FireNet Community
FIRE SAFETY => Fire Alarm Systems => Topic started by: david911cockburn@btintern on November 30, 2010, 10:14:32 AM
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Hi All,
Does anybody know which UK Law sets out what a Fire Alarm System must achieve?
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The Regulatory Reform(Fire Safety) Order 2005 sets out the requirement for raising the alarm in case of fire and in some cases for the automatic detection of fire. The actual requirement will be identified by carrying out a fire risk assessment to determine the appropriate general fire precautions required to protect people from fire. This covers life safety only, not property protection. There are a number of guidance documents publisd by the Government to assist you with this, and are available for free download from the CLG website. Google CLG fire and you ill fnd them.
If installing a fire alarm system it is recommended that it should conform to best practice which in the UK is set out in the various parts of BS5839, and component parts of the system should conform to the various parts of EN54.
NB this is a summary answer only. Hope it helps.
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The Law does not set out what the system must achieve. Under the Fire Safety order it must be "Suitable and Sufficient".
A shout of fire is suitable and sufficient in some circumstances. There is no legislation to say how loud someone must shout.
I think in considering legislation, you must also consider the European directives and how they are incorporated into our Laws, this can cause overlap, eg the fire alarm is required in accordance witht he H&S (Safety Signs and Signals) Regulations- is this the Legal requirement you are seeking?
Whilst the BS series are generally accepted as best practice guidance many of them contain some errors and cannot cover every situation that you may encounter.
I am interested in knowing in what area BS7671 does not comply with the EAW Regs? Always keen to learn.
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I am afraid the Law is rather woolly and was left deliberately so. The problem with actually basing the specification of the fire alarm system in Law is the Law is difficult to change. This has a historic aspect with the Health and Safety at Work Act, prior to this all the requirements for factory safety were specified in law. However what was happening was that by the time the specifications for guarding, let us say a stamping press like Dangerous Machine Mark 1, had passed through all the legislative processes no one was making Dangerous Machine Mark 1 and it was now onto Mark 3a and the law did not apply.
How the process works is the Law refers to an appropriate alarm system which is accepted as BS 5839 and its parts. Hence most cases will be covered by a system compliant to BS5839, but there may be cases where BS 5839 is not appropriate. In these cases a solution could be agreed between the client and the enforcing authority which does not fully conform to BS 5839. On the other hand a new type of alarm system may be invented and manufactured in which case all that needs to be done is to revise BS5839 not go through the entire legislative process.
In a similar way the Highway Code is not Law, however it is used by the Courts as primary guidance as to the proper way of behaving on the road. You will not be charged with breaking the Highway Code, but you will be charged with something like Dangerous Driving and the Courts will use the Highway Code as the guide as to what is or is not Dangerous Driving.
Yes the whole thing is woolly, but that's the way the lawyers make their money.
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David - as someone who knows BS 7671 fairly well, in what way does it fail to match the 'Electricity at work 1989' requirements? There is a clear note from HSE on page ten of the 2008 edition of BS 7671 that installations carried out to BS 7671 "are regarded by HSE as likely to achieve conformity with the relevent parts of of the Electricity at Work Regulations...."
BS 5839 is not based on legal requirements - it was developed by the trade and users from a previous Code of Practice (CP1019, I think) as setting out reasonable requirements for a viable fire alarm system which matches the needs of particular premises. Fire safety legislation then refers to the BS as a guide for those wishing to install a system.
But as Kurnal points out, the type of fire alarm needed in a particular premises is dependent on a risk assessment. For example, a number of the extremely elderly church buildings I give advice to the risk assessment will probably recommend a set procedure for clearing the small congregation from such a building without any recourse to a fixed electrical system which they may not be able to afford and maintain and whose installation would be detrimental to the ancient fabric of the building.
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Not quite clear what you are saying. Please feel free to email your documents- the address is shown at the bottom of my postings.
I might be being thick here but in your previous posting I think you are suggesting that all flexible leads that may be plugged into a supply should incorporate an earth conductor irrespective of whether the appliance supplied has some other conductor or surface that that could become charged and live as a result of a fault condition? Is this what you suggest or have I got it wrong?
If the appliance is double insulated then the provision of an earthing conductor in the cable would only be a safeguard if the live and earth were simultaneously exposed, it would not help if I nicked the cable and only exposed the live conductor?
