Using pulse radiolysis combined with UV absorption spectroscopy, upper limits for the rate constants of the reaction of the FO₂ radical with O₃, CH₄, and CO were determined to be <3.4 × 10^-16, <4.1 × 10^-15, and <5.1 × 10^-16 cm³ molecule^-1 s^-1, respectively. The rate constants for the reactions of FO₂ radicals with NO and NO₂ were measured: FO₂ + NO → FNO + O₂ (10a); FO₂ + NO₂ → products (11). The rate constants for reactions 10 and 11 were determined to be (1.47 ± 0.08) × 10^-12 and (1.05 ± 0.15) × 10^-13 cm³ molecule^-1 s^-1, respectively. Reaction 10a was found to give FNO in a yield of 100 ± 14%. As a part of this work, an upper limit of the reaction of FO radicals with O₃ was determined to be <1.2 × 10^-12 cm³ molecule^-1 s^-1. Results are discussed in the context of the atmospheric chemistry of the FO₂ radical and hydrofluorocarbons.