Quick laboratory methodology for determining the particle filtration efficiency of face masks/respirators in the wake of COVID-19 pandemic

Recent crisis in the form of COVID-19 has rendered wearing of mask mandatory for patients, health care workers and members of public worldwide. This has caused a sudden shift of focus on availability, effectiveness, re-use and development of face masks/respirators. In the current pandemic situation, the shortage of masks has also led to rethinking on strategies of reuse of masks after due sterilization. This work discusses a quick laboratory methodology to test/determine the particle filtration efficiency of face masks/respirators. The testing parameters include the particle capture efficiency of the mask material/full mask, 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 as a 'full mask sampler' to assess the leakages through seams and joints of the mask. Experiments conducted with atomized NaCl test particles on three types of mask viz. commercial N-95 respirator, surgical mask and cloth mask have been used for evolving the methodology. The differences in terms of capture efficiency of aerosol particles for the filter material and for the full mask in face fix/sealed fixture have been linked to improvement of the mask design in development phase. This paper hopes to provide a crucial laboratory link between the mask developers and the certification agencies in the times of urgency. Needless to mention that commercialization of the same is subject to certification from authorized agencies, following standard procedures.

Automated summary

This study presents a quick laboratory method for testing the particle filtration efficiency of face masks and respirators, and discusses the strategy of reusing masks during the current COVID-19 pandemic. Experimental results show that improving mask design can enhance particle capture efficiency and overall mask fit.