Your last posting seems to discuss fire alarms and mains wiring and sorry but it has left me completely confused. We do not have mains powered fire alarms any more.
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David,
I think I see what you are driving at but if any manufacturer claims that 'air' forms part of the double insulation of any portable equipment then I think their equipment is wrongly labelled as being 'double insulated' and this is a matter for trading standards and the like. All double insulated equipment I've ever pulled to pieces has always had two separate lots of insulation.
I'm not too clear about the 'EAWR' business, not having, I admit, read these in detail. But I assume the reference to 'conductors' is what Part 2 'Definitions' of BS7671 (page 24 in the 2008 edition) calls 'extraneous-conductive-part' and which does not form part of the actual installation? In which case BS7671 does deal with the need to earth these in Section 4 Chapter 41 or gives circumstances where it is not necessary to do so. So it is possibly the sort of case that is mentioned above by Mike Buckley where detailed legislative requirements have not kept up with technical developments.
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I'm also confused by this thread and how it applies to the sort of fire alarm systems we use today.
Normally the only mains voltage connection to a system is via the cie (control and indicating equipment)
The cie also requires an earth connection and any metalwork used in the cie (including a hinged door) is connect to this earth.
The fire alarm circuits cables, which are generally only carrying extra-low voltages i.e 24V dc, need to enter the cie through a different access point from the mains supply and these cables invariably also contain an earth conductor which is also connected to the cie earth.
Most fire alarm accessory equipment housings are made of plastic, with the exception of fire alarm bells, and all of these items normally have an earth connection.
Whilst it is true to say that there is some danger from electrical shock because BS does not recommend the use of of a residual current prtotective device (other than where it is necessary to comply with BS7671) the whole system is pretty comprehensively earthed, and I've never heard of any problems with modern systems relating to electric shocks from the equipment.
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Hi David,
We already know that the precise requirements for fire alarm systems are not enshrined in some sort of water-tight set of laws. Even the recommendations are often open for interpretation. We have lived with it for years and can't begin to worry about it any more than we ever have done.
As for the electricians, I can't see their trade bodies allowing them to be held liable for anything that was standard and accepted practice in the past. If some supposed future allocation of 'blame' is something that potentially affects a large number of business people, then politicians will have to do something about it or face the wrath of these people.
You can rest assured that if there is any cost to be paid by anyone for something the politicians have missed in the past, it will be paid for by the general public, directly or indirectly. Business might have to administer it, but they will not lose any money over doing so. This is the way of the world in the UK.
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There are really two separate issues here. One is the requirement to provide a fire alarm, and the other is electrical safety. Both covered by legislation, and both quite separate. Your beef is clearly with the BS7671, which is referenced within BS5839.
At the risk of sounding flippant, if someone was electrocuted by a fire alarm it is not a fire safety problem. The HSE would investigate, not us.
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I have received Davids papers and am happy to forward them to anyone who asks. The files are too big to attach, and I do not have a picturebox account or similar application to link to, if anyone else has such an account I or David will forward the files.
I thought the screen was earthed in a FP200 or MI cable attached to a fire alarm system?
(I only drive them I dont fix them)
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David,
I think I have got some basic idea, after 30 years in the business, about the need for earthing for electrical safety reasons.
For your information, the fire alarm cie requirement is for the metal door or cover to be properly earthed by flexible wiring that goes between the mains incoming earth and that door or cover. It doesn't just rely on a conductive path through a hinge or similar.
Of course organisations will automatically put a disclaimer with any information they produce. This is mainly to cover themselves in respect of errors in information obviously beyond their control. But they can't discard responsibility for absolutely everything with a simple disclaimer, there are certain responsibilites that everyone automatically has.
However, electricians have trade support organisations whose role is to uphold standards, and to inform and train their member If every electrician is doing the same thing based on good practice and advice (even with a disclaimer) then I can't see the whole industry not coming behind and supporting any of them being punished in the future for something they all do and believe is correct.
Furthermore, there is nothing you have mentioned that makes me believe that fire alarm equipment or installations are affected by the problem you have raised. It is a fixed installation with proper earthing, and the problem you have raised seems to be with portable equipment with unearthed electrically conductive surfaces that may be powered from a supply without using an earth. What has that got to do with fixed fire alarm installations?
