The code states a smoke alarm must be present in sleeping area and also outside of sleeping areas in the location of the bedrooms. I have a stair case with a door at the top that opens into a small hall that contains 2 bedroom doors. Should the alarm for outside of bedrooms be placed in the small hall or on the other side of door as your start down the stairs . It seems any smoke from the lower floor will be blocked by the door at top of stairs if I put the alarm in the hall , only a fire in the hall itself would have direct contact with the alarm. The owner wanted the extra door at top of stair so he could leave both bedroom doors open some time since one is a babies room .