R-744 is in ASHRAE safety group A1: lower toxicity and no flame propagation. NIOSH sets its IDLH at 40,000 ppm and its 10-hour exposure limit at 5,000 ppm; OSHA's 8-hour limit is also 5,000 ppm.

Dry ice is solid CO₂. Below its triple-point pressure, 75.1 psia (60.4 psig), CO₂ has no liquid phase. At atmospheric pressure it sublimes — passes directly from solid to gas — at −109°F.

RefrigerantASHRAE R-744

R744 (CO2) PT Chart

Q: Why does R-744 operate transcritically?

Because its critical temperature is 87.8°F (31.0°C): when heat must be rejected above that temperature, CO₂ cannot condense.

Q: What's R-744's GWP?

1, by definition: GWP is measured relative to CO₂. Per kilogram released, R-410A (GWP 2,088) has 2,088 times its 100-year warming effect, and R-404A (GWP 3,922) 3,922 times.

Updated October 12, 2026

R-744 · CO2

A1 Lower toxicity, no flame propagationNatural

AHRI Guideline N-2017 lists no container for R-744^{[4], Table 1}.

CO2

Carbon dioxide (CO₂), the reference gas for global warming potential: EPA notes that CO₂ has a GWP of 1 by definition^[6]. Safety class A1^[1]. Its critical temperature is 87.8°F (31.0°C)^[2]; above it there is no saturation pressure, so the table ends at 87°F. EPA lists it as acceptable in new supermarket systems and new cold storage warehouses^[7]^[8].

R-744 saturation pressure is 220.8 PSIG at −15°F, 440.7 PSIG at 25°F, and 733.1 PSIG at 60°F. These are static saturation pressures. The full table below runs from −40°F to 87°F in 1°F steps. For running pressures by outdoor temperature, see R-744 operating pressures.

Checked against the NIST Chemistry WebBook, SRD 69 — Thermophysical Properties of Fluid Systems: Carbon dioxide, saturation properties^[13] at 15 points from −35°F to 35°F: largest difference under 0.001 psi.

Saturation @ 70°F

838.1 PSIG

GWP (100-yr)

1 US EPA Technology Transitions GWP reference table

Boiling point

—

Sourced facts

ASHRAE safety class: A1^[1]
Chemical formula: CO₂^[1]
GWP (100-yr): 1^[5]
ODP: 0^[7]
Critical temperature: 87.8°F (31.0°C)^[2]
Critical pressure: 1,055 psig (1,070 psia)^[2]
Triple-point pressure: 75.1 psia (518 kPa absolute; 60.4 psig)^[13]

R-744 PT calculator Operating pressures Superheat

R-744 PT chart — printable saturation table

Looking for the R-744 PT chart PDF for shop reference? The complete pressure-temperature saturation table is below: every 1° increment from −40°F to 150°F (or to the refrigerant's critical temperature). Use the Print / Save as PDF button in the table header to download a clean, table-only PDF (the rest of the page is hidden from the print output).

R-744 PT Chart — Pressure-Temperature Saturation Table

Computed with CoolProp 7.2.0 in 1°F steps · hvacptcharts.com

R-744 · 1° increments · °F / PSIG

Tinted rows: 32°F H₂O freeze

R-744 pressure-temperature saturation table in Fahrenheit and PSIG
Temp (°F)	Pressure (PSIG)
−40°F	131.0
−39°F	134.0
−38°F	137.0
−37°F	140.1
−36°F	143.3
−35°F	146.5
−34°F	149.7
−33°F	153.0
−32°F	156.3
−31°F	159.7
−30°F	163.1
−29°F	166.6
−28°F	170.1
−27°F	173.7
−26°F	177.3
−25°F	181.0
−24°F	184.8
−23°F	188.5
−22°F	192.4
−21°F	196.3
−20°F	200.2
−19°F	204.2
−18°F	208.3
−17°F	212.4
−16°F	216.5
−15°F	220.8
−14°F	225.0
−13°F	229.4
−12°F	233.8
−11°F	238.2
−10°F	242.7
−9°F	247.3
−8°F	251.9
−7°F	256.6
−6°F	261.3
−5°F	266.1
−4°F	271.0
−3°F	275.9
−2°F	280.9
−1°F	285.9
0°F	291.0
1°F	296.2
2°F	301.5
3°F	306.8
4°F	312.1
5°F	317.6
6°F	323.1
7°F	328.6
8°F	334.2
9°F	339.9
10°F	345.7
11°F	351.5
12°F	357.4
13°F	363.4
14°F	369.5
15°F	375.6
16°F	381.8
17°F	388.0
18°F	394.3
19°F	400.7
20°F	407.2
21°F	413.8
22°F	420.4
23°F	427.1
24°F	433.8
25°F	440.7
26°F	447.6
27°F	454.6
28°F	461.7
29°F	468.8
30°F	476.1
31°F	483.4
32°F H₂O freeze	490.8
33°F	498.3
34°F	505.8
35°F	513.4
36°F	521.2
37°F	529.0
38°F	536.9
39°F	544.8
40°F	552.9
41°F	561.0
42°F	569.3
43°F	577.6
44°F	586.0
45°F	594.5
46°F	603.1
47°F	611.7
48°F	620.5
49°F	629.3
50°F	638.3
51°F	647.3
52°F	656.5
53°F	665.7
54°F	675.0
55°F	684.4
56°F	694.0
57°F	703.6
58°F	713.3
59°F	723.1
60°F	733.1
61°F	743.1
62°F	753.2
63°F	763.4
64°F	773.8
65°F	784.2
66°F	794.8
67°F	805.5
68°F	816.2
69°F	827.1
70°F	838.1
71°F	849.2
72°F	860.5
73°F	871.8
74°F	883.3
75°F	894.9
76°F	906.7
77°F	918.5
78°F	930.5
79°F	942.6
80°F	954.9
81°F	967.3
82°F	979.8
83°F	992.5
84°F	1005.4
85°F	1018.4
86°F	1031.6
87°F	1044.9

