An electrostatic precipitation method is employed to study the collection efficiency for 21884Po+ ions formed by 222Rn atoms immersed in hydrostatic gaseous argon and helium for electric fields E in the range of 0.01–10 V/cm. The method employs a volume of gas wherein the electric field is reasonably uniform over a ∼25‐cm long drift path, and so neutralization times above 10 s are observable. Measurements are performed on the ion collection efficiency as functions of radon concentration CRn in the 2–80 pCi/l range at argon and helium pressures p in the 0.03–1.0 atmosphere range. Results indicate that while the collection efficiency associated with saturation values of E is essentially independent of both CRn and p, it is proportional to √CRn and p for values of E below the associated saturation values. The roles of various sources of ionization in the gas, which ultimately lead to neutralization of the heavy radioactive ions, are discussed, as are device‐dependent effects generally associated with the finite size (and shape) of the containment vessels employed. Potential implications and applications of the general findings are presented.