Aqueous foam is a mixture of air (or other gas), surfactant and water. Foam can be used in at least two ways for emission control: foam blanketing and foam scrubbing. Foam scrubbing differs from blanketing in that the foam (usually high-expansion) is blown using the contaminated air that is to be treated. Thus, in foam scrubbing the contaminant is inside the foam bubbles. While the release is contained in this manner, a scrubbing process can take place. The foam solution can be formulated to include an appropriate reagent that can 'neutralize' the absorbed gases, if necessary (for example, an acidic additive to neutralize ammonia). Potential applications of foam scrubbing for emergency control are many: the chemical industry (ammonia, hydrogen chloride, sulfuric acid, etc.), municipalities (chlorine tanks at water treatment facilities), and emergency responders (chemical spills, tank truck accidents, etc.) Foam scrubbing could also be used at Superfund sites during excavation to safeguard workers and surrounding communities from releases of volatile toxic materials. The chapter summarizes the available information on foam scrubbing, including results of an EPA research program on the subject. Although largely still in the research stage, the information available to date is encouraging.