A tale of 'two-stories'
O' to the door, pesky thing... creaking, slamming, perhaps pinching a finger or two at times. It's just a hunk of wood over an opening, or is it?
Now more than ever, we need to pay attention to the presence, absence and have control of the doors we come across.
In most two-story residential homes, "open" interior stairs are common connecting the first and second floors. Hence the importance of having the doors closed on the upper floors. Smoke, heat and fire will travel unimpeded to the top floor.
Conversely, many basement stairs are "closed" with at door either at the top or bottom. They afford the home and occupants some protection (at least initially) from smoke and fire travel in the home. This is just one reason why there can be a delay in occupants noting a basement fire.
Take note of the position of the doors at the next fire you go to. Look at the patterns of smoke and heat damage that was either caused or prevented by the status (open or closed) of that simple door.