What changes when the building is empty
The warden structure disappears, since wardens are staff who have gone home. Nobody sweeps the floors to check for stragglers, so an unconscious or trapped person is not found. The assembly point may be unlit and the route to it may cross an unsecured car park. Monitoring may be in place but response times to an unoccupied industrial building differ from those to an occupied one, and the cleaner may be the only person who knows anyone is inside.
None of this means the arrangement is unsafe, but it does mean the daytime plan cannot simply be handed over. The out-of-hours position is a distinct set of answers, and most buildings have never written it down because nobody has asked. Asking is straightforward, and the exercise usually surfaces at least one assumption that turns out not to hold, which is worth discovering in advance.
