We're on how now with strategic retreat. There has to be first physical room for retreat, an actual exit, a physical way out. This can be scoped in advance. And a secondary exit in case of emergency. There should be a metal escape for positive focus if needed. This can frequently be discovered at the time. Then the reasonable explanation.
But don't use the exits unless you really have to or it misses the whole point! See? It is just to make it breathe easier while there. The better they are the less you will need them. Hopefully.