Radon is removed from a gas in an apparatus comprising: (a) a liquid-contacting apparatus having a shielded reservoir containing a fresh working liquid in which radon is soluble; and (b) a means for causing a stream of gas containing radon to pass through the liquid-contacting apparatus. When the radon level in the working liquid reaches a certain level, the working liquid is either taken out of service and stored until the radon level is reduced or the working liquid is diluted with additional working liquid having no radon.