Persons Evacuating a Premises Leaving a Protected Space to Reach a Final Exit

[Messy]

I am having a senior moment and questioning something I previously thought was basic stuff

During an evacuation, when a person enters a protected route, my understanding is that under normal circumstances, they should remain in a protected route until they reach a place of safety.

I have come across a case where the strategy is for persons escaping to use a 20 storey protected staircase with lobbies and pressurisation) and then leave that protected space on the ground floor to travel to the final exit through open plan office and other unprotected areas.

It is fair to say, where this happens, there are two unprotected routes to a final exit on the ground floor that are entirely separated, therefore staff will be able to turn their back and make they way along the alternative route. Several hundred persons (staff) will be required to use the routes.

My concern is all about time. When staff enter the staircase on the top (19th) floor, being protected space and pressurised, there is less urgency for them to reach a place of ultimate safety. However, by the time they reach the ground floor and have the choice of two unprotected routes, separated  by a 30 min FD, I am concerned that smoke from a fire on the ground floor may started to enter the escape route

Any comments - as usual - will be gratefully received

[Owain]

It sounds nuts to me to not have a protected final exit route for a 20 storey building.

And what about disabled refuges on the staircase?  Even if there isn't a lift, a person who can manage a couple of flights of stairs to an upper floor slowly, normally, may be unable to do so in an emergency situation.

[Tom Sutton]

The old blue guide for the FPA 1971 stated,

14.44 Ideally stairway enclosures should lead to a final exit. Where there is only one stairway from the upper floors(s) of a building and a final exit cannot be provided from the stairway enclosure , one of the following arrangements should be adopted.

(a) the provision of two exits from the staircase enclosure each giving access to a final exit by way of routes separated from each other by fire resisting construction (see diagram 14), or

(b) the provision of a protected route from the foot of the stairway enclosure leading to a final exit (see diagram 15)

So if the building was constructed last century could this not be the reason.

[Messy]

Owain, I share your view - especially as the occupancy numbers for this particular premises is quite large

Tom, many thanks for that information as it certainly does provide some context/rationale for this MOE layout, especially as this building is indeed rather old. It is obviously the source of my understanding - in 14.44 (b) - that the protected route should lead to the final exit.

I must have been looking out of the window at Moreton when the alternative - 14.44(a) - was discussed. I did a lot of dozing off in those days

I will embark on a programme of fire door upgrades to beef up the separation between escape routes that are required

Many thanks for your help