There are lots of models, but the only study I’m aware of showed that blue surgical masks had ≈10% efficacy when worn correctly, with cloth masks and gaiters less effective.
Additional ventilation seemed to have better efficacy.
The chart I saw showed that masks are somewhat effective for ingress and somewhat effective for egress contamination. When both parties are wearing the mask, and are social distancing, etc, the effectiveness goes up considerably.
The only singular control that works in a vacuum is a vacuum. So unless you are working in a vacuum, you need to stack controls in your favour. Just like you do in every other situation in life.
I've only ever seen them saying problems with school environments amount to a lack of good air circulation with people breathing the same air in and out amongst themselves for hours at a time. That's exactly what the CDC and everyone else has said to avoid doing, and why the phone apps rate 15 minutes of close proximity as enough exposure to warrant a test.
Just like with rubbing alcohol, time and amount have to be taken into account. Water will put out nearly any household fire. But only if other controls accompany it, and there is enough of that water for enough time to have the desired effect.
She took her mask off to read. They were all in that contaminated environment for most of the day. There is every reason to expect infections in such an environment.
ksaj|4 years ago
The only singular control that works in a vacuum is a vacuum. So unless you are working in a vacuum, you need to stack controls in your favour. Just like you do in every other situation in life.
I've only ever seen them saying problems with school environments amount to a lack of good air circulation with people breathing the same air in and out amongst themselves for hours at a time. That's exactly what the CDC and everyone else has said to avoid doing, and why the phone apps rate 15 minutes of close proximity as enough exposure to warrant a test.
Just like with rubbing alcohol, time and amount have to be taken into account. Water will put out nearly any household fire. But only if other controls accompany it, and there is enough of that water for enough time to have the desired effect.
She took her mask off to read. They were all in that contaminated environment for most of the day. There is every reason to expect infections in such an environment.