I don't believe that fire alarm system companies / designers / installers have anything to worry about in respect of your fears.
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Hi All,
The reason that very little has happened up to this point within the Electrical Industry is because until recently the authorities (including the NHS and the Police) did not recognise the difference between RCD's and MCB's.
If you imagine the difference between cooking in an oven and cooking in a microwave it is easiest to understand, a circuit protected by an RCD 'cooks' its' victim from the inside like a microwave whereas a circuit protected by an MCB or a fuse also leaves the victim 'crispy' on the outside.
Heart attacks are on the increase, but even if the victim survives why would they think that electrocution had been the cause when they had only leant on an innocuous looking radiator?
Now I am worried.
RCD's 'cook' a victim!
MCB's make them crispy!
Medical experts can't recognise electric shock victims!
Prof. K. sort this out! I'm now leaving the building!
Matron! Call 911!
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Sorry if I took this thread off at a tangent. Back to the original question David I would summarise the consensus as follows:
The legal requirement to provide a means of warning in case of fire is a functional rather than a technical one.
For existing buildings the Fire Safety Order places a duty on the Responsible Person to carry out a fire risk assessment in order to determine a suitable and sufficient solution.
For new buildings and alterations to existing buildings the Building Regulations require the developer to make provision for warning and in some circumstances detection of fire.
In both cases if you choose an electrical alarm system to fulfil this requirement then a system designed, installed and maintained in accordance with BS5839 will represent an acceptable solution. However you are not bound to follow this guidance and are free to install whatever system you choose.
If you choose not to follow the guidance and are considered to be in breach of the Fire Safety Order and are charged with an offence which leads to court, the burden of proof falls on the responsible person to prove to the court that their solution provides an equivalent standard of life safety. Similarly for new buildings Approved Document B lists BS5839 as an acceptable solution you have freedom to do something else provided you can convince the Building Authority that your solution is equivalent.
In both cases there are provisions for determination on the technical solution by the Secretary of State.
Hope this helps David, please anybody feel free to modify any of the above if I have not expressed the situation accurately.
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David I am sure there are many here able to answer you but I wondered if you are also aware of another forum
http://firealarmengineers.com/forum/
You may find answers there too.
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Hi Wiz,
Why are you talking about earthing?
I've already explained that other readers were simply curious to know why the 17th Edition of BS 7671 fails to comply with the EAWR, that is the only reason that earthing has been discussed.
The problems concerning fire alarm systems have nothing to do with earthing, please take a look at the drawings that Kurnal has referred to above or read through this forum from the beginning before speaking again, otherwise I'm sorry to be rude but you are just wasting your breath.
David, I'm talking about the things that I understand that have been brought up by your original question, and that seems to me, to be about electrically conductive surfaces not being earthed. Since I am interested in fire alarms, and you claim that they are affected by the problem, this is obviously what grabs my attention.
If I have misunderstood your point then I trust you will be able to explain it a bit better without using silly phrases like RCDs 'cook' people and MCBs make them 'crispy'. I can't believe there are many people on this forum who don't know the difference between an MCB and a RCB, and I believe you are only 'talking down' to them if you use such phrases
Your subsequent explanation was far more useful for those who know very little, but the claims of death being caused by as little as 2mA is hyperbole when talking about everyday situations. Also you make no mention of the affect of muscular reaction when affected by alternating currents.
You have also made scaremongering claims that electricians are going to be punished in the future for following standard practice today. You also claim that fire alarm designers & installers will also be dragged into this problem. I say it is very unlikely to happen.
You admit that your past representations to various authorative organisations have been ignored. I wonder why this is? Why isn't the NICEIC or ECA interested in this supposed 'problem'?
If you are only trying to say that there is clash in some combination of different laws and/or recommendations, then I say that this sort of problem is endemic and affects many areas of life and business, and it obviously doesn't matter that much to anyone.
And where is all the data on the thousands/hundreds/dozens of people being killed every year because of this problem?
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David I am sure there are many here able to answer you but I wondered if you are also aware of another forum
http://firealarmengineers.com/forum/
You may find answers there too.
Thats a sneaky move, Prof! :-\
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Just trying to be helpful as usual Dr Wiz.
