Abstract
A diffuse radioactivity measuring facility has been recording data since 1981. The mean daily values of air radioactivity for the time period February 1981‐April 1986 were never found to exceed the level of 25 counts per minute (cpm). Values recorded during May 1986 were as high as 200cpm due to the arrival of the Chernobil radioactive cloud in the area on 2 May 1986. Radioactivity measured on grass and on concrete was higher by a factor of 2. Gamma‐ray spectroscopy was used to identify the existence of Ru‐103, Ru‐106, Cs‐134, Cs‐137 and I‐131 in the atmosphere of Sindos ten days after the arrival of the cloud. Finally, a correlation coefficient of 0.68 has been estimated in an attempt to correlate diffuse radioactivity and relative humidity on the basis of an assumed linear variation.