Chlorodifluoromethane

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Chlorodifluoromethane
Chlorodifluoromethane-2D-skeletal.svg
Chlorodifluoromethane-3D-vdW.png
Liquid R-22.png
Liquefied chlorodifluoromethane boiling when exposed to STP
Names
Preferred IUPAC name
Chloro(difluoro)methane
Other names
Chlorodifluoromethane
Difluoromonochloromethane
Monochlorodifluoromethane
HCFC-22
R-22
Genetron 22
Freon 22
Arcton 4
Arcton 22
UN 1018
Difluorochloromethane
Fluorocarbon-22
Refrigerant 22
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.000.793 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 200-871-9
KEGG
PubChem CID
RTECS number
  • PA6390000
UNII
UN number 1018
  • InChI=1S/CHClF2/c2-1(3)4/h1H Yes check.svgY
    Key: VOPWNXZWBYDODV-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/CHClF2/c2-1(3)4/h1H
    Key: VOPWNXZWBYDODV-UHFFFAOYAQ
  • ClC(F)F
Properties
CHClF2
Molar mass 86.47 g/mol
AppearanceColorless gas
Odor Sweetish [1]
Density 3.66 kg/m3 at 15 °C, gas
Melting point −175.42 °C (−283.76 °F; 97.73 K)
Boiling point −40.7 °C (−41.3 °F; 232.5 K)
0.7799 vol/vol at 25 °C; 3.628 g/L
log P 1.08
Vapor pressure 908 kPa at 20 °C
0.033 mol⋅kg−1⋅bar−1
−38.6·10−6 cm3/mol
Structure
Tetrahedral
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Dangerous for the environment (N), Central nervous system depressant, Carc. Cat. 3
GHS labelling:
GHS-pictogram-exclam.svg
Warning
H420
P202, P262, P271, P403
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
1
0
1
Flash point nonflammable [1]
632 °C (1,170 °F; 905 K)
NIOSH (US health exposure limits):
PEL (Permissible)
None [1]
REL (Recommended)
TWA 1000 ppm (3500 mg/m3) ST 1250 ppm (4375 mg/m3) [1]
IDLH (Immediate danger)
N.D. [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon (HCFC). This colorless gas is better known as HCFC-22, or R-22, or CHClF
2. It was commonly used as a propellant and refrigerant. These applications were phased out under the Montreal Protocol in developed countries in 2020 due to the compound's ozone depletion potential (ODP) and high global warming potential (GWP), and in developing countries this process will be completed by 2030. R-22 is a versatile intermediate in industrial organofluorine chemistry, e.g. as a precursor to tetrafluoroethylene.

R22 - Chlorodifluoromethane Cylinder R22 - Chlorodifluoromethane Cylinder.png
R22 - Chlorodifluoromethane Cylinder

Production and current applications

Worldwide production of R-22 in 2008 was about 800 Gg per year, up from about 450 Gg per year in 1998, with most production in developing countries. [2] R-22 use is being phased out in developing countries, where it is largely used for air conditioning applications.

R-22 is prepared from chloroform:

HCCl3 + 2 HF → HCF2Cl + 2 HCl

An important application of R-22 is as a precursor to tetrafluoroethylene. This conversion involves pyrolysis to give difluorocarbene, which dimerizes: [3]

2 CHClF2 → C2F4 + 2 HCl

The compound also yields difluorocarbene upon treatment with strong base and is used in the laboratory as a source of this reactive intermediate.

The pyrolysis of R-22 in the presence of chlorofluoromethane gives hexafluorobenzene.

Environmental effects

R-22 is often used as an alternative to the highly ozone-depleting CFC-11 and CFC-12, because of its relatively low ozone depletion potential of 0.055, [4] among the lowest for chlorine-containing haloalkanes. However, even this lower ozone depletion potential is no longer considered acceptable.

