In my opinion, (and I shall limit this response to sleeping accommodation in commercial premises - hotels etc), I interperet the requirement as HD in bedrooms with SD in the MoE, as already discussed in this thread, BS 5839 Part 1; refers to discounting the room of origin, however I have often wondered, (and lets remain in a hotel purpose group), that the rationale behind this was partly influenced by the fact that people were permitted to smoke in the hotel bedroom, the potential for false alarms and wasting FRS attendance resources etc.
More recently, post smoking ban in public places, most hotels are completley smoke free environments including the bedrooms, this could be the opportunity to amend the BS 5839 Part 1; to include SD in bedrooms