7273 and location of detectors

[colin todd]

David, your interpretation of critical is as anomalous as your interpretation of the written word. The most critical doors need cat A. I regret the fact that, as a fire alarm specialist, you think those with expertise on means of escape are wrong in their interpretation of what is critical, but the concept of criticality espoused in the table to which you refer is a well established one, in which staircases in sleeping risks and single staircase situations are more critical than cross corridor doors in a office. This is fairly basic baby talk in fire safety principles.

And you have not read what you wrote again. Nowhere does it say every acoustically linked device must receive the appropriate SPL from 2 sounders. If, however, there were acoustically linked hold open devices on two staircases that were not separated by fire doors then the two could not rely on a single bell. Is this really really very difficult to understand, because, to me, it is what you wrote correctly and then apparently misinterpreted what you wrote down.

Remember that burning building again (sorry wiz but you do somethimes get burning buildings). Bad, bad bad, very very very bad karma if people are trapped and unable to use TWO alternative staircases (which might be the only two means of escape from several upper floors), because just one tiny wee bell failed. That is what you wrote down accurately. Now believe it, or just trust loads of people who do.

[Wiz]

...............Remember that burning building again (sorry wiz but you do somethimes get burning buildings).

Oh Colin, you really are a one! I shook with mirth again!

I don't know where you got it into your head that I don't seem to realise that 'you do somethimes (sic) get burning buildings'.

I do look forward to you confirming where you got this little gem from! Your continual repeating of it must mean it is based on fact.

I believe that you have the wrong end of the stick, but I will gladly continue laughing along with you over my stupidity if you can just point me in the right direction of where I made this faux pas. You see, I think I understand that you sometimes get burning buildings because I've seen the pictures and read the reports. In fact, burning buildings are often uppermost in mind having been in the fire alarm system industry for 30 years.

However, I do feel that you have been somewhat kind to me in comparison to my friend David. I think that David is strong enough to fight his own battles, so I'll leave him to it for now.

But it is obvious to me, that David, like myself and others on this forum, look to our 'betters' for a bit of explanation and guidance on some matters and it is a shame that it is often given with a hefty dose of sarcasm in respect of our inadequacies.

I can assure you that we are all only trying to understand something that we obviously find difficult. In fact we are the ones that are trying to make BSs work. In that context we are, in fact, their biggest supporters.

[colin todd]

Wizzy, I had no idea people were simply seeking advice on things they found too difficult to understand. Now I see things much more clearly..... I was previously misled by comments such as (and I quote):
waste of paper
hands up, I didnt buy it
burn it. best thing you can do with it
men in black overcooked it
and the best one of all (from an ex enforcer) I ignore it completely.

Had I realised that all this somewhat puerile ranting was simply a request to understand a standard that is a bit tricky for non fire alarm engineers (and, yes maybe for some engineers), I would have tried to help. However, from the comments as I re-read them all today, I think many of those  are beyond help, particularly those outside the fire alarm industry who cant be bothered buying it, or who think they are so much above it that they ignore it. (As a matter of record, I dont think you fit into these categories, but are merely frustrated that you cant understand some of the philosophy and practice. I can relate to this as I find the same problem in using a video recorder and, on the basis that I find "The simple guide to brain surgery" is somewhat dificult to understand, and I am not in the field of brain surgery anyway, I tend to ignore it completely too).

Clearly, your conceptual and practical, but I suspect genuine, difficulties with the standard cannot be resolved by a few simplistic words of advice here, nor are they assisted by people who dont understand the technology in the first place jumping on the bandwaggon.

Accordingly, I am pleased to offer the Wizzy fire alarm co unlimited a course on the standard at a specially discounted rate. This is a course that has been presented as a public course for some time, but it is now formally available to the  Wizzyco as an in-house course. The good news is that the whole course only takes half a day as the standard is so simple. The bad news is that, even at the discounted rate, it is quite expensive, but will repay itself in the time you could have been fixing wee alarm systems at a good rate of pay instead of berating the standard to vent your frustrations. I will happily give a price for delivering the course anywhere in the UK except Middlesbrough. Please feel free to  email us for a quotation.

Stop Message Ends. Now off watch on this subject. Returning Home station for refreshments (including a large talisker.)

