[Measurement and calculation of the air activation caused by 15 MeV continuous radiation emitted by a linear accelerator (author's transl)].

: The rate of air activation caused by the 15 MeV continuous radiation of a "Clinac 20" can be concluded from activation measurements in urea tablets. In case of the most unfavourable irradiation conditions, a maximum field size of 35 X 35 cm2, and a distance focus-wall of 450 cm, an air activation of 6, 18 X 10(4) Bq per individual irradiation is calculated. The limit of activity concentration prescribed by the Strahlenschutzverordnung (radioprotection directive) is not reached if a sufficient change of air is guaranteed. This method of measuring the air activation is simple, not time-consuming and can be effected with a high degree of accuracy. Measurements and calculations are compared.