Yes, our masks block very small particles and thus also block viruses like COVID. Our filters are made from 5 different microfiber layers that can remove small particles down to 0.3 microns of even smaller than PM2.5 particles. There is also a carbon fiber layer that removes gasses. Valves on a mask do not fully secure a virus from leaving a mask, so if you have symptoms of a virus, please make sure to use a mask without any valves. Our masks wil reduce the amount of expiration and air coming out of your mask, and they will redirect your cough or sneeze straight down towards the floor.