@jljcolorado and @joeyfox Can I trouble you for expert opinions on this chart?My kid's school district advertises 4-6 refreshes per hour in all spaces. I send an aranet4 packing with my kindergartner every day. Before I show the actual classroom, this is from a parent meeting in the library with maybe 20 people in a space like 100x50x30 feet roughly, a fraction of capacity. 20 sedentary people, one talking. Should CO2 be rising linearly if ventilation is working?

@surfingreg @jljcolorado @joeyfox Your raw number of 688 ppm CO2 is quite low considering 20 people in the room. There is math available and calculations you could conceivably do if you search the web. But, as a CO2 meter owner, my experience suggests that 688 is a very good indoor number consistent with good ventilation.