Kurnal,
The way I had it explained to me by someone who was involved with the writing of the new ADB, was that even if you go to bed and leave to doors open, in the event of a fire starting downstairs it should be picked up by afd, and this should give you time to investigate and make the judgement as to getting straight out, or closing the door and retreating upstairs.
In my opinion, not much thought has given to the worst case scenario, i.e. a rapidly devoloping fire. Fair enough, most house fires probably start quite slowly and a mojority of furniture etc is flame retardant, but the worst WILL happen eventually, whether it involves curtains, a christmas tree (some good video footage of this particular case is on the net), clothing or something else, it can (And one WILL) develop fast.