[quote=“Little_Nemo, post:62, topic:933009”]Of course that point may be low enough that people die before reaching it.
The very high air exchange rate on a passenger jet has already been addressed, but this point caught my interest.
According to a psychrometric chart, the moisture content of air at 20C and 100% RH is 14.76 grams of water per kilogram of dry air. This air has a density of 1.194 kg/m^3. If your bedroom is 4 meters x 4 meters x 3 meters, that’s 48 m^3 of air. You could fully humidify that air with just 834 grams of water, less than a liter; you’d be thirsty, but not dead. Based on earlier calcs, it would take one person about 24 hours of respiration in the room to achieve this (this disregards any water loss due to perspiration).
I’m not sure how to estimate one passenger’s share of cabin volume in a jet, but I’ll wager it’s much less than 48 m^3; I suspect a sealed, full cabin would be extremely humid (and gross) in a relatively short time. You wouldn’t be dead, but you might wish you were.