Ultrafine reactive iron powder was prepared by a high-performance milling procedure using commercially available iron powder. The milled iron material was found to have very high affinity to oxygen. The activated powder reacted at very mild conditions even with traces of oxygen in argon. The deactivated iron material can be easily reactivated by reduction in a stream of diluted hydrogen. The activation occurred at mild conditions. The sorption activity of the iron reactive powder do es not change substantially over several cycles of adsorption - desorption. Iron powder was characterized by the surface area measured by nitrogen adsorption at -196 degreesC. Oxygen capacities were determined in an argon gas flow system. The process described here can be scaled up for industrial use.