A Hydrogen Parallel Charging Unit, also known as H2 Rail, is a system used to fill multiple hydrogen gas cylinders at the same time. It consists of a high-pressure hydrogen storage tank, hydrogen dispensers, and control systems to manage the flow of hydrogen gas to the cylinders. The purpose of the H2 rail is to provide a safe and efficient means of filling the gas, while also ensuring that the hydrogen gas is dispensed at the correct pressure and flow rate