It’s one thing to say that C19 can’t survive long enough on dry surfaces or in the air to infect someone over a few feet away. The time between a water droplet drying on a carbon filter and the virus particle being in the airway of the mask-wearer is shorter than the time delay between sampling a surface and testing it for viable virus. There’s a huge difference between tests that would tell if C19 remains viable for a few seconds after drying out and tests that would tell if it remains viable on the order of how long it takes to inhale.
It looks like an exhaust port that incorporated a heat sink and moisture separator is plausibly more effective at preventing pathogen escape, but it has to be high-volume enough to pass a sneeze without it blowing out along the face.
It’s one thing to say that C19 can’t survive long enough on dry surfaces or in the air to infect someone over a few feet away. The time between a water droplet drying on a carbon filter and the virus particle being in the airway of the mask-wearer is shorter than the time delay between sampling a surface and testing it for viable virus. There’s a huge difference between tests that would tell if C19 remains viable for a few seconds after drying out and tests that would tell if it remains viable on the order of how long it takes to inhale.
You might find https://jamanetwork.com/journals/jama/fullarticle/2763852 of interest in the discussions as well. Both related to the question of just how fast the droplets might dry in air and how well the masks might work in terms of protecting others.
As I read the bit we might need to consider the protection as asymmetric—keeps more out than, possible, in even without considering an exhaust valve.
It looks like an exhaust port that incorporated a heat sink and moisture separator is plausibly more effective at preventing pathogen escape, but it has to be high-volume enough to pass a sneeze without it blowing out along the face.