Halogen table

Selecting the Right Cable can be a Life or Death Decision: Part 1

Posted on Wednesday, October 22, 2014 by Dave Watson

Halogens are the elements in column or group 17 in the Periodic Table of Elements, and include fluorine, chlorine, bromine, iodine, and astatine.  All halogens form acids when bonded with hydrogen and are considered toxic in sufficient quantities.  Halogens are also highly reactive.  The benefit of being highly reactive is that once a halogen reacts with something the resultant molecule is very inert and tends not to be reactive.  Ironically, many of these are used in products people may use every day.  One of the applications of halogens is in cable and wire jackets, as a flame retardant.

In wire and cable we find that the insulating and jacketing materials that we have traditionally used are halogenated.  This would include PVC (polyvinyl chloride), Fluoropolymers such as FEP, PTFE, ETFE, PVDF and so on. Additionally, brominated additives are widely used to make a wide range of thermoplastics less flammable.  Once properly compounded into the insulation and/or jacket material the halogens are stable and provide thermoplastics with a high performance and very good to excellent flame resistance.

So what’s the problem or concern?

When exposed to flame, plastic materials decompose.  This decomposition process frees the halogens into the atmosphere where they may react and form new molecules.  The concern is that the halogens from the burning wire or cable will combine with hydrogen molecule and form acids such as hydrochloric acid and hydrofluoric acid.  In enclosed environments these acids present a very real health concern to the tissue in lungs and eyes.  In the investigation of fatalities in fires, it is often found to be the case that the cause of death was not from burns, but rather from the inhalation of toxic fumes, including acid gases that reduce the efficiency of the lungs and may contribute to asphyxiation.   The enclosed environments of concern include poorly ventilated areas and enclosed areas such as aircrafts, rail cars, and tunnels.

The solution to the forming of dangerous acids is the use of insulation and jacketing materials that are flame retardant but not halogenated.  Alpha Wire is one of the companies that offers a zero halogen cable.  Known as low-smoke, zero-halogen (LSZH) communication and control cables, they can minimize the amount of smoke and toxic fumes released in the event of a fire.  In addition, hydrochloric acid can be extremely corrosive to copper and many materials in general.  Therefore, eliminating any possibility of these acids forming can help keep critical systems connected, even in the most extreme events.

Part 2 will discuss Alpha Wire's LSZH capabilities

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