As world communications improve, a common basis of understanding is essential. It is no longer sufficient to just make measurements, they must be internationally credible. The latest recommendations of ICRP, and the International Standard “evaluation of surface contamination Part 2 Tritium” are applied in practical terms, to achieve accredited measurements for the evaluation of tritium surface contamination. Three main requirements are explained. 1-A calibration reference source with certified emission rate. 2-A calibratable surface measuring instrument. 3-Reproducible measurements of all forms of surface activity.