3. Terminology
(1) Intrinsically safe apparatus: Electrical apparatus in which all the circuits are intrinsically safe circuits.
(2) Associated apparatus: Electrical apparatus in which there are both intrinsically safe circuits and non-intrinsically safe circuits that can affect the safety of intrinsically safe circuits.
(3) Safety barrier: A specific type of associated apparatus, which consists mainly of safety barrier elements, and serves to limit the flow of excessive electrical energy, which is capable of causing ignition of a given explosive gas or vapour of a non-intrinsically safe circuit into concerned intrinsically safe circuits.
(4) Apparatus of category “ia”: Intrinsically safe electrical apparatus and associated apparatus which are incapable of causing ignition of a given explosive gas or vapour with the appropriate safety factors such as:
—when up to two countable faults are- applied and, in addition,
—when non-countable faults produce an onerous condition.