One kilogram of solid PVC allocated 350 liters of gaseous hydrogen chloride, which when dissolved may give more than 2 liters of concentrated (25%) hydrochloric acid. For cable insulation use a soft polyvinyl chloride plastic compound, or a cable. This material contains 50% of various additions (plasticizers, etc.), which strongly alter the combustible properties of the polymer. Plasticizers are already beginning to evaporate at 200 C and light up. The chlorine content is reduced to about 35%, and it is not enough to prevent the spread of fire.

However, with a strong separation of hydrogen chloride solid polyvinyl chloride, removed from the source, not light and fire is extinguished. Due to temperature changes, drawn, created in the cable shafts, gases containing hydrogen chloride are carried away from the fire, penetrate the shield and hardware space and settle on the equipment. In early 1980s, requirements for fire safety cables were reduced mainly to the proliferation of combustion products along the length of cable laid singly or in bunches. To do this, the shell used cable products made of flexible PVC grades O-40, GOST 5960-72 (VVG cables, AVVG, the test compound sample length of 130 mm, 10 mm and a thickness of 2 mm is introduced into the flame of a gas or alcohol burner by keeping him in a flame at an angle of 45 ignition after the sample was pulled out of the flame should go out after not more than 30 seconds) and 30-32 PNC (PNC 40-32) (TU 1328-86).