HFO

Hydrofluoroolefin (HFO) refers to a class of fluorinated olefins used primarily as refrigerants and blowing agents. HFOs are composed of carbon, hydrogen and fluorine and contain at least one carbon–carbon double bond. They were developed as low-global-warming-potential alternatives to conventional hydrofluorocarbons (HFCs) and to replace older, ozone‑depleting substances in some applications.

Environmental and performance characteristics include a substantially lower global warming potential (GWP) than many HFCs, typically below 10 and often in the single digits. Many HFOs have short atmospheric lifetimes, so their long‑term climate impact is limited relative to long‑lived gases. The ozone depletion potential of HFOs is zero since they contain no chlorine. Flammability varies among HFOs; some are mildly flammable while others are non‑flammable, which influences handling and safety requirements and the design of equipment and lubricants.

Primary applications are as refrigerants and as blowing agents for rigid foam insulation. The best‑known example is HFO‑1234yf, widely used in automobile air conditioning as a replacement for R‑134a. Other HFOs, such as HFO‑1234ze, are used in stationary air conditioning and in foam‑blowing processes. They are also considered in other specialty applications where low GWP is a priority.

Safety, handling, and regulation: because some HFOs can be flammable or mildly flammable, appropriate safety measures, leak detection, and ventilation are important in manufacturing, service, and storage. Regulation of HFOs has progressed under global climate frameworks and regional F‑gas regulations, promoting their use as part of phasedown strategies for high‑GWP refrigerants and foam blowing agents.