This European Standard 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 and are hereafter referred to as boilers. Where the word boiler is used, this is to be read as the boiler including its connecting ducts, ducts and terminals, if any. This European Standard covers gas-fired central heating boilers type B11, B11BS, B12, B12BS, B13, B13BS according to the classification in CEN/TR 1749:2009: a) that have a nominal heat input (on the basis of net calorific value) not exceeding 70 kW; b) that use one or more combustible gases of the three gas families at the pressures stated in EN 437; c) where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation; d) where the maximum operating pressure in the water circuit does not exceed 6 bar; e) which are declared in the technical instructions to be either a low temperature boiler or a standard boiler. If no declaration is given the boiler is to be considered a standard boiler; f) which are intended to be installed either indoors or in a partially protected place; g) which are either not intended to produce hot water, or are intended to produce hot water either by the instantaneous or storage principle, the whole being marketed as a single unit. h) which are designed for either sealed water systems or for open water systems. This European Standard is to be used in conjunction with the General Requirements Standard EN 15502 1. For applications within the scope of the PED further requirements may be necessary (e.g. situations where the maximum allowable temperature exceeds 110 °C, or where volume times maximum allowable pressure is over 50 bar x litres). This standard provides requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this standard, the risk associated with this alternative construction shall be assessed. An example of an assessment methodology, based upon risk assessment and which covers the essential requirements of the Gas Appliance Directive, is given in Clause 11. This standard does not cover all the requirements for: i) appliances that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see Annex DD of EN 15502 2 1:2012); j) appliances using flue dampers; k) appliances that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW; l) appliances of the types A, B14, B2, B3, B4, B5 and C; m) appliances intended to be connected to a (common) flue having mechanical extraction; n) appliances with gas/air ratio control; o) modular boilers; p) boilers which can give rise to condensation under certain circumstances; q) boilers intended to be installed in a room with a foreseeable negative pressure relative to the pressure in the flue system. NOTE Negative pressure relative to the pressure in the flue system can for example be caused by mechanical or thermal ventilation in airtight buildings.