This is driving me crazy because different "experts" are giving conflicting advice.  We have 22 flats spread across 4 floors. The corridor to the flat entrances is a compartment with a part 1 smoke detector. There are no alarms as it is a "stay put" building.

There is a single (fire fighting) stairwell which is protected from the flat corridors by 60 minute fire doors. In the roof above the stairs is an AOV which opens when smoke is detected by a detector inside any of the corridors accessing the flats. There is a MCP at the building entrance which allows the fire service to close this vent above the stairs if they wish.

Question:  Should there be a smoke detector in the stair well (a sterile area) to also activate this AOV or should it only open in response to the detection of smoke in one of the flat access compartments. 

Thanks for any comments (ideally quoting any legislation which supports your view)) 

The detailed guidance is in here http://www.smoke-vent.co.uk/documents/SCA Guidance notes rev 3 (Jan 2020).pdf

You don't want a stair vent opening on it's own so other than  some configurations of small single stair buildings you don't want or need stair detection

Thanks Anthony, that is very helpful. My own view was that as the stairwell is a sterile area (so nothing to burn) and even if there was a fire as a result of arson, the safest place for residents is in their flats behind at least 120 minutes of protection, they should call the fire service and not try to use the stairs regardless of the amount of smoke.