Tunable diode laser (TDL) and mass spectrometry have been combined to measure relative formation rate coefficients of each of the four channels contributing to ozone of mass 50 u and 52 u produced in O-16-O-18 mixtures. Only one channel has a large rate coefficient advantage causing almost exclusively the observed isotope enrichment. Collisions to form ozone are end-on reactions. Molecular symmetry plays no apparent role in the ozone isotope enrichment process, regardless, whether or not ozone is produced in collisions with homo- or heteronuclear molecular oxygen. The oxygen isotope exchange process may hold a key in explaining the rate coefficient results.