I don't have a citation, but I don't think it's filtering (in either direction) very well at all. With a cloth or paper mask, I suspect a lot of my exhales are slipping out of the sides and out the top. Instead, I think the mask is catching droplets and absorbing some of the moisture.
I think of it like a device that is acting the way your hand does when you cover your mouth when you sneeze or cough. Your hand isn't filtering in any real way, but you are keeping droplets from flying as far as they otherwise would.
I think a good filter would require something much more like a WWII gas mask or a forced air respirator in a hazmat suit, etc...
I think of it like a device that is acting the way your hand does when you cover your mouth when you sneeze or cough. Your hand isn't filtering in any real way, but you are keeping droplets from flying as far as they otherwise would.
I think a good filter would require something much more like a WWII gas mask or a forced air respirator in a hazmat suit, etc...