Abstract The semiconductor industry has a requirement for ultra high purity gases to process wafers. Ultra high purity hydrogen is one of the gases used by this industry. Currently, the ultra high purity hydrogen used for this industry comes from one of two sources; a cryogenic adsorption system or a palladium membrance system. The purity of cryogenic liquid hydrogen is extremely high. The extensive use of pre-liquefaction purifier technologies is essential for the safe and continued operation of a liquid hydrogen plant. The impurities would solidify in the process flow and result in a system shutdown. This paper will describe the experimental results from a pilot plant system which maintains the high purity of the liquid hydrogen product for delivery to a semiconductor manufacturing facility. A discussion of an atmospheric pressure ionization mass spectrometer used to verify the purity of the gaseous hydrogen will highlight the capabilities of this technology and the dilution system used to calibrate this analyzer.