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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: zimmy on September 07, 2011, 10:01:07 AM
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Hello,
I would appreciate any advice or opinion on the following in order for me to formulate a response.
I am an FRS FSO and have received a Building Regs consult from an AI for a shop premises. The proposal is to demolish existing compartment walls in an unoccupied shop premises to create one large compartment of approx 3800 sq m. The AI is claiming that it satisfies the functional requirements of ADB by offering an independant Computer Fluid Dynamics model showing that the compartment performs better in fire conditions than a compliant model of 2000 sq m.
I have a few issues with this. Clearly, it does not satisfy ADB, being almost double the floor area for a single storey shop. Looking for leeway in BS9999 doesn't help as the standard here is the same.
The CFD models used are quoting a t2 fire growth rate as 'medium' and both BS7974 and BS9999 suggest that a shop should be a 'high' growth rate. This may not matter as the model is comparative between a compliant and non-compliant compartment.
In my opinion, the proposal does not offer any compensating feature, but merely shows the recognised standards to be not applicable. I therefore have a dilemma, to agree the proposal and accept a shop compartment double the size with no compensating features, which may set a precedent and open the floodgates for any shop to do the same, or disagree with the proposal, leaving the FRS to take retrospective action under the FSO which could be problematic and no doubt lead to an appeal.
Does anybody have experience of this, or has anyone allowed increased compartment sizes in similar situations and if so, under what conditions?
I'm grateful for your thoughts.
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The various shop fires I recreated when working at Fire Research showed t2 growth generally of 'high', hence that being what is quoted in the standards, I suspect! I would therefore suggest that you should require them to run the CFD model using the faster growth rate.
I wonder if the CFD model appears to give a better result because in the early stages of the fire the gases have more room to spread out and therefore the smoke layer stays at a higher level during the likely evacuation period?
Sprinklers, particularly fast-response ones, should adequately compensate for a larger area.
Is the shop a 'stand-alone' or part of a complex at all? If the latter then the CFD ought to show if any smoke control/dispersal system can cope or not with the potentially bigger fire from a larger floor area.
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John,
I will indeed ask for the models to be run at a higher growth rate but suspect that as they are comparative, it may not matter what rate is used if the oversize compartment performs better than the compliant one.
My understanding of the model is that the better performance is achieved by the fact that the higher than average roof height can accommodate the smoke and heat for the required time before losing bouyancy. Unfortunately I'm not a qualified engineer and can't fully analyse the results, but it would seem that the standards are based on floor space where they should possibly be based on compartment volume.
I suspect the whole issue is being proposed to avoid the installation of sprinklers, which would allow an unlimited floor area.
The building is a single storey detached, with no other buildings in close proximity. No form of additional ventilation is proposed.
Thanks
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Computational Fluid Dynamics will certainly show that a large volume helps in the evacuation phase, but that is not what compartmentation is all about. Compartmentation is there for a few reasons. One reason is to limit the size of the fire that the fire service will have to deal with, another is to limit the number of people exposed to a fire.
The model should definitely be run at a fast fire growth, and it should be run way past the normal evacuation period, if the fire resistance of the compartment wall was 1 hour, then the model should be run for that same period of time. If more than 2,000m2 is damaged, then they have not acheived the same goal.
Regardless of what the AI says you can enforce suitable measures for reducing the risk of spread of fire under article 8. Tell them you will do this, (Keep good records of any such communications) then if it goes ahead as described, reinstate it afterwards through enforcement. They can appeal the notice, and if the secretary of state decides that it is ok as it is, then at least the decision isn't on your shoulders.
PM me if you want, I may be able to assist more.
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They should also take into account the potential for flashover in the extended timeframe.
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Absolutely... define "...the compartment performs better in fire conditions..."? In the initial stages of the fire, perhaps it does (bigger = greater dispersal volume might = longer to untenable conditions)... but means of escape will take longer and this misses one purpose of compartmentation - which is to limit ultimate fire size - See Section 8 (Compartmentation) in the E&W AD-B - particularly 8.1. I'd intuitively be very surprised if the conclusion of the model was that the peak fire size in the larger compartment were lower than in the smaller...?
I'd also not assume that a different choice of fire growth rate will have the same effect on results, for comparison purposes.
Would be interesting to hear more details of in what respect the results were better?
