This document specifies the test gases, test pressures and categories of appliances relative to the use of gaseous fuels of the first, second and third families. It serves as a reference document in the specific standards for appliances. The document makes recommendations for the use of the gases and pressures to be applied for the tests of appliances burning gaseous fuels. NOTE Procedures for tests are given in the corresponding appliance standards. The test gases and the test pressures specified in this standard are in principle intended to be used with all types of appliances. . However, the use of some test gases and test pressures may not be appropriate in the following cases: appliances with nominal heat input greater than 300 kW; appliances constructed on site; appliances in which the final design is influenced by the user; appliances constructed for use with high supply pressures (notably direct use of the saturated vapour pressure). In these cases, the specific appliance standards may specify other test conditions in order to establish compliance with their requirements.