Why are surgical or self-made masks supposed to be better at protecting others than at protecting oneself? Naively, it seems to me that the percentage of filtered droplets/aerosol should be the same regardless of the direction in which it is breathed.
I think it’s mostly because the mask slows down the flow of exhaled air, which reduces the distance the droplets travel before they evaporate or fall to the ground. You can see this illustrated here and what happens without a mask here.
Aerosolization maybe happens more after exposure to air where water evaporates off of the lipid/protein shell. On exhale into mask it hasn’t had as much time to evaporate and is in humid environment, on inhale brought mask it has made its way over from another person and has had more time to aerosolize in drier air.
Don’t know about percentage of filtered droplets/aerosol in both directions, but I would guess the reasons include:
1. A mask doesn’t protect your eyes
2. You are likely to touch contaminated outer surface of your mask (and then touch your mouth, scratch your eye etc and get infected), but other people probably won’t touch the inner surface of your mask.
Why are surgical or self-made masks supposed to be better at protecting others than at protecting oneself? Naively, it seems to me that the percentage of filtered droplets/aerosol should be the same regardless of the direction in which it is breathed.
I think it’s mostly because the mask slows down the flow of exhaled air, which reduces the distance the droplets travel before they evaporate or fall to the ground. You can see this illustrated here and what happens without a mask here.
Aerosolization maybe happens more after exposure to air where water evaporates off of the lipid/protein shell. On exhale into mask it hasn’t had as much time to evaporate and is in humid environment, on inhale brought mask it has made its way over from another person and has had more time to aerosolize in drier air.
And as mentioned below, large droplets would be caught and kept off surfaces reducing hand to face transfer.
Don’t know about percentage of filtered droplets/aerosol in both directions, but I would guess the reasons include:
1. A mask doesn’t protect your eyes
2. You are likely to touch contaminated outer surface of your mask (and then touch your mouth, scratch your eye etc and get infected), but other people probably won’t touch the inner surface of your mask.