Although industry uses a great number of corrosion monitoring tools and techniques to monitor and control internal corrosion, the measurement of atomic hydrogen flux probably represents less than one percent (1%) of these measurements. The reason for not utilizing this direct measurement technique is not complicated. Over the years, many hydrogen flux monitoring devices have come and gone, and even those that remain today have not fidfilled the expectations that corrosion engineers require for confident monitoring. Vacuum hydrogen flux monitoring has provided an extremely sensitive and reliable method of directly monitoring and controlling the corrosion process in many difficult and complicated areas of hydrocarbon processing and transmission. However, since hydrogen flux is a direct structural measurement of corrosion, it must be accurately positioned. Thk paper details how to correctly position hydrogen flux monitoring, and how atomic hydrogen flux was used in three (3) different case histories.