As an additional environmental concern, R-22 is a powerful greenhouse gas with a GWP equal to 1810 (which indicates 1810 times as powerful as carbon dioxide). Hydrofluorocarbons (HFCs) are often substituted for R-22 because of their lower ozone depletion potential, but these refrigerants often have a higher GWP. R-410A, for example, is often substituted, but has a GWP of 2088. Another substitute is R-404A with a GWP of 3900. Other substitute refrigerants are available with low GWP. Ammonia (R-717), with a GWP of <1, remains a popular substitute on fishing vessels and large industrial applications. Ammonia's toxicity in high concentrations limit its application in small-scale refrigeration applications.

Propane (R-290) is another example, and has a GWP of 3. Propane was the de facto refrigerant in systems smaller than industrial scale before the introduction of CFCs. The reputation of propane refrigerators as a fire hazard kept delivered ice and the ice box the overwhelming consumer choice despite its inconvenience and higher cost until safe CFC systems overcame the negative perceptions of refrigerators. Illegal to use as a refrigerant in the US for decades, propane is now permitted for use in limited mass suitable for small refrigerators. It is not lawful to use in air conditioners or larger refrigerators because of its flammability and potential for explosion.

Phaseout in the European Union

Shipping container for the gas in Japan. Container [( 2%3FT%3F )] GRPU 918195(3)---No,2 [( Pictures taken in Japan )] .jpg
Shipping container for the gas in Japan.

Since 1 January 2010, it has been illegal to use newly manufactured HCFCs to service refrigeration and air-conditioning equipment; only reclaimed and recycled HCFCs may be used. In practice this means that the gas has to be removed from the equipment before servicing and replaced afterwards, rather than refilling with new gas.

Since 1 January 2015, it has been illegal to use any HCFCs to service refrigeration and air-conditioning equipment; broken equipment that used HCFC refrigerants must be replaced with equipment that does not use them. [6]

Phaseout in the United States

R-22 was mostly phased out in new equipment in the United States by regulatory action by the EPA under the Significant New Alternatives Program (SNAP) by rules 20 and 21 of the program, [7] due to its high global warming potential. The EPA program was consistent with the Montreal Accords, but international agreements must be ratified by the US Senate to have legal effect. A 2017 decision of the US Court of Appeals for the District of Columbia Circuit [8] held that the US EPA lacked authority to regulate the use of R-22 under SNAP. In essence the court ruled the EPA's statutory authority [9] was for ozone reduction, not global warming. The EPA subsequently issued guidance to the effect that the EPA would no longer regulate R-22. A 2018 ruling [10] by the same court held that the EPA failed to conform with required procedure when it issued its guidance pursuant to the 2017 ruling, voiding the guidance, but not the prior ruling that required it. The refrigeration and air conditioning industry had already discontinued production of new R-22 equipment. The practical effect of these rulings is to reduce the cost of imported R-22 to maintain aging equipment, extending its service life, while preventing the use of R-22 in new equipment.

R-22, retrofit using substitute refrigerants

The energy efficiency and system capacity of systems designed for R-22 is slightly greater using R-22 than the available substitutes. [11]

R-407A is for use in low- and medium-temp refrigeration. Uses a polyolester (POE) oil.

R-407C is for use in air conditioning. Uses a minimum of 20 percent POE oil.

R-407F and R-407H are for use in medium- and low-temperature refrigeration applications (supermarkets, cold storage, and process refrigeration); direct expansion system design only. They use a POE oil.

R-421A is for use in "air conditioning split systems, heat pumps, supermarket pak systems, dairy chillers, reach-in storage, bakery applications, refrigerated transport, self-contained display cabinets, and walk-in coolers". Uses mineral oil (MO), Alkylbenzene (AB), and POE.

R-422B is for use in low-, medium-, and high-temperature applications. It is not recommended for use in flooded applications.

R-422C is for use in medium- and low-temperature applications. The TXV power element will need to be changed to a 404A/507A element and critical seals (elastomers) may need to be replaced.

R-422D is for use in low-temp applications, and is mineral oil compatible.

R-424A is for use in air conditioning as well as medium-temp refrigeration temperature ranges of 20 to 50˚F. It works with MO, alkylbenzenes (AB), and POE oils.

