Refrigerant

Image: HCFC and HFC atmospheric trends.png

The first air conditioners and refrigerators employed toxic or flammable gases, such as ammonia, sulfur dioxide, methyl chloride, or propane, that could result in fatal accidents when they leaked.{{Cite web |last=Pearson |first=S. Forbes |title=Refrigerants Past, Present and Future |url=http://www.r744.com/files/pdf_597.pdf |url-status=dead |archive-url=https://web.archive.org/web/20180713171048/http://www.r744.com/files/pdf_597.pdf |archive-date=2018-07-13 |access-date=2021-03-30 |website=R744}}

In 1928 Thomas Midgley Jr. created the first non-flammable, non-toxic chlorofluorocarbon gas, Freon (R-12). The name is a trademark name owned by DuPont (now Chemours) for any chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), or hydrofluorocarbon (HFC) refrigerant. Following the discovery of better synthesis methods, CFCs such as R-11,{{Cite web|url=https://www.coolingpost.com/world-news/finally-a-replacement-for-r123/|title=Finally, a replacement for R123?|date=17 October 2013|website=Cooling Post}} R-12,{{cite journal |last1=Hmood |first1=K. S. |last2=Pop |first2=H. |last3=Apostol |first3=V. |last4=Ahmed |first4=A. Q. |date=2017 |title=Refrigerants Retrofit as Alternative for R12 and R134a in Household Refrigerators |url=https://asrjetsjournal.org/index.php/American_Scientific_Journal/article/view/3297 |journal=American Scientific Research Journal for Engineering, Technology, and Sciences |volume=35 |issue=1 |pages=251–265 |access-date=2025-05-28 }} R-123 and R-502 dominated the market.

{{See also|Montreal Protocol}}

In the mid-1970s, scientists discovered that CFCs were causing major damage to the ozone layer that protects the earth from ultraviolet radiation, and to the ozone holes over polar regions.{{cite journal |last1=Molina |first1=Mario J. |last2=Rowland |first2=F. S |title=Stratospheric sink for chlorofluoromethanes: chlorine catalysed destruction of ozone |journal=Nature |date=28 June 1974 |volume=249 |pages=810–812 |doi=10.1038/249810a0 |url=https://courses.seas.harvard.edu/climate/eli/Courses/EPS281r/Sources/Ozone-hole/2-Molina-Rowland-1974.pdf |access-date=October 6, 2024}}{{cite book |last1=National Research Council |title=Halocarbons: Effects on Stratospheric Ozone |date=1976 |publisher=The National Academies Press |location=Washington, DC |doi=10.17226/19978 |isbn=978-0-309-02532-4 |url=https://nap.nationalacademies.org/catalog/19978/halocarbons-effects-on-stratospheric-ozone |access-date=October 6, 2024}} This led to the signing of the Montreal Protocol in 1987 which aimed to phase out CFCs and HCFC{{cite web |access-date=27 July 2023 |date=1 July 2011|title=Air Conditioners, Dehumidifiers, and R-410A Refrigerant |url=https://www.sylvane.com/blog/air-conditioners-dehumidifiers-r-410-a-refrigerant/|website=Sylvane}} but did not address the contributions that HFCs made to climate change. The adoption of HCFCs such as R-22,{{Cite web|url=https://books.google.com/books?id=zMYRAAAAIAAJ&dq=r+22+replaced+r+12&pg=RA1-PA589|title=Clean Air Act Amendments of 1987: Hearings Before the Subcommittee on Environmental Protection of the Committee on Environment and Public Works, United States Senate, One Hundredth Congress, First Session, on S. 300, S. 321, S. 1351, and S. 1384 ...|first=United States Congress Senate Committee on Environment and Public Works Subcommittee on Environmental|last=Protection|date=May 14, 1987|publisher=U.S. Government Printing Office|via=Google Books}}{{Cite book|url=https://books.google.com/books?id=5AGjDf5QkfwC&pg=PA179 |page=179 |title=Fluorinated Hydrocarbons—Advances in Research and Application |edition=2013 |date=June 21, 2013 |publisher=ScholarlyEditions |isbn=9781481675703 |via=Google Books}}{{Cite book|url=https://books.google.com/books?id=zeYGAAAAQBAJ&pg=PA171 |page=171 |title=Refrigeration and Air Conditioning Technology |first1=Bill |last1=Whitman |first2=Bill |last2=Johnson |first3=John |last3=Tomczyk |first4=Eugene |last4=Silberstein |date=February 25, 2008 |publisher=Cengage Learning |isbn=978-1111803223 |via=Google Books}} and R-123 was accelerated and so were used in most U.S. homes in air conditioners and in chillers{{Cite web |url=https://ec.europa.eu/clima/sites/clima/files/docs/0007/mcquay_hfc_scroll_chillers_paper_en.pdf |title=Scroll Chillers: Conversion from HCFC-22 to HFC-410A and HFC-407C |access-date=2021-03-29 |archive-date=2021-07-20 |archive-url=https://web.archive.org/web/20210720201831/https://ec.europa.eu/clima/sites/clima/files/docs/0007/mcquay_hfc_scroll_chillers_paper_en.pdf |url-status=dead }} from the 1980s as they have a dramatically lower Ozone Depletion Potential (ODP) than CFCs, but their ODP was still not zero which led to their eventual phase-out.

