Refrigerant
The fluid inside a heat pump that picks up heat outside and gives it up to the heating water.
It boils at a low temperature, so it can absorb heat even from cold air, and a compressor raises its temperature so the heat can be passed on. Some refrigerants are F gases; others, such as propane (R290), are not, but still need specialist handling.
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Sources
Sources checked 31 October 2026. Guidance, grants and official pages can change.
- Government guidance: Qualifications to work with F gasIn Great Britain, people working on equipment containing F gas, including heat pump systems, need their own F-gas qualification.