HFOs contain hydrogen, fluorine and carbon like the HFCs, but they are distinctly different. They are olefins, which mean they have very short atmospheric lifetimes of a few days, leading to distinct environmental benefits.

HFOs are subject to all the legislation that applies to the supply and use of chemicals, including REACH in the EU.

HFOs are the fourth generation of refrigerants, with each generation being a step-change improvement on the previous generation. HFOs offer many of the key properties of existing HFCs, but with very low GWPs (Global Warming Potential).