Wouldn't it be more practical to have a prominent CO2 monitor and only exchange the air (maybe by opening the door for a few seconds) if it CO2 gets too high ?

Wouldn't it be more practical to have a prominent CO2 monitor and only exchange the air (maybe by opening the door for a few seconds) if it CO2 gets too high ? Maybe it's hard keeping a co2 monitor operating in humid sauna conditions, I dunno. Also, given that many saunas are not airtight, I wonder what a steady state CO2 concentration would be. It may be high, but not dangerous.