Which of the following refrigerant categories is most likely to harm the ozone layer?

The category of refrigerants most likely to harm the ozone layer is chlorofluorocarbons, commonly known as CFCs. CFCs contain chlorine, which, when released into the atmosphere, can break down ozone molecules. The ozone layer is crucial for protecting the Earth from harmful ultraviolet (UV) radiation. When CFCs reach the stratosphere, ultraviolet light splits the chlorine atoms from these compounds, which then react with ozone (O3) and lead to its depletion.

In contrast, hydrofluorocarbons (HFCs) do not contain chlorine and therefore do not have the same detrimental effect on the ozone layer as CFCs. Hydrofluoroolefins (HFOs) are also designed to be more environmentally friendly, with a low potential for ozone depletion. Ammonia (NH3), while toxic and posing other environmental hazards, does not impact the ozone layer in the same way as CFCs.

This understanding highlights the importance of selecting refrigerants that pose minimal risk to the ozone layer and the environment, underscoring why CFCs are specifically regarded as harmful.