My personal interest is filtering on ingress. I can feel the pressure when I breathe in, the air is going through the mask for sure.
On egress, just a quick look at the valve, it's going to stop the velocity and either block or drop particles - however ineffective that might be on egress there is NO WAY it is worse then what I see others wearing (surgical / thin cloth etc), mask off the nose, mask off while they eat etc.
Finally - folks historically have a natural "self interest" motivation. Ie, if you let folks act in a self interested way - personal protection, personal comfort - you are likely going to be better off policy wise.
You can do a rough risk computation yourself I guess. Both ingress and egress is worse if you have a valve though. Does seem like egress is still a bit better than what other people do (in this model at least - which could be wrong), but one shouldn't set one's standards by "what other people do".
"one shouldn't set one's standards by "what other people do""
In policy matters one can and should.
This is the stupidity I think of the scientists here.
If others are wearing surgical and little cloth masks, only wearing them a little bit, but then they say I can't wear my valved N95 (which I do very carefully) it's both totally arbitrary and unfair (my exhalations are still equal too or less others).
They also miss that the tradeoff might not be between my 5 hours of N95 use in a relative high workrate environment and something perfect, but that I will join with just about everyone else and ignore what they say, or go down to something like a surgical mask for comfort. Or take my mask off more for comfort to "drink" etc.
I'm convinced many folks on HN sit behind computers in empty rooms alone and NOT wearing a mask. If you have to wear a mask every day - these issues would matter a lot more.
The perception, of course, is that you are not filtering egress. Since the objective is/appears to be to filter egress, people will obviously take askance.
This can't be resolved without a bunch of additional training.
Of course if we'd done THAT, we wouldn't be in this situation in the first place, and the whole discussion would be moot. %-/
p.s. I worked on-site at a factory doing industrial automation for a lot of the time; I really liked FFP2 masks because they fit better and my glasses didn't cloud up.
Masks with valves were available (because part of one's regular PPE at times before the pandemic), but no longer permitted.
Yeah, that said FFP2's I think are per WHO only supposed to be for medical professionals - so use is discouraged outside that setting.
"This said, the World Health Organization does not recommend the use of FFP2 for everyone, stating that non-medical face coverings should be used by the general public under the age of 60 who do not have underlying health conditions. FFP2 masks are best used as personal protective equipment (PPE) by healthcare workers or those caring for someone who may have Covid-19 in a community setting. "
On egress, just a quick look at the valve, it's going to stop the velocity and either block or drop particles - however ineffective that might be on egress there is NO WAY it is worse then what I see others wearing (surgical / thin cloth etc), mask off the nose, mask off while they eat etc.
Finally - folks historically have a natural "self interest" motivation. Ie, if you let folks act in a self interested way - personal protection, personal comfort - you are likely going to be better off policy wise.