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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.
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  • 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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  • 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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