Hydrofluorocarbons (HFCs) such as R-134a,{{Cite web|url=https://www.achrnews.com/articles/135112-whats-happening-with-r-134a|title=What's Happening With R-134a? | 2017-06-05 | ACHRNEWS | ACHR News|website=achrnews.com}}{{cite web |url=https://www.techtips.ie/Hella-Ireland/aircon-conversion-r12r134a.pdf |date=1 October 2005 |access-date=27 July 2023 |title=Conversion R12/R134a |work=Behr Hella Service GmbH }} R-407A,{{Cite press release |url=https://www.achrnews.com/articles/110226-r-407a-gains-snap-ok |date=22 June 2009 |title=R-407A Gains SNAP OK |website=achrnews.com }} R-407C,{{Cite web|url=https://www.achrnews.com/articles/110377-june-26-2009-emerson-approves-r-407a-r-407c-for-copeland-discus-compressors?v=preview|title=June 26, 2009: Emerson Approves R-407A, R-407C for Copeland Discus Compressors|website=achrnews.com}} R-404A,{{Cite web |date=1 May 2017 |first=John |last=Tomczyk |url=https://www.achrnews.com/articles/134928-whats-the-latest-with-r-404a|title=What's the Latest with R-404A?|website=achrnews.com}} R-410A{{Cite web|url=https://www.achrnews.com/articles/84438-taking-new-refrigerants-to-the-peak?v=preview|title=Taking New Refrigerants to the Peak|website=achrnews.com}} (a 50/50 blend of R-125/R-32) and R-507{{cite web | url=https://www.osti.gov/etdeweb/biblio/167601 | title=R502/R22 - replacement refrigerant R507 in commercial refrigeration; R502/R22 - Ersatzkaeltemittel R507 in der Gewerbekuehlung. Anwendungstechnik - Kaeltemittel | date=31 December 1995 | last1=Koenig | first1=H. }}{{cite web | url=https://www.osti.gov/biblio/211821 | osti=211821 | title=System performance comparison of R-507 with R-502 | date=31 December 1995 | last1=Linton | first1=J. W. | last2=Snelson | first2=W. K. | last3=Triebe | first3=A. R. | last4=Hearty | first4=P. F. }} were promoted as replacements for CFCs and HCFCs in the 1990s and 2000s. HFCs were not ozone-depleting but did have global warming potentials (GWPs) thousands of times greater than CO₂ with atmospheric lifetimes that can extend for decades. This in turn, starting from the 2010s, led to the adoption in new equipment of Hydrocarbon and HFO (hydrofluoroolefin) refrigerants R-32,{{Cite web|url=https://www.coolingpost.com/world-news/daikin-reveals-details-of-r32-vrv-air-conditioner/|title=Daikin reveals details of R32 VRV air conditioner|date=6 February 2020|website=Cooling Post}} R-290,{{Cite web|url=https://www.coolingpost.com/world-news/refrigerant-blends-to-challenge-hydrocarbon-efficiencies/|title=Refrigerant blends to challenge hydrocarbon efficiencies|date=22 December 2019|website=Cooling Post}} R-600a, R-454B,{{Cite web|url=https://www.achrnews.com/articles/144613-an-hvac-technicians-guide-to-r-454b?v=preview|title=An HVAC Technician's Guide to R-454B|website=achrnews.com}} R-1234yf,{{cite web |url=https://autoexpert.com.au/posts/the-truth-about-new-automotive-ac-refrigerant-r1234yf |title=The truth about new automotive A/C refrigerant R1234YF | date=25 July 2018 }}{{cite journal |url=https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=2524&context=iracc |last=Kontomaris |first=Konstantinos |title=HFO-1336mzz-Z: High Temperature Chemical Stability and Use as A Working Fluid in Organic Rankine Cycles |year=2014 |journal=International Refrigeration and Air Conditioning Conference |quote=Paper 1525}} R-514A,{{Cite web|url=https://www.coolingpost.com/world-news/trane-adopts-new-low-gwp-refrigerant-r514a/|title=Trane adopts new low GWP refrigerant R514A|date=15 June 2016|website=Cooling Post}} R-744 ({{CO2}}),{{Cite web|url=https://www.coolingpost.com/features/r404a-the-alternatives/|title=R404A – the alternatives|date=26 February 2014|website=Cooling Post}} R-1234ze(E){{Cite web|url=https://www.coolingpost.com/products/carrier-expands-r1234ze-chiller-range/|title=Carrier expands R1234ze chiller range|date=20 May 2020|website=Cooling Post}} and R-1233zd(E),{{Cite web|url=https://www.coolingpost.com/world-news/carrier-confirms-an-hfo-refrigerant-future/|title=Carrier confirms an HFO refrigerant future|date=5 June 2019|website=Cooling Post}} which have both an ODP of zero and a lower GWP. Hydrocarbons and {{CO2}} are sometimes called natural refrigerants because they can be found in nature.

