Final answer:
Refrigerants that must be recovered before opening or disposing of appliances include R-12, R-22, and R-500, which are harmful to the environment.
Step-by-step explanation:
Refrigerants that must be recovered before opening or disposing of appliances include R-12, R-22, and R-500. These refrigerants are classified as CFCs (chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons), which have been found to be harmful to the environment because they contribute to ozone depletion. It is important to recover and properly dispose of these refrigerants to prevent their release into the atmosphere.