Antifouling agents for free radical polymerization were first developed over 20 years ago primarily for vinyl chloride suspension polymerizations. Since then there have been many improvements in the performance and application of antifouling agents. The application of antifouling agent has been expanded from suspension polymerizations to mass, solution and emulsion polymerization and also to many other resins besides PVC. Antifouling agents act by inhibiting the free radical polymerization at the reactor surfaces, thus reducing the frequency of reactor cleaning and improving product quality. Antifouling agents do not nterfere with the polymerization kinetics or negatively impact product quality. Commercial scale application of antifouling agents typically takes only about 5 to 10 minutes per batch and is applied after every batch. Antifouling agents are approved by the FDA for food contact for some resins.