Answer to Question #7193 Submitted to "Ask the Experts"

Thank you for your question pertaining to air sampler calibration.

If your question is about the calibration of the flow meter of the air sampler, then NRC Regulatory Guide 8.25 and NUREG-1400, both titled "Air Sampling in the Workplace," address this issue. Section 5.2 of Regulatory Guide 8.25 states that flow-rate meters for air samplers should be calibrated annually and after repairs or modifications to the flow rate meter. NUREG-1400 section 5.2.4 specifically addresses the calibration of rotometers and offers an in-depth discussion into the methods and provides references for this calibration. So there is no threshold at which calibration should be performed for flow-rate meters. Like all other instruments used for radiation measurements, they should be calibrated before use for the range of expected conditions.

There is a threshold for when air sampling should be performed, and if using fixed-head air samplers, when air sampling needs to be representative. Table 1 and Table 2 of Regulatory Guide 8.25 provide these criteria, with greater in-depth discussion in NUREG-1400.

Eric W. Abelquist, PhD, CHP