R-427A is for use in air conditioning and refrigeration applications. It does not require all the mineral oil to be removed. It works with MO, AB, and POE oils.

R-434A is for use in water cooled and process chillers for air conditioning and medium- and low-temperature applications. It works with MO, AB, and POE oils.

R-438A (MO-99) is for use in low-, medium-, and high-temperature applications. It is compatible with all lubricants. [12]

R-458A is for use in air conditioning and refrigeration applications, without capacity or efficiency loss. Works with MO, AB, and POE oils. [13]

R-32 or HFC-32 (difluoromethane) is for use in air conditioning and refrigeration applications. It has zero ozone depletion potential (ODP) [2] and a global warming potential (GWP) index 675 times that of carbon dioxide.

Physical properties

PropertyValue
Density (ρ) at −69 °C (liquid)1.49 g⋅cm−3
Density (ρ) at −41 °C (liquid)1.413 g⋅cm−3
Density (ρ) at −41 °C (gas)4.706 kg⋅m−3
Density (ρ) at 15 °C (gas)3.66 kg⋅m−3
Specific gravity at 21 °C (gas)3.08 (air is 1)
Specific volume (ν) at 21 °C (gas)0.275 m3⋅kg−1
Density (ρ) at 15 °C (gas)3.66 kg⋅m−3
Triple point temperature (Tt)−157.39 °C (115.76 K)
Critical temperature (Tc)96.2 °C (369.3 K)
Critical pressure (pc)4.936 MPa (49.36 bar)
Vapor pressure at 21.1 °C (pc)0.9384 MPa (9.384 bar) [14]
Critical density (ρc)6.1 mol⋅l−1
Latent heat of vaporization (lv) at boiling point (−40.7 °C)233.95 kJ⋅kg−1
Heat capacity at constant pressure (Cp) at 30 °C (86 °F)0.057 kJ.mol−1⋅K−1
Heat capacity at constant volume (Cv) at 30 °C (86 °F)0.048 kJ⋅mol−1⋅K−1
Heat capacity ratio (γ) at 30 °C (86 °F)1.178253
Compressibility factor (Z) at 15 °C0.9831
Acentric factor (ω)0.22082
Molecular dipole moment 1.458 D
Viscosity (η) at 0 °C12.56 μPa⋅s (0.1256 cP)
Ozone depletion potential (ODP)0.055 (CCl3F is 1)
Global warming potential (GWP)1810 (CO2 is 1)

It has two allotropes: crystalline II below 59 K and crystalline I above 59 K and below 115.73 K.

The pressure-enthalpy R22 properties, using Refprop 9.0 database, using the International Institute of Refrigeration reference. R22 ph.gif
The pressure-enthalpy R22 properties, using Refprop 9.0 database, using the International Institute of Refrigeration reference.
Thermal and physical properties of saturated liquid refrigerant 22: [15] [16]
Temperature (K)Density (kg/m^3)Specific heat (kJ/kg K)Dynamic viscosity (kg/m s)Kinematic viscosity (m^2/s)Conductivity (W/m K)Thermal diffusivity (m^2/s)Prandtl NumberBulk modulus (K^-1)
23014161.0873.56E-042.51E-070.11457.44E-083.40.00205
2401386.61.13.15E-042.27E-070.10987.20E-083.20.00216
2501356.31.1172.80E-042.06E-070.10526.95E-0830.00229
2601324.91.1372.50E-041.88E-070.10076.68E-082.80.00245
2701292.11.1612.24E-041.73E-070.09626.41E-082.70.00263
2801257.91.1892.01E-041.59E-070.09176.13E-082.60.00286
2901221.71.2231.80E-041.47E-070.08725.83E-082.50.00315
3001183.41.2651.61E-041.36E-070.08265.52E-082.50.00351
3101142.21.3191.44E-041.26E-070.07815.18E-082.40.004
3201097.41.3911.28E-041.17E-070.07344.81E-082.40.00469
3301047.51.4951.13E-041.08E-070.06864.38E-082.50.00575
340990.11.6659.80E-059.89E-080.06363.86E-082.60.00756
350920.11.9978.31E-059.04E-080.05833.17E-082.80.01135
360823.43.0016.68E-058.11E-080.05312.15E-083.80.02388

