Yup. In my city, on windy winter days the CO2 is as low as it gets, in the low 400's. But on a hot windless summer day in a temperature inversion, my meter wil

Yup. In my city, on windy winter days the CO2 is as low as it gets, in the low 400's. But on a hot windless summer day in a temperature inversion, my meter will read 700 or even 800 outdoors, as the CO2 from vehicles and maybe even power plants just sits around without going anywhere. In the winter, if my indoor reading is 800 I open the window a crack to improve my concentration. On certain days in the summer, I just accept it's going to be 1,000 indoors and there's nothing I can do about it.