[David Rooney]

Sorry for the long winded post but there you go….

CT - David, your interpretation of critical is as anomalous as your interpretation of the written word. The most critical doors need cat A.

DR – And who decides what doors are critical, the code doesn’t put responsibility on anybody except “a competent person.”

7273-4 Introduction
Often, the acceptability of the devices, and of the type of device used, will be determined by a risk assessment carried out by a competent person. Building control bodies and fire and rescue authorities can give advice in particular circumstances.

DR – well has anybody told them that because I thought this forum was populated by such persons but it seems that despite nearly 1000 views of this topic none have come forward to offer clarification of any part of this standard. Or is it simply testimony to the fact no one else actually understands it either?


CT- I regret the fact that, as a fire alarm specialist, you think those with expertise on means of escape are wrong in their interpretation of what is critical, but the concept of criticality espoused in the table to which you refer is a well established one, in which staircases in sleeping risks and single staircase situations are more critical than cross corridor doors in a office. This is fairly basic baby talk in fire safety principles.

DR – I can’t see where I’ve said anyone with expertise on means of escape is wrong in their interpretation of what is critical. Perhaps you could point it out?

To my simple mind, if a door on a staircase can fail to close for any reason (software failure or failure of the sounder knocked off the wall by the men shifting the office around) then personally I don’t want to be on the floor at the top of that staircase if a fire breaks out.

I still don’t see why there is one rule for acoustics and one for hardwired systems. I understand there is a concept of some doors more critical than others I just disagree that any door should be left open if the technology exists to close it as regardless of whether the door is on a staircase or subdividing a corridor the action of leaving that door open in a fire condition is increasing the risk to life and property in that area and beyond – bad karma?

From what I can see “those with the expertise” appear to have left the door open (!) for misinterpretation in favour of boosting sales of cheaper acoustic options by building owners, electricians, odd job men and fire companies (of which none of whom have ever heard of this standard or care.)

I have referred to the table in Annexe A which shows that some doors can in particular instances be categorized A, B or C. I find this a little ambiguous as again, I have no misconception that we are competent to be able to carry out a risk assessment and make a judgment as to how these doors should be categorized, but even less competent is the building administrator who wants the cheapest option. Again, the standard puts it in the hands of the enforcers who in my experience so far have less knowledge of the standard than I do, or choose to ignore it, and by virtue of these facts would appear they too are not competent to make such assessments.

“This annex describes the category of system that is likely to be specified
(e.g. by other standards or by enforcing authorities/bodies) in particular
circumstances.”

At the moment we have Joe Public who has gone and bought very well marketed acoustic devices and installed them anywhere and everywhere without thought of assessment or “categories” and I haven’t heard of any devices being removed at the request of the “enforcing” authorities in any of the big office/public buildings that we maintain. And being incompetent, who are we to suggest to the client they should be removed and replaced with a Cat A device?

Perhaps we should give them your phone number ?


CT - And you have not read what you wrote again. Nowhere does it say every acoustically linked device must receive the appropriate SPL from 2 sounders. If, however, there were acoustically linked hold open devices on two staircases that were not separated by fire doors then the two could not rely on a single bell. Is this really really very difficult to understand, because, to me, it is what you wrote correctly and then apparently misinterpreted what you wrote down.

DR – Well if you read what I wrote again, you will note I asked a question for clarification, I didn’t make a statement. But the following clause to which I assume you refer doesn’t seem to mention staircases separated by fire doors as you do it simply mentions the number of locations, or have I misinterpreted it again?

11.4 In the case of acoustic actuation, failure of any single fire alarm sounder should not prevent the actuation of release mechanisms for self-closing fire doors at more than one location at which the doors protect stairways that form means of escape in the event of fire.

I have buildings where acoustic devices are installed on two sets of doors (forming a lobby) on various floor levels off a staircase and buildings where devices are installed on double doors to the staircase, and perhaps 10 metres away down the corridor on more double doors dividing the corridor. In each case there is a single sounder within ear shot of these devices. General alarm levels in the buildings are acceptable.

So would you interpret all these doors in the two examples as being in the same location and therefore the single sounder in earshot arrangement acceptable?