Price history and availability

Refrigerants price history Refrigerants-Prices-Wikipedia-2016-08-25.svg
Refrigerants price history

EPA's analysis indicated the amount of existing inventory was between 22,700t and 45,400t. [17] [18] [ when? ]

Year201020112012201320142015–20192020
R-22 Virgin (t)49,90045,40025,10025,60020,200TBD0
R-22 Recoupment (t)------2,9502,950----
R-22 Total (t)49,90045,40025,10028,60023,100----

In 2012 the EPA reduced the amount of R-22 by 45%, causing the price to rise by more than 300%. For 2013, the EPA has reduced the amount of R-22 by 29%. [19]

Related Research Articles

<span class="mw-page-title-main">Chlorofluorocarbon</span> Class of organic compounds

Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propane.

<span class="mw-page-title-main">Isobutane</span> Chemical compound

Isobutane, also known as i-butane, 2-methylpropane or methylpropane, is a chemical compound with molecular formula HC(CH3)3. It is an isomer of butane. Isobutane is a colorless, odorless gas. It is the simplest alkane with a tertiary carbon atom. Isobutane is used as a precursor molecule in the petrochemical industry, for example in the synthesis of isooctane.

<span class="mw-page-title-main">Freon</span> Registered trade name for halocarbon products

Freon is a registered trademark of the Chemours Company and generic descriptor for a number of halocarbon products. They are stable, nonflammable, low toxicity gases or liquids which have generally been used as refrigerants and as aerosol propellants. These include chlorofluorocarbons and hydrofluorocarbons, both of which cause ozone depletion and contribute to global warming. 'Freon' is the brand name for the refrigerants R-12, R-13B1, R-22, R-410A, R-502, and R-503 manufactured by The Chemours Company, and so is not used to label all refrigerants of this type. They emit a strong smell similar to acetone. Freon has been found to cause damage to human health when inhaled in large amounts. Studies have been conducted in the pursuit to find beneficial reuses for gases under the Freon umbrella as an alternative to disposal of the gas.

<span class="mw-page-title-main">Refrigerant</span> Substance in a refrigeration cycle

A refrigerant is a working fluid used in cooling, heating or reverse cooling and heating of air conditioning systems and heat pumps where they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are heavily regulated because of their toxicity and flammability and the contribution of CFC and HCFC refrigerants to ozone depletion and that of HFC refrigerants to climate change.

Propane refrigeration is a type of compression refrigeration. Propane (R290) has been used successfully in industrial refrigeration for many years, and is emerging as an increasingly viable alternative for homes and businesses. Propane's operating pressures and temperatures are well suited for use in air conditioning equipment, but because of propane’s flammability, great care is required in the manufacture, installation and servicing of equipment that uses it as a refrigerant.

R-410A is a refrigerant used in air conditioning and heat pump applications. It is a zeotropic but near-azeotropic mixture of difluoromethane (CH2F2, called R-32) and pentafluoroethane (CHF2CF3, called R-125). R-410A is sold under the trademarked names AZ-20, EcoFluor R410, Forane 410A, Genetron R410A, Puron, and Suva 410A.

<span class="mw-page-title-main">Icemaker</span> Consumer device for making ice, found inside a freezer

An icemaker, ice generator, or ice machine may refer to either a consumer device for making ice, found inside a home freezer; a stand-alone appliance for making ice, or an industrial machine for making ice on a large scale. The term "ice machine" usually refers to the stand-alone appliance.

<span class="mw-page-title-main">Vapor-compression refrigeration</span> Refrigeration process

Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air conditioning of buildings and automobiles. It is also used in domestic and commercial refrigerators, large-scale warehouses for chilled or frozen storage of foods and meats, refrigerated trucks and railroad cars, and a host of other commercial and industrial services. Oil refineries, petrochemical and chemical processing plants, and natural gas processing plants are among the many types of industrial plants that often utilize large vapor-compression refrigeration systems. Cascade refrigeration systems may also be implemented using two compressors.

