Surgical/cotton masks protect other people from your sneezing and breathing out aerosolized virus. N95 masks do the same, but also protect you from 95% of part

Surgical/cotton masks protect other people from your sneezing and breathing out aerosolized virus. N95 masks do the same, but also protect you from 95% of particles that meet the following: "The particle size distribution will be a count median diameter of 0.185±0.020 micrometer and a geometric standard deviation not exceeding 1.6. Each respirator filter unit will be challenged with an aerosol concentration of 100 ± 10 mg/m3" https://www.cdc.gov/niosh/npptl/stps/pdfs/TEB-APR-STP-0001-508.pdf https://www.cdc.gov/niosh/npptl/stps/pdfs/TEB-APR-STP-0001-5... They are also tested for air flow rates to meet standard for inflow and outflow. They don't protect you against the virus, they protect you against the aerosols that may be carrying the virus. Face shields are for protecting against liquids and solids, not particles. They might be useful for people like checkout clerks, but a fixed screen would do the same.