The choice of electrical materials, and especially their coatings, is a major factor in preventing the onset and spread of fires.The behavior tests of electrical materials in the event of fire are dictated by the CEI (Italian Electrical Committee) standards: these indications take into consideration both the type of environments in which the electrical systems are installed and the function of the plants themselves. In order to prevent the spread of flames, the material used must:
- have a high resistance to critical temperatures before igniting;
- do not propagate fire, flame or dangerous heat radiation;
- do not emit dangerous toxic smokes or gases during combustion.
The risks for electric cables in case of fire
In the event of a fire, the electric cables can constitute, in fact, an element of serious danger for the spread of flames in the surrounding environment, favoring:
- the feeding of the flames which determines, in addition to a less controllable propagation of the fire, an increase of the economic damage caused by the latter;
- the darkening of the rooms due to the smoke that invades them, which is the main obstacle to the evacuation of people in danger;
- action of corrosive gases, the spread of which can cause significant damage that, in extreme cases, also damage the reinforced concrete structures of buildings;
- action of toxic, harmful or even lethal gases for humans.
In order to verify the behavior of the cables subjected to the flames, a series of tests has been developed in order to qualify the same cables in relation to the non-propagation of the fire, the emission of toxic and corrosive fumes and gases and the resistance to fire.
The correct choice of cables therefore becomes of fundamental importance to safeguard the structures and people in case of danger.
Which cables to use to prevent or contain fires
For fire prevention, the type of cable used is a determining factor and depends on many aspects: the material used, its thickness, its weight per linear meter and the installation system.
Depending on their fire behavior, electrical cables can be divided into:
- flame-retardant cable: called passive safety cables, they prevent / delay the spread of fire, but do not actively protect people and things. Among other things, flame resistant cables are only effective if installed by themselves: if the cables are installed in a bundle, the fire spreads thanks to the latter (to consider that two cables less than 25 cm apart are a bundle );
- fire-retardant cable: in this case, the resistance capacity is aimed at the propagation of the fire, instead of the flame, which consists in the protection even in the case of laying in a bundle. It is worth remembering, however, that if the fire-retardant cables are installed in a larger number than that provided by the product standards, their self-extinguishing is no longer guaranteed;
- LSOH cable (Low Smoke Zero Halogen): defined as active safety, this type of cable makes an important contribution to reducing the level of risk of people and things in case of fire, as they limit the emission of opaque smokes to minimum levels , toxic and corrosive gases, at the same time guaranteeing a lower environmental impact;
- fire resistant cable: also defined as active safety, but with a further turn-around; this type of cable is designed to keep running for a certain period of time even when it is hit by flames. Fire-resistant cables, for example, are specifically used to power emergency services.
It seems clear that the different types of cable can radically change the fate of a structure in which a fire spreads: it may happen, in fact, that the cause of the flames are the cables themselves, mainly due to short circuits and problems of installation.
Choosing the safest cable to lay, which guarantees the safety of the people involved in the fire and, at the same time, a limitation to the damage of the structure, becomes a fundamental task.
To date, the most compliant solution is undoubtedly the halogen free cable, because it falls within both the environmental safety regulations, such as the new CPR, and in the field of protection for those laying the cable and for those who live in the home.