Enhanced fire performance

The commonest insulation used today is PVC .Its ignition temperature is sufficiently high for it not to be regarded as a flammable material , that is to say , a fault in the cable is unlikely to ignite the insulation . But if a dire from some toehr cause engulfs the cable , PVC will burn and give off dense smoke and acid fumes which can create a hazard greater than the original fire . To avoid misunderstanding here , it should be added that a cable fault , particularly if the insulation is damage , can ignite adjacent material such as loose paprt or timber , even if it does not ignite its own insulation  .
In order to give better performance in fires , alternative materials have been developed . One type of cable for enhanced fire performance has XLPE insulation with cable armouring bedded in a compound which has low smoke and fume properties it is designated LSF ; it consist of inorganic fillers in polymers such as ethly vinyl acetate and ethylene propylene rubber . THe construction is illustrated
  Other cables have EPR ( ethylene propylene rubber ) insulation with a sheath of elastomer which is heat and oil resistance and flame retardannt , and is therefore designated HOFR . These cables are available with and without a cable armouring between the insulation and the sheath .
  It will not come as a surprise that the better performance of the cable , the more expensive it is . Consequently , it is important to consider carefully the application and precise requirements . It has olny been possible here to give an indication of special purpose cables available . In practice , final selection cannot be made without discussion with manufracturers and suppliers .