No? You use filtered outside air to mix it down to outside levels and only then add concentrated gas (cryogenically separated from the same outside air). It would probably be just a few pounds of oxygen (instead of a few pounds of scrubbing mixture that needs to be trucked in and out).
If you can just flood in outside air then you don't need any pure gas at all.
If need pure gas, for example you're trying to avoid losing your air conditioning or you're aiming for sub-ambient CO2, then you can't mix in lots of outside air. For the former you'd need enormous amounts of cooling and humidity adjustment, and for the latter outside air will actually make your job harder. So in those circumstances, the math is very simple. A human outputs X CO2, you want X to be a fraction of a thousandth of the air, you either scrub it or you add thousands of X in purified oxygen+nitrogen.
Versus several pounds of scrubbing mixture.