Estimation of airborne viral emission: quanta emission rate of SARS-CoV-2 for infection risk assessment

Giorgio Buonanno; Luca Stabile; Lidia Morawska

highlight that the presence of the infected individual remaining inside for 10 minutes leads to an 269 increase in the quanta concentration in the volume: in particular, a higher peak of quanta 270 concentration was recognized, as expected, for reduced ventilation (NV) with respect to the 271 mechanical ventilation (MV). People entering the pharmacy after the infected individual are 272 exposed to a certain quanta concentration during their 10-min time, and the resulting risk for their 273 exposure (evaluated through equation (4)) is just a function of the quanta concentration trend. For 274 example, people entering the microenvironment around the quanta concentration peak are at a 275 higher risk than people entering the pharmacy later. Figure 2 shows an example of a customer 276 entering at min 26 and leaving at min 36: the risk for this 10-min exposure is 2.4% in natural 277 ventilation conditions and 1.0% in mechanical ventilation conditions. During the entire exposure 278 time of such a scenario (3 hours and 10 minutes), 179 customers (after the infected individual) enter 279 the pharmacy and each of them receive their own risk. In particular, the average risk of the 179 280 customers is 2.0% for NV conditions and 0.4% for MV conditions, then leading to a R0 (among the 281 customers) of 3.52 and 0.68, to which must be added the R0 of the five pharmacists exposed for the 282 entire period. Similar trends, not shown here graphically for the sake of brevity, were obtained for 283 all the scenarios investigated, then leading to the evaluation of the R0 for each of them as described 284