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Would be interesting to hear more details of in what respect the results were better?
me too :)
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Fishy,
As you suggest, the results are based on teneble conditions at 2m height taking longer in the larger compartment - common sense i know, but also claim that as travel distances are compliant and both compartments are smoke logged by anticipated FS arrival time, these are not applicable. The temperature at 2m is also lower. There is no reference to peak fire size in the results, but a t2 medium growth rate reaching a peak of 15mW after 15 mins is quoted in the parameters for the models.
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Part of the functional requirement B3 is:
Where reasonably necessary to inhibit the spread of fire within the building, measures shall be taken, to an extent appropriate to the size and intended use of the building, comprising either or both of the following:
a) Sub-division of the building with fire resisting construction
b) installation of suitable automatic fire suppression systems
Also ADB 8.1 states that the object is twofold:
a) To prevent rapid fire spread which could trap occupants of the building; and
b) to reduce the chance of fires becoming large, on the basis that large fires are more dangerous, not only to occupants and fire and rescue personnel, but also to people in the vicinity of the building.
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And a t2 fire with a fast growth rate is at 38MW by 15mins.
Look at what perimeter they have used too. A growing fire has an ever-changing perimeter. (The above calc indicates a perimeter of about 30m) A quick spreadsheet I set up for a 6m high building of this area has the potential to be at a stage conducive to full involvement / flashover at about 8 minutes, so the perimeter given is largely academic as the whole area could be involved. This will clearly be a longer time than the smaller compartment would take, but the difference is the size that the fire can be. Your version is almost 4,000m2 of fire, when the code compliant version is 2000m2 of fire.
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I would whole-heartedly throw my weight (which is sadly increasing) behind Civvy's and Fishy's comments. The AI and the fire engineers here are quite simply talking rubbish. They have displayed a complete lack of knowledge and understanding of the aims of the building regs and fire safety legislation. They are buffoons of the first order and you can tell them that I said so. I have seen so many similar displays of incompetence that this doesn't surprise me but it does dishearten me slightly. I'll bet I, and some others on here, could have a good guess at who the AI and fire engineers are.
I was just about to post the quotes that Civvy just posted - don't have to now. The size limitation is nothing to do with protecting means of escape (not directly anyway) or maintaining smoke at a certain height, it's about keeping the fire to a reasonable size for a reasonable period of time. As Civvy's already said, to demonstrate that their building is as safe as a code compliant one they would have to show that the fire will not be larger than 2,000 sq m in area after an hour of burning. How will the fire know to stop spreading when it reaches 2,000 sq m? I have a sneaking suspicion, it won't!
The proposal is nonsense and I would not hesitate to reject it as unsatisfactory. Frankly, it's reckless, arrogant and even insulting for the proposers to even put this forwards.
I suggest you get a big red ink pad, a big rubber stamp that says, "b[censored]s" and that you stamp each page of the proposal before sending it back.
More seriously though, you should heed Civvy's advice to record all correspondence concerned with this proposal so that your route to enforcement, if it goes ahead as proposed, is supported and eased. Civvy's said it all really, don't know why i'm bothering - just wanted to support his comments because the affrontery of proposals like this irritate me.
Stu
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In the case of a fuel controlled fire, based on an assumed 550 kW/m2the difference in heat release rates between the two compartment sizes are considerable:
Compartment of 2,000m2 reaches 1.1 GW.
Compartment of 3,800m2 reaches 2.09 GW.
:o
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And don't forget to complain about the AI. He is either blatantly lying in order to get the work, or he is too stupid to be allowed to make such decisions.
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And don't forget to complain about the AI. He is either blatantly lying in order to get the work, or he is too stupid to be allowed to make such decisions.
Completely agree - I work for a large AI - speak to ACAI or the Construction Industry Council (the body that issues our licence to operate)
Sadly, as an industry this kind of thing, where people don't know there limitations, have insufficient knowledge or cynically/weakly will accept anything a client proposes to them, is becoming all too commonplace.
"Depressed" of Altrincham
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A thought - not sure where you are, Zimmy, but some of the larger Metropolitan fire authorities have specialist Fire Engineering departments whose job it is to review/interrogate fire engineered solutions (I'm being generous) such as this. I know LFB does, for example. Might be worth a call to see if they'll share their knowledge, over the 'phone or even take a quick look at the proposals for you?
