[en] Accidental releases of radioactivity from fission reactors will consist of active vapors and aerosols. Composition of the released plume or cloud will depend on the energy of release and fission product volatility. In accidents at Windscale and SL-1, ¹³¹I was the predominant isotope present in both the initial cloud and later release. Thus an air sampling system was developed for efficient radioiodine collection. The air sampling, readout, and dose assessment system was developed to be used in the environment after loss of containment accidents. The system can detect less than 1 rem dose commitments to thyroids of 5 year old children for immersion times of 10 hours or less. The air mover can be operated on either 110V ac power or 12V dc power available from vehicles with cigar lighter sockets. An inorganic silver loaded silica gel adsorber was developed for high mehyl iodine, HOI, and elemental iodine efficiency and low noble gas efficiency. A peal away high efficiency particulate filter permits the gaseous and particulate sample fractions to be evaluated separately. Predicted particulate iodine is combined with the adsorbed component to account for the total radioiodine in a given sample