Odor control at wastewater facilities includes a wide variety of methods. These methods include the following: source control; limit the production of odor (within sewers and treatment plants); treat odors in the liquid phase; cover, ventilate, and treat foul air; and enhance dispersion of released odorants. This session of the Specialty Conference is involved primarily with only one of these methods: the treatment of foul air in various types of systems. Owners and engineers need to be aware of how this method is integrated with the other methods of odor control so that the entire odor problem is solved cost-effectively.