Measurement were made of the interaction of 8Kr, 133Xe, CH3I (131I) and I2 (131I) with various silver zeolites and activated charcoals under varying relative humidities and temperatures. Results show silver zeolite has significantly less interaction with noble gases and high adsorption efficiencies for CH3I making it superior to charcoal for airborne radioiodine monitoring. The penetration of airborne iodine activity into the silver zeolite filter bed was also examined. CH3I penetrated slightly deeper than I2 at the same air flow velocity; however, at 17.4 feet per minute, no more than 5% of the iodine activity in either form penetrated deeper than 1 cm into the filter bed. The sensitivity of the iodine-131 activity detection system was found to be approximately 2.5% (1% = 2.22 x 104 counts per minute/Â¿Ci) at the 364 Kev photopeak with a 100 Kev energy window width.