low fire hazard (LFH) performance

Low Fire Hazard (LFH) conduit systems are becoming an increasing part of the specification in many cabling applications. Public buildings, retail outlets, high rise office blocks, hospitals and transport installations - these are just a few of the instances where Low Fire Hazard products may be demanded.

Low Fire Hazard systems are required to protect personnel and property in the event of a fire and may be demanded by specifiers, occupiers, fire services or even insurers.

At Flexicon we define a Low Fire Hazard product by having all of the following properties:

  • Highly Flame Retardant to prevent a fire or limit its development if one does start.
  • Low Smoke emission in the event of a fire to enable personnel to see their way to escape.
  • Low Toxicity in the event of a fire to ensure personnel are not overcome during their escape.
  • Halogen Free gives an indication of low smoke and low toxicity. It also rules out halogen acid gas emission - a fact that is of interest to insurers as acid smoke can destroy computer equipment and damage the structure of a building

Tests Used

  • Flame Retardancy BS EN IEC 61386 tests that conduits and fittings are self extinguishing. Vertical samples of conduit are subjected to a 1KW flame test. Fittings are subjected to a 750°C glow wire test.

    BS EN ISO 4589 determines the Limiting Oxygen Index (LOI) of a material. This is the percentage of oxygen in the air that would have to be present for the material to burn. Normal air contains 21% oxygen, BS 6853:1999, the UK code of practice for railway rolling stock requires 28% LOI for overground and 34% LOI for underground passenger carriages.

    UL 94 is a UL (Underwriters Laboratories) standard to assess the flammability of materials. Classifications are HB, V2, V1, and V0 in order of increasing flame retardancy. UL 94 HB allows horizontal burning up to a certain rate, UL 94 V0 is highly flame retardant.

  • Standards All of the following standards assess flame retardancy, smoke emission and toxicity including halogen content.
    BS 6853 UK rolling stock
    LUL 1-085 London Underground rolling stock and stations
    NFF 16-101/2 French rail rolling stock
    DIN 5510 German rail rolling stock
    TS 45545 New European rail rolling stock
    AS/NZS 1530 Australian/New Zealand rail rolling stock
    Defence Standard 61-12 part 31 UK Ministry Of Defence
  • Toxicity is evaluated by burning a sample of material under known conditions. The fumes are analysed to find the volume of each gas that is given off. The volume of each gas is multiplied by its toxic potency to give a toxicity index for the material.
  • Smoke Opacity is evaluated by burning a known amount of product or material in a specified smoke chamber. A light is shone through the smoke and the loss in transmittance of light is measured over time.

Buyer Beware

All four properties:Highly Flame Retardant , Low Smoke, Low Toxicity , Halogen Free, must be present to claim LFH.

Halogen free does not assure low smoke and low toxicity.

A low smoke and fume product may not be self-extinguishing let alone highly flame retardant. Ensure your supplier provides performance data on all four aspects of Low Fire Hazard performance.

Full independent test reports are available on request.

Performance of Flexicon LFH Products

FU, SSU, FB, FUSSB and metal fittings

These products are made exclusively of metal (steel, stainless steel or brass) and are all inherently low fire hazard.

Fully compliant to LUL Std I-085 LUL product registration certificate 296.

FPI, FPIH, FPISS and FPIHSS
Self extinguishing to EN 61386
Flame retardant LOI = 22%
Low smoke to BS6853 maximum opacity Ao = 0.05
Low toxicity toxicity index to BS6853
Annex B = 1.32
Ignition and fume rating to NFF16-101/2 = I4F2
Halogen, sulphur & phosphorus free
LFHU, LFHP, LTBRDLFH and LFHUBRD
Self extinguishing to EN 61386
Flame retardant LOI = 43%
UL 94 V0
Low smoke to BS6853 maximum opacity Ao = 0.01
Compliant to BS 6853:1999 -
  • Table 7 Interior use, for Categories 1a, 1b, II
  • Table 8 Exterior use, for Categories 1a, 1b, II
Compliant with GM/RT2120 issue 2, Appendix 1
Low toxicity toxicity index to NES713 = 1
Compliant to LUL Std I-085 Limited and dispersed use. LUL product registration certificate 297
Halogen, sulphur & phosphorus free
FPR, FPRSS and FPRTC
Self extinguishing to EN 61386
Flame retardant LOI = 35%
UL 94 V0
Low smoke to BS6853 maximum opacity Ao = 0.01
Compliant to BS 6853:1999 -
  • Table 7 Interior use, for Categories 1a, 1b, II
  • Table 8 Exterior use, for Categories 1a, 1b, II
Compliant with GM/RT2120 issue 2, Appendix 1
Low toxicity toxicity index to BS6853
Annex B = 0.99
Ignition and fume rating to NFF16-101/2 =I2F1
DIN 5510 rating = S4 SR2 ST2
Compliant to LUL Std I-085 Limited and dispersed use. LUL product registration certificate 297
Halogen, sulphur & phosphorus free
FPAS and FPAH
Self extinguishing to EN 61386
Flame retardant LOI = 26%
UL 94 V2
Low smoke to BS6853 maximum opacity Ao = 0.02
Low toxicity toxicity index to BS6853
Annex B = 1.55
Ignition and fume rating to NFF16-101/2 = I4F1
Halogen, sulphur & phosphorus free
Nylon Fittings
Self extinguishing to EN 61386
Flame retardant LOI = 28%
UL 94 V2
Low smoke to BS6853 maximum opacity Ao = 0.03
Compliant to BS 6853:1999 -
  • Table 7 Interior use, for Category II
  • Table 8 Exterior use, for Category II
Compliant with GM/RT2120 issue 2, Appendix 1
Low toxicity toxicity index to NES713 = 10
Annex B = 1.55
Ignition and fume rating to NFF16-101/2 = I3F2
Halogen, sulphur & phosphorus free
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