IEC/TS 62271-304:2008 applies to indoor enclosed switchgear and controlgear complying with IEC 62271-200 and IEC 62271-201, intended to be used in service conditions more severe with respect to condensation and pollution than the normal service conditions specified in IEC 62271-1. This technical specification covers equipment where any of the insulation is exposed to indoor climatic conditions. This first edition of IEC/TS 62271-304 cancels and replaces the first edition of IEC/TS 60932, published in 1988, and constitutes a technical revision. This revised document has been basically changed to be updated to today's use of high-voltage switchgear and controlgear up to 52 kV. The contents of the corrigendum of January 2010 have been included in this copy.