An international intercomparison of soil gas radon and radon exhalation measurements

The Environmental Measurements Laboratory hosted the Sixth International Radon Metrology Programme Intercomparison Test and Workshop (IRMP6) from 12-15 June 1995. Thirty participants representing 24 different institutions from 11 countries attended. Laboratory exercises consisted of 220Rn and 222Rn concentration measurements from a source container, and exhalation measurements from a 226Ra-spiked concrete slab and a "normal" concrete slab. Field exercises included soil gas radon measurements and radon exhalation measurements. In this report, we pooled the participants' data and used the ratio of the standard deviation (SD) to the arithmetic mean, expressed as a percentage, to assess participant agreement for each exercise. For the exhalation measurements from the 226Ra-spiked slab, this value is 37%; for soil gas 222Rn, this value is 120%, 36% and 27% for each depth range, 0.4-0.5, 0.6-0.75 and 0.9-1.0 m, respectively; for the surface exhalation measurements, this value is 34%. For the drum 222Rn measurements, the percent SD after removing a linear trend was 13%. These results indicate that sampling errors are greater than instrument errors.