Which of the following refrigerants are banned under the Montreal Protocol?

The correct answer highlights that chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are banned under the Montreal Protocol due to their harmful effects on the stratospheric ozone layer. The Montreal Protocol was established to combat ozone depletion by phasing out the production and consumption of these ozone-depleting substances.

CFCs were commonly used in refrigeration, air conditioning, and aerosol propellants, while HCFCs were introduced as transitional substitutes. However, it was recognized that HCFCs still pose a risk to ozone depletion, leading to their subsequent regulation as well.

In contrast, while hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) have been associated with high global warming potential, they were not included in the original provisions of the Montreal Protocol. They are now subject to discussions for regulation under amendments to address climate change, but are not outright banned as CFCs and HCFCs are.

Ammonia and CO2, while used as refrigerants, are not banned under the Montreal Protocol. Additionally, propane and butane are classified as hydrocarbons and are generally less impactful on ozone depletion, thus they