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I think that particular forum is full and there are a few people who may not be as restrained and polite as the members here, and anyway they're no where near as clever as Kurnal....... ;D
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I think that particular forum is full and there are a few people who may not be as restrained and polite as the members here,
You must be referring to that stroppy ESP person? ;)
Yes we are fortunate in our members they very rarely get abusive and can be relied on to give people the benefit of the doubt.
It sometimes isnt easy to express yourself in a chatroom such as this without the other cues such as body language etc and I am often suprised at how some of my postings are not read in the way I intended. Especially when trying to be humorous or brief. Brief responses are so often seen as flippant, ignorant or arrogant.
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It sometimes isnt easy to express yourself in a chatroom such as this without the other cues such as body language etc and I am often suprised at how some of my postings are not read in the way I intended. Especially when trying to be humorous or brief. Brief responses are so often seen as flippant, ignorant or arrogant.
Yes and to think Wiz has been critical of me in the past for my responses, yet he has been very bolshy toward a new member. A timely reminder that all is not as it seems on an internet forum without having the benefit of tone of voice and body language.
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I believe David is exaggerating the 'problem' he claims and also scaremongering somewhat. However he is entitled to his opinions and I welcome his views. I just hope he that he doesn't believe that I have to agree with everything he says and allows me to question his claims that I don't believe in or understand.
I also tend to be a touch sarcastic when I believe that someone is 'talking down' to me or other members. I apologise unreservedly to David911 if he has been hurt by my sarcasm.
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David I have not shared your documents with anybody, I am happy to forward them to anyone who requests it but have no access to a server on which to place them for general access. Other members who regularly post photos do have such access and may be able to help.
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If I have designed, installed and maintained in accordance with the accepted best practice guidance BS5839 I will have nothing to fear from the judge.
Is it safe enough? Better minds than mine have decided that it is.
Your argument has some merit no doubt but s it not similar to the following scenario?
The Highway code says I should drive at a maximum of 30 mph in a built up area. If I hit a child at 30mph I will kill them. If I hit a child at 20mph I probably will not. So the Highway code is a dangerous document. It should say we should all drive at a maximum of 5mph and a man should walk in front with a red flag to warn pedestrians.
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ELECTRIC SHOCKS
The effect of an AC electrical shock on a human being depends very much on the AC cycle frequency and the voltage.
There are also numerous factors that affect the effect of an electric shock, and probably most importantly, the route through the body which it takes
A human being exhibits an electrical resistance between dry fingertip to dry fingertip of up to about 100K Ohm. This means a current of approx. 2.3 mA would flow at a voltage of 230V. This would barely be felt.
Even if the electrical circuit is backed up by an 100A fuse, this doesn't mean that 100A would flow through the human body because the electrical resistance of the body limits the current that can flow.
Obviously sometimes, due to skin moisture etc, the resistance to electrical flow will be far less and then a higher current will flow and the electric shock will be felt much more.
Many 'mains voltage testers' rely on the human body providing part of the electrical circuit to illuminate the neon. A resistor incorporated within the tester circuit restricts the current flow to well below 1mA where it cannot even be felt.
Electricians suffer electric shocks from mains voltages many times throughout their working lives without any ill effects.
Many electricians actually test for the prescence of 230V AC mains voltages by earthing a finger of one hand and then touching the suspected 'live' conductor with the thumb of the same hand. This causes just a bit of a tingle.
Touching a 50 Hz AC electrical potential with a finger generally causes the the arm muscles to involuntarily to contract drawing the finger away from the source.
Generally there are very few fatal electrocutions to humans at current flows of less than 100ma.
If a human exhibited a resistance of only 1000 Ohms (perspiring greatly?) then the current flow at 230V would be 230mA and highly probably fatal.
The Guiness Book of Records that someone survived an electric shock from a 340,000 V source.
However, no-one should ever underestimate the potential dangers of electric shocks.
If the electric shock caused a burn which broke the skin and the outermost layer of the epidermis then the electrical resistance of the body will dramatically reduce. This burning is normally mostly a problem at voltages over approx. 400V.
Ventricular Fibrillation may occur at currents as low as 50mA and if electrodes are placed directly either side of the heart at currents as low as 1 microAmp.
AC is more likely to induce fibrillation than DC voltages.
The higher the AC cycle the more chance that muscles will actually seize than contract.