<span class="mw-page-title-main">2,2-Dichloro-1,1,1-trifluoroethane</span> Chemical compound

2,2-Dichloro-1,1,1-trifluoroethane or HCFC-123 is considered as an alternative to CFC-11 in low pressure refrigeration and HVAC systems, and should not be used in foam blowing processes or solvent applications. It is also the primary component of the Halotron I fire-extinguishing mixture.

<span class="mw-page-title-main">Air source heat pump</span> Most common type of heat pump

An air source heat pump (ASHP) is a heat pump that can absorb heat from air outside a building and release it inside; it uses the same vapor-compression refrigeration process and much the same equipment as an air conditioner, but in the opposite direction. ASHPs are the most common type of heat pump and, usually being smaller, tend to be used to heat individual houses or flats rather than blocks, districts or industrial processes.

Natural refrigerants are considered substances that serve as refrigerants in refrigeration systems. They are alternatives to synthetic refrigerants such as chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), and hydrofluorocarbon (HFC) based refrigerants. Unlike other refrigerants, natural refrigerants can be found in nature and are commercially available thanks to physical industrial processes like fractional distillation, chemical reactions such as Haber process and spin-off gases. The most prominent of these include various natural hydrocarbons, carbon dioxide, ammonia, and water. Natural refrigerants are preferred actually in new equipment to their synthetic counterparts for their presumption of higher degrees of sustainability. With the current technologies available, almost 75 percent of the refrigeration and air conditioning sector has the potential to be converted to natural refrigerants.

Refrigerant reclamation is the act of processing used refrigerant gas which has previously been used in some type of refrigeration loop such that it meets specifications for new refrigerant gas. In the United States, the Section 608 of 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.

<span class="mw-page-title-main">1,1-Dichloro-1-fluoroethane</span> Chemical compound

1,1-Dichloro-1-fluoroethane is a haloalkane with the formula C
2H
3Cl
2F. It is one of the three isomers of dichlorofluoroethane. It belongs to the hydrochlorofluorocarbon (HCFC) family of man-made compounds that contribute significantly to both ozone depletion and global warming when released into the environment.

<span class="mw-page-title-main">R-407C</span> Mixture used as a refrigerant

R-407C is a mixture of hydrofluorocarbons used as a refrigerant. It is a zeotropic blend of difluoromethane (R-32), pentafluoroethane (R-125), and 1,1,1,2-tetrafluoroethane (R-134a). Difluoromethane serves to provide the heat capacity, pentafluoroethane decreases flammability, tetrafluoroethane reduces pressure. R-407C cylinders are colored burnt orange.

<span class="mw-page-title-main">1-Chloro-1,1-difluoroethane</span> Chemical compound

1-Chloro-1,1-difluoroethane (HCFC-142b) is a haloalkane with the chemical formula CH3CClF2. It belongs to the hydrochlorofluorocarbon (HCFC) family of man-made compounds that contribute significantly to both ozone depletion and global warming when released into the environment. It is primarily used as a refrigerant where it is also known as R-142b and by trade names including Freon-142b.

<span class="mw-page-title-main">Hydrofluoroolefin</span> Class of chemical compounds

Hydrofluoroolefins (HFOs) are unsaturated organic compounds composed of hydrogen, fluorine and carbon. These organofluorine compounds are of interest as refrigerants. Unlike traditional hydrofluorocarbons (HFCs) and chlorofluorocarbons (CFCs), which are saturated, HFOs are olefins, otherwise known as alkenes.

