Abstract
Recent crisis in the form of COVID-19 has rendered wearing a face mask mandatory for patients, health care workers and even members of public worldwide. This has caused a sudden shift of focus on availability, effectiveness, re-use and development of face masks. It is imperative that commercialization of face masks is subjected to certification, following standard procedures, from authorized agencies. However, at times, there is a need to conduct a quick investigation on their performance, specially, when new materials are being used for making the masks. In the current pandemic situation, the shortage of masks has also led to a rethinking on strategies of reuse of masks after due sterilization. For such situations, a quick laboratory methodology to test/determine the effectiveness of face mask respirators has been developed. The testing parameters include the particle capture efficiency of the mask material, pressure drop and the fit factor. Two different, simple, make-shift set-ups have been adopted for the present context. The first is used to measure the intrinsic particle capture efficiency and pressure drop of the filter material and the second is employed as a ‘full mask sampler’ to assess the leakages through seams and joints. For particle filtration efficiency, measurements in optical particle diameter range (0.3-20 µm) are most important as they cover the most penetrating particle size (MPPS) range; nevertheless, we also measured aerosol number concentration in sub-micrometer and ultrafine size ranges. Experiments conducted with atomized NaCl test aerosols, using these setups on three types of face masks viz. commercial N-95, surgical mask and cloth mask have been used for the validation and interpretation of results. This paper hopes to provide a crucial laboratory link between the face mask developers and the final certification agencies in the times of urgency.
A numerical analysis of pressure drop and particle capture efficiency by rectangular fibers using LB-DE methods