It is the lightest and the smallest of the inert gas molecules. Therefore, it flows through small leaks easily. Even very small amounts can be easily identified. It operates in the high and ultra-high vacuum ranges. The high percentage of hydrogen is mainly because when the steel pipe is produced at the mill it is quenched in a hydrogen atmosphere and it permeates the steel.
Carbon monoxide is relatively high too because it is a product of the heating process.
With the high voltage on, the electron beam energy increases thus hydrogen and other gases like Carbon monoxide are knocked off the surface of the pipe, this increases the overall pressure. A bakeout of the RGA and the system accelerates the outgassing rates and results in reduced pump-down times. In many cases a bakeout is needed to efficiently remove low-vapor pressure impurities from the walls. A thorough bakeout helps clean the surface and usually results in reduced contribution of the RGA sensor to the background signals. As the RGA is used, deposits form on the ionizer part and on the filter components.