Cable safety - a matter of life and death

Cable safety ratings aren't very sexy. There's plenty of information about Category 6, optical fibre and wireless technology but you could bet your bottom dollar that it would make front-page news if a cabling contractor was charged for manslaughter because he installed cabling that propagated a fire instead of suppressing it.

While this may be a little melodramatic, the point stands that this is an extremely important issue that hasn't been given due attention. More importantly, our legal system stipulates that every professional practitioner has a responsibility, or 'duty of care', to the community. And in the cabling industry, that duty of care extends beyond simply supplying and installing equipment that is 'fit-for-purpose' in carrying communications services around the office to its occupants. That duty of care extends to ensuring a safe working environment is provided for the occupants and the public in general.

Consider this hypothetical situation:

A multi-storey building is engulfed in flames, and two people die in the blaze. A coroner's inquiry is immediately established to determine the cause of the deaths. The tenant and building owner also lodge insurance claims against their substantial losses from the fire.

In response to the claims, the insurance company requests a report from the Fire Brigade on the extent of the damage as well as the cause of the fire. To firstly qualify the size of the payouts they need to make and secondly, to identify any parties who may bear responsibility for the fire and who they can sue to offset the insurance payouts.

At the same time, the coroner has ordered a full investigation by the Fire Brigade to establish how the people were killed, what prevented them from escaping the burning building, and if any party had failed in its duty of care to the victims.

The Fire Brigade firstly assesses the damage to the building and its contents, then advises the insurance companies, who subsequently pay out the claims by the tenant and building owner. However, the Fire Brigade find in the smouldering ruins of the building, remains of bundles of data cable, partially burned, but still bearing the markings 'CMX (UL)'. The Fire Brigade consult the Underwriters Laboratory (UL), as Subject Matter Experts for qualification of the cabling, who advise that the cable is a Residential rating cable, not suitable for installation in commercial buildings because of its poor flame retardancy when installed in bundles.

Armed with this information, the insurance companies set out to recoup the monies paid out for the claims. The insurance companies sue the building owner for operating a building that was not suitable for occupancy due to the unsafe materials used in it, which caused the fire to spread through the building. This triggers a series of lawsuits and counter-lawsuits between several parties in an attempt to escape the blame and pass it onto someone else:

• Builder sues the consultant
• Consultant sues the installer
• Installer sues the cable vendor
• Cable vendor counter-sues the Installer
• Installer counter-sues the consultant
• Consultant counter-sues the builder
• Builder counter-sues the insurance companies
• The only winners here are the lawyers.

Furthermore, the coroner who has been notified of the Fire Brigade's discovery of inappropriate cabling in the building subpoenas all parties to the coronial inquiry to establish who should be charged with negligence for causing the deaths of the office workers.

Not a pretty picture. Although hypothetical, similar circumstances have actually occurred in other parts of the world, with individuals and companies being held liable for the deaths and property loss due to negligence of this type on their part.

The Insurance Council of Australia (ICA) says that where negligence is found, the insurance companies can take subrogation action to recoup any monies paid out. This is a vehicle that allows insurance companies to find out who is in the wrong, and to take legal action against a party or number of parties who are found responsible. Multiple parties can be held accountable through 'proportionate' liability.

"It is vitally important for cabling professionals to be aware of legislation that outlines their duty of care for public safety."

Industry standards for fire safety

There are a number of industry standards that cover fire safety, including Standards Australia, the Building Code of Australia, IEC in Europe, and UL and NEC in USA. All of these cover similar issues, but there are significant differences.

Standards Australia

Surprisingly, the primary standard AS/NZS 3080:2002 has very little to say about fire safety. However, AS/NZS 3000 refers to S008, which in turn refers to AS/NZS 2053 and AS/NZS 3191, which states that for Combustion Propagation Testing:

"The cord shall be self-extinguishing. After all burning has ceased, the surface of the sample shall be wiped clean, and the charred or affected portion shall not extend to within 50 mm of the lower edge of the clamp fitted at the top. During the test, any falling particles shall not ignite the tissue paper underlay."

It also refers to additional notes, which state in part:

"Fire, however, is a complex phenomenon...There must be a constant awareness of the interrelated factors and effects of important variables in using this test to assess the fire hazard in any particular situation (eg, in high vertical runs of bunched cables)."

