PEAK's Precision Hydrogen Standard Hydrogen generator uses PEM electrolytic cell to electrolyze ultra-pure water to produce hydrogen. Theoretically, 18 grams of ultra-pure water (1mol H2O) can produce 22.4L of hydrogen (at normal temperature and pressure). However, the pure water consumed by the hydrogen generator depends mainly on the working load of the generator. If the hydrogen generator is working most of the time, naturally, the pure water consumed is more. Similarly, if the hydrogen generator is in standby for most of the time, it consumes very little ultra-pure water.