However, the statistics show that there are surprisingly very few fatal electrocutions of humans from the domestic power supply, without the circumstances of moisture being involved in some way, in respect to how close we all come to it every day.
The introduction of electrical safety devices such as RCDs have greatly contributed to this.
FIRE ALARMS
The Oxford Dictionary definition of the term 'radial' is 'diverging in lines from a common point'. In fire alarms we use this term to describe a method of circuit wiring to differentiate it from loop wiring.
The use of a minimum of two alarm sounder circuits in fire alarms when using radial circuits is to
try to prevent losing all sounders should a fault occur and so that occupants of an evacuated building don't return to an unsafe building thinking that the fire aalrm system had been reset because they've heard the sounders silence. In fact BS5839-1 actually recommends (but doesn't insist) that just one sounder is connected to one of the circuits and positioned adjacent to the main control and indicating equipment (which is likely to be positioned close to the main entrance to a building).
To try and achieve the same level of cover on loop wired systems BS5839-1 recommends that the first or last device on a loop is an alarm sounder mounted adjacent to the cie and then protected either side by a loop short-circuit isolator. I believe an earlier post suggested that other devices might be connected as the first devices, which is incorrect.
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"Now if you will all forgive me I will indulge in some theoretical 'scaremongering' simply because this is the easiest way to get the point across: Audible warning devices are constantly transmitting a message, if they are operating there is a fire, if they are operating intermitantly there is a fire somewhere close by and if they are silent you are safe. Therefore if during a fire a person reaches an area where the audible warning devices are silent that person will assume that they have reached a safe place, therefore if those audible warning devices have failed and the fire is actually close by that person could be hurt as a result!"
In my view this is the wrong interpretation. If the audible alarms are operating you must leave the premises to a place of safety. If they are operating intermitantly this is part of a phased evacuation process and you should prepare to evacuate. Once the evacuation has started you should evacuate the premises and not return until told it is safe to do so.
Once the evacuation has started a person is not safe until they have reached a place of ultimate safety (normally outside the building).
The audible warning devices are tested as part of the weekly fire alarm test and any failures should be noted. Having done that the occupier has done everything that is "reasonably practicable" to ensure the system is operating. No court case.
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David I am sure there are many here able to answer you but I wondered if you are also aware of another forum
http://firealarmengineers.com/forum/
You may find answers there too.
Started off well, got interesting, feeling drowsy, dreams of http://www.electriciansforums.co.uk/, ZZZZZzzzzzzzzz........
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David I am sure that Wiz was not trying to mislead anybody he was expressing his point of view. And very few people have a better technical and practical understanding of fire alarms.
I can relate to some of what he says, when I left school and before joining the fire service I worked in a TV repair shop in the old days of valves when most sets had a "Live chassis" - the intention was that the neutral was connected directly to the chassis of the set. That was in the days when many homes were still on round pin plugs which were often reversible. Many of the old timers when servicing in the field used to very quickly and lightly touch the chassis of a set before working on it to check if it was "live ".
To be honest I feel this discussion on earthing is going outside the remit of the firenet forum and may be better exercised on other forums.
As far as people getting killed or injured by fire alarm sounders failing, there is no evidence of this occuring. All fire brigades fill in a FDR1 form to report on all fires and one thing they are required to specifically report is the failure of fire safety systems. If you wish to persue this you could ask the DCLG for their data.
But I served 31 years in a fire brigade and never encounrtered this as a problem, yes alarms were eventually damaged by serious fires but the people had long since left. After all the goal in most buildings is the early detection of fire by smoke detectors and the efficient evacuation of a building when the alarm sounds, in most buildings to be complete within 2.5 minutes of the alarm sounding.
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Is this incident documented in the public domain? How was the signal to evacuate passed around?
I would be interested to know the detail of what happened.
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"A couple of years ago one of the Hospitals in London evacuated 800 staff and 80 patients in complete silence during a fire!"
It is wrong to associate raising the alarm with bells and sirens going off all over the place. There are places where it is impractical or even dangerous to use the "usual" type of sounder. The classic example always used to be cinemas and theatres where a certain tune played over a tannoy system would alert the staff to start evacuating the audience. Also in hospitals there is a question of whether alarm bells going off would cause more problems by uspetting and panicing the patients or whether another system should be used.
