1.1 This document specifies the constructional requirements for fans constructed to Group II G (of explosion groups IIA, IIB and hydrogen) categories 1, 2 and 3, and Group II D categories 2 and 3, intended for use in explosive atmospheres. NOTE 1 Operation conditions for the different categories of fans used in this document are defined in Clause 4. NOTE 2 For category 1 D fans, requirements provided in this document are not sufficient to ensure safety. In addition, explosion protection measures as specified in EN 1127 1:2019 are required to prevent ignition in the case of rare malfunctions. NOTE 3 Technical requirements for explosion group IIC (other than hydrogen) are not given in this document. Where such atmospheres are present, additional explosion protection measures as specified in EN 1127 1:2019 can be needed. 1.2 This document does not apply to group I fans (fans for mining), cooling fans or impellers on rotating electrical machines, cooling fans or impellers on internal combustion engines, vehicles or electric motors. NOTE 1 Requirements for group I fans are given in EN ISO/IEC 80079 38:2016. NOTE 2 The requirements for electrical parts are covered by references to electrical equipment standards. 1.3 This document specifies requirements for design, construction, testing and marking of complete fan units intended for use in potentially explosive atmospheres in air containing gas, vapour, mist and/or dusts. Such atmospheres can exist inside (the conveyed atmosphere (flammable or not)), outside, or inside and outside of the fan. NOTE This document covers mechanical equipment, in particular fans. The “protection concept” as specified in EN ISO 80079 37:2016 is constructional safety. Requirements for marking are given in EN ISO 80079 37:2016. 1.4 This document is applicable to fans working in ambient atmospheres and with normal atmospheric conditions at the inlet, having — absolute pressures ranging from 0,8 bar to 1,1 bar, — and temperatures ranging from −20 °C to +60 °C, — and maximum volume fraction of 21 % oxygen content, — and an aerodynamic energy increase of less than 25 kJ/kg. NOTE 1 25 kJ/kg is equivalent to 30 kPa at inlet density of 1,2 kg/m3. This document can also be helpful for the design, construction, testing and marking of fans intended for use in atmospheres outside the validity range stated above or in cases where other material pairings need to be used. In this case, the ignition risk assessment, ignition protection provided, additional testing (if necessary), manufacturer's marking, technical documentation and instructions to the user, clearly demonstrate and indicate the equipment's suitability for the conditions the fan can encounter. NOTE 2 Temperatures below −20°C can be considered. Material suitability can require specific evaluation for these temperatures. With lower temperature the explosion pressure increases, which leads to increased test pressures (see A.3) and can require specific testing. Although the standard atmospheric conditions in EN ISO 80079 36:2016 give a temperature range for the atmosphere of −20 °C to +60 °C the normal ambient temperature range for the equipment is −20 °C to +40 °C unless otherwise specified and marked.