Light propagation within N95 filtered face respirators: A simulation study for UVC decontamination.

Lothar Lilge,Tanner Young‐Schultz,Angelica Manalac,Chengjin Wang,Vaughn Betz,Frank X Gu,Ron Hofmann,Madrigal Weersink,Abdallatif Satti Abdalrhman,Aldrich Ngan,Fynn Schwiegelshohn

doi:10.1002/jbio.202000232

Abstract

This study presents numerical simulations of UVC light propagation through seven different filtered face respirators (FFR) to determine their suitability for Ultraviolet germicidal inactivation (UVGI). UV propagation was modeled using the FullMonte program for two external light illuminations. The optical properties of the dominant three layers were determined using the inverse adding doubling method. The resulting fluence rate volume histograms and the lowest fluence rate recorded in the modeled volume, sometimes in the nW cm-2 , provide feedback on a respirator's suitability for UVGI and the required exposure time for a given light source. While UVGI can present an economical approach to extend an FFR's useable lifetime, it requires careful optimization of the illumination setup and selection of appropriate respirators.

Highlights

Rapid local or global outbreaks of disease, such as SARS, Ebola and COVID-19 caused by SARS-CoV-2, cannot be forecast despite the general knowledge that they will sporadically occur
The death rate associated with SARS-CoV-2 induced COVID-19 ranges from 1.3% (Russia) to 15.5% (France) June 8th, 2020 [3] and an average mortality rate of 3.7%, underscoring the need for a very high level of protection for health care workers
We aim to show respirator models suitable or unsuitable for further UVC decontamination

Summary

Introduction

Rapid local or global outbreaks of disease, such as SARS, Ebola and COVID-19 caused by SARS-CoV-2, cannot be forecast despite the general knowledge that they will sporadically occur. Health care providers are at risk during such outbreaks. Out of the 8096 reported cases during the 2002-2004 SARS outbreak, 1706 (21%) were health care workers [1], as were 221 of the 3956 fatalities in Sierra Leone during the 2019-2020 Ebola outbreak [2]. The death rate associated with SARS-CoV-2 induced COVID-19 ranges from 1.3% (Russia) to 15.5% (France) June 8th, 2020 [3] and an average mortality rate of 3.7%, underscoring the need for a very high level of protection for health care workers. Regular face masks are recommended for the broader public to reduce the infection rate further

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