AbstractRate constants for the reactions of O3and OH radicals with furan and thiophene have been determined at 298 ± 2 K. The rate constants obtained for the O3reactions were (2.42 ± 0.28) × 10−18cm3/molec·s for furan and<6 ×10−20cm3/molec·s for thiophene. The rate constants for the OH radical reactions, relative to a rate constant for the reaction of OH radicals withn‐hexane of (5.70 ± 0.09) × 10−12cm3/molec·s, were determined to be (4.01 ± 0.30) × 10−11cm3/molec·s for furan and (9.58 ± 0.38) × 10−12cm3/molec·s for thiophene. There are to date no reported rate constant data for the reactions of OH radicals with furan and thiophene or for the reaction of O3with furan. The data are compared and discussed with respect to those for other alkenes, dialkenes, and hete