do dual hose portable a.c. still suck out co2

I was told that if you buy a dual hose ( one intake and one outake) portable a.c. that you can run you a.c. and co2 at the same time without sucking co2 out of the room. This puzzled me because from what i have read about dual hose a.c. is that the intake hose is just to suck in air to help cool down the motor of the a.c. thus letting it perform better. My problem is that even with the intake hose there is still a huge intake on back of the actual a.c. unit.wont they still suck the room from the air via the big intake on back of the actual unit yet still sucking out co2. Im confused. Somebody please help.