The environmental organization Greenpeace provided funding to a former East German refrigerator company to research alternative ozone- and climate-safe refrigerants in 1992. The company developed a hydrocarbon mixture of propane and isobutane, or pure isobutane,{{Cite web |title=Greenfreeze: A revolution in domestic refrigeration |url=https://www.ecomall.com/greenshopping/greenfreeze.htm |access-date=2022-07-04 |website=ecomall.com}} called "Greenfreeze", but as a condition of the contract with Greenpeace could not patent the technology, which led to widespread adoption by other firms.{{cite web|title=Happy birthday, Greenfreeze! |date=25 March 2013 |url=http://p3-raw.greenpeace.org/international/en/news/Blogs/makingwaves/happy-birthday-greenfreeze/blog/44473/ |work=Greenpeace|archive-url=https://web.archive.org/web/20200408034609/http://p3-raw.greenpeace.org/international/en/news/Blogs/makingwaves/happy-birthday-greenfreeze/blog/44473/ |access-date=8 June 2015|archive-date=2020-04-08 }}{{cite web|title=Ozone Secretariat |url= http://ozone.unep.org/Events/4C1_PublicInfo_Awards97.shtml|archive-url =http://webarchive.loc.gov/all/20150412225008/http://ozone.unep.org/Events/4C1_PublicInfo_Awards97.shtml |url-status=dead|archive-date=12 April 2015|publisher=United Nations Environment Programme}}{{cite news|last=Gunkel|first=Christoph|title=Öko-Coup aus Ostdeutschland|url= http://www.spiegel.de/einestages/oeko-revolution-aus-ostdeutschland-wie-foron-den-ersten-fckw-freien-kuehlschrank-der-welt-erfand-a-951064.html |date=13 September 2013|work=Der Spiegel |language=de|access-date=4 September 2015}} Policy and political influence by corporate executives resisted change however,{{cite journal |doi=10.1111/1467-9388.00275 |title=Making a Difference: A Case Study of the Greenpeace Ozone Campaign |year=2001 |last1=Maté |first1=John |journal=Review of European Community & International Environmental Law |volume=10 |issue=2 |pages=190–198 }}Benedick, Richard Elliot Ozone Diplomacy Cambridge, MA: Harvard University 1991. citing the flammability and explosive properties of the refrigerants,{{Cite web |last=Honeywell International, Inc. |date=2010-07-09 |title=Comment on EPA Proposed Rule Office of Air and Radiation Proposed Significant New Alternatives Policy (SNAP) Protection of Stratospheric Ozone: Listing of Substitutes for Ozone-Depleting Substances – Hydrocarbon Refrigerants |url=https://downloads.regulations.gov/EPA-HQ-OAR-2009-0286-0170/attachment_1.pdf}} and DuPont together with other companies blocked them in the U.S. with the U.S. EPA.{{cite web|url=http://www.greenpeace.org/brasil/pt/Noticias/discurso-de-frank-guggenheim-n/|title=Discurso de Frank Guggenheim no lançamento do Greenfreeze | Brasil|website=Greenpeace.org|access-date=10 June 2015|archive-date=24 September 2015|archive-url=https://web.archive.org/web/20150924024715/http://www.greenpeace.org/brasil/pt/Noticias/discurso-de-frank-guggenheim-n/|url-status=dead}}{{cite web|url= https://www.greenpeace.de/themen/klimawandel/klimaschutz/der-greenfreeze-endlich-den-usa-angekommen|title=Der Greenfreeze - endlich in den USA angekommen|language=de |website=Greenpeace.de|date=28 December 2011|access-date=10 June 2015}}

