R-454B and R-32 Change Cylinders, Leak Detectors and Ignition Checks on the Job

"Working with R-454B is not a giant shift from working with R-410A," a February 2024 Johnson Controls service deck by Mark Petty says. The shift that does arrive falls on cylinder threads, leak detectors, the check for ignition sources and a charge limit tied to the room.

ASHRAE 34, ASHRAE 15, ASHRAE 15.2 and UL 60335-2-40 are sold documents, and their full text was not reviewed for this article. It rests on EPA's Federal Register rules, ASHRAE's free addenda and manufacturer literature, and cites clause numbers only where those addenda print them. On any job, the unit's installation manual and the locally adopted code govern.

Two Refrigerants in One Safety Group

EPA's SNAP Rule 23 (86 FR 24444, May 6, 2021) cites ASHRAE 34-2019 for the "A" lower-toxicity class, and the Johnson Controls deck explains the rest: 2 for flammable and L for a burning velocity under 10 centimeters per second. R-32 is difluoromethane alone. R-454B is 68.9 percent R-32 and 31.1 percent R-1234yf, and the deck says that as a 400-series blend it must leave the cylinder as a liquid. EPA listed both for new equipment only, finding that equipment built for nonflammable refrigerant may contain ignition sources. Existing tubing can be reused if inspected and found suitable.

Cylinders, Recovery and the Truck

Lennox says service valves on its R-454B equipment stay right-hand threaded while A2L cylinders are left-hand, so hoses need an adapter at the tank. Johnson Controls describes a red band or a red-painted top.

Rheem's contractor sheet says recovery procedures stay the same, and Lennox says recovery machines and vacuum pumps must be certified for A2Ls. Daikin's service manual for its 7.5- and 10-ton R-32 commercial splits calls for a cylinder labeled for R-32, with working relief and shutoff valves, evacuated and if possible cooled beforehand, on a calibrated scale and filled to no more than 80 percent, with the system electrically isolated. EPA's 2021 rule points to the Clean Air Act section 608(c)(2) ban on knowingly venting substitutes. Trane and Lennox say existing Section 608 certification carries over.

One published transport limit does not match the federal text. Trane's April 2025 contractor guide says technicians are limited to 225 pounds of A2L refrigerant in service vehicles. DOT's materials-of-trade exception, 49 CFR 173.6, allows a Division 2.1 or 2.2 material in a cylinder up to 220 pounds gross weight, caps all materials of trade on a vehicle at 440 pounds aggregate gross weight and requires that the driver be informed of the material. Lennox and Johnson Controls both set a 125-degree F storage ceiling, and Trane says indoor quantity limits vary with the facility and its sprinklers.

A Handheld Detector and a Factory Detection System

HTPG's November 2025 A2L manual and Daikin's manual both prohibit ignition sources during a leak search, including a halide torch. HTPG says electronic detectors must suit the refrigerant, be calibrated in a refrigerant-free area and be set at no more than 25 percent of the lower flammability limit (LFL). It accepts bubble and fluorescent methods but warns against detergents containing chlorine.

The refrigerant detection system (RDS) is built into the equipment. In the Johnson Controls sequence, the sensor reports a leak, the control board interrupts the heating or cooling call and the blower runs to dilute the refrigerant. On the Daikin line, sensors act above 25 percent LFL and mitigation holds for five minutes after readings fall. Daikin says a zone controller must be powered through its accessory board so dampers open during mitigation, and that the A2L sensor comes out before coil cleaning and goes back before restart.

Ignition Sources, in the Standard and on the Checklist

Section 8.11.1 of ASHRAE 15-2022, as printed in Addendum o, bars flame-producing devices and hot surfaces over 1,290 degrees F from an A2L or B2L machinery room, apart from those used for maintenance or repair or installed under Section 8.9.9. In the field, Daikin requires a survey for ignition risks, "No Smoking" signs and continuity of earth bonding, with a dry powder or CO2 extinguisher next to the charging area for hot work. Johnson Controls warns against discharging capacitors with a spark near the system. Rheem says to cut the circuit open instead of using a torch and to flow nitrogen while brazing.

