Specifies the dimensioning of clearances and creepage distances for spacings equal to or less than 2 mm for printed wiring board and equivalent constructions, where the clearance and the creepage distance are identical and are along the surface of solid insulation. The dimensioning in this standard is more precise than that provided by IEC 60664-1. However, if the precision provided by this standard is not required, IEC 60664-1 may be applied instead. This standard is based on the following criteria for dimensioning: - minimum clearances independent of the micro-environment; - minimum creepage distances for pollution degrees 1, 2 and 3 to avoid failure due to tracking; - minimum creepage distances to avoid flashover across the insulating surface. A test method is specified for allocating unclassified insulating material to the relevant water adsorption group. The following major technical changes are: - Amendment of Japanese mains conditions with regard to the rated impulse voltages, the rationalized voltages and the nominal voltages of supply systems for different modes of overvoltage control. - Amendment of dimensioning of clearances smaller than 0,01 mm. Alignment of the table and the corresponding formula regarding test voltages for verifying clearances at different altitudes. - Amendment of interpolation of the creepage distance values for functional insulation. - Revision of the former Clause 4 "Tests and measurements" (now Clause 6) to achieve a more detailed description of the tests and their purpose, the test equipment and possible alternatives. Has the status of a basic safety publication in accordance with IEC Guide 104.