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I lead such a department, and I am sure we would be happy to help on a more official basis. To be honest it doesn't even take a fire engineer to disprove this, it is the basics of Building Regulations. They are 'proving' the wrong thing. (Essentially they are proving* suitability under B1, not B3)
* I am using the term in its loosest sense
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Many thanks for all your informed comments, opinions and suggestions. Fishy, consultation with our neighbouring Service has also been initiated, and the opinion received is in line with the above points. I'm now satisfied that the line I was first intending to take has been reinforced by the opinions offered and was concened that I may have been overriding any set precedents, it would appear not.
Thanks again
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Just riding on the back of the original posting, if this property were in London, section 20 of the London Building Act may also apply.
Section 20 is a residual part of the London Building Acts (Amendments) Act 1939 which deals with fire safety in tall or large cube buildings. Although many of the original technical requirements are now included in Part B5 of the Building Regulations there are still some elements that will only apply under Section 20.
It is a matter of fact whether a building comes under Section 20 or not and the criteria is based on size and use alone. Any building in Inner London that is constructed or extended since 1939 will be Section 20 if:
a) it has a height of greater than 30m, or
b) it has a height of greater than 25m and a storey that has a floor area in excess of 930m2, or
c) it is a building of the warehouse class or used for trade or manufacture and has a cubical extent of more than 7,100m3. Where building works controlled under the Building Regulations are carried out to one of these buildings it is likely that they will also need Section 20 consent. Consent can only be given by the local authority, even if the Building Regulations application is being controlled by an Approved Inspector.
I am interested in the implications of this and how it is applied in relation to shops or as section 20 puts it "used for trade".
Many of the guides produced by the local authorites simply refer to storage buildings but I was looking at a modern retail park in East London recently and it was clear that section 20 had been applied to fairly small modern purpose built retail sheds. This was confirmed by the operator of the park.
The one in question had a total footprint of 1500m2 - fine for a single compartment under ADB but as it was over 8 m high fell well over the 7100m cube bringing it into the Section 20 threshold. The building in question had a full height drop down curtain cutting it in half and furthermore roof vents with additional provision for make up air at a low level. Probably a mistake by the designers I reckon but it will cost to make an application to change it so my client is likely to leave it as is..
Well thats ok but my thoughts were as a firefighter I would be much happier entering fire in a shop building with a ceiling height of 8m rather than one of the same size with a 4m high ceiling.
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Hi Zimmy, firstly I hope you're still reading...I've been trying to get on through the new anti-spam since you posted.
This thread is a fascinating education in Fire Engineering sources and for that reason alone is a good read, however, there being many ways to skin a cat I have an alternative approach as a suggestion for you:
if you are able to get hold of the procedural guidance document on Building Regulations consultations, it gives very clear guidance on what each party to the consultation process is responsible for.
In the case of a F&RS, this is to comment on apparent compliance with the FSO once the building has been occupied, AND other applicable legislation.
This means that it is not our responsibility to tell the AI how to do his (or her) job, nor to check whether the job is done properly in respect of compliance with the Building Regs.
We should be confining our comments to compliance with the FSO with the exception that we also have a duty to comment under the F&RS Act 2004. Under this Act, a suitable comment in this situation would run along the lines of...'if you build it like this then *** F&RS cannot guarrantee to be able to fight a fire in the premises and may resort to defensive fire fighting techniques. In this case you could expect the building to be a total loss in the event of a fire.'
Once this comment has been made, 1) the F&RS is covered against critisism when the building burns out due to an otherwise small fire, and 2) the occupier will need to disclose this to any prospective insurers and will find premiums to be a tad high. Also, the AI will not be able to hide this piece of information from his client and will look somewhat less professional in any meeting explaining the situation to his client.
The only other exception, for completness is that B5 should be checked thoroughly as there is no second bite of the cherry to put right any deficiencies here. I have found the same approach to be very powerful when trying to persuade AIs to build in adequate FFing facilities as well.
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RonH, welcome to the forum.
The procedural guidance does state that we can offer our observations under Building Regulations. In the perfect world all AI's and BC bodies would do their jobs properly, and all we would be commenting on would be the need to do a fire risk assessment, and act on its findings. In the same perfect world the BC bodies would lead the pre-submission meetings (As stated in the procedural guidance) instead of sitting there sheepishly, scared of losing the submission to any another AI who is willing to accept a load of 'engineered' drivel.
