Organic Hydrofluoro‐Olefins (HFOs) and Hydrochlorofluoro‐Olefins (HCFOs)

Abstract

Abstract Refrigerants that were generally toxic and flammable in the early 1900s were eventually replaced with chlorofluorocarbons (CFCs) in the early 1930s. Since then, they have undergone significant evolution, mostly driven by regulatory actions. The evolution pattern involves an initial phaseout of CFCs to hydrochlorofluorocarbons (HCFCs) followed by hydrofluorocarbons (HFCs), and finally to the current products which include a double bond in their structure and are referred to as hydrofluoro‐olefins (HFOs) and hydrochlorofluoro‐olefins (HCFOs); the term hydro(chloro)fluoro‐olefins (H(C)FOs) is employed when referring to both HFOs and HCFOs. These chemicals were/are also used as foam‐blowing agents, solvents, and propellants. Unlike HFCs and HCFCs, which are saturated organic compounds, H(C)FOs are unsaturated organic compounds (olefins or alkenes) and are composed of hydrogen, fluorine, and carbon (HFOs), or hydrogen, chlorine, fluorine, and carbon (HCFOs). The evolution of these products has mostly been driven by regulatory actions that were aimed at addressing their environmental impact. Initial scrutiny was placed on their stratospheric ozone depletion effects and later on their impact on global warming. H(C)FOs are generally categorized as having zero ozone depletion potential (ODP) and low global warming potential (GWP) and are considered more environmentally friendly, making them suitable substitutes for CFCs, HCFCs, and HFCs. The H(C)FOs reviewed in this chapter have relatively low toxicity and do not pose any health concerns for humans or the environment under normal use conditions. Toxicity datasets for a select number of substances have been reviewed by external scientific committees such as WEEL and ASHRAE as well as various regulatory bodies. Toxicological summaries of five representative commercial H(C)FOs are described in this chapter.