[en] Since 1954 levels of radioactivity in the off-site environment surrounding underground nuclear testing areas have been measured to assure that the testing is in compliance with existing radiation protection standards. To assess off-site radiation levels, routine sampling networks for milk, water, and air are maintained along with a dosimetry network and special sampling of food crops, soil, etc., as required. For the purpose of implementing protective actions, providing immediate radiation monitoring, and obtaining environmental samples rapidly after a release of radioactivity, mobile monitoring personnel are also placed in areas downwind of the NTS or other test areas prior to each test. Analytical results showing radioactivity levels above naturally occurring levels have been published in reports covering the test series or test project