The paper is authored by Daniel Colbourne Ph.D. FInstR. By analysing the history of the use of flammables this paper will give a comprehensive background to the when, why, how and where of their use. It explores their role in the emergence of mechanical refrigeration, how they have supported the implementation of the Montreal Protocol and how the range of applications is now expanding. It also explains how different flammability classifications and safety requirements have emerged.
Refrigeration history is interspersed with the use of flammable refrigerants. During the 19th century, many of the early inventions employed flammable refrigerants. Until the time when CFCs became commercialised in the 1930s about a quarter of smaller systems used a variety of different flammable refrigerants, including ethyl ether (R610), methyl chloride (R40), ethyl chloride (R160), methylene chloride (R30), methyl formate (R611) and isobutane (R600a) and the majority of industrial/commercial systems used ammonia (R717).
Whilst most of the refrigerants for smaller systems became substituted with CFCs, this was primarily due to mitigation of toxicity hazards, rather than ignition risks. As the Montreal Protocol came into force there were numerous studies assessing alternatives, including flammable HFCs and HCs. Initially, the domestic appliance sector briefly opted for R134a, but following the Greenpeace ‘Greenfreeze’ campaign, virtually all European manufacturers adopted R600a.
From the early 1990s, HCs became used more widely in small commercial and intermittently in other subsectors. In parallel, refrigeration safety standards were revised and amended to reflect the use of this technology. A decade or two later, safety standards were modified again to include the 2L lower flammability safety classification, igniting the commercialisation of flammable HFCs; primarily the introduction of tetrafluoropropene (R1234yf) in car AC systems and then difluoromethane (R32) in air conditioners.
This paper traces the use of flammable refrigerants through textbooks, technical articles and patents, from the middle of the 18th century to the present day, breaking it into four “eras”, mirroring the extent of use of flammables at the time.
The full paper can be downloaded here. This paper is made available for free (registration required).