What term describes devices like CAD, ATD, or EIC used to verify the accuracy of measurements?

The term that accurately describes devices like CAD (Calibration and Audit Device), ATD (Active Test Device), or EIC (Environmental Indicator Calibration) used to verify the accuracy of measurements is "standards."

Standards are used to establish a benchmark for measurement and ensure that the readings from testing devices align with recognized levels of accuracy. These devices help to confirm that radon measurement equipment is functioning correctly and producing reliable results. By utilizing standards, professionals can calibrate their instruments and ensure consistency across measurements, enhancing the credibility of radon testing.

In contrast, other terms refer to different concepts in measurement processes. Blanks are typically used to assess contamination levels, and controls represent conditions maintained constant during an experiment to ensure that any observed changes are due to the independent variable. References might work similarly, but they are more often used as a source of verification or comparison rather than a benchmark for calibration, thus making "standards" the most suitable term for the devices mentioned in the context of verifying measurement accuracy.