The institute of nuclear physics of Orsay is accepted by the Ministry of Labour to insure the surveillance of workers individual external exposure against the danger of ionizing radiations and to execute monitoring of radiation protection. The dosemeters studied in this report are the photographic film dosemeters ( for x rays, gamma rays and beta {sup -} rays), the trace detectors (fast neutrons) and the radio thermo luminescent dosemeters. For each type, the principle and how to use it are given