This document specifies the requirements and test methods concerning, in particular, the construction, safety, fitness for purpose, and rational use of energy, as well as the classification and marking of gas-fired central heating boilers that are fitted with atmospheric burners, fan-assisted atmospheric burners or fully premixed burners, and are hereafter referred to as "boilers". This document applies to boilers of type C, as listed in 4.2: that use one or more combustible gases of the three gas families at the pressures stated in Tables 14 and 15; that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW, but not exceeding 1000 kW, including modular boilers; where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation; where the maximum operating pressure in the water circuit does not exceed 6 bar; which can give rise to condensation under certain circumstances. The document applies to boilers designed for sealed water systems or for open water systems. The document does not contain all the requirements necessary for boilers: intended to be installed in the open or in living rooms; permanently fitted with more than one flue outlet; of the condensing type; intended to be connected to a common flue having mechanical extraction; type C21, C41, C51, C61, C7 and C81 boilers; fitted with a forced draught burner in accordance with EN 676; producing hot water for domestic purposes. This document only covers type testing.