The Low Smoke Myth

The Low Smoke myth!

Many polymeric cable manufacturers claim the polymers they use for insulation and jackets are low smoke.
They often justify this by claiming compliance to tests like BS EN 61034.

These smoke obscuration tests are dependent on a specific sample weight of cable burned in a specific room / air volume. These results are not predictive end use simulations.

Smoke generation can be greater on high heating before flame and smoke volume is directly related to the amount of material burnt. 

 Small Fire Lots Of Smoke 1Small Fire Lots Of Smoke 2

Images from Singapore MRT 2013 - Newton Underground Station. Cable overloaded and caught fire.

So how can a BS-EN 61034 low smoke cable give off so much smoke?

PVC gives off more smoke in flame but PE / XLPE (polyethylene) gives of more smoke on heating without flame.

Material

 Thickness (mm)

 Maximum Specific Optical Density (DM) Non Flaming

 Flaming

 Plastics;

 

 

 

 UPVC

 3

 400

 580

 Polyethylene

 3

 590

 83

 FR Polyethylene

 3

 790

 780

 Polypropylene

 3

 550

 162

 FR Polypropylene

 3

 820

 600

 Polystyrene

 3

 476

 960

 PMMA

 3

 63

 117

 Plasticised PVC

 0.75

 430

 650

 

Plasticized UPVC is used to make general electric cable. In flaming and none flaming mode both feature high smoke outputs, indeed very bad as a fire proof cable…

FP200 & FP600 use polyethylene – In a direct flame yes it shows as low smoke generation factor…. But under overload, short circuit or internal heat for any reason… 590DM is a lot of smoke!

It doesn’t take an actual fire to cause an emergency evacuation, smoke with no fire is more common and extremely costly!

 

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