BS 9991

[Clevelandfire 3]

Colin where would draw the line. An extra metre here or an extra ten metres there or would you go the whole hog and say 100 metres is fine and throw b*gger to the guidance? If you say no to 100 metres why not if an extra metre is fine.

[colin todd]

Samuel, All the statistical evidence from those who allegedly were at the fires shows there is no difference that would justify longer water supplies. Ever opened fire statistics, Samuel. 

Clevey, it doesnt matter about where you draw the line.  You miss the point. If domestic sprinklers will control a fire adequately in low rise, so they will in high rise.

[kurnal]

The BRE did a study on the cost effectiveness of residential sprinklers and their method of calculation based on financial parameters only identified a reasonable benefit in installing sprinklers in high rise blocks over 11m

http://www.bre.co.uk/page.jsp?id=422

But this study was based on the reduction in deaths injuries and financial loss within the unit itself.
Whilst it it reasonable to assume that a sprinkler controlled fire will pose much less of a hazard to persons outside the flat of origin than a ventilation controlled fire, is it reasonable to allow a doubling of travel distances where a sprinkler system is provided?
Does any one know of any evidence or research that has been used to inform this decision?

[colin todd]

Kurnal, as if....... Everyone knows two things, old bean:

1. Sprinklers are the answer to everything from global warming to the world economic crisis. Who says so? The sprinkler trade so it must be right.

2. When a number is too small, what do you do? Double it.  It worked for the compartmentation of shops.  When people were badgering Wee B's political bosses about the figure in the consultation document being too small, he doubled it.  Then when they thought no one was looking, they tried to halve it.  But people noticed so they left it as it was.  That's how fire safety codes are written.  It about works, provided there is some vague hand waving basis that underlies the figures one draws from thin air.  I cannot criticise (nor would I cos wee b is a cool dude). Remind me to tell you sometime where the 4000 sq metres for duplication of fire alarm sounder circuits came from.  Actually, perhaps dont remind me. I will keep it for my memoirs.

[kurnal]

I have been reading further into BS9991. I noticed that no special mention is made of doors enclosing smoke shafts. This is also the case with ADB and Toddys latest doorstop. In respect of vents associated with fire fighting shafts, BS9999 makes a general comment about fire resisting doors to all shafts but I can find no specific reference in respect of lower buildings incorporating ventilation shafts.

The doors in question being the AOV that opens into the shaft on the level at which smoke is detected and works in conjunction with a vent at the head of the shaft. I was going to suggest adding a comment to table 11 - provisions for fire doors - that just like any other protected shaft that bridges compartment floors these doors should have half the fire resistance of the structure and incorporate smoke seals.   

Then I remembered that this shaft will be open at the head so is there justification to treat them differently?

The door on the level of the fire will always be open so the half fire resistance rule would not really stack up. But on the other hand because the shaft is leading from a protected corridor, lobby or staircase it should never be exposed to the radiated heat of a fire on the corridor  side and certainly not on the shaft side.

Furthermore there should be no pressure differential within the shaft that could cause smoke to pass out of the (open) shaft  via the edges of the closed AOV doors at other levels allowing smoke into other floors.

So do we need fire or smoke seals at all? And do we need fire doors come to that?

I have an opinion but would be interested in hearing your views.

[wee brian]

The Smoke Control Assoc did a guide to cover all this stuff, The plan was to put some of it in 9991. Maybe they missed this bit.

[Phoenix]

Hi kurnal,

There might be a problem if the top of the shaft is obstructed. There are a number of reasons why the reliability of an AOV (if fitted) might be compromised or the open top of the shaft might be partly or completely obstructed.  With no or little opening at the top the pressure in the shaft will increase and possibly force smoke out into lobbies (starting at the top of the building).

Cool smoke that doesn't have much buoyancy might drift in and out of the shaft affecting floors other than the fire floor, especially if the day is hot and still and a reverse stack effect might be expected (this might push smoke into lower lobbies).

These are not likely but conceivable.

You make a point that illustrates that these doors/vents only need integrity and not insulation - same as other doors.

Stu

[kurnal]

Thanks to all for your contributions, on careful reading for the third time I did find the answers to some of my concerns and we had a good meeting at FIA HQ to produce a very detailed and lengthy response.

Particular thanks to Colin Todd and Phil Martin for burning the midnight oil on this one.

[nearlythere]

Remind me to tell you sometime where the 4000 sq metres for duplication of fire alarm sounder circuits came from.  Actually, perhaps dont remind me.

Well it was actually 2000sq M at one time and fire alarm sounder circuits used to be singular. Cos thats how codes are written.

[thebuildinginspector]

Just out of interest, does anyone know when this standard is due to be published?  I know that the consultation has closed and that the comments have been reviewed, but when is the final version due out for public consumption?

Ta muchly