A low‐temperature infrared‐absorption study has been performed to investigate the annealing behavior of the carbon‐oxygen complexes causing the peaks at 1104 cm-1 (C‐OA complex) and 1108 cm-1 (C‐OD complex). Upon annealing, the concentrations of the C‐OA and C‐OD complexes quickly reach the quasithermal‐equilibrium values described by the mass‐action law. The obtained formulas of this mass‐action law indicate that both of these two complexes involve a carbon atom and an oxygen atom. For the annealing temperatures higher than 800 °C, the quasithermal‐equilibrium concentration of the C‐OA complex increases with increasing temperature. A hypothetical explanation is proposed for this unusual temperature dependence. © 1995 American Institute of Physics.