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C.3 Advised sensitivity of direct measurement and scanning survey techniques

Direct measurement and scanning survey techniques should be capable of measuring levels below the established DCGLs – detection limits of 10-50% of the DCGL should be the target (see Section 3.3.7). Cost, time, best available technology, or other constraints may create situations where the above stated sensitivities are deemed impractical. Under these circumstances, higher detection sensitivities may be acceptable. Although service providers and instrument manufacturers will state detection limits, these sensitivities are usually based on ideal or optimistic situations and may not be achievable under site-specific measurement conditions. Detection limits are subject to variation from measurement to measurement, instrument to instrument, operator to operator, and procedure to procedure. This variation depends on geometry, background, instrument calibration, abundance of the radiations being measured, counting time, operator training, operator experience, self-absorption in the medium being measured, and interferences from radio-nuclides or other materials present in the medium. The detection limit that is achievable in practice should not exceed the DCGL. See section 3.3.7 for more detailed information.