R-125 PT Chart and Refrigerant Profile

Where you will find R-125

R-125 (HFC-125, pentafluoroethane) is rarely the refrigerant on a nameplate. You meet it inside blends. It is the nonflammable, higher-pressure component in most HFC mixes:

It also carries much of each blend’s GWP. At 3,500 it is well above R-32 (675) and R-134a (1,430); in R-410A, the 50% R-125 share accounts for 1,750 of the 2,088 total. The GWP chart shows the effect across blends.

Outside blends, pure HFC-125 is best known as a fire suppression agent. EPA SNAP has listed HFC-125 (FE-25, MH125) as an acceptable total-flooding agent since March 18 1994, for use per NFPA 2001, and NAF S-125 (HFC-125 with 0.1% d-limonene) since Aug 21 2003. A-Gas supplies it for data centers, telecom sites, aviation, maritime, museums and power plants. Those are fire-protection systems, not refrigeration circuits.

Handling and charging pure R-125

As a single-component refrigerant, R-125 has no glide and does not fractionate, so it can be moved as vapor or liquid. One pressure applies at each temperature: 97.0 psig at 40°F and 261.4 psig at 100°F on this chart.

We found no manufacturer charging guidance for systems running on neat R-125, and it does not appear on EPA’s refrigeration end-use pages we checked. Use the PT chart above as a reference, for example to identify a cylinder by its standing pressure, not as a charging target.

Do not try to “correct” a leaked blend by adding pure R-125. Blend composition is held to tight tolerances under AHRI Standard 700; R-422A, for example, must contain 84.1–86.1% R-125. A gauge reading cannot confirm the mix, so a fractionated or contaminated charge gets recovered and replaced with the blend itself.

Oil and compatibility

BITZER lists POE, PVE and AB for R-125. In practice the oil follows the blend and the compressor, not the component: R-404A and R-410A systems run POE, while some R-22 retrofit blends with R-125 also run with mineral oil or AB. Check the compressor maker’s approval for the specific blend. See the refrigerant oil guide.

Safety, handling and recovery

R-125 is A1: lower toxicity, no flame propagation. It is a Section 608 high-pressure refrigerant. Its liquid saturation pressure at 104°F is 291.3 psia (276.6 psig), inside the 170–355 psia band, and its critical temperature is above 104°F, so it is not very-high-pressure.

Venting is prohibited. Type II or Universal certification covers refrigeration appliances that use it, and sales of HFC refrigerants have been limited to certified technicians since Jan 1 2018. Recover high-pressure appliances made after Nov 15 1993 to 0 in Hg under 200 lb of charge and 10 in Hg at 200 lb or more (refrigerant recovery).

The legacy label color for R-125 in AHRI Guideline N-2017 Table 1 is medium brown (tan), PMS 465. R-407C is also medium brown, so read the label, not the paint. New cylinders since Jan 1 2020 are light green-gray (RAL 7044) (cylinder colors).

Status

HFC-125 is a regulated substance under the AIM Act with an exchange value of 3,500 (40 CFR 84 Appendix A). Production and import allowances are 60% of baseline in 2024–2028, 30% in 2029–2033, 20% in 2034–2035 and 15% from 2036. The phasedown counts the R-125 in every blend above, so it bears on the supply of R-404A, R-507A, R-410A and the R-22 drop-ins.

As a neat refrigerant its GWP is above every Technology Transitions limit for new systems. Servicing existing equipment with R-125 blends remains legal. For blends that cut R-125 content, see R-404A replacement and R-410A replacement.