Beginning on 14 November 1994, the U.S. Environmental Protection Agency restricted the sale, possession and use of refrigerants to only licensed technicians, per rules under sections 608 and 609 of the Clean Air Act.{{cite web|url= http://www.epa.gov/ozone/title6/608/608fact.html |title=Complying With The Section 608 Refrigerant Recycling Rule | Ozone Layer Protection - Regulatory Programs |website=Epa.gov |date=21 April 2015|access-date=10 June 2015}} In 1995, Germany made CFC refrigerators illegal.{{cite web|title= Greenfreeze: a Revolution in Domestic Refrigeration|url= http://www.ecomall.com/greenshopping/greenfreeze.htm |website=ecomall.com |access-date=8 June 2015}}

In 1996 Eurammon, a European non-profit initiative for natural refrigerants, was established and comprises European companies, institutions, and industry experts.{{Cite web|url=http://www.eurammon.com/about-eurammon|title=Company background|access-date=2021-03-15|archive-date=2020-02-20|archive-url=https://web.archive.org/web/20200220124551/http://www.eurammon.com/about-eurammon|url-status=dead}}{{cite report |publisher=IPCC/TEAP |title=Safeguarding the ozone layer and the global climate System: issues related to Hydrofluorocarbons and Perfluorocarbons |year=2005 |url=https://www.ipcc.ch/report/safeguarding-the-ozone-layer-and-the-global-climate-system/ }}{{cite journal |url=https://www.science.org/doi/10.1126/science.289.5477.270 |doi=10.1126/science.289.5477.270 |title=Causes of Climate Change over the Past 1000 Years |year=2000 |last1=Crowley |first1=Thomas J. |journal=Science |volume=289 |issue=5477 |pages=270–277 |pmid=10894770 |bibcode=2000Sci...289..270C |url-access=subscription }}

In 1997, FCs and HFCs were included in the Kyoto Protocol to the Framework Convention on Climate Change.

In 2000 in the UK, the Ozone Regulations{{cite web|url=https://www.gov.uk/government/policies/protecting-and-enhancing-our-urban-and-natural-environment-to-improve-public-health-and-wellbeing/supporting-pages/controlling-ozone-depleting-substances-and-fluorinated-greenhouse-gases |title=2010 to 2015 government policy: environmental quality |website=GOV.UK |date=8 May 2015|access-date=10 June 2015}} came into force which banned the use of ozone-depleting HCFC refrigerants such as R22 in new systems. The Regulation banned the use of R22 as a "top-up" fluid for maintenance from 2010 for virgin fluid and from 2015 for recycled fluid.{{citation needed|date=March 2021}}

With growing interest in natural refrigerants as alternatives to synthetic refrigerants such as CFCs, HCFCs and HFCs, in 2004, Greenpeace worked with multinational corporations like Coca-Cola and Unilever, and later Pepsico and others, to create a corporate coalition called Refrigerants Naturally!.{{cite web|title=PepsiCo Brings First Climate-Friendly Vending Machines to the U.S.|url=http://phx.corporate-ir.net/phoenix.zhtml?c=78265&p=irol-newsArticle&ID=1270984&highlight=|access-date=8 June 2015|website=phx.corporate-ir.net}} Four years later, Ben & Jerry's of Unilever and General Electric began to take steps to support production and use in the U.S.{{cite web|title=Climate-Friendly Greenfreezers Come to the United States|date=2 October 2008 |url=http://www.nbcnewyork.com/news/green/Climate-Friendly_Greenfreezers_Come_to_the_United_States.html|access-date=8 June 2015|publisher=WNBC}} It is estimated that almost 75 percent of the refrigeration and air conditioning sector has the potential to be converted to natural refrigerants.{{Cite press release|last=Data|first=Reports and|date=7 August 2020|title=Natural Refrigerants Market To Reach USD 2.88 Billion By 2027 {{!}} Reports and Data|url=http://www.globenewswire.com/news-release/2020/08/07/2074791/0/en/Natural-Refrigerants-Market-To-Reach-USD-2-88-Billion-By-2027-Reports-and-Data.html|access-date=17 December 2020|website=GlobeNewswire News Room}}

