This part of IEC 60079 specifies the general requirements for construction@ testing and marking of electrical apparatus and Ex components intended for use in explosive gas atmospheres. Unless modified by one of the parts in the IEC 60079 series@ electrical apparatus complying with this standard is intended for use in hazardous areas in which explosive gas atmospheres@ caused by mixtures of air and gases@ vapours or mists@ exist under normal atmospheric conditions of ? temperature ?C20 ??to +60 ?? ? pressure 80 kPa (0@8 bar) to 110 kPa (1@1 bar); and ? air with normal oxygen content@ typically 21 % v/v. The application of electrical apparatus in atmospheric conditions outside this range may need special consideration.