Natural Smoke Ventilation

[David Rooney]

gotcha .............

Thank you ....


I tried the link on the Colt website direct ... maybe it doesn't like Chrome .... don't worry I'll open it and have a look in explorer later.

[Tom Sutton]

Which document tells me about battery standby, cable specifications etc
Which document tells me about the system operation ie. should only the fire floor AOV open or can others open as a fire progresses ?

It appears that on your first question most of the information you require should be found in BS EN 12101-10:2005 Power Supplies.

On your second question I can only find it in the colt and feta guidance which is not very detailed, I think you would be better looking at the reasons why.

The first possibility is any vents open above the fire could smoke log the lobbies, this would depend on the level of the neutral plane.

The second possibility is, in a fire situation the vent shaft is acting as a chimney and any additional air entering the shaft reduce the chimney updraft therefore the effectiveness of the fire venting system. This could be the reason why all the vents should be closed except the floor on fire and the staircase vent.

Considering the principle of multi storey flats, each floor should be compartmented by 60 min separation and the FRS be in attendance within that time, who will take over the manual control of the fire venting system.

My thoughts for what they are worth - dive in the slit trench and put my tin hat on.

[David Rooney]

Yep I got that .... thanks Tom.

But I haven't got a shaft ... the vents open to air so there is no chimney effect.

I can understand why you don't want vents above the fire floor to be open, and building regs simply says "all others to remain closed", but what I'm looking for is the definitive regulation that says that either you should not be able to open a vent other than on the fire floor ever,(excepting the stair vent) or that there are conditions where other vents may be opened and the opening of the vents is the responsibility of the brigade ... or something along those lines.

And if that is the case then surely you shouldn't install "breakglass" units that could be operated by every man and his dog ??

[Tom Sutton]

David

I think the SCA Guidance on Smoke Control to Common Escape Routes in Apartment Buildings (Flats and Maisonettes) says it all and it referrers to ADB page 29 and how I read it is,

Yours situation falls under

a) a minimum of 1.5 m vent, in your case automatically opened and that is all it says.

b) is if you were using a vent shaft and one of the requirements requires only the vent on the fire floor lobby and staircase has to open the others to remain closed, plus other conditions.

I believe MCB's are acceptable and the environmental additions also.

Back to my slit trench

Check out http://www.feta.co.uk/associations/hevac/specialist-groups/smoke-control-association

[kurnal]

Yep I got that .... thanks Tom.

But I haven't got a shaft ... the vents open to air so there is no chimney effect.

I can understand why you don't want vents above the fire floor to be open, and building regs simply says "all others to remain closed", but what I'm looking for is the definitive regulation that says that either you should not be able to open a vent other than on the fire floor ever,(excepting the stair vent) or that there are conditions where other vents may be opened and the opening of the vents is the responsibility of the brigade ... or something along those lines.

And if that is the case then surely you shouldn't install "breakglass" units that could be operated by every man and his dog ??

David the guidance does imply that the risk from open vents  elsewhere than on the fire floor is less  where there is no shaft- see the difference between test procedures in paras 9.2 and 9.3 for an example of this. It is however still referred as being undesirable earlier in the specific guidance. I agree with Tom that the FETA guidance is about the best you will find on the topic. It also makes the point that the ADB guidance for natural ventilation is based on a very limited fixed fire size scenario with doors opening for specific periods and specific durations. It is all very arbitrary and may fall apart completely if the fire size is bigger, if self closers are defective or if people leave their doors open whilst trying to save possessions.

In short it could be argued that fully engineered and calculated systems of ventilation would be more robust but many such solutions are stlll based on the same BRE / ADB fire criteria so equally open to question.

The potential unreliability coupled with the stay put policy makes it essential for fire fighters override controls to be provided and these should be marked and sited to avoid the risk of vandalism as described in the guidance.

I guess the main point is that the ventilation arrangements are there to supplement the main contribution to fire safety in these buildings- its the fire compartmentation that makes these buildings safe.

Hope this has been useful.

[David Rooney]

It's certainly a learning curve !! 

But yes all very useful so thanks all for the taking the time to reply.

[Tom Sutton]

David do you learn anything from the Colt Webinar I think I recognised your two questions. 

[David Rooney]

Yep twas I !!!

And yes ..... as the man said, only one floor vent should only be open at a time (ignoring the stair vent)

If the FB decide to open another vent then the original floor vent should close.

This is how I've seen other systems working but they use their own "controller" that locks all other vents out ... and they use a key switch on every floor for the FB to use to decide whether to open a different vent - automatically closing the original.

My scenario is different as they've used standard yellow breakglasses on each floor that anyone can operate and the fact more than one vent can be open at a time.

So I can't see how my system complies .........