The next step in the transition to environmentally safer refrigerants is phase out of R-22. It is the most widely used refrigerant, both in the United States and on a global basis. Its application range in residential, commercial, industrial, and transport systems is broader than for any other refrigerant and spans cooling capacities from 2 kW to 33 MW (1/2 to 9,500 tons). There is no single-compound refrigerant to directly replace R-22. As a results, over 100 refrigerants - mostly blends - have been considered as replacements for R-22 and R502 (a widely used blend containing R-22 for low-temperature, commercial refrigeration). The main selection criteria have been environmental properties, comparative efficiencies, safety considerations, and materials compatibility.The specific replacement of R-22 depends on the application. The primary replacement in unitary air-conditioners and heat pumps - the largest use of R-22 - is R-410A. Most major equipment manufacturers already offer R-410A products for common sizes and efficiency levels. Current use of R-410A is less than 8% of traditional R-22 products, but this fraction is likely to exceed 80% in the United States by the end of 2007 and approach 100% by the end of 2009.
ASHRAE American Society for Heating, Refrigeration and Air Conditioning Journal
and Domanski, P.
R-22 Replacement Status, ASHRAE American Society for Heating, Refrigeration and Air Conditioning Journal, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860951
(Accessed July 3, 2022)