The highlight of your comment should be that 800 staff and 80 patients were safety evacuated during the fire, not that they weren't deafened by the bells whilst they were doing it!
The main thrust is to look at the goal, which is to get everybody out in case of a fire, and then follow it up with the method, which is normally, but not necesarily, a BS5839 Fire Alarm System.
Thank you for your offer to look at the diagrams but I am not an electrician or a fire alarm installer and they would probably mean nothing at all to me.
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Mike answered the point for me. Yes he is absolutely right that the purpose of the fire alarm in these situations is to alert all those who need to be alerted. Once that is done the noise prevents good communications and causes distress to those who are totally dependent on others to assist them to escape. When I produce an emergency plan for a care home I usually suggest that once all staff and visitors and anyone else who is intended to leave under their own steam is accounted for, then the alarm should be silenced but not re-set. This gives the staff chance to communicate and minimises distress for those in their rooms who are awaiting assistance and who may well be waiting a long time if they are at the opposite end of the building to the fire. Hospitals likewise have their own HTM codes for fire safety including special provisions in the design of the fire alarm system. You can download or obtain these here:
http://www.dh.gov.uk/en/Publicationsandstatistics/Lettersandcirculars/Firecode/index.htm
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I stand by everything I mentioned in my previous post including all the facts and figures that I mentioned.
I am certainly not trying to mislead anybody and resent the implication.
I am certainly not going to allow contentious claims to go unchallenged on Firenet, otherwise the unwary may take them at face value
Obviously, it is up to the readers to decide who or what they want to believe and I feel that my point has been made in adding another viewpoint to the claims being made.
Furthermore, I also won't be drawn in to a childish slanging match with someone who admits that he has been ignored by all the authorities and banned for life from forums peopled by just those who should know all about the subject!
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Thanks Wiz. Your postings are always well informed and well argued. Moderating a forum can be challenging, as a member of other forums I have seen the damage that can be caused when people deliberately post incorrect material or make outrageous or offensive claims or comments. It is easy for the regulars to become disillusioned and to turn away from a forum when this starts to happen and hope this does not happen with firenet.
By the same token I always try to give people the benefit of the doubt and welcome the chance to share knowledge and experience amongst ourselves and with new posters. However whilst it is good to challenge existing practice and standards this should be argued from a certain foundation of knowledge, the role of the forum in educating people I think is more to point people to the sources of information and then discuss, rather than to try and educate people from the base level.
I think as other forums are specifically set up to discuss electrical safety we should draw a line under that particular discussion and leave the arguments on equipotential bonding to them. I know it was I who asked David to expand on this but in hindsight it was clearly taking us outside the scope of firenet. I hope you both agree.
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Hi Mike/Kurnal,
I don't actually disagree, some NHS staff hate fire alarm systems going of all of the time, but it shouldn't of taken me to go around and warn everybody, should it?
I have another first hand example that I remembered over the weekend: It was at a furniture store in Canterbury that had two entrances, the main entrance was at the rear where the car park was therefore the CIE and single bell were located there, but before the Fire Brigade arrived two students stopped for a chat outside the front door which delayed their entry, as they were chating the plate glass window next to the front door exploded on to the street in front of them!
Could have been nasty.
I posed a question on the Electricians Forum yesterday concerning why the 17th Edition of BS 7671 fails to comply with EAWR 1989 and I have now been banned for life from the Forum.
Now thats' what I call freedom of speech!
Would anybody care to ask them "why they are still using a fusing factor so many years after we all stopped using fuses?" on my behalf.
David Im confused.
Are you saying that at this particular hospital there was a fire alarm activation and all the sounders failed?
Or were the alarms deliberately silenced by staff?
If it was the latter then I could quite understand that (as per Mike Buckley's excellent summary above)
If it was the former I'd find that very difficult to believe.
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is this a wind up?
shoot me now
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is this a wind up?
shoot me now
It's not you who needs shooting, Graeme.
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is this a wind up?
shoot me now
It's not you who needs shooting, Graeme.
We can't all be on drugs...... this really is happening..!!
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For those that have seen the film Inception, this could be a dream within a dream within a dream.
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Hi David
Im not suggesting you are telling fibs, but it is difficult to believe that this actually happened for several reasons.
