ADSORPTION OF RN-222 BY OPEN-FACED AND DIFFUSION-BARRIER CANISTERS ATDIFFERENT CONDITIONS OF TEMPERATURE AND HUMIDITY

Open-faced and diffusion-barrier charcoal canisters were individually exposed to a fixed temperature, humidity, and radon concentration in a chamber for a period of 7 d. The radon progeny activity in the canist er under study was measured every 3 h. A total of 15 runs were made fo r the open-faced canisters and nine runs for the barrier canisters wit h temperatures and absolute humidities ranging from 15-30 degrees C an d 0-15 g m(-3), respectively. In addition, several runs were made with the radon, temperature, and humidity changing during the 7 d. Results show that open-faced canisters adsorb radon up to 60% more efficientl y at 15 degrees C than at 30 degrees C while the barrier canisters sho w little temperature dependence. The barrier canisters are much less s ensitive to humidity effects than the open-faced canister. When used t o measure the radon concentration in air, the open-faced canister inte grates over a period of only similar to 48 h while the barrier caniste r integrates over a period of similar to 96 h. The short integration t ime and the interference of water adsorption by open-faced canisters i ndicate that the open-faced canisters should be used for exposure time s of 48 h and no longer.