UV light dosage distribution over irregular respirator surfaces. Methods and implications for safety

Aurora Baluja; Justo Arines; Ramon Vilanova; Carmen Bao-Varela; Maria Teresa Flores-Arias

Two masks models were simulated: model SAFE 231FFP3NR and the model Aura 9322 3M. The first model was simulated with a truncated pyramid of dimensions (long, width, high) 17cm x 4cm x 9cm. The base of 4 cm corresponds to the case were the masks are slightly open. The second model was simulated with a truncated pyramid of dimensions 17cm x 9cm x 5cm. The masks were placed in two rows and three columns as they are planned to be in the disinfection box. Additionally, two different orientations were simulated with respect to the long side of the box, parallel and perpendicular. Blue colors correspond to a reference amount of light. Green color represents a value equal to two times the reference value, yellow corresponds to three times, amber to four times, and red to 5 times. Similarity was observed between the measured data and the simulations. In both cases, as long as we move away from L2, a reduction in the irradiance is calculated, getting the minimum exposure in the right side of the respirator mask on the right. Both, measured data and simulations reflect that in region C of figure 4 we get half of the exposure obtained at D, and one third of that at E. Additionally, comparing the two light distribution obtained for the two orientations of the respiratory masks, the shadows obtained with the masks parallel to the long side of the box, are less pronounced. Hence, this orientation is suggested as the preferred one. Figure 5 compares the pseudocolor maps of the light distribution inside the disinfection box using three and four lamps. Note the difference between using three or four lamps, as four lamps provide a more uniform light distribution with less difference in the light amount. With four lamps we also diminish the shadows in the face of the mask of the right side.