Even with my limited knowledge of fire alarm systems, I simply can't accept that all of the sounders failed.
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So let me get this right... The fire is severe enough to MELT the sounder(s) but has not in this time allowed smoke to spread out of the compartment where it started and activated another detector? This is of course assuming that the compartment was small enough in the first place to only have one detector. Don't you think you might be stretching the credibility of the scenario just a little bit?
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So it's a real scenario? What happened next then?
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In a two zone overlapping bell system each zone is supposed to be able to provide an adequate decibel level on its' own, just in case the other zone is in down time........
The above isn't a requirement of BS5839-1. Providing such a system seems like a good idea but the extra expense obviously isn't considered worthwhile by BS.
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Early total sounder failure did occur at Hendersons, Woolworths & the Rose and Crown however this was purely down to one of two factors:
a) 240V AC only supply, with mains failure leading to non function
b) The use of non fire resistant cabling on sounder circuits
That is why fire alarm systems are now 24V DC providing at least 30 minutes of alarm after 24 hours mains failure and that for years protected cable had to be used on sounder circuits (& now all circuits).
This seems to do the job and in most well managed buildings 5-10 minutes of alarm should be enough to ensure evacuation (some larger & public buildings and those with a more complex evacuation strategy excepted). Sure eventually any system would fail due to fire damage, but I would be worried as to why anyone would still be inside at this time.
I've encountered system failure, but this is often in buildings with pre BS5839 systems or due to a massive panel failure, but on the latter daily visual panel inspection & weekly tests picked these up promptly and contingencies put in place.
So it seems we are trying to over engineer things a little here!
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Anthony B. Those were my thoughts exactly.
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Me too, guess great minds do indeed think alike
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For those that have seen the film Inception, this could be a dream within a dream within a dream.
haha! ;D
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David,
You have been drip feeding details about the hospital incident so it has been very difficult to understand exactly what happened. Could you please relate the entire incident to give a better idea of what happened.
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Maybe he was just fed up of you going on about it?
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True, he might of had diarrheoa.
verbal?
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I engaged the engineer in conversation on the subject. I can't remember the exact conversation but I did most of the talking
So did he actually tell you anything? It's not clear how if you "did most of the talking"?
Was it this one BTW? http://news.bbc.co.uk/1/hi/7168206.stm (http://news.bbc.co.uk/1/hi/7168206.stm)
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It cant have been Meerkat it must have been another major hospital fire.
The Investigation report conducted by the NHS does not mention any problems with the fire alarm.
http://www.preventionweb.net/files/13954_reviewoflondonhospitalfires1.pdf
Or maybe there is a conspiracy of silence?
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Well the numbers in the BBC report for patients and staff evacuated are exactly the same as the example given by David (though I understand numbers may have been over-reported by the BBC at the time?) and this fire certainly seems to have started in the upper areas of the building. But as you say Kurnal it can't be the same building because there's no mention of fire alarms failing in the official report.
I'll go and look for another one.
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I'd go so far as to suggest that the report infers that the fire alarm did operate because it reports Dr Jones as saying, "We did think it could have been a false alarm". I'm assuming that the 'it' was the sound of the fire alarms.
Yeah, David must have been talking about another London hospital with a fire in the roof area about 3 years ago.
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You lot are enjoying this one aren't you?
Its like your christmas presents to stretch your fire safety knowledge muscle!
Just remember play nice or they will be no mince pies for you all
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It is interesting looking at the NHS report where the Major Incident Plan came unstuck when no-one had the "time" to invoke it. It reminds me of an exercise I ran which was designed to test a hospital's Major Incident Plan. It too came unstuck because no-one invoked a Major Incident, as far as the Brigade was concerned the incident did not trip the Major Incident Catagory, the same for the Police and the Ambulance Service. No one at the Hospital invoked their Major Incident Procedure because no one else said it was a major incident.
It makes me wonder how many Major Incident Plans would fail because there is not a clear directive as to when a major incident occurs and who should invoke the procedures.
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We (well some of us) are assuming it went silent because it failed - more likely that it was silenced prematurely as I know of that happening loads of times with incidents......
.....New Look anyone???
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Or it was silenced as part of the procedure to prevent unnecessarily alarming patients?
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I'm losing the will to live which on firenet is very unusual