The low temperature defect chemistry is analyzed for ZrO2(Y2O3), SrZrO3(Y2O3), and SrTiO3. In this temperature regime, the oxygen incorporation is no longer in equilibrium but the internal ionization reaction of electrons (holes) with redox-active impurities is still reversible. The concentration of ions with a specific valence state is quantified by EPR for ZrO2(Y2O3), while the electrical conductivity is considered for SrZrO3(Y2O3) and SrTiO3. It is shown that the experimental low-temperature results can well be explained in this way. If the experiments are appropriately conducted, an additional degree of freedom is introduced, which is the freezing-in temperature. The technological and scientific relevance with respect to materials research is discussed.