The Ever Useful Dr. Lilge takes on Mask DecontaminationAnd, as usual, his research keeps in mind the needs of those in poorer countries.
Journal of BIOPHOTONICS Inside Cover Lothar Lilge Angelica Manalac Madrigal Weersink Fynn Schwiegelshohn Tanner YoungSchultz Abdallatif Satti Abdalrhman Chengjin Wang Aldrich Ngan Frank X. Gu Vaughn Betz Ron Hofmann First published: 22 December 2020 
FULL ARTICLE 1 INTRODUCTION
Rapid local or global outbreaks of disease, such as SARS, Ebola and COVID19 caused by SARSCoV2, cannot be forecast despite the general knowledge that they will sporadically occur. Health care providers are particularly at risk during such outbreaks. For example, out of the 8096 reported cases during the 2002 to 2004 SARS outbreak, (21%) were health care workers, as were 221 of the 3956 fatalities in Sierra Leone during the 2019 to 2020 Ebola outbreak. The death rate associated with SARSCoV2 induced COVID19 ranges from 1.3% (Russia) to 15.5% (France) June 8, 20203 and an average mortality rate of 3.7%, underscoring the need for a very high level of protection for health care workers. Hence, the use of N95 disposable filtering facepiece respirators (FFR) is restricted to front line health care professionals in most North American jurisdictions. Regular face masks are recommended for the broader public to reduce the infection rate further.
The current COVID19 pandemic has severely stressed supplies of personal protective equipment (PPE), including N95 FFR (N95 FFRs). In response, healthcare facilities worldwide are forced to extend the use or reuse of their N95 FFRs. Few options can be adopted for N95 FFR reuse. The US Food and Drug Administration (FDA) emergency use authorization (EUA) guidance states that vaporized hydrogen peroxide gas plasma or hydrogen peroxide vapor (HPV) can be used for FFR decontamination if various conditions are satisfied, such as being free of visible damage and visual soil/contamination.5 Due to postprocessing form loss, vaporized hydrogen peroxide gas sterilization is not authorized for use with respirators containing cellulosebased or paper materials. Moreover, these techniques are not readily available in some middle and lowincome countries. Among the alternative methods, ultraviolet light germicidal irradiation (UVGI) is promising and is recommended by the US centers for disease control and prevention.
...........................................
4 CONCLUSION
UVGI is a reasonable approach for FFR decontamination to extend a respirator's usable lifetime when supply chains are restricted during public health emergencies. Both the investment costs and environmental impact are low. Operator exposure to harmful UV radiation and ozone can be minimized by simple technical safety measures. However, to achieve consistent, fast and complete decontamination, the photonsource positions need to be paired to the respirator shape, and the optical properties of the FFR model to be irradiated needs to be determined at the UVGI wavelength, to establish the minimum required exposure time based on photon distribution simulations as described here.