Reply to Smart Restart APS- ventilation studies

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Reply to "Smart Restart APS- ventilation studies"

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[quote=Anonymous][quote=Anonymous][quote=Anonymous]The Smart Restart group is in way over their heads. They are making gross assumptions in their calculations. Thankfully, APS is consulting with actual experts and following best practices. Looks like we will learn more about it tonight. [/quote]

Perhaps. But just remember who has a bigger reason to withhold or shade some information. APS has not exactly been forthcoming with this information and seems to be providing it now because Smart Restart rang alarm bells.

I read on AEM that APS is going to say that all but 46 of its classrooms will have 4 air changes per hour (ACH), on a scale of 6.  That doesn't sound too bad.  But here are the stratifications of that scale: 6 is ideal; 5-6 is excellent; 4-5 is good; 3-4 is bare minimum; below 3 is low.

So getting almost all APS classrooms to 4 ACH is both "good" AND the "bare minimum" that is safe. To get to 5 or even 6 ACH would not take many more steps and you don't have to be an expert to know that. There are a ton of resource papers from Harvard (Dr. Joseph Allen and other building safety experts) that give schools advice on this stuff.  Personally, I'd like to know which schools and which classrooms within those schools have just the bare minimum.  And how APS intends to improve the air quality in those rooms/schools so everyone has at least a full good.[/quote]

Joseph Allen fully supports a 4 ACH - that is really all that is needed - sure 6 is higher but it is not required and only a modest reduction in transmission risk going from one to the other. I think there was a wrong study used in the SR work that pointed to a 50% reduction in risk going from 4 ACH to 6 ACH but that was for a single case of a very infectious person with measles - which are much more infectious than COVID. Going from 4 to 6 actually only provides less than 1% risk reduction based on other studies. I think that is shown in the studies linked on that AEM post you reference.   The fact that 6 ACH is listed as optimal is, perhaps, bad wording when the 4 ACH is completely acceptable. Allen has tweeted this and written op-eds on all of this.  I think APS put out documents that disclosed the rooms. Also, in the School Docs that APS just released for tonight's Board Meeting it looks like APS is putting in additional HEPA filters for some rooms based on the expert's work.  And it looks like all those rooms have windows that can and do open.  [/quote]

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