The combustion of fuel in oxygen rather than in air is one route to allow for the large-scale capture and storage of CO2. An alternative to the conventional air separation to produce oxygen, which imposes a significant energy penalty, is chemical looping air separation (CLAS). CLAS exploits the cyclic oxidation and reduction of solid oxygen materials. Here, the equilibrium partial pressure curves and the redox behavior for two potential materials (the perovskites SrFeO3-δ and SrMn0.1Fe0.9O3-δ) are derived from experiments. For the redox tests, a low dead volume micro reactor, operated as a differential packed bed, was used. This system enabled measuring the process of reduction at the 10 ms scale. Experiments were carried out between 798 and 898 K, with pO2 varied between 0 and 0.21 atm. All perovskites showed good performance during experiments lasting 1000 cycles. Despite similar chemical composition, the measured oxygen chemical potential and reduction kinetics differed between the tested materials significantly.