This part of ISO 4491 specifies a method for the determination of the hydrogen-reducible oxygen content of metallic powders containing 0,05 % (m/m) to 3 % (m/m) oxygen. The method is applicable to unalloyed, partially alloyed or completely alloyed metal powders and also to mixtures of carbides and binder metal. It is not applicable to powders containing lubricants or organic binders. The method may be extended to powders containing carbon by the use of a special catalytic device. This part of ISO 4491 shall be read in conjunction with ISO 760 and ISO 4491-1.