This International Standard describes a test method which can provide preliminary differentiation between similar insulating materials, with respect to their resistance to damage when exposed to high-voltage, low-current arc discharges, occuring close to their surfaces. The discharges cause localized thermal and chemical decomposition and erosion and eventually a conductive path forms across the insulating material. The severity of the test conditions is gradually increased: in the early stages a low-current arc discharge is repeatedly interrupted, whereas in the later stages, the arc current is raised in successive steps.