Freon is a non-combustible gas that is used as a refrigerant in air conditioning applications. This freon undergoes an evaporation process over and over again to help produce cool air that can be circulated throughout your AC system. freon is available in a couple of different applications, with some costing more than others depending on the availability of the product. When people refer to an AC system needing to be recharged or refilled, they are referring to the levels of freon.