R-744 pressure-temperature saturation table in Celsius and kPa
Temp (°C)	Pressure (kPa)
−40°C	903
−39°C	941
−38°C	979
−37°C	1,019
−36°C	1,059
−35°C	1,101
−34°C	1,144
−33°C	1,188
−32°C	1,233
−31°C	1,279
−30°C	1,326
−29°C	1,375
−28°C	1,425
−27°C	1,476
−26°C	1,528
−25°C	1,581
−24°C	1,636
−23°C	1,692
−22°C	1,750
−21°C	1,808
−20°C	1,868
−19°C	1,930
−18°C	1,993
−17°C	2,057
−16°C	2,122
−15°C	2,189
−14°C	2,258
−13°C	2,328
−12°C	2,400
−11°C	2,473
−10°C	2,547
−9°C	2,624
−8°C	2,701
−7°C	2,781
−6°C	2,862
−5°C	2,945
−4°C	3,029
−3°C	3,115
−2°C	3,203
−1°C	3,292
0°C H₂O freeze	3,384
1°C	3,477
2°C	3,572
3°C	3,669
4°C	3,768
5°C	3,868
6°C	3,971
7°C	4,075
8°C	4,182
9°C	4,290
10°C	4,401
11°C	4,514
12°C	4,628
13°C	4,745
14°C	4,864
15°C	4,986
16°C	5,109
17°C	5,235
18°C	5,364
19°C	5,495
20°C	5,628
21°C	5,763
22°C	5,902
23°C	6,043
24°C	6,186
25°C	6,333
26°C	6,482
27°C	6,635
28°C	6,790
29°C	6,950
30°C	7,112

CoolProp 7.2.0 · PSIG/kPa = gauge · PSIA = PSIG + 14.6959 · kPa(abs) = kPa(gauge) + 101.325

Full saturation values at 1° increments. Toggle between °F / PSIG and °C / kPa. Use Print / Save as PDF for laminated shop reference, or download the CSV / JSON below for use in other tools. R-744 PT chart data: CoolProp 7.2.0 (published Helmholtz equations of state / mixture models — see the source citations above).

Lower toxicity, no flame propagation

Lower toxicity (Occupational Exposure Limit ≥ 400 ppm). No flame propagation in air at standard atmospheric pressure and 60°C. R-134a, R-22, R-410A, R-404A, R-744 (CO2) are A1.

Flammability: None (no flame propagation)
Toxicity: Lower (OEL ≥ 400 ppm)

Classification per ANSI/ASHRAE Standard 34-2022^{[1], safety group definitions and refrigerant safety classifications}. See full reference.

Saturation pressure-temperature curve

Pressure

Temperature

Highlight at°F

Quick lookup — R-744

Temp:°F

838.1PSIG(5,779 kPa)

Range: −40 to 87°F Open full PT calculator →

Common service temperatures

32°F

491PSIG

Freezing

45°F

594PSIG

Heat-pump heat

70°F

838PSIG

Standard

75°F

895PSIG

Test ref

80°F

955PSIG

Warm

95°F

—

Summer peak

Saturation values from CoolProp 7.2.0^[2]. Operating pressure on a running system differs — see what R-744 operating pressures should be.

At a glance

Chemistry

CO2

Carbon dioxide

Lubricant compatibility

POEPAGMO

Critical point 87.8°F (31.0°C)^[2].

Common applications

New supermarket systems (EPA SNAP: acceptable)^[7]
New vehicle A/C (EPA: acceptable, subject to use conditions)^[10]

Properties

Critical point
87.8°F (31.0°C) at 1,055 PSIG
Molar mass
44.01 g/mol
ODP
0
GWP (100-yr)
1 US EPA Technology Transitions GWP reference table IPCC: AR4 1 · AR5 1 · AR6 1
New-equipment status (US)
Not an AIM Act regulated substance; 40 CFR 84.54 GWP limits don't apply.

What is R-744?

R-744 is carbon dioxide (CO₂)^[9], the reference gas for global warming potential (GWP 1 by definition)^[6], with an ODP of 0^[7].

Its critical temperature is low: 87.8°F (31.0°C)^[2]. Above that temperature there is no separate liquid and vapor, so there is no saturation pressure. A system that rejects heat above 87.8°F cannot condense the CO₂, so it runs transcritically^[2].

