[slashdot2008]

I don't think it is an unfortunate narrative. two people wearing masks without valves is twice the reduction in likelihood that either one gives the other covid. If someone does have covid the mask without the valve will greatly reduce the concentration of virus particles in the air around them. I think that is working as intended!

[petertodd]

Masks that aren't worn correctly tend to have very low efficiencies, because the air just bypasses the mask at the edges. Depends on many factors like the type, how hard you are breathing, etc. But filtering just 20% of the air breathed in is quite possible. And let's face it, people intentionally wear them incorrectly all the time because they suck to wear.

If you and I both have 50% filtration, that's the equivalent of 75% filtration. For the person who is vulnerable, that is much less effective than just wearing a 95% minimum filtration valved N95 mask/respirator properly.

It's just ridiculous that an elderly man on a flight, sitting next to a healthy 15 year old more likely to be killed by a flu infection(1), will be told to take off his valved N95 respirator here in Canada, to protect that 15 year old. I have friends who have seen this happen first hand.

1) https://www.cdc.gov/flu/symptoms/flu-vs-covid19.htm

[makomk]

With the typical masks available to and worn by ordinary people, exhalation pressure seems to cause a lot of air to bypass the mask too - except that instead of doing it via a well-designed valve that redirects the airflow somewhere sensible, it blows out the top and steams up glasses or out the sides and towards whoever's standing behind you.