This appendix describes the monitoring instrumentation, sampling procedures, and data analyses used to measure or estimate the reported releases of tritium. The accuracy of reconstructing the atmospheric tritium source term is largely dependent on the type of monitors used to measure the releases. Atmospheric tritium releases have been monitored using dehumidifiers, silica gel monitors, Kanne ionization chambers, the stack tritium monitor (STM), the Berthold tritium monitor (BTM), the stack monitor integrator (SMI), and the FORMS in the reactor and tritium facilities on the Savannah River Site (SRS). This appendix describes the monitoring equipment and how it was used. We have performed an extensive review of documentation, but it has been difficult to determine the exact times that each type of monitor operated at each of the facilities. Radiological Assessments Corporation (RAC) researchers identified no clear deficiency in the methodologies used at SRS. Therefore, we initially believed that no correction factors should be applied to the SRS data in producing the final source term estimates presented in Chapter 4.1. To verify that this was an acceptable conclusion, we used an uncertainty assessment to evaluate the effectiveness of the monitors. This appendix presents the estimated uncertainty of the tritium measurements by type of monitor. Using the results of the uncertainty assessment, we concluded that the “best estimate” values should be used as the atmospheric tritium source term without correction, and the range of uncertainty should be applied to release data by facility and year. If more information is found about the monitors or when they were used in each facility, we can apply these results more specifically.