In 2006, the EU adopted a Regulation on fluorinated greenhouse gases (FCs and HFCs) to encourage to transition to natural refrigerants (such as hydrocarbons). It was reported in 2010 that some refrigerants are being used as recreational drugs, leading to an extremely dangerous phenomenon known as inhalant abuse.Harris, Catharine. "Anti-inhalant Abuse Campaign Targets Building Codes: 'Huffing’ of Air Conditioning Refrigerant a Dangerous Risk." The Nation's Health. American Public Health Association, 2010. Web. 5 December 2010. https://www.thenationshealth.org/content/39/4/20

From 2011 the European Union started to phase out refrigerants with a global warming potential (GWP) of more than 150 in automotive air conditioning (GWP = 100-year warming potential of one kilogram of a gas relative to one kilogram of CO₂) such as the refrigerant HFC-134a (known as R-134a in North America) which has a GWP of 1526.{{Harvnb|IPCC AR6 WG1 Ch7|2021|p=}} In the same year the EPA decided in favour of the ozone- and climate-safe refrigerant for U.S. manufacture.{{cite web|url= http://www.greenpeace.org/usa/en/campaigns/global-warming-and-energy/green-solutions/greenfreeze/ |title=GreenFreeze|work=Greenpeace}}{{cite web|url= https://www.epa.gov/snap/substitutes-household-refrigerators-and-freezers |title=Significant New Alternatives Program: Substitutes in Household Refrigerators and Freezers|website=Epa.gov|date=13 November 2014|access-date=4 June 2018}}

A 2018 study by the nonprofit organization "Drawdown" put proper refrigerant management and disposal at the very top of the list of climate impact solutions, with an impact equivalent to eliminating over 17 years of US carbon dioxide emissions.{{Cite web|url=https://www.nationalgeographic.com/environment/2019/04/disposing-old-cfcs-refrigerants-reduces-climate-change-greenhouse-gases-cheaply/|archive-url=https://web.archive.org/web/20190429113314/https://www.nationalgeographic.com/environment/2019/04/disposing-old-cfcs-refrigerants-reduces-climate-change-greenhouse-gases-cheaply/|url-status=dead|archive-date=April 29, 2019|title=One overlooked way to fight climate change? Dispose of old CFCs.|last=Berwald|first=Juli|date=29 April 2019|website=National Geographic - Environment|access-date=30 April 2019}}

In 2019 it was estimated that CFCs, HCFCs, and HFCs were responsible for about 10% of direct radiative forcing from all long-lived anthropogenic greenhouse gases.{{Cite web |url=https://www.esrl.noaa.gov/gmd/aggi/aggi.html |title=The NOAA Annual Greenhouse Gas Index (AGGI) |publisher=NOAA Global Monitoring Laboratory/Earth System Research Laboratories |author=Butler J. and Montzka S. |year=2020 }} and in the same year the UNEP published new voluntary guidelines,{{cite web|url=http://www.unenvironment.org/news-and-stories/story/new-guidelines-air-conditioners-and-refrigerators-set-tackle-climate-change|title=New guidelines for air conditioners and refrigerators set to tackle climate change|last=Environment|first=U. N.|date=31 October 2019|website=UN Environment|language=en|access-date=30 March 2020}} however many countries have not yet ratified the Kigali Amendment.

From early 2020 HFCs (including R-404A, R-134a, and R-410A) are being superseded: Residential air-conditioning systems and heat pumps are increasingly using R-32. This still has a GWP of more than 600. Progressive devices use refrigerants with almost no climate impact, namely R-290 (propane), R-600a (isobutane), or R-1234yf (less flammable, in cars). In commercial refrigeration also {{CO2}} (R-744) can be used.

