Little Hole In The Bottom Of The Window

You ever notice that little hole in the bottom of your window? That’s the breather hole, and besides keeping in warm air so you don’t get too chilly, it regulates pressure — ensuring that should anything happen to the outer pane of the window, the pressure won’t cause the inner pane to break, at which point you’d suddenly be sucking in oxygen at 35,000 feet. Consider it Phase 1 before you get to the masks.