Well, as a fire officer myself, i would have to say that in a situtation such as your's all the doors leading into the stair well should be fire rated with automatic closeing devices. That hall way has to have a rating of sometime if it is a means of escape! should should also have emergency lighting to light your way out. if all the doors are closed in the stairwell it should take quite awhile for the somke to fill it. it may also have a emergency fan in the top of the stair well to extract the smoke if there is a alrm activation.