Freezers, fridges, air conditioners, and heat pumps all contain refrigerant. Some kinds of refrigerant damage the ozone layer or contribute to global warming if released to the atmosphere.

Current Refrigerants

GWP - 100-year Global Warming Potential (relative to CO2)
ODP - Ozone Depletion Potential

       | Common Name | GWP    | ODP
-------+-------------+--------+----------
R-290  | Propane     | 3      | 0
R-32   |             | 675    | 0
R-134a | Freon-134a  | 1430   | 0.000015

Banned Refrigerants

       | Common Name | GWP    | ODP
-------+-------------+--------+-----
R-12   | Freon-12    | 10,900 | 1.00
R-22   |             | 1760   | 0.05

Manufacture of R-12 was banned in 1996 as part of the Montreal Protocol.

R-22 was a temporary replacement for R-12; it's manufacture and import was banned in Canada in 2020.

Ozone Depletion

Scientists first observed a thinning of the ozone layer in 1985. It was quickly determined that CFCs were a major contributor to ozone depletion. The Montreal Protocol was adopted in 1987, and the ban came into effect in 1989.