In Vitro Aerodynamic Comparison of Protective Masks

Most of the causative agents of respiratory infectious diseases are transmitted by droplets or through the air aerosols, and protective masks are recommended as a basic non-pharmaceutical intervention for prevention or slowing down their spread. In the conditions of the pandemic, there is a shortage of commercial masks and materials for their production, and an insufficient number of laboratories authorized to test protective equipment, have resulted in an increased need for new potential materials for making masks and alternative methods for their testing. In this research, a simple and fast method for testing the efficiency of particle filtration is proposed as the most important parameter of mask quality. The method is based on the passage of fluticasone propionate aerosol through the mask sample and then through the eight-stage Andersen cascade impactor in order to particles were classified on the basis of size, considering that the efficiency of filtration depends to the greatest extent on the size of the investigated particles. The filtration efficiency of the mask is determined by the mass of the particles that pass through the mask compared to the positive control. Masks with different properties and filtration mechanisms were tested: medical mask, filtering half mask and several different cloth face masks, and the results showed that the method is adequate for all tested types of protective masks. Although the filter half mask and medical mask showed the highest filtration efficiency for all particle sizes, multi-layer cloth masks can represent an equally good barrier to larger particles and significantly reduce the spread of droplet-borne viruses through and therefore as a last resort, they can represent a good alternative in cases of shortage of commercially available certified materials and masks.