Smoke vents in multi occ office building

[Mar62]

Going back to a post i put up a while ago. I have been trying to find a definitive 'guide' as to where and when a smoke vent is required in a multi occupancy office use premises. Have gone through various documents inc App Doc B but cannot find any useful guidance that I can use to help resolve an argument discussion. Would it be as simple as single staircase - yes, external escape staircase available - no? Buildings i am particularly referring to have 5 floors. Any help appreciated...

[AnthonyB]

You may find some older offices with vents to some stairs - back in the pre ADB & BS5588 series days the Offices part of CP3 (which most people know of for it's flats section) required stairs without an external wall (& thus no windows) to have a roof vent.

[Tom Sutton]

I understand in the past flats where designed on a concept known as smoke dispersal and the object was to keep escape routes free of smoke at least tenable. This is why many blocks of flats had open walkways but when they were enclosed they had to provide SHEV systems.
 
The remainder of premise, used the smoke containment concept, which included offices and they only vented certain areas, which included staircases. Examples for instance, firefighting shafts, protected lobbies to staircases, atriums, and car parks so it depends what is required in the premises to see if SHEV are required.

Time to get in my slit trench and wait, on goes my tin hat.

[Mar62]

Reason why i am asking is that recently a client's multi occ office building - 5 floors with a basement tenant, single staircase was put under enforcement notice after a small fire in the basement tenant area. One of the LFB's requirements was to install a smoke vent within the staircase. I haven't been able to find a clear definitive answer as to what / when required - putting flats premises to one side for the moment though. Just wondering if anyone could point me in the right direction to get some information.

[Tom Sutton]

Is the staircase double door protected conforming to ADB vol 2 (4.34 page 51) if not they may be asking for the ventilation as an alternative?

[Mar62]

Tom many thanks for your reply. there are double door protected lobbies on the 4th and 5th floors only. After reading the section i think you have answered my question. I just couldn't see the wood for the trees and find the right section and words i needed. So thank you very much indeed.