AARST_Radon_Reporter_July_2023

THE RADON REPORTER | 11 RESEARCH Good News: Results are In from the International Intercomparison of Radon Calibration Facilities All radon measurements are based on the calibration of their system in a calibration chamber. But, how do calibration chamber operators know exactly what their radon concentrations are, and how sure are they? Obviously, if one calibration chamber is “off” on its concentration compared with another calibration chamber, there could be huge repercussions. The overall system for standardizing measurements in the world relies on a chain of traceability from some national authority who sets the standard, and then every calibrating facility compares with this standard, down through a series of secondary and tertiary calibration facilities. This system is pretty easy for gases that do not change over time, like carbon monoxide, which can be purchased in cylinders of certified concentrations. However, such simple acquisition is not possible for radon gas, so each chamber must generate its own radon gas by using a radium source, calculating the number of radon atoms emitted from their radium source, then calculating the concentration based on dilution in their volume of air. This sounds tricky enough, but different chambers use different types of radium sources–some pump air through a solid pumice stone type material infused with radium, others pump air through a radium-infused powder, and others use special flow-through solid radium sources. How can chambers be sure of the accuracy of the concentrations that they use to calibrate thousands of instruments? Intercomparisons between chambers provide such assurance and are vital to ensuring confidence in the accuracy of measurements and the millions of dollars spent in response to measurement results. continued on page 12