The classification of hazardous areas where explosive gas atmospheres may be present

•IEC EN 60079-10-1 is the actual international standard for hazardous areas classification.•The extent of zones calculated with the standard does not match the real volume of explosive mixture.•New formulas and procedures to evaluate the extent of hazardous zones are proposed.•The proposed formulas and procedures are presently adopted by the Italian guide for classification.

The classification of hazardous areas where explosive gas atmospheres may be present is prescribed by European directives, international and national standards.This paper briefly outlines the area classification procedure and describes the approaches adopted by the international standard. Then a new approach to the calculation of the extent of zones, developed by the author and adopted by the Italian guide for classification of hazardous zone, is presented.