Abstract: A new type of radon progeny monitor called an electret radon progeny integrating sampling unit (E-RPISU) using an electret ion chamber to measure radon progeny concentration. A conventional 1 LPM particulate air sampling system is used to collect the radon progeny on a roughly 3.5 cm2 filter that is mounted on a side of an electret ion chamber such that the collected progeny are exposed to the inside of the chamber. Alpha radiation emitted by the progeny collected on the filter ionizes the air in the approximately 220 ml chamber. Ions of opposite polarity collect on the surface of the electret of suitable thickness and reduce its surface voltage. A specially built surface voltmeter is used to measure the electret voltage before and after sampling. The electret voltage drop that occurs during the sampling period is proportional to the time integrated progeny concentration. A similar unit with a screen in the place of filter is used to measure unattached progeny concentration.

Abstract: An electret ion chamber based radon monitor is employed as a method of measuring radium-226 and dissolved radon-222 concentrations in water. The procedure consists of taking a known volume of water and placing it in a container of known volume and determining the equilibrium radon concentration in the air phase above the water using an electret ion chamber radon. The radon concentration in the original water sample is calculated from the radon concentration of the air phase. A detailed theory is proposed and experimental results reported. Given a 200 ml water sample, it is typically possible to measure radon concentration of 160 pCi/l with an accuracy of 10% in a one day measurement. One pCi/l of Ra-226 can be also determined with an accuracy of 10% over a 10 day period.

Abstract: An electret ion chamber for monitoring radon comprises a housing having an electret holder and a cover. The cover is attached to a plunger which closes over the electret when the cover is in place and is removed from the electret when the cover is opened. The plunger effectively turns "on" and "off" the radon monitor with the opening and closing of the cap. In very short term and very long term radon monitors, this turn on and off feature is not needed.

Abstract: A small enclosed chamber with an electrostatically charged electret attached to the inner chamber wall. A filtered hole in the chamber permits radon or other radioactive gas to enter by diffusion. Positive or negative ions (depending on the polarity of the electret charge) formed in the chamber air by the decay of the radioactive gas move to and collect on the electret surface by virtue of its electrostatic attraction to ions of opposite polarity. These ions accumulate and cause a measurable reduction in the surface voltage of the electret which reduction is proportional to the time integrated concentration of the radioactive gas in the chamber. The electret surface voltage of the reduction value is used to calculate the average concentration of the radioactive gas during the exposure period. The electret thickness and chamber volume can both be increased to increase the sensitivity of the invention to radioactive gases such as radon, tritium or carbon-14 dioxide or such other radioactive gases.

Abstract: Radioactive gas, particularly radon, is measured in the subsoil environment by electrostatically charging one or two electrets and placing the electret(s) within a chamber having openings protected by a filter which permits gas to flow through the openings while preventing particles from flowing through the openings. The chamber with the electrostatically charged electret(s) and the detector is placed in a receiver formed within the hollow wall of an elongated probe. Foam cushions surround the chamber and assist in the filtering. An open material, such as steel wool, holds the foam in place and the next lower section of the probe holds the steel wool in place. When sampling is done at only one level, the next lower section is the soil moving nose of the probe. Holes in the side wall near the nose admit subsoil gas into the receiver.