This standard describes a method for empirical and conventional determination of the biochemical oxygen demand of water by dilution and seeding. The method is applicable to all waters with a BOD greater than or equal to 3 mg of oxygen per liter and not exceeding 6 000 mg of oxygen per liter. For BOD greater than 6 000 mg oxygen per liter, this method can also be used, but errors caused by the necessary dilutions lead to interpreting the results with circumspection. The results obtained are the product of the combination of chemical and biochemical actions. They do not have the rigor or ambiguity of those derived from the application of a single and well-determined process, but they nevertheless provide an indication that allows the quality of the water to be evaluated. The results may be influenced by the presence of various substances. Toxic substances used against microorganisms, such as bactericides, toxic metals or free chlorine, can inhibit biochemical oxidation. The presence of algae or nitrifying microorganisms can artificially produce high results.