[David Rooney]

Wizzy, I had no idea people were simply seeking advice on things they found too difficult to understand. Now I see things much more clearly..... I was previously misled by comments such as (and I quote):

men in black overcooked it

To quote it properly I asked

"So what does it actually take to get the men in black to admit they've overcooked it and rethink ??"

Hardly a berating statement of the standard or the writers.

I too can appreciate the the reason for the standard. I admit I find it very difficult to understand and interpret and haven't met anybody else - fire alarm system engineers, control officers, architects, consultants or fire officers yet who can explain it fully.

I don't think that means we are all thick, it suggests to me the commentary is insufficient and the wording of parts of the standard is not clear enough to the target audience it's aimed at.

It's not a personal critisism it's just a fact.

[Allen Higginson]

I see it talks of acoustic coupling as well - been a long time since I had an acoustic coupling as our two boys are light sleepers.

[colin todd]

David,  Thank you for your offer to market our services. The number is 01252 792088. Of course you should tell them to get a consultant if they cannot deal with something themselves.  Many thanks in advance for the future referrals.

[David Rooney]

David,  Thank you for your offer to market our services. The number is 01252 792088. Of course you should tell them to get a consultant if they cannot deal with something themselves.  Many thanks in advance for the future referrals.

No problem Colin, I'll include it within the emergency pack containing bushmills, prozac and the number for the local samaritans....!   

[colin todd]

Also pass it on to  Wizzy fire alarms as he has not ordered the course yet

[Wiz]

Wizzy, I had no idea people were simply seeking advice on things they found too difficult to understand. Now I see things much more clearly..... I was previously misled by comments such as (and I quote):
waste of paper
hands up, I didnt buy it
burn it. best thing you can do with it
men in black overcooked it
and the best one of all (from an ex enforcer) I ignore it completely.

Had I realised that all this somewhat puerile ranting was simply a request to understand a standard that is a bit tricky for non fire alarm engineers (and, yes maybe for some engineers), I would have tried to help. However, from the comments as I re-read them all today, I think many of those  are beyond help, particularly those outside the fire alarm industry who cant be bothered buying it, or who think they are so much above it that they ignore it. (As a matter of record, I dont think you fit into these categories, but are merely frustrated that you cant understand some of the philosophy and practice. I can relate to this as I find the same problem in using a video recorder and, on the basis that I find "The simple guide to brain surgery" is somewhat dificult to understand, and I am not in the field of brain surgery anyway, I tend to ignore it completely too).

Clearly, your conceptual and practical, but I suspect genuine, difficulties with the standard cannot be resolved by a few simplistic words of advice here, nor are they assisted by people who dont understand the technology in the first place jumping on the bandwaggon.

Accordingly, I am pleased to offer the Wizzy fire alarm co unlimited a course on the standard at a specially discounted rate. This is a course that has been presented as a public course for some time, but it is now formally available to the  Wizzyco as an in-house course. The good news is that the whole course only takes half a day as the standard is so simple. The bad news is that, even at the discounted rate, it is quite expensive, but will repay itself in the time you could have been fixing wee alarm systems at a good rate of pay instead of berating the standard to vent your frustrations. I will happily give a price for delivering the course anywhere in the UK except Middlesbrough. Please feel free to  email us for a quotation.

Stop Message Ends. Now off watch on this subject. Returning Home station for refreshments (including a large talisker.)

Colin, I accept that the comments you highlight have been made on this thread, but only one of them is by me. In response to someone saying they couldn't currently find their copy of BS7273-4, I light-heartedly wondered if they had 'burnt it, because that was the best thing to do with it!'

I maintain my opinion that this BS is confusing and difficult to understand. It seems that others agree with me. No-one on this forum, apart from yourself, has professed to understand it, but that shouldn't be a surprise, if you have been involved in some way with it's production.

We, who are prepared to state that we find it difficult to understand, are those that want to make it work.

If we are making the comments that we find it frustrating and difficult to understand, do we deserve to be treated as idiots? We have two options; one is to pretend to understand it, the other is to admit to not understanding it and to seek help with input from others on this forum. Obviously, this 'input' may not always going to your liking, but we are entitled to our own opinions.

