Which is a characteristic of CO2 refrigerants?

The characteristic that CO2 refrigerants are considered environmentally friendly is primarily due to their low global warming potential (GWP) and zero ozone depletion potential (ODP). Unlike many traditional refrigerants, CO2 refrigerants do not contribute to ozone layer depletion or have significant contributions to climate change, making them a more sustainable option in terms of environmental impact.

While CO2 refrigerants do operate at higher pressures compared to traditional refrigerants—such as those using hydrofluorocarbons (HFCs)—this characteristic is not the focus regarding their environmental friendliness. Additionally, the requirement for specialized equipment for recovery and recycling, though true, doesn't directly relate to the eco-friendly aspect. Lastly, while CO2 is considered non-flammable, it is not the primary reason it is classified as environmentally friendly, which hinges on its minimal negative impact on global warming and ozone depletion.