[en] The discussions in breakout session C2 are summarized. The topics discussed include the information that is required which provides the user with the knowledge of how each type of chemical treating agent works in order to avoid a pleasant surprises where a material is used on a spill. Several categories of chemical agents are discussed. The participants felt that some of the questions which should be addressed include the development of laboratory methods for measuring effectiveness which have been verified by field tests, information on the short- and long-term impact of using various agents, as well as answering the question why a certain category of chemicals should not be used