Efficiency Evaluation of N95 FFRs Under Cyclic and Constant Flows

A previous study on the efficiency of the N95 filter using a constant flow and a polydispersed aerosol showed that the maximum particle penetration in these filters was obtained for a size of particles of less than 100 nm and that the penetration exceeded the threshold penetration of 5 % for air flows higher than 85 L/min. [...] The second objective was to compare the efficiency of N95 FFRs under cyclic flows with the ones under constant flows equal to the cyclic flow minute volume, mean inhalation flow (MIF) and PIF. [...] For example, some toxicity studies of the UFPs and NPs found a good correlation between the surface area and the biological effects [1,17,18], while others found a better correlation between the number of particles and the biological effects [19]. [...] For a sinusoidal flow (as selected for all cyclic flows in this study), regardless of the breathing frequency, the PIF is π times the minute volume and π /2 times the MIF (or the MIF is twice the minute volume). [...] The results of both studies indicated that the penetration measured with the cyclic flow was typically higher than the penetration obtained by the equivalent constant flow [58,59].