My current employer is meticulous about hanging mezuzos. He hired a rav who is an expert in this particular mitzvah, and he went around identifying every doorway. (Some of which are non-obvious, like where the metal between the tiles in the ceiling makes the top of the “door-frame”.)
On the way down the hall, I did a double-take. There was the alarmed emergency door, with the mezuzah on the left and angled the wrong way. It was as though the rabbi decided that unlike every other doorway from the hall, this one ran in the other direction — into the hall rather than outward from it. It actually took me over a day before I realized why — from the outside, this door is the entrance to the hall. You enter through the lobby, up the stairs and through the emergency door and into the hall. Whereas the other doors are from the hall to a particular destination.
And it took me another day to realize the basic mussar point, why the mezuzah‘s placement was non-obvious to me.
When I think of an emergency, I’m thinking of how I would escape. How the door would get me out of the hall in case of a fire. However, if there were a fire on one of the higher floors, the door would be used to let them escape to a lower level. There is a self-centerdness, at least when thinking of survival, that kept me from thinking of the doorway objectively, as being a way in in addition to being a way out.