Cables and reaction to fire

lyledunn:


Not sure what you mean by 7671 requiring risk assessment OMS, but I do understand the imperatives for designers selecting cables with better performance in fire.

BS 7671 leaves this selection to the designer - so it is risk based.


However, imperatives should be evidence-based and I can find nothing in the way of forensic reports detailing the contribution cabling made in real fire situations.

Agreed - but there is a certain amount of evidence behind this - if only to say that xxkg/m of PVC cable in an escape route could produce yy/kg of smoke - but if OHLS was used it would be a lower quantity of smoke.


For example, it would seem reasonable that cables with improved fire performance are installed say in a hotel situation but, equally, not unreasonable that they are not. Some designers, on the other hand, will  opt for the former under the pressure of perceived imperatives.

Or under their common law duty of care to their client?


In other words, if the designer specifies LSF cable for the bedrooms, for example, they might assume that risk has been reduced from what it otherwise would have been had standard twin and earth cables been used. Since bunching would be unlikely in the voids above bedrooms, fire safety may not have been improved one jot but it just seems that by specifying LSF the right thing has been done irrespective of cost to the client. 

Sure - but bunching in corridors would be a different matter  - it could easily be shown that say OHLS cabling on metallic containment was readily observable as a safer solution (in fire conditions for MoE


Dont get me wrong, I am an advocate of  meticulous consideration of fire safety measures for buildings but I just get the impression that we are responding in an almost knee-jerk fashion due to rightful focus on recent tragic fires.

Maybe - but it is a scenario worthy of consideration by any competent designer - and in some sectors has been for many years. As a designer I'm happy to work with a client and other designers to achieve coordinated fire safety solutions for buildings that use of the tools available to enhance safety for both users of buildings and for FRS should they be called on to get people out "under smoke"

 

lyledunn:


Not sure what you mean by 7671 requiring risk assessment OMS, but I do understand the imperatives for designers selecting cables with better performance in fire.

BS 7671 leaves this selection to the designer - so it is risk based.


However, imperatives should be evidence-based and I can find nothing in the way of forensic reports detailing the contribution cabling made in real fire situations.

Agreed - but there is a certain amount of evidence behind this - if only to say that xxkg/m of PVC cable in an escape route could produce yy/kg of smoke - but if OHLS was used it would be a lower quantity of smoke.


For example, it would seem reasonable that cables with improved fire performance are installed say in a hotel situation but, equally, not unreasonable that they are not. Some designers, on the other hand, will  opt for the former under the pressure of perceived imperatives.

Or under their common law duty of care to their client?


In other words, if the designer specifies LSF cable for the bedrooms, for example, they might assume that risk has been reduced from what it otherwise would have been had standard twin and earth cables been used. Since bunching would be unlikely in the voids above bedrooms, fire safety may not have been improved one jot but it just seems that by specifying LSF the right thing has been done irrespective of cost to the client. 

Sure - but bunching in corridors would be a different matter  - it could easily be shown that say OHLS cabling on metallic containment was readily observable as a safer solution (in fire conditions for MoE


Dont get me wrong, I am an advocate of  meticulous consideration of fire safety measures for buildings but I just get the impression that we are responding in an almost knee-jerk fashion due to rightful focus on recent tragic fires.

Maybe - but it is a scenario worthy of consideration by any competent designer - and in some sectors has been for many years. As a designer I'm happy to work with a client and other designers to achieve coordinated fire safety solutions for buildings that use of the tools available to enhance safety for both users of buildings and for FRS should they be called on to get people out "under smoke"