We report herein the design and preparation of microgels that are responsive to both O-2 and CO2 gases. The microgels were synthesized through soap-free emulsion copolymerization of O-2-responsive monomer 2,3,4,5,6-pentafluorostyrene (FS) and CO2-responsive monomer 2-(diethylamino)ethyl methacrylate (DEA) with N,N'-methylenebis(acrylamide) (BisAM) as the cross-linker. The P(DEA-co-FS) microgels dispersed in aqueous solution could undergo volume phase transitions triggered by O-2 and/or CO2 aeration. The particles were very responsive to CO2, while their responsivity to O-2 was moderate. Microgels having different levels of the responsivity could be designed and prepared by varying the FS content in the copolymer. The phase transitions were also highly reversible, and the initial states of microgels could be easily recovered by "washing off "the trigger gases with N-2. Multicycle O-2, CO2, and N-2 aerations were applied, and no loss in the dual gas responsivity and switchability was observed.