A refrigerant needs to have: a boiling point that is somewhat below the target temperature (although boiling point can be adjusted by adjusting the pressure appropriately), a high heat of vaporization, a moderate density in liquid form, a relatively high density in gaseous form (which can also be adjusted by setting pressure appropriately), and a high critical temperature. Working pressures should ideally be containable by copper tubing, a commonly available material. Extremely high pressures should be avoided.{{citation needed|date=July 2023}}

The ideal refrigerant would be: non-corrosive, non-toxic, non-flammable, with no ozone depletion and global warming potential. It should preferably be natural with well-studied and low environmental impact. Newer refrigerants address the issue of the damage that CFCs caused to the ozone layer and the contribution that HCFCs make to climate change, but some do raise issues relating to toxicity and/or flammability.{{cite news |last=Rosenthal |first=Elisabeth |author2=Lehren, Andrew |date=20 June 2011 |title=Relief in Every Window, but Global Worry Too |newspaper=The New York Times |url=https://www.nytimes.com/2012/06/21/world/asia/global-demand-for-air-conditioning-forces-tough-environmental-choices.html?pagewanted=1&_r=1&hp |url-access=limited |access-date=21 June 2012}}

With increasing regulations, refrigerants with a very low global warming potential are expected to play a dominant role in the 21st century,{{harvnb|Yadav et al|2022}} in particular, R-290 and R-1234yf. Starting from almost no market share in 2018,{{harvnb|BSRIA|2020}} low GWPO devices are gaining market share in 2022.

{{main|Refrigerant reclamation}}

Coolant and refrigerants are found throughout the industrialized world, in homes, offices, and factories, in devices such as refrigerators, air conditioners, central air conditioning systems (HVAC), freezers, and dehumidifiers. When these units are serviced, there is a risk that refrigerant gas will be vented into the atmosphere either accidentally or intentionally, hence the creation of technician training and certification programs in order to ensure that the material is conserved and managed safely. Mistreatment of these gases has been shown to deplete the ozone layer and is suspected to contribute to global warming.{{Cite web|url=http://www.eia.doe.gov/oiaf/1605/ggrpt/|title=Emissions of Greenhouse Gases in the United States 1998 - Executive Summary|date=18 August 2000|archive-url=https://web.archive.org/web/20000818233746/http://www.eia.doe.gov/oiaf/1605/ggrpt/|archive-date=18 August 2000}}

With the exception of isobutane and propane (R600a, R441A, and R290), ammonia and CO₂ under Section 608 of the United States' Clean Air Act it is illegal to knowingly release any refrigerants into the atmosphere.{{cite web|title=Frequently Asked Questions on Section 608|url=http://www.epa.gov/ozone/title6/608/faq.html#q2|work=Environment Protection Agency|access-date=20 December 2013}}{{cite web|title=US hydrocarbons|url=http://hydrocarbons21.com/articles/us_epa_lifts_venting_prohibition_for_snap_approved_hydrocarbons|access-date=5 August 2018}}

Refrigerant reclamation is the act of processing used refrigerant gas that has previously been used in some type of refrigeration loop such that it meets specifications for new refrigerant gas. In the United States, the Clean Air Act of 1990 requires that used refrigerant be processed by a certified reclaimer, which must be licensed by the United States Environmental Protection Agency (EPA), and the material must be recovered and delivered to the reclaimer by EPA-certified technicians.{{Cite web|url=https://www.law.cornell.edu/uscode/text/42/7671g|title=42 U.S. Code § 7671g - National recycling and emission reduction program|website=LII / Legal Information Institute}}

File:R407C eng.PNG-enthalpy diagram, isotherms between the two saturation lines]]

{{main|List of refrigerants}}

Refrigerants may be divided into three classes according to their manner of absorption or extraction of heat from the substances to be refrigerated:{{citation needed|date=December 2013}}

• Class 1: This class includes refrigerants that cool by phase change (typically boiling), using the refrigerant's latent heat.
• Class 2: These refrigerants cool by temperature change or 'sensible heat', the quantity of heat being the specific heat capacity x the temperature change. They are air, calcium chloride brine, sodium chloride brine, alcohol, and similar nonfreezing solutions. The purpose of Class 2 refrigerants is to receive a reduction of temperature from Class 1 refrigerants and convey this lower temperature to the area to be cooled.
• Class 3: This group consists of solutions that contain absorbed vapors of liquefiable agents or refrigerating media. These solutions function by the nature of their ability to carry liquefiable vapors, which produce a cooling effect by the absorption of their heat of solution. They can also be classified into many categories.

