This International Standard specifies a method, by determination of carbon dioxide (CO2), for the evaluation in an aqueous medium of the ultimate biodegradability of organic compounds at a given concentration by aerobic microorganisms. The method applies to organic compounds which are: a) water-soluble under the conditions of the test, in which case removal of DOC may be determined as additional information (see annex D); b) poorly water-soluble under the conditions of the test, in which case special measures may be necessary to achieve good dispersion of the compound (see, for example, ISO 10634); c) non-volatile or which have a negligible vapour pressure under the conditions of the test; NOTE For volatile substances use for example ISO 9408 or ISO 14593. d) not inhibitory to the test microorganisms at the concentration chosen for the test. NOTE The presence of inhibitory effects can be determined as specified in 8.3, or by using any other method for determining the inhibitory effect of a compound on bacteria (see, for example, ISO 8192).