Brazing preparation varies by manufacturer. Johnson Controls calls for removing the refrigerant, evacuating and running dry nitrogen, while HTPG's manual labels evacuation and inert-gas purging optional for A2Ls once refrigerant is out. EPA's required label on fixed equipment warns against auxiliary devices in ductwork that may be ignition sources unless listed for the appliance, and Daikin says electronic air cleaners must run through its accessory board or be disabled or removed.

Where the 4-Pound Line Comes From

EPA's use conditions require equipment to meet UL 60335-2-40, 3rd edition, dated Nov. 1, 2019, which EPA says covers charge sizes, ventilation and usage space. EPA also requires minimum room area marked near the indoor unit's nameplate and red markings (PMS 185 or RAL 3020) extending at least 1 inch at service ports and field connections.

Published thresholds sit close together without matching. Trane's guide says UL 60335-2-40 requires sensors on ducted systems above 3.91 pounds of A2L charge. Lennox says products above 4 pounds carry added requirements. Trane's Steve Kujak wrote in Contracting Business on Sept. 10, 2025, that under ASHRAE 15 a charge under 4 pounds needs no detection or mitigation. He describes an alarm within 30 seconds and mitigation beginning within 15 seconds of the alarm for high-probability systems above that level, and a maximum charge from the effective dispersal volume calculation, based on the circuit with the largest charge.

Machinery rooms follow separate rules. Addendum o sets ventilation triggers by Table 8-1, which it does not reprint, and Addendum w adds a path using a Class I, Division 2 designation with Section 8.9.6 ventilation and refrigerant detection. New York City's 1 RCNY 7011-01 requires its emergency alarm within 30 seconds of exposure above 25 percent LFL or the detector's upper limit, whichever is lower. Trane points to AHRI's A2L building code map for state adoption.

Sources

1. EPA, SNAP Rule 23 final rule, 86 FR 24444, May 6, 2021. govinfo.gov
2. EPA, Fact Sheet, Proposed SNAP Rule 27, October 2025. epa.gov
3. EPA, SNAP Rule 27 supplemental notice, 91 FR 17176, April 6, 2026. federalregister.gov
4. EPA, "Phasedown of Hydrofluorocarbons: Reconsideration of Certain Regulatory Requirements," final rule, 91 FR 31284, May 26, 2026. federalregister.gov
5. ASHRAE, Addendum f to ANSI/ASHRAE Standard 15.2-2022, approved July 31, 2024. ashrae.org
6. ASHRAE, Addendum o to ANSI/ASHRAE Standard 15-2022, approved July 31, 2024. ashrae.org
7. ASHRAE, Addendum w to ANSI/ASHRAE Standard 15-2022, August 2024. ashrae.org
8. Legal Information Institute, 49 CFR 173.6, Materials of trade exceptions. law.cornell.edu
9. New York City Department of Buildings, 1 RCNY 7011-01, A2L Refrigerating Systems. nyc.gov
10. Mark Petty, Johnson Controls, "Ducted System's A2L Best Practices: Installation and Service," February 2024. us-ac.com
11. Rheem, "A2L Steps to Success." centuryac.com
12. Lennox, "Introducing Lennox' 2025 Compliant Refrigerant." lennoxpros.com
13. Trane, "Getting Ready for A2L Refrigerants," REFR-SLB007-EN, April 11, 2025. tranetechnologies.com
14. Daikin Comfort, Service and Troubleshooting, DC6/DH6 R-32 commercial split systems, RSD6512301. daikincomfort.com
15. HTPG, A2L Equipment Installation and Operation Manual, IOM-A2L-SYS-1125. htpg.com
16. Steve Kujak, Contracting Business, "ASHRAE Standard 15 Offers Contractors Guidance and Flexibility When Working with A2L Refrigerants," Sept. 10, 2025. contractingbusiness.com