Abstract :
Both the CENELEC and IEC Standards dealing with intrinsic safety contain reference curves which are essentially the same as the minimum igniting current and voltage curves presented by Widginton in 1968. The validity of some of these curves, particularly those for capacitive circuits, has been questioned. In 1974 IEC Sub-Committee SC31-G `Intrinsic safety´ set up a Working Group, WG2 `Ignition data´. The author indicates what progress has so far been made by the WG, and also provides some information on reference curves for high-voltage resistive circuits, a subject outside the WG´s remit
