HVAC PT Data

Pressure-temperature charts, field calculators and refrigerant data for HVAC/R technicians

PT data: CoolProp 8.0 equations of state, US units

The A2L refrigerant transition

New residential and light commercial air conditioners and heat pumps made since January 1, 2025 use refrigerants with a GWP below 700, which in practice means the A2L (mildly flammable) refrigerants R-454B and R-32. This hub explains what the transition changes for a technician: the EPA rules and their dates, including the 2026 amendment that removed the installation deadline for R-410A systems built before 2025; the ASHRAE 34 safety classes; refrigerant detection systems; recovery machines and cylinders rated for flammable refrigerants; and the cylinder colors and markings in use now.

Each page cites the Federal Register, the eCFR, EPA, ASHRAE, ICC, AHRI or the manufacturer document it relies on and shows when it was last reviewed. Rules in this area have changed several times since 2023, so the date matters.

  • A2L refrigerants guide

    A2L is the ASHRAE 34 safety group for refrigerants with lower toxicity (A) and lower flammability (2L). R-32 and R-454B now go into new US residential AC and heat pumps; the service work is familiar, but tools, ignition control, leak detection, labels and charge limits all change.

  • Refrigerant flammability and safety classes

    Every refrigerant gets a two- or three-character ASHRAE 34 safety group: a letter for toxicity (A lower, B higher) and a number for flammability (1, 2L, 2, 3). R-410A and R-22 are A1, R-32 and R-454B are A2L, propane is A3 and ammonia is B2L.

  • Recovery machine and cylinder compatibility for A2L refrigerants

    Use a recovery machine certified for flammable refrigerants (EPA Appendix B4, which adds UL 1963 Supplement SB) and a recovery cylinder rated for the refrigerant on A2L systems. Carrier and Rheem require A2L-rated service equipment on R-454B units. Evacuation levels are the same as for any other high-pressure system.

  • AIM Act refrigerant rules for HVAC/R techs

    The AIM Act works through three EPA programs: a cap on HFC production and import (down to 60% of baseline for 2024–2028), Technology Transitions limits on the GWP of refrigerant in new equipment, and emissions rules for leak repair, reclaimed refrigerant and cylinders. None of them makes it illegal to service an existing R-410A or R-404A system.

  • R-410A phase-out

    R-410A is not banned. You can still buy it (with Section 608 certification), service and recharge existing systems, replace a failed condensing unit, and install new split systems built or imported before Jan 1, 2025. What ended is the manufacture of new R-410A systems for new installations, and supply is shrinking under the HFC production cap.

  • R-22 phase-out

    R-22 production and import in the US ended on Jan 1, 2020, and new R-22 equipment stopped in 2010. Servicing an existing R-22 system is still legal using recovered, recycled, reclaimed or pre-2020 stock. Recovered R-22 can only be sold to someone else after an EPA-certified reclaimer has reclaimed it.

  • Refrigerant detection systems and leak mitigation

    A refrigerant detection system is a sensor plus a control board that runs the indoor blower and locks out heating and cooling when it detects refrigerant, so a leak is mixed into the room air instead of pooling. Whether a system needs one depends on its charge and the room area it serves, under UL 60335-2-40 and the manufacturer's tables.

  • Refrigerant cylinder colors

    Since Jan 1, 2020, AHRI Guideline N has called for every new refrigerant container to be painted light green-gray (RAL 7044), whatever it holds. A red band on the shoulder or top marks a flammable refrigerant (class 2L, 2 or 3). The old per-refrigerant colors now appear only on labels, so identify the refrigerant from the label, never from the paint.

  • A2L charge limits and minimum room area

    An A2L system's total charge sets the smallest room it can serve. The manufacturer's table gives a minimum room area for each charge by release height, and a refrigerant detection system with circulation lowers that minimum. Use the table in the installation manual for the exact system, corrected for altitude.

  • Installing and servicing A2L systems

    A2L work uses the same brazing, pressure test and vacuum steps as R-410A, with extra rules on top: A2L-rated tools, no ignition sources near an open system, brazed or UL 207 joints only, an A2L-compatible leak check after charging, the total charge on the label and a working refrigerant detection system before you leave.

  • A2L building codes and state adoption

    The 2024 International Mechanical, Residential, Building and Fire Codes contain the A2L provisions, and the 2024 Uniform Mechanical Code references ASHRAE 15 and 15.2 and UL 60335-2-40. A code only applies where a state or city adopts it, or where a law allows A2Ls, so check the AHRI map for a dated snapshot and confirm with the local building official.

  • EPA refrigerant leak repair rules

    Owners must repair leaks once an appliance's leak rate passes 10% (comfort cooling), 20% (commercial refrigeration) or 30% (industrial process refrigeration). That applies to R-22 and other ODS systems with 50 lb or more under 40 CFR 82.157, and from January 1, 2026 to HFC systems with 15 lb or more under 40 CFR 84.106. Residential and light commercial AC and heat pumps are excluded from the HFC rule.