The reactions of O(1D) with CFCs (chlorofluorocarbons) and halons are known to have large rate constants in the order of 10-10 cm3 molecule-1 s-1, and could possibly affect the stratospheric lifetime of these ozone layer depleting substances. However, decomposition rates of CFCs and halons in the stratosphere are in general determined mainly by photolysis rate, and the reaction with O(1D) is almost negligible for CFCl3 (CFC−11) and halons whose photolysis rates are high. However, as the photolysis rate decreases for such as CF2Cl2 (CFC−12), CF3Cl (CFC−13), the importance of O(1D) reaction increases.