The R- numbering system was developed by DuPont (which owned the Freon trademark), and systematically identifies the molecular structure of refrigerants made with a single halogenated hydrocarbon. ASHRAE has since set guidelines for the numbering system as follows:{{cite web |author1=ASHRAE |author2=UNEP |title=Designation and Safety Classification of Refrigerants |url=https://www.ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20addenda/34_2004_add-g.pdf |website=ASHRAE |access-date=1 July 2023 |date=Nov 2022}}

R-X₁X₂X₃X₄

• X₁ = Number of unsaturated carbon-carbon bonds (omit if zero)
• X₂ = Number of carbon atoms minus 1 (omit if zero)
• X₃ = Number of hydrogen atoms plus 1
• X₄ = Number of fluorine atoms

• R-xx Methane Series
• R-1xx Ethane Series
• R-2xx Propane Series
• R-4xx Zeotropic blend
• R-5xx Azeotropic blend
• R-6xx Saturated hydrocarbons (except for propane which is R-290)
• R-7xx Inorganic Compounds with a molar mass < 100
• R-7xxx Inorganic Compounds with a molar mass ≥ 100

• Number Only Most symmetrical isomer
• Lower Case Suffix (a, b, c, etc.) indicates increasingly unsymmetrical isomers

• Number Only If only one isomer exists; otherwise:
• First lower case suffix (a-f):
• a Suffix Cl₂ central carbon substitution
• b Suffix Cl, F central carbon substitution
• c Suffix F₂ central carbon substitution
• d Suffix Cl, H central carbon substitution
• e Suffix F, H central carbon substitution
• f Suffix H₂ central carbon substitution
• 2nd Lower Case Suffix (a, b, c, etc.) Indicates increasingly unsymmetrical isomers

• First lower case suffix (x, y, z):
• x Suffix Cl substitution on central atom
• y Suffix F substitution on central atom
• z Suffix H substitution on central atom
• Second lower case suffix (a-f):
• a Suffix =CCl₂ methylene substitution
• b Suffix =CClF methylene substitution
• c Suffix =CF₂ methylene substitution
• d Suffix =CHCl methylene substitution
• e Suffix =CHF methylene substitution
• f Suffix =CH₂ methylene substitution

• Upper Case Suffix (A, B, C, etc.) Same blend with different compositions of refrigerants

• R-Cxxx Cyclic compound
• R-Exxx Ether group is present
• R-CExxx Cyclic compound with an ether group
• R-4xx/5xx + Upper Case Suffix (A, B, C, etc.) Same blend with different composition of refrigerants
• R-6xx + Lower Case Letter Indicates increasingly unsymmetrical isomers
• 7xx/7xxx + Upper Case Letter Same molar mass, different compound
• R-xxxxB# Bromine is present with the number after B indicating how many bromine atoms
• R-xxxxI# Iodine is present with the number after I indicating how many iodine atoms
• R-xxx(E) Trans Molecule
• R-xxx(Z) Cis Molecule

For example, R-134a has 2 carbon atoms, 2 hydrogen atoms, and 4 fluorine atoms, an empirical formula of tetrafluoroethane. The "a" suffix indicates that the isomer is unbalanced by one atom, giving 1,1,1,2-Tetrafluoroethane. R-134 (without the "a" suffix) would have a molecular structure of 1,1,2,2-Tetrafluoroethane.

The same numbers are used with an R- prefix for generic refrigerants, with a "Propellant" prefix (e.g., "Propellant 12") for the same chemical used as a propellant for an aerosol spray, and with trade names for the compounds, such as "Freon 12". Recently, a practice of using abbreviations HFC- for hydrofluorocarbons, CFC- for chlorofluorocarbons, and HCFC- for hydrochlorofluorocarbons has arisen, because of the regulatory differences among these groups.{{citation needed|date=August 2015|ASHRAE std 34-1997, Section 5.2.2 = }}

