Upper-room ultraviolet air disinfection might help to reduce COVID-19 transmission in buildings: a feasibility study

Abstract

As the world’s economies come out of the lockdown imposed by the COVID-19 pandemic, there is an urgent need for technologies to mitigate COVID-19 transmission in confined spaces such as buildings. This feasibility study looks at one such technology, upper-room ultraviolet (UV) air disinfection, that can be safely used while humans are present in the room space, and which has already proven its efficacy as an intervention to inhibit the transmission of airborne diseases such as measles and tuberculosis. Using published data from various sources, it is shown that the SARS-CoV-2 virus, the causative agent of COVID-19, is highly likely to be susceptible to UV-C damage when suspended in air, with a UV susceptibility constant likely to be in the region 0.377–0.590 m2/J, similar to that for other aerosolised coronaviruses. As such, the UV-C flux required to disinfect the virus is expected to be acceptable and safe for upper-room applications. Through analysis of expected and worst-case scenarios, the efficacy of the upper-room UV-C approach for reducing COVID-19 transmission in confined spaces (with moderate but sufficient ceiling height) is demonstrated. Furthermore, it is shown that with SARS-CoV-2, it should be possible to achieve high equivalent air change rates using upper-room UV air disinfection, suggesting that the technology might be particularly applicable to poorly ventilated spaces.

SARS-CoV-2 Survival on Surfaces and the Effect of UV-C Light

“…The attention paid to hygiene practices towards the body and the surfaces has led to several modifications in human habits and to the development of innovative and efficient cleaning procedures. As well as the chemical ones, physical disinfection methods may be rapid and less time-consuming thanks to the possibility for them to be exerted by automated instruments and to the possibility of being carried out on solid surfaces and aerosols [ 14 ].…”

“…In this context, beyond the standard disinfection methods such as chemical ones, ultraviolet germicidal irradiation (UVGI) has a potential role. In particular, UV-C light at wavelengths of about 254 nm exerts bactericidal and virucidal effects, and it is widely used in the environmental disinfection of enclosed spaces [ 14 ]. UV-C light induces chemical modifications of nucleic acids, leading to the blocking of replication mechanisms [ 15 ].…”

Ultraviolet germicidal irradiation (UVGI) for in-duct airborne bioaerosol disinfection: Review and analysis of design factors

“…Therefore, directly applying the UV rate constant extracted from Table 1 will underestimate the UVGI performance (lower UV rate constant of microbes in water than in aerosols). To convert available laboratory data from the liquid phase to the aerosol phase, some studies introduced a species-dependent concept of “UV rate constant ratio of aerosol and liquid” to correlate the UV rate constant of a group of the same types of viruses in different phases [ 57 , 63 ]. Using this methodology, researchers estimated that the UV rate constant of the coronavirus in air is 1.8–6.0 times higher than that in liquid [ 63 ].…”

Severe acute respiratory syndrome coronavirus-2 medical solid waste treatment: A need for efficient and effective strategies in low-resourced settings

“…Using published data from various sources, it is shown that the SARS coronavirus-2, the causative agent of COVID-19, is highly likely to be susceptible to UI-C damage when suspended in air, with a UI susceptibility constant likely to be in the region 0.377–0.590 m 2 J −1 , similar to that for other aerosolized coronaviruses ( Beggs et al, 2020 ).…”