I have been considering your very kind offer of a half-day course on BS7273-4 at a discounted rate. I have discussed it with my colleagues (There is no Wizzy fire alarm company as you believe, but I do have daily contact with a large number of people who would possibly benefit from such a course)

My discussions with these people have revealed two concerns to their potential interest in attending such a course.

Firstly, they say they are not interested in a course that would be presented in a manner that was sarcastic and arrogant. Can you provide them with any reassurances on this point?

Secondly, they wonder if such a half-day course would really be sufficient for them to get a even a reasonable understanding of the subject, based on their difficulties in understanding what has been written in the BS? To ascertain this they have asked me to ask you if the 'course trainer' could first provide an explanation on this forum, of the following single sample BS 7273-4 clause;

5.1.3   Category C actuation

Category C actuation is designed to be fail-safe under the conditions of Category B actuation, but, in Category C actuation, there is no direct communications path between the fire alarm CIE and the release mechanism; actuation of the release mechanism is facillitated by other control, or similar, equipment (e.g. the control equipment of an access control system, or of an electrically controlled hold-open system).
Accordingly, any circuit between the fire alarm CIE and other control equipment needs to fail safe (see 10.6). It should be noted that, in category C actuation, the critical signal path is deemed to end at the other control equipment. However, it is preferable, subject to conformity to the relevant standard for the other equipment, that the release mechanism is actuated in the event of an open or short circuit of wiring between the the other control equipment and any release mechanism (see Note 10.6)

I appreciate the difficulties in trying to understand such a clause presented in the manner above and without reference to the notes and terms and definitions etc., but my colleagues hope to be able to use the explantion in tandem with what they can read in their copies of the BS, to ascertain their ability to get a worthwhile result from the proposed course.

I thank you for your help in this matter and hope we will be able to take you up on your offer.

[colin todd]

1. Wizzy. There is nothing certain in life other than death, taxes and chewing of gum by the inspecting officers of a large metropolitan fire and rescue service. So, I can offer no assurances of anything. I tend to meet fire with fire, and the postings in this thread are mostly along the lines of I can't understand it , so it must be rubbish, rather than I can't understand it, could someone explain. I find this arrogant and ignorant. I would love to know why the universe is expanding, but find books on quantum physics very difficult to understand, but I tend not to be-rate them and make stupid comments about them such as certain posters, other than your goodself, have made. Given that the standard was endorsed by just about every organization that is anything in the fire world, I find it difficult to believe that there is a fundamental flaw in the standard, rather than a flaw in the capacity of some people (other than your goodself, who merely have some difficulty with the practical engineering of some of the recommendations) to understand quite basic fire safety principles that I thought were adequately explained in the commentary of the clauses (which is why, when invited by BSI to write a guide to the code of practice, I thought there would be no market for it).
2. I have been doing public half day courses in BS 7273-4 for some time, and training is 20% of the turnover of our consulting practice. Under our ISO 9000 system, the delegate feedback on every course we do is independently analysed. At last count, delegate satisfaction was running at around 90% across all the courses we do. Our last customer complaint was in 2006, and related to lack of political correctness in describing how an optical smoke detector works (which I still maintain is related to the fact that women can never see to drive through fog because they never dip the bleeding headlights). The view I take is that the lady in question will now never forget how an optical smoke detector works AND she will dip her headlights when she drives through fog, making the roads of Britain safer for the rest of us to drive on (and all this included in the course fee).
3. You can have as long as you want for the course. If you wish to pay for a day, that's fine too. We can spend some of it talking about Joanna Lumley's legs, as we will probably run out of things to say about BS 7273-4, since understanding the recs is easy as falling of a log (albeit that going away and engineering them may take some time and effort). I find Joanna more interesting than BS 7273-4, though as she ages it becomes more and more a close run thing.
4 Alas, it is not company practice, to do free offers as incentive to buy training, and since, whether we sell a half day course or not will make little difference to the company shareholders, its not something I am inclinded to do. Equally, I cannot believe anybody has difficulty understanding the clause you describe, particularly as we drew a picture to support it. If you look at the drawing, the clause is prefectly clear. Not only that, but that very clause was discussed in depth with a security body to make sure they could understand it before we finalized it. It is a bit tricky to comply with, but then it is only a RELAXATION of a previous recommendation of BS 7807, which the fire alarm industry (and no doubt ex enforcers selling their expertise as consultants) seemed to ignore, so we made it less onerous.

