Intercomparison and intercalibration of active and passive radon detectors in North America

The state of the art of the most commonly used instrumentation for radon measurements was evaluated at an intercomparison exercise held at the Environmental Measurements Laboratory, between April 24, and May 10, 1990. More than 50 sets of active and passive devices were submitted for evaluation by 30 laboratories from private firms, local, state and federal agencies and universities. There were basically five different types of detectors representing the majority of instruments used to assess the indoor airborne concentration of radon. After exposure, the devices were returned to the participating laboratories for analysis. The results reported to EML indicate that the overall performance was good with the majority of the participating laboratories reporting mean results within 10% of the EML reference values. In general, the majority of radon measuring devices gave slightly lower readings than the reference values. The individual measurements made with activated carbon collectors of both the open face and diffusion barrier type and the electret/ionization chambers showed the best precision and accuracy. The nuclear track detectors showed mixed results, exhibiting the largest measurement errors. This suggests that there are problems with sensitivity and with quality control procedures that must be addressed to improve their performance. 7 refs., 1 fig., 2 tabs