When looking for A/C leaks, CO2 is a great way to find very small ones. Since the CO2 molecule is so small, it will move through small leak sites with very low resistance. Additionally the pressure when charging the air conditioning is much higher than the refrigerant in the low side of the system. By utilizing CO2, the air conditioning system can be safely pressurized up to 160 psi, this is a great advantage that allows very small molecules under greater pressure out of the leak site. With a much higher volume flow rate of undiluted CO2, any size leak from very small to very large is much easier to detect with the dedicated electronic CO2 sniffer.
Information provided by: Automotive Test Solutions, Inc.