Im also interested in which air conditioners are recirculating. I'm looking at the surpentown 9000 btu portable air conditioner which has a great energy efficiency rating and requires no permanent installation. I'm not sure if it would exhause Co2 or odor. Anyone with vast ac knowledge know how portable ac's exhaust hot air, or even regular ac's. Do they draw air from the room? I dont want to be blowing all my Co2 and delightful aromas outside!!