I don't remember seeing it mentioned
anywhere, but it was probably the "smoker's door "

Some years ago my mother worked at a
nursing home, and that was what the employees
did, prop a door open for the benefit of those
that could sneak back for a couple of puffs.
That stopped when a few of the elderly people
decided to waltz on out to who knows where.
Then they had a detector of some kind that sounded
an alarm when one of the special bracelet wearing
residents would try to pass. An elderly woman
defeated that by stripping everything from her
body, bracelet clothes underwear and all and
running naked out the door and out through the
neighborhood

More than a few places I've worked had
" smoker's doors" propped open when they
were supposed to be securely locked.
Those sliding security grates too.