BS 9991

[nearlythere]

The time limit matters not but I would be interested in the answer to the question set at

ok let me rephrase the question. Why is 10 minutes supply okk for a flat at 29m in height but you need 20 minutes for a flat at 31m.

if any one knows why this is.  What is so magic about 11m etres, 18 metres, 30 metres and 50 metres.  History will do.

12m,18m & 30m when converted to imperial make nice round numbers - 40, 60 & 100 - maybe?

[CivvyFSO]

You won't be happy until someone mentions the wheeled escape will you?

[SamFIRT]

Civvy why are fires bigger in higher buildings?

They are not.

They have the potential to be so................ due to enhanced ventilation effects.

If a window for example were to fail on the 16th floor there will be a pressure differential on the windward side of the building as against the leeward side of the building. This is exacerbated by the wind gradient ensuing wind at that level will be greater velocity than at ground level.

This can cause higher temperatures and accelerated fire development in compartments and breaking out of compartments both upwards and downwards.

Al la Harrow Court, Stevenage. Shirley Towers, Southampton.  Lakanal House, Camberwell. Etc etc

Add to that the difficulty in accessing the fire and getting sufficient water pressure/flow to fight a fire at that level; fires can be bigger at higher levels.

[kurnal]

I am formulating a response to the draft document and would be grateful for the help of any one who would like to contibute. I do have an electronic copy of the draft which I would be prepared to share with anyone who will make time to read it and let me have their considered opinions for submission back to BSI. The deadline for responses to BSI is the 15 October so I would need to receive any responses from firenet members by 1 October.

[colin todd]

Samuel, Interesting theory, but I dont think there is any statistical evience to suport it in practice, which is why I still want to know from Civvy (who has meticulously avoided the question) as to why he thinks you need the sprinklers in a flat at 31m to run for longer than a flat at 29m.

[CivvyFSO]

First of all, I answered it quite directly.

They are not. If I were to defend the choice of sprinklers being required over 30m then I would suggest that beyond 30m you have almost zero chance of having something turn up at your window that you can escape via.

Secondly, I believe that the two standards in BS9251 are for different things. One (domestic) is to protect the MOE from the flat/room in question, the other (residential) is to ensure that a building is protected in order to secure the MOE for other people beyond the room of origin. (While still protecting the MOE better than the domestic standard) If the BS people have decided that a sprinkler system is required above 30m then I would assume (I stand to be corrected) it is not primarily to protect the persons in the flat of origin, but to protect the building, and the people in that building. This is clearly not achieved by installing a system that is only designed to protect the MOE from the affected flat/dwelling.

Also:
ADB has a distinct change in the guidance at 30m.
BS9999 has a distinct change in the guidance at 30m.
BS9991 Has a distinct change in the guidance at 30m.

I am sure you can take it up with them.

In fact, get a comment in on the draft review. That would be a better use of your time.

[CivvyFSO]

And, to clear something up, I am not saying that the domestic system is suitable under 30m, the domestic system is only suitable to protect the MOE as mentioned before. This is regardless of height.

[colin todd]

I think I would challenge your interpretation, and in any case, BS 9251 assumes that all other fire precautions are as per code rather than relaxed. But dont worry civvy, I will get my comments in. Trying to get you to see the light and commenting on the draft are not mutually exclusive.

[CivvyFSO]

From BS9251 Terms and Definitions:

domestic occupancy
individual dwelling for occupation as a single family unit used or constructed or adapted to be used wholly
or principally for human habitation, such as individual dwelling houses, individual flats, maisonettes and
transportable homes, with a maximum individual room size of 40 m2

residential occupancy
occupancy for multiple occupation not exceeding 20 m in height, with a maximum individual room size
of 180 m2, such as apartments, residential homes, houses of multiple occupancy (HMOs), blocks of flats,
boarding houses, aged persons homes, nursing homes, residential rehabilitation accommodation and
dormitories

Which part of this, coupled with the greater water requirement in the residential occupancy, does not make it clear that domestic systems are only there to protect the individual flat/house/shed?

[colin todd]

which bit of it does?

[SamFIRT]

Samuel, Interesting theory, but I dont think there is any statistical evience to suport it in practice

Not been to many fires have you Colin?

[CivvyFSO]

which bit of it does?

I would hazard a guess at the red bits.

[Stinky]

It is clear that this new draft has not benefitted from the input of a fire engineer.  Apparently the fire engineer who was meant to be consulted, did not turn up to any of the meetings.
It is obvious that everyone pro-sprinklers has been lobbying for sprinklers!

Are the proposed additional measures in places commensurate to the actual risks and experiences present in buildings today? Importantly to link staircases to basements, where is the evidence to suggest that this is a significant issue that now requires sprinklers to be considered to address this?  Has a cost benefits study been conducted to reflect these recommendations?  Beyond this have any of these issues been ratified by CLG as many of these are moving away from current national policy and as we all know at Building Regs stage many BCO’s will be very reluctant to move away from the written guidance.

[kurnal]

The FIA has set up a small working group to review and collate responses to the draft document from member companies. We are meeting on 6 October. I am happy to take forward any observations from firenet members to the group.

[CivvyFSO]

where is the evidence to suggest that this is a significant issue that now requires sprinklers to be considered to address this?

Are basement fires not a specific problem?