I must be missing something here, why can't you use the back door if
the front is unopenable for whatever reason. There should be, and in
modern properties there must be, an alternative exit method. There
should not be a safety issue if the front or any other door is not
accessible.

We have a back door. The front door is at the bottom of the stairs. The back
door is through the back room and kitchen, both very likely rooms for the
fire to be in, either from cooking, malfunctioning appliances or forgotten
candles.

Christian.