Common refrigerant is a term used to describe substances that are used to cool and maintain temperatures in refrigerators and other cooling systems. Two of the most common refrigerants are Freon (5 letters) and Dryice (6 letters). Freon is a chlorofluorocarbon (CFC) gas that is used in many refrigeration and air conditioning systems. Dryice is a solid form of carbon dioxide that is used to keep food and other items cold.