Oxygen scavengers are typically made of materials that can react with and remove oxygen from the surrounding environment. We use materials for oxygen scavengers in the pharmaceutical industry including iron powder, ascorbic acid, and sodium sulphite. Iron powder is a popular choice for oxygen scavengers because it reacts with oxygen to form iron oxide, which is not harmful to the products being protected. Ascorbic acid and sodium sulphite also react with oxygen to form harmless by-products. The specific composition of an oxygen scavenger will depend on the application and the specific requirements for the product being protected.