increasing UV dose is associated with decreasing survival fraction of viruses and bacteriophages; increasing relative humidity is associated with decreasing susceptibility to UV radiation; UV dose and corresponding survival fraction are affected by airflow pattern, air changes per hour, and UV device location; and UV radiation is associated with decreased transmission in both animal and human studies. This comprehensive synthesis of the scientific evidence examining the impact of UV radiation on virus transmission can be used to guide implementation of systems to mitigate airborne spread and identify priorities for future research.

Risk of Infection Due to Airborne Virus in Classroom Environments Lacking Mechanical Ventilation

“…Attempts to disinfect the classroom air through use of portable UV-C generating devices had no effect upon the number of transmission events observed, regardless of the UV device fan speed or the amount of time of UV treatment. Some evidence suggests that the specific type of airborne virus as well as the wavelength of UV light along with various environmental conditions could affect disinfection results (26), although no impact was observed with the units used in this study.…”

“…No fan speed proved to be more effective than the control room tested contemporaneously without the UV units. Importantly, results observed for UV mitigation here may not be representative of all UV-based disinfection approaches or their efficacy, as device design and application vary widely (26).…”