Also, since compartmentation has more in common with B5 requirements, then I believe that we should fight tooth and nail to give our troops the best that Building Regulations is intended to give them. If the firefighting facilities (including compartmentation) within a building are not sufficient to enable our firefighters to enter a building to perform the duties that they are employed to do, then the developer has probably not met the functional requirements of the Building Regulations. If the developers want to build such a building then there is an official route for them to take, and that is via a relaxation. (Which takes the decision away from an AI, and sticks it firmly at the feet of the Local Authority)
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RonH, welcome to the forum.
The procedural guidance does state that we can offer our observations under Building Regulations. In the perfect world all AI's and BC bodies would do their jobs properly, and all we would be commenting on would be the need to do a fire risk assessment, and act on its findings. In the same perfect world the BC bodies would lead the pre-submission meetings (As stated in the procedural guidance) instead of sitting there sheepishly, scared of losing the submission to any another AI who is willing to accept a load of 'engineered' drivel.
Also, since compartmentation has more in common with B5 requirements, then I believe that we should fight tooth and nail to give our troops the best that Building Regulations is intended to give them. If the firefighting facilities (including compartmentation) within a building are not sufficient to enable our firefighters to enter a building to perform the duties that they are employed to do, then the developer has probably not met the functional requirements of the Building Regulations. If the developers want to build such a building then there is an official route for them to take, and that is via a relaxation. (Which takes the decision away from an AI, and sticks it firmly at the feet of the Local Authority)
Hi Civvy FSO, thanks for the welocome. I hope your still reading? I'm not too good at this forum lark.. far too long between posts, but here goes:
I agree with everything you have put here, especially with providing Fire fighters with the best possible chances of fighting a fire and surviving. The only issue I would have is that there is no requirement for the BC or AI to pass on our 'observations' to the client. Yes, we are entitled to make observations, but these do not carry any weight. Much more effective is to make a 'comment' under the other legislation heading, usually the Fire and Rescue Services Act. These comments must be passed to the client, who is usually not impressed to hear that the building will not satisfy the F&RS.
I have had some very positive results using this approach, from AIs who seemed determined to cut provisions for fire fighting to the bone and beyond.
By using the AI's tools to do his job for him, we are making him look good. By using our tools to do our job, we show up those who are not doing such a good job themselves.
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Late into this I know but out of intrest if something was so obviously wrong can not state that as soon as the building opens the fire authority will take action under the rro to put it right which might end up costing the punter and the a.i. some hard earned wonga?
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Late into this I know but out of intrest if something was so obviously wrong can not state that as soon as the building opens the fire authority will take action under the rro to put it right which might end up costing the punter and the a.i. some hard earned wonga?
Hi Cleveland Fire 3,
this is absolutely right, and the whole point (stated 3 times in bold in the 'Building Regulations and Fire Safety Procedural Guidance Document') of the Building Regulations consultation process: to prevent this from happenning.
Failure on the part of either the AI / BC or Fire officer to advise on matters required in addition to Building Regs does not in any way prevent enforcement under the FSO at a later stage, even if this is on day 1 of occupation.
However the problem which started this topic was one where the matter (excess uncompartmented area) was a requirement of the Building Regulations, not the FSO. In this case, the matter could not be made good afterwards using the FSO, as it is not an immediate occupant life safety issue, rather an issue of whether it is physically possible to fight the fire without putting fire fighters in a perilous position.
The base justification for the 2000 sq m limit is: a jet of water will only stay coherent for 25m. Therefore, in a compartment of dimensions greater than 50x50 (2250 sq m) there will be areas where a fire cannot be reached by fire fighters, without entering the compartment, thus putting themselves in immediate danger. Hence compartments over this size need to have other methods of controlling a fire.
if the compartment is built to 3800 sq m without additional compensatory features, then the FRS should inform the AI / BC that they might be unable to fight a fire and would therefore adopt defensive tactics: in effect standing outside roasting sausages on very long sticks! This comment would be made under the Fire and Rescue Services Act, as an advisory comment only. However, as it is not an 'observation' on compliance with the Building Regulations, the AI /BC is required to pass this comment on to the applicant. Observations do not need to travel any further than the AI / BC!