The standard is applicable to hand and automatically fired appliances having nominal heat outputs up to 50 kW, the primary function of which is to provide hot water for central heating and/ or domestic use, and which are designed for use only with open vented systems at a working pressure not exceeding 2 bar. In addition to their primary function of providing hot water these appliances also provide space heating to the place of installation. These appliances may burn naturally occurring or manufactured solid mineral fuels, peat briquettes, natural or manufactured wood logs and biomass based products which are in the form of an identifiable consistent product or be multi-fuel in accordance with the appliance manufacturer' s instructions.