The requirement to have halogen free and low smoke cable is driven by the behavior of instrument cable sheath when exposed to fire. By having halogen free properties, the cable sheath is expected not to produce toxic smoke which can be dangerous to personnel during fire.
Instrument Cable with low smoke specification shall have lower smoke density when exposed to fire compared to standard sheath, hence only producing little amount of smoke. The installation of cable with low smoke specification in the facilities is intended that the burnt cable will not worsen the situation in case of fire.
Halogen properties for cable shall meet IEC 60754, while low smoke properties shall meet IEC 61034.