The term COOLING GAS can be summarized by the crossword solution FREON, which is a five-letter word. FREON is a brand name for a group of chlorofluorocarbon (CFC) compounds used as refrigerants and aerosol propellants. It was developed in the 1930s and was widely used in air conditioners, refrigerators, and aerosol cans until it was phased out in the 1990s due to its contribution to ozone depletion.