In the past 20 years of practice, mining cables have undergone a transformation from non flame retardant to flame retardant, especially since the implementation of the test methods and judgment rules for flame retardancy of coal mine cables (MT 386-1995, MT386-2011), which have effectively controlled and improved the flame retardancy of coal mine cables. However, the current flame-retardant cables used in coal mines (which mostly use chlorine containing polymers as sheath materials) release a large amount of smoke when heated and burned. Although the transmittance measured by IEC 61034 or GB/T 17651'1998 is below 10%, the released hydrogen chloride (HCl) gas content is high, exceeding 100 mg/g and even reaching 200-300 mg/g. Such thick smoke, combined with toxic gases such as H2S and CO, can irritate and poison the human respiratory system. In the narrow environment underground, disaster victims are unable to escape the scene of the fire. According to foreign fire records, this type of casualties in "secondary disasters" accounts for 70% to 80% of the total number of fire casualties. In the number of casualties in coal mine fire accidents in China, the proportion of people affected by "secondary disasters" is also very large.

When flame-retardant or non flame-retardant materials such as cables burn, they release a large amount of smoke and toxic gases such as CO and HC1. In order to avoid or reduce the "secondary disasters" of fire accidents, the Electrotechnical Commission (IEC) formulated and revised IEC607541 and

IEC607542， This is to limit the amount of toxic gas released during cable combustion (with HC1 content<5 mg/g, pH>4.3, conductivity<10 tts/ram for the aqueous solution of corrosive gases released during combustion). In 1991, IEC61034 was formulated to limit the amount of smoke released during cable combustion (with a specified smoke transmittance of>60%). The UK has established engineering standards NES-718 and NES-713. The American standard MILS24643 directly uses the NES-713 standard to detect the toxic gas content released during cable combustion (with a specified toxicity index<5).

All these standards provide effective and reliable basis for limiting the smoke and toxic gases released by the combustion of flame-retardant or non flame-retardant materials such as cables. However, in the high-risk industry of coal mines, China's coal mine cables are almost blank in the control of low smoke and low toxicity (halogen).

The degree of environmental pollution caused by the combustion of low smoke and low halogen flame-retardant cables used in mining is smaller than that caused by the combustion of flame-retardant cables used in coal mines, which means that the use of low smoke and low halogen flame-retardant cables in coal mines reduces or minimizes the "secondary disasters" caused by cable combustion; Simultaneously meeting the performance requirements of coal mine cable materials is the main direction for future promotion. It is necessary and important to develop and apply low smoke, low toxicity (halogen) flame-retardant cables for coal mines.