A guide for technical committees specifying dimensioning requirements for products in accordance with IEC 60664-1. Significant items covered are as follows: a) nominal system voltage(s) or rated insulation voltage(s); b) overvoltage category of the products; c) pollution degree. A diagram for dimensioning of clearances and creepage distances for low-voltage equipment (up to 2 000 m) is also given. This is a technical report - type 3. Has the status of a basic safety publication in accordance with IEC Guide 104. This application guide is only applicable to IEC 60664-1 Ed.1 (1992).