Flats can be designed to such a level of fire safety that if one flat has a fire, just the flat involved evacuates and everybody else stays put, the fire brigade review this on arrival and may consider advising others to leave.
To achieve this standard
-all floors and walls between flats and between flats and stairs are fire resisting to a one hour standard if below 18m high or 90mins if less than 30m high,
-all flat entrance doors to a half hour standard with self closers,
-all flats designed with an entrance lobby, no inner rooms, maximum travel distance 9m in flat to bedroom door,
-limited travel distance of 7.5m in a dead end corridor off the stairs if the corridor is provided with an automatic ventialtor or window of 1.4m2 or 4.5m if not ventilated,
- no fire risk or ancillary accommodation in the stairway if single staircase
- opening windows or automatic vents in the staircase.
If it achieves all of these its considered safe to stay put and theres no need for a common areas fire alarm system.
If it doesn't hit all these points then it needs a common areas fire alarm and detection system because its possible that a fire in a flat could affect the staircase cutting off others means of escape and trapping them in the building. The reaosnable compromise in my opinion is L2 with smokes in the common parts and heat detectors inside each entrance door, and self contained LD3 in each unit. Audibility of common areas alarm can be problem.
As far as I recollect the first buildings that were constructed to this safe stay put design were from 1971 onwards, though some older buildings in London particularly will be found because their building bylaws allowed for this design much earlier. There are other designs as well such as balcony approach where stay put may be safe- I was tilting the answer to the case in point.
Sounds a bit familiar Dave- not a poison chalice I trust?
