This Standard specifies the methods for determination of gaseous inorganic fluorine compounds in flue gas as fluoride ions and calculation of hydrogen fluoride concentration. In this Standard, the flue gas means the gas exhausted from flue, chimney, duct, etc. (hereafter referred to as “duct”）in combustion of wastes, smelting process of aluminium, manufacturing process of chemical fertilizer, manufacturing process of glass, etc. The gaseous inorganic fluorine compounds are those passing through the filter having not less than 99.5 % in collection efficiency of particles of 0.3μm. The fluoride ion is the designation of F.