A presentation of the results of this investigation was given at the first annual Argonne Undergraduate Symposium at Argonne National Laboratory on November 2, 1990, and the following abstract was included in the anthology of papers presented at the conference.The Effects of Moisture Gain in Activated Charcoal When Measuring Radon Concentrations in Air by Liquid Scintillation Methods, M.D. Reese*, D.R. Ober, D. Govaer, Department of Physics and Astronomy, Ball State University, Muncie, IN 47306.Because of the high counting efficiency and automation, liquid scintillation detectors provide an attractive method for determining radon concentrations in air. In this study, a two-gram quantity of activated charcoal was placed in a vial and used to measure radon in air, no desiccant was included in the vial. A series of 48-hour measurements were made with standard canisters and vials, each containing activated charcoal. The canisters were then analyzed in the traditional method using sodium iodide detectors. In the analysis of the vials, 10 ml of scintillation fluid was added to each. After approximately ten hours, the samples were counted in a liquid scintillation system. A comparison of the results indicated a good linear relationship between the results obtained by standard canister methods and an adjusted counts per minute of the vials. The results also indicated that it is possible to apply water correction factors to the vials in a similar manner as is done in the canister method, thereby obtaining similar concentration results in both methods.