Thread by @jeffreytran

.@co2detective 24 hours of co2 with the cooperation of my son’s preschool, which we appreciate very much. The chart is bounded by outside air.. picking up and dropping off the sensor. The levels aren’t great but there is some good info here. 1/

We can see how the system clears CO2 overnight.. though don’t know if it was running full out. Can anything be inferred about the overall transfer rate here I wonder. 2/

Unfortunately there are no windows by design, just a door that opens onto a street. They open it when the kids are at recess and this seems to work pretty well.. the easiest adjustment might be to put a fan in door to try to clear the entire room here.. 3/

Clearly this does exchange air. Potentially they could try to do it at another time (nap time?) as a reset but there’s a good chance that would be against regulations.. 4/

I need to ask for a daily schedule but my guess is that this peak is lunch. Do CO2 levels spike when masks are off? I’m not sure how the math works. Obviously it would be good if they could vent during this time but the same limitations apply. They do have two hepa filters.. 5/

I would definitely add a Corsi-Rosenthall cube or two (why not?) and put it near the kids when eating. Of course this won’t change the CO2, but perhaps this data may emphasize that need.. that this is the riskiest time. 6/

There’s a nap-time in there and I hypothesize that this is that lull which would be interesting. The kids don’t wear masks, but perhaps they breath less as well (and are spread out to the greatest extent possible). I think the nap is less a problem than lunch. 7/

I asked my kid if he wore his mask during nap-time as a trial-balloon and he looked at me like I was an idiot. “I don’t wear a mask when I sleep!” Obviously he could, but I’m not sure this is really the main problem. 8/

I’m not sure exactly what goes on the rest of the day but my guess is that over time that there will be pretty stable pattern. Perhaps the late day peak is transient? There is a late day snack, so perhaps that is it. 9/

I’ll just send the graph to the school, note the key features (the most noteable is the mid-day clearance). It seems like the overall levels are higher than we would like? Perhaps the hvac system could be tweaked? Mostly after seeing the trouble you’ve had.. 10/

.. I’m grateful that the school is supportive of monitoring. They said that perhaps they would get their own units (there are three classrooms) and having that would help them make adjustments and adjust their protocols. 11/

In general this school does a good job (with other protocols as well). Much of the problem is intrinsic to the overall situation, which is.. not great. 12/12