Some older air conditioning models use Freon as a coolant. Freon is a trade name that includes chemical compounds like chlorofluorocarbons (CFCs) and hydrofluorocarbons (HCFCs). These compounds have negative effects on the ozone layer and lead to environmental damage and human health risks like skin cancer. The United States phased out CFCs in the 1990s and is currently phasing out HCFCs, particularly the common refrigerant known as HCFC-22 or R-22.
If you own an air conditioner that uses HCFC-22, you are not required to replace it, but its coolant will become much more difficult and expensive to buy. If your AC unit is an older model, replacing it with a more eco-friendly one can simultaneously benefit your budget and the environment.