The HVAC is continuously circulating air from the time it is on until after school when it turns off. There is some time before school and maybe 20min after school when it is on.
They have settled on only pulling air from the outside instead of recycling the warm or cool air in the room.
And having some kind of agreement on the merv rating of the filters. It may be merv 7(but I'm not sure.)
How much would it cost to retrofit a bunch of schools with this stuff?
Ideally you'd do both. Have better air circulation, and institute masks when the regional caseload goes above a certain threshold.
Even things like a box fan in a window are probably significantly more effective than scooby doo masks.
That's fine year-round in the south and southwest. Not so much in the rest of the country though.
Most I've seen cited by mask proponents either don't use control groups (and thus can't really distinguish btwn other factors that correlate with mask wearing) or are laboratory tests just testing what % of particles are blocked by masks--which ignores almost every relevant question about mask mandates and relies on suspect theoretical models about how covid actually transmits between people.
I'm mystified why people on both sides are so up in arms about masks, but nobody gives one shit about uncontroversal and more effective mitigation techniques like air filtration and circulation.
An infected kid in classroom without proper air circulation could fill the classroom with enough virus to cause a super spreader event--mask or no-cotton/surgical mask.