Something like a surgical mask can help a bit even if other unmasked sick people are around, but nowhere near as much as a proper respirator. It’s something like 25%-40% more effective vs. without one, and it goes up from there if everyone is wearing one and they are properly fitted. Some respirators don’t protect anyone from a sick wearer (like painter’s masks with cartridges and an unfiltered exhaust) but others do (like N95s/FFP2s).
Something like a surgical mask can help a bit even if other unmasked sick people are around, but nowhere near as much as a proper respirator. It’s something like 25%-40% more effective vs. without one, and it goes up from there if everyone is wearing one and they are properly fitted. Some respirators don’t protect anyone from a sick wearer (like painter’s masks with cartridges and an unfiltered exhaust) but others do (like N95s/FFP2s).