have published simulations that suggest that cloth masks work a lot better than masks with valves at preventing the spread of Covid-19 and other viruses. Whether or not this works the same in real life, it is something to consider when choosing what to use. It is likely that practical concerns are key in this. If you are a frequent face toucher, or someone who sweats a lot and have had the self waterboarding experience that I have in summer, valve respirators are not just a Goth fashion statement. Just make sure you’re using a quality product and your filters have full coverage and you change them often enough.