As we all know, the combustion and spread of fire of objects must have three elements: combustible, heat and air.
(1) The insulation materials and protective layers of various types of cables that are widely used so far are mostly made of combustible organic matter. Although cables made of oil, paper and asphalt have been eliminated, many old factories still continue to use them. Cables made of polyethylene, cross-linked polyethylene, polypropylene, polystyrene, natural rubber and other materials are widely used. The oxygen index of these materials is 19 or below, and they can generally ignite at 300℃~400℃. Moreover, the heat generated during combustion is greater than that of coal of the same weight. Therefore, once cables made of these materials catch fire, they will not extinguish themselves and will spread. This is the main reason for the spread and expansion of cable fires.
(2) When wires and cables catch fire, a large amount of toxic gases in the smoke will reach a certain concentration, which will harm human health and even cause death.
(3) There are also examples where wires and cables extinguish themselves quickly after catching fire and almost no accidents occur, but this is mainly related to factors such as cable type, quantity, number of layers of layout and environmental conditions.
(4) The combustion test conducted on a single PVC cable using the old standard did not show any flame retardancy. However, in the case of large-scale installation of multiple cables, once the cables catch fire, the cables will supply combustion materials to each other, causing high temperatures over a large area, causing the cables to spread and not extinguish themselves. Under the condition of supplying the same amount of air, the flame retardancy rate and flame propagation rate of horizontal installation are smaller than those of vertical installation.
