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Cables and reaction to fire

lyledunn
Why do you suppose that the MHCLG did not feel it necessary to mandate levels of performance for cables with respect to their reaction to fire as was their prerogative under CPR?

Clearly the current non-prescriptive approach is either working or there is no significant evidence that cables and wiring systems have unduly contributed to the propagation of a fire or resulted in emissions that made a situation untenable when it would not have otherwise been. 

Further, what does it actually mean in the note in 422.2.1 that cables need to satisfy the requirements of the CPR in terms of their reaction to fire? I can find nothing specific in the CPR other than the need for CE marking and the requirements placed on the manufacturers for technical information.
  • Former Community Member
    0 Former Community Member
    The Construction Products Regulation (CPR) isn't a new thing - it's been around a long time - cables are just the latest "product" to fall under the CPR


    Lisa, your ex colleague should be made to visit a burns unit  - might sharpen the mind next time an alarm is ignored.


    Designers should be focused on this, as avoidance of unwanted fire signals has been in the relevant BS and EN standards for a while - it's important that people are not lulled into believing it's just another false alarm and don't react. It used to frighten the life out of me watching students all hanging out of the accommodation block window watching FRS arrive to yet another false alarm - until it become a real alarm and no one reacts


    Regards


    OMS
  • 0
    Being in a burning building is an interesting experience. Two things: a fire extinguisher is no use at all (but could be effective first aid for e.g. a fire in a waste bin); you cannot see a thing.


    Then I joined the RN and did fire training.
  • 0
    A few years ago I was in the fairly crowded departure lounge of a small Irish airport (think 5 gates of which about 2 in active use), when the fire alarm sounded. Absolutely no one reacted or evacuated. I made sure I was near a fire escape door that led directly outside, but didn't actually evacuate. The thing that really surprised me is that none of the staff seemed to know what to do. I had assumed they would either be encouraging evacuation or assuring us it was a false alarm, but they just quietly ignored it too.
  • 0
    Well, as noted, the problem is bias - by designing fire alarms to  err on the side of never missing  a real  fire, the probability of an alarm being false becomes very high.

    If however instead of 

    False negative 1%

    False positive 99% or whatever we have at the moment

    it was more like 50:50 - and I do realise that means that some of the time there will be  a real fire but the alarm does not actually go off, then, and only then, folk would take fire alarms seriously.

    Right now of course people quite correctly compensate by ignoring all alarms as most are actually false positive.

    I do recall our headmaster in exasperation at our failure to take fire drill seriously arranging for a stair well to be filled with smoke.  It was very interesting to see the entirely different exit patterns, and speed of response. But, only the first time, not the second.
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    wallywombat:

    A few years ago I was in the fairly crowded departure lounge of a small Irish airport (think 5 gates of which about 2 in active use), when the fire alarm sounded. Absolutely no one reacted or evacuated. I made sure I was near a fire escape door that led directly outside, but didn't actually evacuate. The thing that really surprised me is that none of the staff seemed to know what to do. I had assumed they would either be encouraging evacuation or assuring us it was a false alarm, but they just quietly ignored it too.



    The staff may have been given instructions not to evacuate until they were told to.


    I once worked in a factory like that.  If the alarm went off, you waited to be told that your area needed to be evacuated.
     

  • 0
    I remember seeing a documentary some years back. Someone alone in a fake waiting room with hidden cameras etc waiting for a (fake) job interview. Fire alarm goes off, and test subject normally leaves the room. Put some actors in the room too, with instructions to ignore any alarm etc. This time the subject looks around, sees no one else reacting, and waits. Pump a bit of stage smoke under the door and the subject still waits. *Lots* of smoke has to be pumped before they break with the others and evacuate. Peer pressure is a hell of a thing.
  • 0

    wallywombat:

    A few years ago I was in the fairly crowded departure lounge of a small Irish airport (think 5 gates of which about 2 in active use), when the fire alarm sounded. Absolutely no one reacted or evacuated. I made sure I was near a fire escape door that led directly outside, but didn't actually evacuate. The thing that really surprised me is that none of the staff seemed to know what to do. I had assumed they would either be encouraging evacuation or assuring us it was a false alarm, but they just quietly ignored it too.




    I had a vacation job with Marks and Spencer. They took alarms seriously. The instructions were to shepherd customers out of the store in the event of a fire alarm. Doubtless, there was some concern that otherwise pilfering might occur. In the event of a bomb alert (bear in mind late 1970s and conflict in Palestine/Israel) just get out!

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    Chris Pearson:

    ....a fire extinguisher is no use at all ...




    I disagree with this. If the only way out is a window I would far rather have a fire extinguisher to put through it than try to smash it with my hands.....

    I did my fire training with the merchant navy rather than the RN but it was certainly valuable experience. If it was a small fire (waste paper basket as suggested, perhaps) I would feel quite confident tackling it with a fire extinguisher, though if it actually was a waste paper basket I would probably just upend it as being a more reliable means of extinguishing. The real purpose of fire extinguishers in buildings is not to enable the occupants to put the fire out but rather if the occupants find their escape blocked by fire to give them a chance to get through. The fire brigade are the professionals so let them deal with the fire (and don't make them have to rescue you first).

    False alarms are a definite problem but they are nowhere near as prevalent as they used to be. The addressable fire detection systems which were developed in the 1980's and subsequently did a lot to minimise the problems. I mentioned having been in hotels where the fire alarm had gone off - these were not fires but were the alarms reacting correctly (twice through someone in the restaurant at breakfast burning toast activating an alarm and at least once due to a resident leaving the bathroom door open while showering). The fact that this was 100% correct functioning of the detectors is a pretty high success rate.

    Alasdair

  • 0

    these were not fires but were the alarms reacting correctly (twice through someone in the restaurant at breakfast burning toast activating an alarm and at least once due to a resident leaving the bathroom door open while showering). The fact that this was 100% correct functioning of the detectors is a pretty high success rate.




    To most people that would be interpreted as a 100% failure rate, and adds to the intuition  that most fire alarms can indeed be safely ignored. This is very dangerous.

    A sensor that cannot tell the very significant difference between burnt toast or steam and a real fire, is not making the correct decision, or is the wrong sort of sensor for the location. However, the price of making the sensor less sensitive is to mean that occasionally a real fire will not be detected, or more likely, will be detected later. That is the risk balance.


  • 0

    mapj1:



    To most people that would be interpreted as a 100% failure rate




    Unfortunately I have to agree with you there. I am not 'most people' but I agree there was no fire in any of the cases. However there is no improvement in the technology that will stop this sort of failure - perhaps issuing fines to people who are idiotic enough to ignore the instructions to close the bathroom door, etc. would work, but that is not technology improvement. As you say, making the sensor less sensitive could make a difference but at the moment you can't guarantee a fire will be detected so reducing the chance of detecting a fire would not be an acceptable option. There was a hotel fire about six weeks ago that caused chaos in the M4/M5 interchange area (Premier Inn at Cribb's Causeway) where the hotel was a total loss (and in fact collapsed into the road, which is what caused the chaos) but there were no casualties. If you ask any of those who were in the hotel at the time if they would accept a reduction in the sensitivity of the detectors I am willing to put money on what the answer would be.

    Alasdair

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