A blowing agent is a substance used to create a cellular structure in materials, primarily in the production of foams. When heated or chemically reacted, blowing agents release gas, which expands and forms bubbles within a liquid or solid matrix. This process is essential in manufacturing products like polyurethane foam and polystyrene foam, which are widely used in insulation and packaging. Blowing agents can be classified into physical and chemical types. Physical blowing agents, such as carbon dioxide or nitrogen, are gases that expand when heated. Chemical blowing agents, like azodicarbonamide, undergo a chemical reaction to produce gas. Both types contribute to the lightweight and insulating properties of foam products.