EPA 609 unique fittings and labels
This page covers what the SNAP use conditions in 40 CFR Part 82, Subpart G say about unique fittings, detailed labels and warning labels for MVAC substitute refrigerants, including retrofits. SAE standards such as J639 and J2844 are incorporated by reference; we name them but do not describe their contents beyond what the CFR text states. Conditions are legal requirements; we mark EPA's comments, which are not, and say when a condition binds manufacturers. Each point quotes the rule and links to it.
The short answer
Under the SNAP use conditions in 40 CFR Part 82, Subpart G, Appendix D, each covered refrigerant (several named retrofit refrigerants and all refrigerants listed in later Notices of Acceptability as CFC-12 substitutes in MVACs) may only be used with a set of fittings unique to it, and the fittings must be used on all containers, can taps, recovery, recycling and charging equipment and system service ports. As of June 3, 2022, the HFO-1234yf conditions in Appendix B require small-can fittings with a 0.5-inch diameter, 16 threads per inch and a left-hand thread. When a retrofit is performed, the person doing it must apply a label to the air conditioning system in the engine compartment, and no substitute refrigerant may be used to top off a system that uses another refrigerant.
Each part of this answer is quoted from the rule below.
Fitting and label conditions in the Appendix B listings
Appendix B's R-152a listing (new CFC-12 automobile MVAC equipment only) has a condition addressed to manufacturers: they must adhere to all the safety requirements listed in a Society of Automotive Engineers (SAE) standard.
“Manufacturers must adhere to all the safety requirements listed in the Society of”
The standards named for R-152a are SAE J639 (adopted 2011), including unique fittings and a flammable refrigerant warning label, and SAE J2773 (adopted February 2011).
“Automotive Engineers (SAE) Standard J639 (adopted 2011), including unique fittings and a flammable refrigerant warning label as well as SAE Standard J2773 (adopted February 2011)”
As of June 3, 2022, the HFO-1234yf conditions require HFO-1234yf MVAC systems to adhere to all of the safety requirements of SAE J639, including requirements for a flammable refrigerant warning label, a high-pressure compressor cutoff switch and pressure relief devices, and unique fittings.
“As of June 3, 2022: (1) HFO-1234yf MVAC systems must adhere to all of the safety requirements of SAE J639,4 7 including requirements for a flammable refrigerant warning label, high-pressure compressor cutoff switch and pressure relief devices, and unique fittings.”
Under the same HFO-1234yf conditions, fittings for connections with refrigerant containers for professional servicing must be consistent with SAE J2844.
“For connections with refrigerant containers for use in professional servicing, use fittings must be consistent with SAE J2844.6 7”
As of June 3, 2022, the HFO-1234yf conditions require fittings for connections with small refrigerant cans, for consumer or professional use, to have a 0.5-inch diameter, a thread pitch of 16 threads per inch and a left-hand thread direction, consistent with SAE J2844.
“For connections with small refrigerant cans for consumer or professional use, use fittings must have a diameter of 0.5 inches, a thread pitch of 16 thread per inch, and a left thread direction, consistent with SAE J2844”
In Appendix B's CO2 listing (CFC-12 motor vehicle air conditioning, new equipment only), a condition requires CO2 MVAC systems to adhere to the standard conditions identified in SAE J639 (2011 version), including a high pressure system warning label, a compressor cut-off switch and unique fittings.
“The use of CO2 in MVAC systems must adhere to the standard conditions identified in SAE Standard J639 (2011 version) including: Installation of a high pressure system warning label; Installation of a compressor cut-off switch; and Use of unique fittings with:”
For CO2, the unique fitting for the MVAC low-side has an outside diameter of 16.6 mm, +0/−0.2 mm (0.6535 inches, +0/−0.0078 inches).
“Outside diameter of 16.6 +0/−0.2 mm (0.6535 +0/−0.0078 inches) for the MVAC low-side;”
For CO2, the unique fitting for the MVAC high-side has an outside diameter of 18.1 mm, +0/−0.2 mm (0.7126 inches, +0/−0.0078 inches).
“+0/−0.2 mm (0.7126 +0/−0.0078 inches) for the MVAC high-side;”
CO2 refrigerant service containers use a fitting with an outside diameter of 20.955 mm, +0/−0.127 mm (0.825 inches, +0/−0.005 inches), and a right-hand thread direction.
“Outside diameter of 20.955 +0/−0.127 mm (0.825 +0/−0.005 inches) and righthand thread direction for CO2 refrigerant service containers.3”
The service container fitting requirement applies only to refrigerant service containers used while servicing the MVAC under the Subpart B servicing rules.
“3 The refrigerant service containers fitting requirement applies only to refrigerant service containers used during servicing of the MVAC, in accordance with the provisions established for MVAC servicing under 40 CFR part 82, subpart B.”
What makes a fitting unique (Appendix H)
Appendix H sets criteria for unique fittings for CFC-12 automobile and non-automobile motor vehicle air conditioners, retrofit and new.
