The elements of a fire extinguisher are constructed with metal. While the pressure vessel is constructed of aluminum alloy, the valve may be made of either steel or plastic materials. The handle and safety pins are generally steel.
Several steps are taken to manufacture a fire extinguisher. For a tank or cylinder type extinguisher, the pressure vessel must be formed, the chemical agent must be loaded, and the valve must be created, as well as the other hardware and hoses.
The pressure vessel is created when a puck-shaped disc is "impact extruded" on a large press. Pressure is applied when the piece is put into a die and struck at high velocity with a metal tool. The extraordinary energy liquefies the aluminum, causing it to form into an open-ended cylinder. Spinning may be done to increase the wall thickness and reduce the diameter of the extinguisher, while rolling the metal together. After the spinning process, the threads must be added and hydrostatic testing, cleaning and painting of the vessel is needed before it is placed in an oven and baked to cure the paint.
The extinguishing agent is added to the vessel accordingly. The process depends upon the type of extinguisher (whether stored pressure or a gas cartridge is used). The vessel is then sealed.
After the extinguishing agents have been added and the vessel sealed, the valve (either metal or plastic), is added. The last step is assembling the handle, pins and mounting bracket using a "cold form" technique. The final details include placing decals and instructions on the extinguisher. These will help the user determine which type of fire ought to be extinguished with the vessel (whether an electrical fire, liquid or paper and wood fire).