Is is safe to deal with wiring after only shutting off the room's fuse, but not the main switch?
And here is why you check it before hand, even though you have turned off that room.  People get into Junction boxes and re-wire - joining two separate circuits into one - in that case one circuit in the house can be fed from two breakers (as long as they are on the same phase).  Always check with testor - and NOT JUST  a proximity induction testor - but an actual touch the wires testor.  OK.  Be safe.