Carbon dioxide CO2 (R744) is a non-flammable, natural, low cost refrigerant with negligible direct global-warming impact and ozone-depletion potential compared to traditional hydrofluorocarbons (HFC). CO2 refrigerant is becoming more widely used in the refrigeration industry.

As high CO2 levels are a potential health risk, CO2 level must be monitored in places where potential refrigerant leaks can occur.