Evaluating an Ultraviolet C System for Use During SARS-CoV2 Pandemic and Personal Protective Equipment Shortage

The supply of N95 masks and filtering facepiece respirators (FFRs) has been limited nationally owing to the coronavirus disease 2019 pandemic. Ultraviolet C (UVC) light has been suggested as a potential option for decontamination of FFRs by the Centers for Disease Control. There has been a lack of publications characterizing UVC dose distribution across FFRs.

A UVC light box and FFR rack system was assembled using low-pressure mercury lamps peaked at 254 nm and aluminum flashing to reduce shadowing effect. Dose was characterized with the use of ultraviolet (UV) intensity labels and an ultraviolet germicidal irradiation (UVGI) National Institute of Standards and Technology traceable meter. Ozone production was evaluated after extended bulb run time.

Calibration of UV intensity labels was noted to have color-change saturation at 100 mJ/cm². Dose measurements with the UV intensity labels on the FFR demonstrated symmetrical dose to all surfaces, but symmetry was not supported by measurements with the UVGI meter. There was substantial dose fall off on the lateral aspects of the FFR. No ozone production was noted in the UVC system.

UV intensity labels for characterization of dose provided a false suggestion of symmetry compared with the UVGI meter. Estimates of appropriate exposure times to reach 1000 mJ/cm² should be significantly increased to account for geometry of FFR and lateral dose fall off.