Distance of smoke detector from a held-open cross corridor door

Hi, appreciate this is more fire regs than wiring regs but hopefully someone can help clarify.

There will be doors separating a corridor in an apartment building, that will be held open by détentes. 

Full smoke detection coverage to Cat L4 will be provided using smoke detectors with a coverage radius of 7.5m.

Does BS5839-1 require a smoke detector to be within a specific distance of the held open door, on either side? Or is the 7.5m rule ok?

I know BS5839-1 states a max distance of 1.5m from a stairwell door, however the above scenario are simply doors to separate long corridor sections.


  • You need to ask where would you put the detectors if the doors were not there - open (But also does the door frame significantly lower the height of the ceiling  ? ) ,and then  ask the same if they were a wall (closed) and have adequate detection coverage for both cases. 

    As you describe it it sounds like detectors spaced based on  7.5m rule will probably be OK, so long as the doors are in the middle. If not then the furthest  detector cannot  be more than that distance from the doors so the detectors may end up being a bit closer than the maximum spacing.

    but wait  for other responses as there are others on here who may be aware of a corner case not described.