No smoke without fire... (Guide to low fire hazard cables)

Many building projects now call for the use of cables that, in the event of a fire, are less hazardous to people when they burn. There are two key features – reduced smoke emission to minimise hazards from smoke inhalation and aid evacuation, and no or minimal halogen combustion products which are highly toxic. These must not be confused with Fire Retardant cables, which are designed to continue to perform for extended periods in the event of fire eg. in voice evacuation systems, and have an altogether quite different and much more complex construction.

The original cause of the problem is that the most commonly used cable insulating and jacketing material is PVC. Advantages are its cheapness, and that, with the addition of various elastomers, it can be made extremely flexible and remain so at lower temperatures. Disadvantages are that it’s nasty when it burns, as it produces considerable amounts of smoke and releases toxic halogen compounds.

For deployable cabling therefore, PVC remains the main jacketing material. For lowest cost there is plain PVC, for improved flexibility there is "Arctic" grade – most commonly used on mains cables – and then there are more complex proprietary compounds used on many audio and video cables where exceptional flexibility is required and where a "semi-matt" ("satin") surface finish is required.

So, to create cables that are less hazardous in the event of fire, various compounds have been developed. These are typically described as "low smoke, zero halogen" or "low fire hazard". The bad news is that they lack flexibility and discolour easily – but as cables made from these are going to be in ducts or ceiling voids, that’s not really a problem. They are obviously not recommended for deployable use!

Some confusion is caused as a result of some manufacturers using four-letter acronyms for these types which they have registered as trademarks, but which have become commonly used to describe the cable style. "LSOH", the best known, is a trademark of Pirelli General plc, one of the earliest developers of this kind of material. Most other meaningful combinations of these letters (including Z for zero or N for no instead of O) are also registered trademarks. Consequently Canford cannot use these in the catalogue – instead we use our own mark – "LFH".

Canford cable conformance to BS EN Specifications

BS EN 60332 / IEC 60332 (replaces BS EN 50265)

Part 1 (BS EN 60332-1) applies to single wires (cables) and requires a vertical flame test with a maximum flame climb of 450mm

Part 2 (BS EN 60332-2) applies to very thick copper conductors and is not relevant to audio, video, data and low level control cables

Part 3 (BS EN 60332-3) applies to ‘bunched’ wires (cables). This part of the specification is intended to apply to large cable bundles in building cable ducts. (Additional specifications apply to air conditioning ducts or similar where a forced air supply is present.) Advice should be taken from local regulators to determine if this part applies to your installation.

All PVC, LFH and Special PUR cables manufactured for Canford by Draka, conform to the requirements of BS EN 60332-1 / IEC 60332-1 and can be referred to as "Low Fire Hazard" within the context of this specification (provided the installation is not required to conform to Part 3)

However - for a cable to be described as "Low Smoke and Halogen Free" (the term expected to be used in future BS / EN / IEC specifications) it must additionally meet the requirements of:

IEC 60754-1 Halogen and Acid Gas Free
IEC 60754-2 Halogen and Acid Gas Free
IEC 61034 3m3 Smoke test

All cables manufactured for Canford by Draka and described by us as "LFH" meet these requirements and can be described as "Low Smoke and Halogen Free".

Application specification BS 6701:2004 Telecommunications equipment and Telecommunications cabling – specification for installation, operation and maintenance.

All Canford PVC, LFH and PUR cables falling under the terminology "telecommunications cables" (audio, video, data) can be classed as ‘Low fire hazard’ within the guidelines of BS 6701: 2004.

Low Fire Hazard versions of "standard" audio and video cables

Most of the main installation cables in Canford’s range are already available in low fire hazard versions. If another design is required, not currently shown as being available in LFH, please contact the sales team. Subject to minimum order quantities, most Canford designs can be made with an LFH construction.

Cable Jacket/Sheath Names and Acronyms with respect to Fire Properties

Acronym Term Material Fire tests
PVC None Polyvinyl chloride IEC60332.1
FRLS Fire Retardant Low Smoke Polyvinyl chloride IEC60332.1
LSPVC Low Smoke PVC Polyvinyl chloride IEC60332.1
LSF Low smoke and reduced Chlorine Polyvinyl chloride IEC60332.1
LSOH Low Smoke 0 Halogen Polyethylene1 None
LFH (Canford) Low Fire Hazard Polyethylene + fillers2 or Special PUR IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034
LSOH Low Smoke 0 Halogen Polyethylene + fillers2 IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034
LSZH Low Smoke Zero Halogen Polyethylene + fillers2 IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034
LSNH Low Smoke No Halogen Polyethylene + fillers2 IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034
LSHF (HFLS) Low Smoke Halogen Free Polyethylene + fillers2 IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034
OHLS 0 Halogen Low Smoke Polyethylene + fillers2 IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034
HFFR Halogen Free Fire Resistant Polyethylene + fillers2 IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034
LSF Low Smoke and Fume Polyethylene + fillers2 IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034
FRNC Flame Retardant No Chlorine/Corrosion Polyethylene + fillers2 IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034, sometimes IEC 60332-3
FRNC Flame Retardant Non Corrosive Polyethylene + fillers2 IEC60332.1, IEC 60754-1, IEC 60754-2 and IEC 61034, sometimes IEC 60332-3

1 Products of combustion of polyethylene do not include any halogens, therefore the resulting smoke is halogen-free
2 "Fillers" referred to above are the co-polymers used to retard and control the combustion

Certification should be sought from trade mark holders or users of the above terms that cables conform to the specifications listed.

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