Hydrogen and oxygen come separately into H₂ separator and O₂ separator, where they are cooled by cooling water and separated from the mixture of gas-lye by gravity. After that H₂ gas come into the H₂ washer for lye drop to be removed which is contained in gas by DM water, at the same time the gas is cooled by coil-piped cooler which is erected in the washer. Finally, the hydrogen through the demister which locates at the top of washer to eliminate the water drop, then flows into the hydrogen drying unit via pneumatic valve for further purification. Oxygen processing will be expelled to atmosphere.