Refrigerants are classified under regulations such as ISO 817/5149, AHRAE 34/15, & BS EN 378. The pressures of these gases can range from {{cvt|700-1000|kPa}}. They can also be at temperatures as low as {{convert|-50|°C|disp=sqbr}} and as high as over {{convert|100|°C|disp=sqbr}}. Refrigerants have varying classifications of flammability: A1 class are non-flammable, A2/A2L class are flammable, and A3 class are extremely flammable and/or explosive. Toxicity also varies; B1 class refrigerants have low toxicity, while B2 refrigerants are moderately toxic and B3 refrigerants are highly toxic.{{Citation needed|date=February 2025}} These regulations relate to situations where these refrigerants are released into the atmosphere in the event of an accidental leak, not while circulated.{{Cite journal |last1=Li |first1=Yalun |last2=Yang |first2=Jialiang |last3=Wu |first3=Xilei |last4=Liu |first4=Ying |last5=Zhuang |first5=Yuan |last6=Zhou |first6=Peixu |last7=Han |first7=Xiaohong |last8=Chen |first8=Guangming |date=2023-05-01 |title=Leakage, diffusion and distribution characteristics of refrigerant in a limited space:A comprehensive review |url=https://www.sciencedirect.com/science/article/abs/pii/S2451904923000847 |journal=Thermal Science and Engineering Progress |volume=40 |pages=101731 |bibcode=2023TSEP...4001731L |doi=10.1016/j.tsep.2023.101731 |issn=2451-9049|url-access=subscription }} Due to these regulations, most refrigerants may only be handled by qualified/certified engineers for the relevant classes; in the UK, C&G 2079 is required for A1-class refrigerants, while C&G 6187-2 is required for A2, A2L, and A3-class refrigerants.{{Citation needed|date=February 2025}} Due to their non-flammability, non-explosivity, and non-toxicity, A1 class refrigerants have been used in open systems (where they are consumed when used rather than circulated) like fire extinguishers, inhalers, computer rooms, and insulation since 1928.{{Citation needed|date=February 2025}}

ASHRAE Standard 34, Designation and Safety Classification of Refrigerants, assigns safety classifications to refrigerants based upon toxicity and flammability. ASHRAE assigns a capital letter to indicate toxicity and a number to indicate flammability. The letter "A" is the least toxic and the number 1 is the least flammable.{{cite web |title=Update on New Refrigerants Designations and Safety Classifications |date=April 2020 |publisher=American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) |url=https://www.ashrae.org/file%20library/technical%20resources/refrigeration/factsheet_ashrae_english_20200424.pdf |accessdate=October 22, 2022 |archive-date=February 13, 2023 |archive-url=https://web.archive.org/web/20230213130357/https://www.ashrae.org/file%20library/technical%20resources/refrigeration/factsheet_ashrae_english_20200424.pdf |url-status=dead }}

• Brine (Refrigerant)
• Section 608
• List of Refrigerants

{{Reflist|30em}}

{{reflist|group=EPA}}

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• {{cite web |ref= {{harvid|ARB|2022}}

|title=High GWP refrigerants |url=https://ww2.arb.ca.gov/resources/documents/high-gwp-refrigerants

|publisher=California Air Resources Board

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• {{cite web |ref= {{harvid|BSRIA|2020}} |title=BSRIA's view on refrigerant trends in AC and Heat Pump segments |url=https://www.bsria.com/us/news/article/bsrias_view_on_refrigerant_trends_in_ac_and_heat_pump_segments/ |date=2020 |access-date=2022-02-14}}
• {{cite journal |ref= {{harvid|Yadav et al|2022}} |last1=Yadav |first1=Saurabh |last2=Liu |first2=Jie |last3=Kim |first3=Sung Chul |title=A comprehensive study on 21st-century refrigerants - R290 and R1234yf: A review |journal=International Journal of Heat and Mass Transfer |date=2022 |volume=122 |page=121947 |doi=10.1016/j.ijheatmasstransfer.2021.121947 |s2cid=240534198 |doi-access= |bibcode=2022IJHMT.18221947Y }}

• [https://web.archive.org/web/20041112075806/http://www.epa.gov/nonco2/econ-inv/table.html US Environmental Protection Agency page on the GWPs of various substances]
• [http://www.green-cooling-initiative.org/ Green Cooling Initiative on alternative natural refrigerants cooling technologies]
• [http://www.iifiir.org/medias/medias.aspx?instance=EXPLOITATION&setlanguage=EN International Institute of Refrigeration] {{Webarchive|url=https://web.archive.org/web/20180925041045/http://www.iifiir.org/medias/medias.aspx?instance=EXPLOITATION&setlanguage=EN |date=2018-09-25 }}

{{HVAC}}

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Category:Heating, ventilation, and air conditioning

Category:Industrial gases