Fourier transform infrared (FTIR) smog chamber techniques were used to measure k(Cl + CF3CFHCF2OCF3) = (4.09 +/- 0.42) x 10(-17), k(OH + CF3CFHCF2OCF3) = (1.43 +/- 0.28) x 10(-15), k(Cl + CF3CFHCF2OCF2H) = (6.89 +/- 1.29) x 10(-17), and k(OH + CF3CFHCF2OCF2H) = (1.79 +/- 0.34) x 10(-15) cm(3) molecule(-1) s(-1) in 700 Torr of N-2/O-2 diluent at 296 K. The atmospheric lifetimes of CF3CFHCF2OCF3 and CF3CFHCFOCF2H are approximately 40 and 32 years, respectively. Chlorine atom-initiated oxidation of CF3CFHCF2OCF3 and CF3CFHCF2OCF2H gives CF3C(O)F in molar yields of 82 +/- 5% and 96 +/- 6 respectively. The 100-year time horizon global warming potentials of CF3CFHCF2OCF3 and CF3CFHCF2OCF2H relative to CO2 are 4530 and 4340. Results are discussed with respect to the atmospheric chemistry of hydrofluoroethers.