What exactly are "intrinsically safe circuits" and what cables can be used in such circuits? ?

A number of ignition protection types exist to eliminate the dangers posed, for example, by ignitable sparks in explosive atmospheres. As well as for instance the use of pressure-resistant engine casings (ignition protection type d "drive enclosure"), this also includes amongst others intrinsic safety (ignition protection type i "intrinsic safety").
Intrinsic safety is a technical property, in which special construction principles are applied to prevent the occurrence of dangerous situations, even in the event of a fault. Electrical or electronic devices with ignition protection type "i" are used especially in explosive atmospheres for measurement and control purposes. Power is supplied to electrical equipment via a safety barrier, which limits the voltage and current such that the minimum ignition energy and temperature of an explosive gas, dust or vapour mixture is never reached. Intrinsically safe circuits are therefore used in explosive environments in which no sparks or thermal effects must occur that may ignite an explosive atmosphere. The operating voltage and current must not generate sufficient energy to cause an explosion.

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