Comment by masklinn

An other fun danger of insufficiently aerated rooms: in wine countries, until cellars aeration became more widespread a huge danger was CO buildup in cellars from fermentation, to these days people regularly die during initial fermentation, and a warning you get is "if you see somebody unconscious at the bottom of the cellar stairs you do not go down to help, you call the firefighters, trying to help just ensures they have two bodies to retrieve".