A self-contained breathing device for use in fighting fires comprising a hood for covering a wearer's head, a membrane for sealing the hood to create a breathing chamber inside the hood, and a source of oxygen disposed inside the hood. The source of oxygen is connected to the user by a conduit inside of the hood, and another conduit directs user-exhaled carbon dioxide to the source of oxygen. The breathing device includes a visual indicator inside of the hood that reacts to the presence of a gas within the hood and provides visual feedback to the user based on a quantity of the gas present in the hood.