This European Standard specifies ranges, construction, performances, output characteristics and testing of rotary displacement gas meters (hereinafter referred to as RD meters or simply meters) for gas volume measurement. This European Standard applies to rotary displacement gas meters used to measure the volume of fuel gases of at least the 1st, 2nd and 3rd gas families, the composition of which is specified in EN 437:2003+A1:2009, at a maximum working pressure up to and including 20 bar over an ambient and gas temperature range of at least "10 °C to +40 °C. This European Standard applies to meters that are installed in locations with vibration and shocks of low significance (class M1) and in closed locations (indoor or outdoor with protection as specified by the manufacturer) with condensing or with non-condensing humidity or, if specified by the manufacturer, open locations (outdoor without any covering) with condensing humidity or with non-condensing humidity, and in locations with electromagnetic disturbances (class E1 and E2). The standards apply to mechanical meters with mechanical index, electronic devices are not covered by this standard. Unless otherwise specified in this standard: all pressures used are gauge; all influence quantities, except the one under test, are kept relatively constant at their reference value. This European Standard applies to meters with a maximum allowable pressure PS and the volume V of less than 6 000 bar · litres or with a product of PS and DN of less than 3 000 bar. This European Standard can be used for both pattern approval and individual meter testing. Cross-reference tables are given in: Annex A for the tests that need to be undertaken for pattern approval; Annex B for individual meter testing. Some parts of this standard cover meters with mechanical index only. The risk philosophy adopted in this standard is based on the analysis of hazards including pressure. The standard applies principles to eliminate or reduce hazards. Where these hazards cannot be eliminated appropriate protection measures are specified.