Antimony(III) Oxide is the inorganic compound with the formula Sb2O3. Antimony Trioxide is an industrial chemical and also occurs naturally in the environment. It is the most important commercial compound of antimony. It is found in nature as the minerals valentinite and senarmontite. Antimony Trioxide is a chemical used in the manufacture of some polyethylene terephthalate (PET) plastic, which is used to make food and beverage containers. Antimony Trioxide is also added to some flame retardants to make them more effective in consumer products, including upholstered furniture, textiles, carpeting, plastics, and children’s products.