There's a fire door in the room I work in, but I don't think every room has one. So some people must have been genuinely trapped.

I've never actually seen Predator, although I think I sat in front of at least part of Predator 2 at one point without paying much attention. I assume the Predator does some similar sort of thing?

You could probably chuck a monitor through the window if you were really stuck.

That might be less fun for the people on the first floor, but yes, there would have been a variety of ways out given enough motivation. I didn't really mean "trapped" in the sense of "really actually likely to starve to death in there if the locks don't start working again", more in the sense of "unable to get out without causing somebody a serious inconvenience, no matter who it turns out to be".

I assume the Predator does some similar sort of thing?

Yes, though the antecedants may be confused. The IR door lock represents the alien, the predator, who has heat vision. You represent Arnie. The coat represents implausibly high heat capacity river mud. All that's necessary is for you to smash the lock with your bare hands and it'd be perfect; you can't say you're not tempted.

It would, of course, be vastly more amusing (in a glad-I'm-a-long-way-away kind of way) if, for the sake of accuracy, the door also featured a thermonuclear self-destruct system keyed to activate in the unlikely event that anyone succeeded in escaping from the building.

I don't think every room has one. So some people must have been genuinely trapped.

This is legal where you live?

Allowing for the possibility of trapping someone in case of a fire seems rather dodgy to me.