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Life Cycle Climate Performance (LCCP) is an evolving method to evaluate the carbon footprint and global warming impact of heating, ventilation, air conditioning (AC), refrigeration systems, and potentially other applications such as thermal insulating foam. It is calculated as the sum of direct, indirect, and embodied greenhouse gas (GHG) emissions generated over the lifetime of the system “from cradle to grave,” i.e. from manufacture to disposal. Direct emissions include all climate forcing effects from the release of refrigerants into the atmosphere, including annual leakage and losses during service and disposal of the unit. Indirect emissions include the climate forcing effects of GHG emissions from the electricity powering the equipment. The embodied emissions include the climate forcing effects of the manufacturing processes, transport, and installation for the refrigerant, materials, and equipment, and for recycle or other disposal of the product at end of its useful life.

The Significant New Alternatives Policy is a program of the EPA to determine acceptable chemical substitutes, and establish which are prohibited or regulated by the EPA. It also establishes a program by which new alternatives may be accepted, and promulgates timelines to the industry regarding phase-outs of substitutes.

References

  1. 1 2 3 4 5 NIOSH Pocket Guide to Chemical Hazards. "#0124". National Institute for Occupational Safety and Health (NIOSH).
  2. ↑ Rosenthal, Elisabeth; Lehren, Andrew W. (20 June 2012). "Relief in Every Window, but Global Worry Too". The New York Times . Archived from the original on 21 June 2012. Retrieved 21 June 2012.
  3. ↑ Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Sart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine (2002). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_349. ISBN   978-3527306732.
  4. ↑ The Montreal Protocol on Substances that Deplete the Ozone Layer. UNEP, 2000. ISBN   92-807-1888-6
  5. ↑ "HCFC-22 (Chlorodifluoromethane)". NOAA Earth System Research Laboratories/Global Monitoring Division. Retrieved 12 February 2021.
  6. ↑ "Guidance for Stationary Refrigeration & Air-Conditioning" (PDF). Department for Environment, Food and Rural Affairs. Archived (PDF) from the original on 10 March 2016. Retrieved 8 September 2015.
  7. ↑ "SNAP Regulations". 4 November 2014. Archived from the original on 10 October 2015.
  8. ↑ "Mexichem Fluor, Inc. v. EPA". Archived from the original on 17 August 2017.
  9. ↑ "Ozone Protection under Title VI of the Clean Air Act". 14 July 2015. Archived from the original on 25 January 2016.
  10. ↑ "Natural Resources Defense Council v. EPA". Archived from the original on 10 December 2020.
  11. ↑ "THEORETICAL EVALUATION OF R22 AND R502 ALTERNATIVES" (PDF). Archived (PDF) from the original on 5 April 2015.
  12. ↑ Retrofit Refrigerants Archived 24 June 2013 at archive.today
  13. ↑ "Protection of Stratospheric Ozone: Determination 33 for Significant New Alternatives Policy Program". 21 July 2017.
  14. ↑ "Frogen R-22 – Frogen UK: Refrigerant and Cooling Specialists". frogen.co.uk. Archived from the original on 25 January 2017. Retrieved 23 April 2018.
  15. ↑ Holman, Jack P. (2002). Heat Transfer (9th ed.). New York, NY: McGraw-Hill Companies, Inc. pp. 600–606. ISBN   978-0-07-240655-9.
  16. ↑ Incropera 1 Dewitt 2 Bergman 3 Lavigne 4, Frank P. 1 David P. 2 Theodore L. 3 Adrienne S. 4 (2007). Fundamentals of Heat and Mass Transfer (6th ed.). Hoboken, NJ: John Wiley and Sons, Inc. pp. 941–950. ISBN   978-0-471-45728-2.{{cite book}}: CS1 maint: numeric names: authors list (link)
  17. ↑ "Protection of Stratospheric Ozone: Adjustments to the Allowance System for Controlling HCFC Production, Import, and Export". federalregister.gov. 3 April 2013. Archived from the original on 4 March 2016. Retrieved 23 April 2018.
  18. ↑ "Protection of Stratospheric Ozone: Adjustments to the Allowance System for Controlling HCFC Production, Import, and Export". federalregister.gov. 3 April 2013. Archived from the original on 4 March 2016. Retrieved 23 April 2018.
  19. ↑ Specialty Cooling and Heating (Blog) January 22, 2013 Archived 6 October 2013 at the Wayback Machine

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