Relative rate techniques were used to measure k(OH + n-C₄F₉OC₂H₅) = (6.4 ± 0.7) × 10^-14 and k(OH + i-C₄F₉OC₂H₅) = (7.7 ± 0.8) × 10^-14 cm³ molecule^-1 s^-1 at 295 K leading to estimates of ≈0.9 and 0.7 years for the atmospheric lifetimes of n-C₄F₉OC₂H₅ and i-C₄F₉OC₂H₅, respectively. A pulse radiolysis technique was used to measure k(F + HFE-7200) = (5.6 ± 2.1) × 10^-11 cm³ molecule^-1 s^-1 (HFE-7200 = C₄F₉-OC₂H₅) at 296 K. Using FTIR-smog chamber relative rate techniques the following rate constants were determined at 296 K: k(F + HFE-7200) = (5.5 ± 1.1) × 10^-11, k(Cl + HFE-7200) = (2.7 ± 0.6) times; 10^-12, and k(Cl + C₄F₉OC(O)CH₃) < 7 × 10^-13 cm³ molecule^-1 s^-1. Two competing loss mechanisms for C₄F₉-OCHO(•)CH₃ radicals were identified in 700 Torr of N₂/O₂ diluent at 296 K; reaction with O₂ and decomposition via C-C bond scission with k_O2/k_decomp = 0.026 ± 0.010 Torr^-1. The Cl atom initiated oxidation of HFE-7200 in N₂/O₂ diluent gives two products: C₄F₉OC(O)CH₃ and C₄F₉OC(O)H. C₄F₉OC(O)CH₃ is the major atmospheric oxidation product of HFE-7200; C₄F₉OC(O)H is a minor product. The results are discussed with respect to the atmospheric chemistry of hydrofluoroethers.