This technical report gives guidance on the method of testing of ASSEMBLIES under conditions of arcing in air due to an internal fault. The purpose of this test is to assess the ability of the ASSEMBLY to limit the risk of personal injury, damage of ASSEMBLIES and its suitability for further service as a result of an internal arcing fault. The test procedure given in this technical report applies only: – to enclosed, floor-standing or wall-mounted low-voltage switchgear and controlgear assemblies according to IEC 61439-2 (power switchgear and controlgear assemblies – PSC ASSEMBLIES); NOTE This technical report can be used as a reference for arc fault tests of other products, but adaptations of the test procedures and acceptance criteria can apply taking into account the specifics of such other ASSEMBLIES or products. – to situations when doors and covers of the ASSEMBLY are closed and correctly secured. When tests under different or more severe conditions are agreed between the user and the manufacturer, this technical report can be used as a guide. The test procedure given in this technical report takes into consideration: – the effects of the internal overpressure acting on covers, doors, etc.; – the thermal effects of the arc or its roots on the enclosures and of ejected hot gases and glowing particles. The test procedure given in this technical report does not cover: – other effects which can constitute a risk, such as toxic gases and loud noises; – conditions during maintenance work, open doors or similar; – access to the top and bottom of the ASSEMBLY. This is a voluntary test made at the discretion of the manufacturer.