...tie in a secondary CO2 line with a junction and quick action valve that will inject CO2 into the air jet's flow. In case of a fire that the jet can't extinguish a simple push or twist will cut off the normal atmospheric flow and inject CO2 directly onto the fire. Much safer (and cheaper) than continuous flowing CO2 into the area's atmosphere.
Plus, even with an exhaust fan you would need to have a high flow system with a dedicated intake that completely changes the area's atmosphere to prevent CO2's effects on a body. Normal atmospheric CO2 is 0.04%. 3% causes mental confusion, heart and blood pressure problems and 8% unconsciousness. So, anything that increases CO2 in an enclosed area is dangerous. Any safety/insurance inspection noticing such a setup will result in a shutdown of the business until removed/corrected. Usually meaning big bucks. Hope this helps.