“CFC-12 Automobile and Non-automobile Motor Vehicle Air Conditioners, Retrofit and New Criteria for Uniqueness of Fittings”
High-side screw-on fittings for each refrigerant must differ from the high-side screw-on fittings of all other refrigerants, including CFC-12, and from CFC-12's low-side screw-on fittings.
“(1) High-side screw-on fittings for each refrigerant must differ from high-side screw-on fittings for all other refrigerants, including CFC-12, and from low-side screw-on fittings for CFC-12;”
A refrigerant's high-side and low-side screw-on fittings must differ from each other, to protect against connecting a low-pressure system to a high-pressure one.
“(3) High-side screw-on fittings for a given refrigerant must differ from low-side screw-on fittings for that refrigerant, to protect against connecting a low-pressure system to a high-pressure one;”
For each type of container, each refrigerant's fitting must differ from the fitting used on that type of container for all other refrigerants, including CFC-12.
“(7) For each type of container, the fitting for each refrigerant must differ from the fitting for that type of container for all other refrigerants, including CFC-12.”
Under Appendix H's criteria for unique MVAC fittings, “differ” for screw-on fittings means the diameter differs by at least 1/16 inch or the thread direction is reversed. Changing only the thread pitch is not enough.
“(b) For screw-on fittings, “differ” means that either the diameter must differ by at least 1⁄16 inch or the thread direction must be reversed (i.e. right-handed vs. left-handed). Simply changing the thread pitch is not sufficient.”
Appendix H states one exception to the 1/16-inch difference requirement: the small can fittings for GHG-X4 and R-406A.
“(c) The sole exception to the 1⁄16 inch difference requirement is the difference between the small can fittings for GHG-X4 and R-406A.”
For quick-connect fittings, “differ” means a person using normal force and normal tools, including wrenches, must not be able to cross-connect the fittings.
“For quick-connect fittings, “differ” means that a person using normal force and normal tools (including wrenches) must not be able to cross-connect fittings.”
Retrofit fittings, labels and topping off (Appendix D)
Appendix D sets conditions for several named refrigerants used as CFC-12 substitutes in retrofitted MVACs, and for all refrigerants submitted for, and listed in, later Notices of Acceptability as CFC-12 substitutes in MVACs.
“In addition, the use of a) R-406A/“GHG”/“McCool”, “HCFC Blend Lambda”/“GHG-HP”, R-414A/“HCFC Blend Xi”/“GHG-X4/“Autofrost”/“Chill-It”, R-414B/“Hot Shot”/“Kar Kool”, and R-416A/“HCFC Blend Beta”/“FREEZE 12” as CFC-12 substitutes in retrofitted MVACs, and b) all refrigerants submitted for, and listed in, subsequent Notices of Acceptability as substitutes for CFC-12 in MVACs, must meet the following conditions.”
Under Appendix D, each refrigerant may only be used with its own unique set of fittings, designed by the manufacturer of the refrigerant.
“Each refrigerant may only be used with a set of fittings that is unique to that refrigerant. These fittings (male or female, as appropriate) must be designed by the manufacturer of the refrigerant.”
The fittings must be used on all containers of the refrigerant, on can taps, on recovery, recycling and charging equipment, and on all air conditioning system service ports.
“The fittings must be used on all containers of the refrigerant, on can taps, on recovery, recycling, and charging equipment, and on all air conditioning system service ports.”
Using the refrigerant with a fitting designed by anyone else, or using an adapter or deliberately modifying a fitting to use a different refrigerant, violates this use condition.
“Using a refrigerant with a fitting designed by anyone else, even if it is different from fittings used with other refrigerants, is a violation of this use condition. Using an adapter or deliberately modifying a fitting to use a different refrigerant is a violation of this use condition.”
When a retrofit is done, the person doing it must put a label on the air conditioning system in the engine compartment.
“The person conducting the retrofit must apply a label to the air conditioning system in the engine compartment that contains the following information:”
The label gives the name and address of the technician and the company that did the retrofit.
“The name and address of the technician and the company performing the retrofit.”
If the refrigerant is or contains an ozone-depleting substance, the label must carry the phrase “ozone depleter”.
“If the refrigerant is or contains an ozone-depleting substance, the phrase “ozone depleter”.”
If the refrigerant shows flammability limits measured under ASTM E681, the label must say “This refrigerant is FLAMMABLE. Take appropriate precautions.”
“If the refrigerant displays flammability limits as measured according to ASTM E681, the statement “This refrigerant is FLAMMABLE. Take appropriate precautions.””
The label's background color must be unique to the refrigerant.
“The background color must be unique to the refrigerant.”
No substitute refrigerant may be used to top off a system that uses another refrigerant. The original refrigerant must first be recovered under the section 609 rules.
“No substitute refrigerant may be used to “top-off” a system that uses another refrigerant. The original refrigerant must be recovered in accordance with regulations issued under section 609 of the CAA prior to charging with a substitute.”
Sources
- eCFR: 40 CFR Part 82, Subpart G, Appendix B (as of Nov 3, 2026)Checked November 5, 2026