AS/NZS 2053 "Conduits and Fittings for Electrical Installations" specifies criteria similar to AS/NZS 3191.

While these Standards are quite explicit in addressing fire tests and performance criteria, there is little guidance on duty of care with regard to fire safety.

The Building Code of Australia

The BCA has a lot more information about fire safety, but most of it deals with the design of the building and the fire ratings of the structural elements of a building. Useful information is found in Section C - Fire Resistance: Performance Requirement CP4 - "A material must resist the spread of fire to limit the generation of smoke and heat, and any toxic gases likely produced appropriate to any fire safety systems installed in the building."

The Underwriters Laboratory (UL)

Fortunately there are comprehensive fire safety specifications to be found at UL, which is world renowned for its work in qualifying fire safety. Copper communications cable is classified as 'CM type' and, in Australia, most commercial installations would typically use CMR (Riser Rated), CM (Commercial Rated) or CMG (General Rated) cables. For residential or small commercial installations, CMX (Limited Residential Rated) rated cables could be used instead. CMP (Plenum Rated) is an unnecessarily high rating for Australia. Optical fibre cables are similarly classified.

The IEC standards

European cabling standards contain a similarly high level of guidance for cablers, but have a slightly different approach to the Americans. There are three types of fire safety categories - fire retardancy, smoke emission and halide gas emission. All of these can be used independently or combined to qualify a single cable. These parameters are defined in the following IEC Standards:

• IEC 331 Fire Resistance
• IEC 332 Fire Retandance
• IEC 1034 Low Smoke Emissions
• IEC 754 Zero Halogen Emissions

Within each of these categories, there are several levels of fire safety performance denoting the degree of fire retardancy and emissions. These ratings apply to both copper and fibre cables.

How cables suppress fire

The insulating materials in communications cables contain chemicals that act as fire suppressants. The type of chemicals used determine how the fire is suppressed and what by-products are given off.

PVC-based cables (Riser, Commercial, General and Residential Rated) use halide-based chemicals, such as chlorine, as their fire suppressants. When PVC burns, it gives off a halide gas, which rapidly absorbs oxygen, thereby starving the fire, causing it to self-extinguish. PVC is a very efficient fire retardant, but its by-products can be hazardous. In high concentrations, chlorine gas is quite toxic and when combined with oxygen and water vapour, a by-product is hydrochloric acid, which is also potentially hazardous.

Plenum rated cables do not contain halide-based chemicals such as PVC, but instead use fluoro-polymers such as Teflon to suppress flames. These chemicals are also efficient in suppressing fires, and emit very low levels of smoke, and no toxic fumes or vapours. The trade-off here is cost, as Teflon is a vastly more expensive material than PVC. A Plenum rated cable is about twice the price of its commercial rated equivalent.

Low Smoke Zero Halogen (LSZH) rated cables use metal hydroxide chemicals to suppress flames rather than PVC or Teflon. Metal hydroxides give off water vapour when exposed to fire, which suppresses the propagation of fire along a burning cable. These chemicals, however, are less efficient in suppressing a fire than PVC, but do not have harmful by-products.

Identifying safety ratings from cable markings

Any cable that is UL listed, that is, tested and rated to a particular fire safety rating, will have its rating printed on the cable. This would typically include the fire safety rating, the approval reference number and the UL identifier, which is either the UL logo or UL in parentheses.

There is no such thing as the perfect cable that meets all the fire safety criteria, has phenomenal transmission performance, and costs very little. Cable manufacturers have been juggling these three elements for years.

Transmission performance is influenced by the chemical composition of the dielectric, or insulation. So the manufacturers must find a happy medium that satisfies both requirements, while keeping the costs down as well. Typically, the better the performance, the better the fire safety rating and the higher the costs.

In a competitive market, there is often pressure to compromise on something, and with little knowledge of fire safety, or its perceived importance, this is often the one that is potentially compromised. Armed with knowledge of fire safety ratings and the choices available on the market, however, professionals involved in cabling can be competitive and maintain their duty of care.

The lack of interest in cable safety ratings in Australia may be put down to good fortune - we have never had a major fire disaster to draw our attention to the matter. On the other hand, the US and European cabling markets are very interested in fire safety because they have experienced fire disasters. Hence we have extensive guidelines on their initiatives in this field to draw from, in the form of standards and other commercial information, in order to successfully maintain a professional duty of care.