Oxygen evolution experiments in low- and high-T_c ceramic superconductors are used to identify the desorption kinetics and activation energies. It is found that oxygen desorps at 600 °C from Cu-O chains (where present) with an activation energy of 1.2 eV, whereas the desorption from other oxygen-containing planes occurs at 800 °C with a higher activation energy of 2.8 eV.