The applications of halogen-free cables are provided in the Low Voltage Electrotechnical Regulations (REBT), which are called “wire HS” or “High Security”.
They are safe wires because their insulation do not contain any chemical element of group 17 of the periodic table, that is to say, neither fluorine nor chlorine nor bromine nor iodine and nor astatine. All of them are elements so reactive that they are never found in nature without mixing with others. The result of the combustion of materials of this type is a large amount of corrosive, toxic and opaque smoke. Therefore, the halogen-free cables, in case of fire, are much better behaved than, for example, PVC (it contains chlorine).
We can distinguish a halogen-free cable, from a PVC one by the following aspects:
- Insulation marking: The first one is marked with a “Z” while the second with a “V”;
- Color: Green and black, respectively;
- And their reaction during fire of a lighter: Nonexistent smoke and faint smell, in the case of halogen-free. And black with a strong, unpleasant odour, in the case of PVC.
Halogens are highly reactive. So, they can be harmful to biological organisms in sufficient quantities. Its high reactivity is due to the large electronegativity its atoms have for their highly effective nuclear charges.
By contrast, the halogen-free cables minimize the harmful effects arising in case of fire, because the components used in isolation are flame retardants. Therefore, it is possible to extend the time of evacuation of a burning building, introducing fire resistance and a high capacity to not spread the fire. Also they help to reduce the risks from inhalation of gases, as they emit no fumes and less opaque toxic gases. This too leads to less corrosion of equipment and electronic circuits produced by smoke as well, greater visibility for firefighters to access the fire outbreaks.
UNE 21-147/1 establish that such cables must be used in electrical installations. In fact, since 2003 its use is required in the construction of new housing. Although it is also recommended in old facilities under review.
Did you know the existence of halogen-free cables? Are they installed into the building you live or work?