The adsorption characteristics of airborne radioiodine on the impregnated charcoal were studied of partial adsoption isotherms (range of concentration of iodine was 1~20 ppm V/V) was measured of it was linear at the beginning rose slowly and reached saturation at last. By method of extrapolation the adsorption capacity corresponding to of extreme low concentration was obtained below 2 ppm. The adsorption capacity was used to evaluate breakthrough time of impregnated charcoal for removing iodine. The dependences of adsorption efficiency on the ambient conditions (temprature

relative humidity

and superficial velocity) were studied.