Thread by @MyrneStol

@sri_srikrishna @RanuDhillon @T_Inglesby @kprather88 @AbraarKaran My estimates were too aggressive, of sorts.

However I have seen no argument to disregard ACH's from natural ventilation, and significant natural ventilation is desirable: for low CO2. Also, a CR-box can certainly do a little more than 400 CFM, just at expense of more noise.

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@sri_srikrishna @RanuDhillon @T_Inglesby @kprather88 @AbraarKaran Total CADR from #CorsiRosenthalbox'es needed to get to 12 ACH, given known natural ventilation:

900x8 classroom:
0 ACH ➡️ 1440 CFM
1 ACH ➡️ 1320 CFM
2 ACH ➡️ 1200 CFM
6 ACH ➡️ 720 CFM

900x10 classroom:
0 ACH ➡️ 1800 CFM
1 ACH ➡️ 1650 CFM
2 ACH ➡️ 1500 CFM
4 ACH ➡️ 1200 CFM

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@sri_srikrishna @RanuDhillon @T_Inglesby @kprather88 @AbraarKaran Few thoughts on the numbers:
Natural ACH can probably be estimated with 'citizen science' and 'citizen math'.
Having to run a CR-box at higher speed is not an unfair 'price' of bad (less than 2 ACH) ventilation.
The best case of 6 ACH in a smaller classroom will be very rare.

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@sri_srikrishna @RanuDhillon @T_Inglesby @kprather88 @AbraarKaran Summing up, for 12 ACH, you'd need 3 to 4 CR-boxes per classroom that in principle should be run at low speed (400 CFM), but, in context of bad ventilation (which can be checked by anyone by measuring CO2) may have to be run at higher speed (more noise) giving around 500 CFM.

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@sri_srikrishna @RanuDhillon @T_Inglesby @kprather88 @AbraarKaran I have to qualify that ventilation "can checked by anyone". This is not fair. Almost paradoxically, an #Aranet4 costs more than a #CorsiRosenthalBox .
We'd need a lending program (libraries!) or so. And otherwise it would in fact be cheaper to deploy an *additional* CR-box.

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@sri_srikrishna @RanuDhillon @T_Inglesby @kprather88 @AbraarKaran Yet on the other hand: Somehow planning that every school has at least one good CO2 meter is also not a bad idea.

In fact, I think it's pretty *mundane* idea (that is, I'd say not something really up to debate), in the context of this pricing / sizing conversation.

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@sri_srikrishna @RanuDhillon @T_Inglesby @kprather88 @AbraarKaran @threadreaderapp please unroll