Abstract: A method and composition for controlling odor emission from toilet holding tanks for prolonged intervals of at least 48 hours consisting essentially of adding to the toilet holding tank an effective amount of an additive composition consisting essentially of a quaternary compound selected from the class consisting of alkyl dimethyl benzyl ammonium chloride and alkyl diethyl benzyl ammonium chloride where the alkyl group contains 12-18 carbon atoms, inclusive; formaldehyde; and an acid buffer sufficient to buffer the composition in the toilet system to a pH in the range of 4-5. The effective amount is that which is sufficient to maintain a concentration of at least 100 parts per million of the additive composition throughout the prolonged interval.