Experience with fire accidents of buildings reveals that most of the casualties happen due to the smoke generated when the whole building burns. Smoke is considered to be the root cause of deaths and therefore international guidelines for cabling of multi dwelling apartments, office buildings, etc must be followed.
Indoor cables apart from meeting international specifications for optical, mechanical, and environmental characteristics must meet specifications for fire resistance also. Indoor fiber optic cables are manufactured with an outer sheath material having fire resistance or flame retardant characteristics.
The poisonous smoke generated out of burning fiber optic cables used in the indoor areas has its root in the outer sheath material mostly. The outer sheath material coming in contact with the fire at first shall not allow the fire to propagate to subsequent locations of the cable. The outer sheath should act as a self extinguisher or it should not allow propagation of fire. Another criterion is to reduce the smoke being generated if fire catches the cable. The outer sheath material used on indoor cable contained Poly Vinyl Chloride (PVC). The presence of chlorine generates more smoke and leads to more casualties due to smoke in case of fire.
Since chlorine material belongs to the Halogen group in the periodic table of elements, the presence of chlorine is often called the presence of halogen material. The absence of halogen material is required for low smoke. Generation poisonous halogen gas is thus reduced with the use of zero halogen material.
Flame retardant is often abbreviated as FR in the fiber optic cable industry. Fiber optic cable manufacturers may print the code on the cable that the fiber optic cable is complying with international flame retardant standards. IEC 60331 and 60332 are two of such standards. Flame retardant materials often possess oxygen index values of greater than 30.
For Noncorrosive fiber optic cables, the cable sheath and the secondary coating materials do not contain corrosive materials. Corrosive materials are materials that attack electronic equipment and the respiratory system. Some of the commonly used corrosive materials are materials that include chlorine, bromine, and fluorine. Polyvinyl chloride produces corrosive chlorine when it is burnt.
Low smoke zero halogen material used for outer sheath generates very little smoke in case of fire. Some people call it zero halogen or halogen-free or Non-halogen. Halogen-free cables belong to the class of Non-corrosive cables and therefore do not contain corrosive halogen. It does not mean that Halogen-free materials do not contain corrosive materials.
Obviously, superior quality fire and flame resistant or retardant cable will have fire resistant or flame retardant and low smoke, zero halogen, Non-corrosive properties. While looking for an indoor cable, fiber optic installers shall search for a fiber optic cable supplier who can meet most of the international specifications related to fire resistant characteristics. It is the commitment and social responsibility of the fiber optic installers towards the safety of human beings. It is not simply the technology, but a human consideration required while choosing for an indoor fiber optic cable.