Refrigerant

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A refrigerant is a working fluid used in the cooling, heating, or reverse cooling/heating cycles of air conditioning systems and heat pumps, where they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are heavily regulated because of their toxicity and flammability,^[1] as well as the contribution of CFC and HCFC refrigerants to ozone depletion^[2] and the contribution of HFC refrigerants to climate change.^[3]

Refrigerants are used in a direct expansion (DX) circulating system to transfer energy from one environment to another, typically from inside a building to outside or vice versa. These can be air conditioner cooling only systems, cooling & heating reverse DX systems, or heat pump and heating only DX cycles. Refrigerants can carry 10 times more energy per kg than water, and 50 times more than air.^[4]

Refrigerants are controlled substances that are classified by several international safety regulations and, depending on their classification, may only be handled by qualified engineers due to extreme pressure, temperature, flammability, and toxicity.