As I am now very bored with this subject, please contact us if you wish to have some training for WIZZYCO at a favourable rate. Otherwise, to be honest, I feel sure if you just spend a little more time going through the standard, it will all fall into place and you can save WIZZYCO money. Joking apart, I do hate to take fees for something that does not really need specialist input, but if you feel you really do want that, you are welcome to buy a course.

[Wiz]

Colin, thank you for your reply.

[Wiz]

Further to previous posts about how to interface to a BS7273-4 system, this, after much discussion with equipment manufacturers, by advice on this forum, and some deep thought on the matters are my understanding of how we can meet the BS recommendations for category A systems with the equipment currently available:

Non-addressable systems

The interfacing to the fire alarm system can only be carried out at the control panel.

All EN54 panels should have the recommended monitoring in clause 5.1.1 (except possibly the one for disablement) to operate the panel's fault relay, as standard. Some panels also have the disablement monitoring (either operating the fault relay or a seperate disablement relay). A panel that can monitor all the faults recommended in 5.1.1 is required. All these fault conditions would need to be tested on commissioning.

The fire, fault, and if seperate, disablement relay contacts would all be wired in series to the fail-safe BS7273-4 signalling relay. At least one of the fire, fault & disablement relays would have to be normally energised. (I understand that EN54 requires this of fault relays).


Addressable systems

If the interfacing is to be carried out at the panel then the requirements are as the non-addressable system above.

If the interfacing is on the addressable loop then an interface that is loop powered energised in it's normal condition is required (Hochiki manufacture such a device). With other interfaces it will be necessary to also wire a simple relay powered from the loop and wire the contacts of both relays in series to the fail-safe BS7273-4 signalling relay.


I would welcome comments from those that are interested in the above summary so that we can 'tweak' it until it is correct and understandable to everyone.

[David Rooney]

Addressable systems

If the interfacing is to be carried out at the panel then the requirements are as the non-addressable system above.

If the interfacing is on the addressable loop then an interface that is loop powered energised in it's normal condition is required (Hochiki manufacture such a device). With other interfaces it will be necessary to also wire a simple relay powered from the loop and wire the contacts of both relays in series to the fail-safe BS7273-4 signalling relay.


I would welcome comments from those that are interested in the above summary so that we can 'tweak' it until it is correct and understandable to everyone.

Hello Wiz...

Seems about right to me.... my only question is still regarding the action of the Hochiki I/O - do you know if it changes state on "software failure" and what that means?

Re the "other interfaces" I've also been advised by Apollo in the past not to power relays directly from a loop... but just to be clear, are you suggesting a relay connected to the loop (permanently energised) in turn connected to its own closed contacts (open on power fail) in series with the normally closed on the I/O (the "part 4 relay") so if either one opens the magnet releases?

[Allen Higginson]

Addressable systems

If the interfacing is to be carried out at the panel then the requirements are as the non-addressable system above.

If the interfacing is on the addressable loop then an interface that is loop powered energised in it's normal condition is required (Hochiki manufacture such a device). With other interfaces it will be necessary to also wire a simple relay powered from the loop and wire the contacts of both relays in series to the fail-safe BS7273-4 signalling relay.


I would welcome comments from those that are interested in the above summary so that we can 'tweak' it until it is correct and understandable to everyone.

Hello Wiz...

Seems about right to me.... my only question is still regarding the action of the Hochiki I/O - do you know if it changes state on "software failure" and what that means?

Re the "other interfaces" I've also been advised by Apollo in the past not to power relays directly from a loop... but just to be clear, are you suggesting a relay connected to the loop (permanently energised) in turn connected to its own closed contacts (open on power fail) in series with the normally closed on the I/O (the "part 4 relay") so if either one opens the magnet releases?

Hi Dave - as 5839/en54 recommendations the CIE should indicate a fault due to sotware failure anyway via the watchdog so I (personally!) think it's a red herring.
I'm still missing the failsafe recommendations of the actual I/O but maybe I just get snowblind when it comes to that part!!