EFFECTS OF NEGATIVE-ION GENERATORS ON RADON-PROGENY AND THORON-PROGENY CONCENTRATIONS IN AN OCCUPIED RESIDENCE

Operation of negative ion generators in three rooms of an occupied res idence caused decreases in indoor concentrations of the radon decay pr oducts Po-218, Pb-214 and Bi-214, and of the thoron progeny Pb-212. Ac tivity levels of Pb-212 were lowered more than those of Pb-214, result ing in a decrease in the potential alpha energy concentration ratio, P AEC(Tn:Rn). The change in PAEC(Tn:Rn) is a function of the halflives o f Pb-214 and Pb-212 and their respective precursors and is similar to the effect brought about by increased room ventilation. Decay products are also removed from indoor air by plateout of charged particles on room walls. Plateout rates calculated for Pb-214 suggest that even in well-ventilated houses, the potential alpha energy concentration of ra don is affected as much by wall plateout as by infiltration of outside air.