Gives principles for the design, construction and operation of industrial appliances that are heated by the combustion of a fuel, i.e. ovens, furnaces, boilers, dryers and the like. It deals with the safety of the fuel combustion process, and with safety in relation to combustible vapours, dusts, etc. that may occur or be generated within an appliance. Methods of calculating critical appliance characteristics, explosion relief areas, and air dilution volumes are given.