The Clean Agent cylinders are manufactured, tested and stamped in accordance with DOT 4BW500 or DOT 4B500. All cylinders are equipped with back pressure type valve. A piston in the valve bore is equipped with a rubber seal that keeps the HFC-227ea Clean Agent under pressure within the cylinder. A small hole in the piston allows cylinder pressure to be equalized on both sides of the piston. Since the area at the top of the piston is greater than the area at the bottom of the piston, the net force seals the piston against the valve discharge outlet. When the cylinder pressure on the top of the piston is relieved by means of automatic or manual activation, there is only cylinder pressure acting against the piston seal, and the piston slides to it’s full open position, allowing cylinder discharge through the distribution piping network.