Hello all! I'm a sales rep here at << company name removed by moderator>>, we manufacture conformal coating/curing systems. Normally, i'd just ask one of our engineers this question, but production as been shut down for the week as we move to a new facility, so I am out of contact. A customer just asked me this question about his system. The customer has one of our 4ft IR-curing ovens. Basically, its a long rectangular box with a conveyor running through it with two open ends. On top of the conveyor, we have a 12 inch air knife (McMaster Carr 5191K27) that allows for the injection of in this case 100% CO2 into the oven. The air knife amplifies incoming air by 30:1 and @80psi injects gases at 40.8CFM (3.4 SCFM/inch) On the conveyor we have a 300CFM exhaust blower that pulls plain air through the side holes, allowing air to flow over the product, and then out a vent hole in the bottom. So...the customer asked me what PSI the input to the Air Knife should be to create a flow of through the oven (from the current provided by the exhaust) that contains 0.5% CO2. Now, I know the naturally occurring amount of CO2 that would be flowing naturally is 0.387% (i think). So the other .4613% CO2 has to come from the air knife i would think...i just don't know at what PSI input to the air knife would allow an CFM output from it that would mix with the flowing air from the exhaust that would create a .5% CO2 flow. Any help/answer/advice would be greatly appreciated!