The original design of a vacuum hydrogen permeation monitor has been modified. The new rigid foil can be (a) accurately calibrated to give quantitative results; (b) monitored for process/ambient temperature changes; and, (c) corrected for temperature variations. The design provides an accurate measurement of hydrogen flux and can be used over a wide range of temperatures. The modified foil can be sized to meet specific user requirements. This monitor has been used in both laboratory and field situations to measure hydrogen flux rates. The results of the field tests are used to assess the potential for hydrogen damage (HIC) and to provide a detailed evaluation of the corrosion
processes occurring within a process vessel. Keywords: hydrogen diffusion, hydrogen monitors, hydrogen flux, HIC, threshold hydrogen concentration