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

BackgroundThe supply of N95 mask or filtering facepiece respirator (FFR) has been limited nationally due to the Covid-19 pandemic. 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.MethodsA UVC light box and FFR rack system was assembled utilizing low pressure mercury lamps peaked at 254 nm and aluminum flashing to reduce shadowing effect. Dose was characterized with the use of UV intensity labels and a UVGI (ultraviolet germicidal irradiation) NIST (National Institute of Standards and Technology) traceable meter. Ozone production was evaluated after extended bulb run time.ResultsCalibration of UV intensity labels were noted to have color-change saturation at 100 mJ/cm 2. Dose measurements with the UV intensity labels on the FFR demonstrated symmetric dose to all surfaces but symmetry 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.ConclusionsUV intensity labels for characterization of dose provided a false suggestion of symmetry when compared to 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.