Trifluoromethoxymethane (CF3OCH3, HFE-143m) is a promising alternative for dichlorodifluoromethane (CCl2F2, CFC-12) as a refrigerant. Because of its low flammability, it is expected to be used in binary mixtures with inflammable hydrofluorocarbons (HFCs). In this study, we measured the critical parameters of binary mixtures of HFE-143m with four HFCs-pentafluoroethane (CHF2CF3, HFC-125), 1,1,1,2-tetrafluoroethane (CH2FCF3, HFC-134a), 1,1,1,2,3,3,3-heptafluoropropane (CF3CHFCF3, HFC-227ea), and 1,1,1,2,3,3-hexafluoropropane (CHF2CHFCF3, HFC-236ea). The uncertainties were 10 mK in temperature, +/-0.5 kPa in pressure, +/-1 kg m(-3) in density, and +/-0.5% in composition (molar base). The HFCs were selected for the similarities of their normal boiling points. The experimental data were correlated with equations proposed by Higashi.