Size- and Time-Dependent Particle Removal Efficiency of Face Masks and Improvised Respiratory Protection Equipment Used during the COVID-19 Pandemic. - Anja Pogacnik Krajnc; Luka Pirker; Urska Gradisar Centa; Anton Gradisek; Igor B. Mekjavic; Matej Godnic; Metod Cebasek; Tina Bregant; Maja Remskar (Sensors, 2021)