A Scalable Method of Applying Heat and Humidity for Decontamination of N95 Respirators During the COVID-19 Crisis

Loïc Anderegg; Cole Meisenhelder; Chiu Oan Ngooi; Lei Liao; Wang Xiao; Steven Chu; Yi Cui; John M Doyle

is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.04.09.20059758 doi: medRxiv preprint note that a convection oven has no direct line of sight to any radiative heat sources, which would have the potential to damage the masks. For testing purposes, the lids of the containers were modified to allow a temperature and humidity sensor (SHT30 DFR0588) inside. We found that the humidity will drop rapidly in the presence of a small hole in the lid. The gap between the wires and the lid were thus sealed with 10 minute epoxy with a working temperature of 93 o C. For temperature verification, we also used both a K type thermocouple (readout with a SR630) and an IR thermometer (Fluke 561). Figure 3 shows the humidity as a function of time within each container as well as the variability of humidity on the volume of water added. We find that 500 uL is the optimal amount of water for the 1.25 qt. container. We also find that the humidity takes between 10-15 minutes to reach the 60% level. This is an important consideration when applying this method as at least 10 additional minutes should be added to the heating cycle to achieve the desired time at target humidity. The temperature rises to within 2 o C of the target temperature in a similar time.