What type of freon do Older refrigerants contain?

Older refrigerants, particularly those used before the 1990s, commonly contain chlorofluorocarbons (CFCs) such as R-12 and R-11. These substances were widely utilized in refrigeration and air conditioning systems due to their efficiency. However, due to their ozone-depleting properties, many of these refrigerants have been phased out and replaced with more environmentally friendly alternatives like hydrofluorocarbons (HFCs) and natural refrigerants.