Where R-744 is used

New supermarket systems^[7]
New cold storage warehouses^[8]
New vehicle A/C, subject to EPA's use conditions^[10]

Regulatory & phase-down status

R-744 is not a regulated substance under the AIM Act, so the HFC phase-down and the 40 CFR 84.54 limits do not apply to it^{[11], 42 U.S.C. 7675(c)(1)}. Its GWP of 1 is far below the 150 limit that 40 CFR 84.54(a)(13) sets for new light-duty vehicle A/C^{[3], §84.54(a)(13)}.

EPA lists R-744 as acceptable in new supermarket systems^[7].

Service notes

Copeland approves different lubricants for R-744 depending on the compressor model, including POE and PAG lubricants^{[12], R-744 row}.

Its triple-point pressure is 75.1 psia (60.4 psig)^[13], so liquid CO₂ cannot exist at atmospheric pressure; at 1 atm it sublimes at −109°F^[14].

Operating cycle

Standard residential cycle (40°F evap / 110°F condenser) does not apply to R-744. Its critical temperature is 87.8°F — below the typical 110°F residential condensing point. Above the critical temperature no saturation state exists, so the high side would operate transcritically rather than condensing. A standard 4-stage cycle diagram is not meaningful here.
R-744 is used in: New supermarket systems (EPA SNAP: acceptable), New vehicle A/C (EPA: acceptable, subject to use conditions) — applications with much lower condensing temperatures than residential AC.

Phase-down timeline

R-744 is not an AIM Act regulated substance (not one of the 18 HFCs in 42 U.S.C. 7675(c), and not a blend containing one). The 40 CFR 84.54 GWP limits don't apply.

Global warming potential, in context

Industrial refrigeration & cascade systems

Retrofit and replacement paths

R-744 replaces

Reading the R-744 pressure-temperature chart

R-744's table is a single saturation curve from −40°F to 87°F; its critical temperature is 87.8°F^[2]. Above 87.8°F there is no saturation pressure, so the table stops at 87°F.

No saturation above 87.8°F means no condensation above 87.8°F

R-744 vs R-404A, R-22: saturation pressure

Saturation pressure (PSIG, gauge) for R-744 vs R-404A, R-22. Each column shows the percent difference from R-744. Source: CoolProp 7.2.0 dataset.
Temp	R-744	R-404A	R-22
0°F	291.0	33.7(−88%)	24.0(−92%)
40°F	552.9	86.9(−84%)	68.6(−88%)
70°F	838.1	149.3(−82%)	121.4(−86%)

Frequently asked

›What is the normal operating pressure of R-744?

Operating pressure depends on evaporator load and ambient; for suction and discharge by outdoor temperature, see What pressure should R-744 be?. The saturation pressures are in the PT table and the comparison table on this page.

›Why does R-744 operate transcritically?

Because its critical temperature is 87.8°F (31.0°C)^[2]: when heat must be rejected above that temperature, CO₂ cannot condense.

›What's R-744's GWP?

1, by definition: GWP is measured relative to CO₂^[6].

Per kilogram released, R-410A (GWP 2,088) has 2,088 times its 100-year warming effect, and R-404A (GWP 3,922) 3,922 times^[5].

›What lubricant does R-744 use?

Copeland approves different lubricants for R-744 depending on the compressor model, including POE and PAG lubricants^{[12], R-744 row}.

›Is R-744 safe?

R-744 is in ASHRAE safety group A1: lower toxicity and no flame propagation^[1]. NIOSH sets its IDLH at 40,000 ppm and its 10-hour exposure limit at 5,000 ppm; OSHA's 8-hour limit is also 5,000 ppm^[14].

›Why is R-744 used in supermarket refrigeration?

R-744 is not a regulated substance under the AIM Act, so 40 CFR 84.54 does not restrict it^{[11], 42 U.S.C. 7675(c)(1)}, while R-404A (GWP 3,922) has been unacceptable in new supermarket systems under SNAP since January 1, 2017^[7].

›What is dry ice?

Dry ice is solid CO₂^[14]. Below its triple-point pressure, 75.1 psia (60.4 psig)^[13], CO₂ has no liquid phase. At atmospheric pressure it sublimes — passes directly from solid to gas — at −109°F^[14].

Download this dataset

Full PT chart for R-744 · CC BY 4.0 · attribute the source

CSV JSON

Sources & citations

[1]
ANSI/ASHRAE Standard 34-2022, Designation and Safety Classification of Refrigerants (free read-only version). ASHRAE. 2022. https://www.ashrae.org/technical-resources/standards-and-guidelines/read-only-versions-of-ashrae-standards (accessed October 2, 2026)
[2]
CoolProp 7.2.0. CoolProp (I. H. Bell, J. Wronski, S. Quoilin, V. Lemort). https://coolprop.org/ (accessed October 2, 2026). Bell, I. H.; Wronski, J.; Quoilin, S.; Lemort, V. Pure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp. Ind. Eng. Chem. Res. 53, 2498–2508 (2014). https://doi.org/10.1021/ie4033999
[3]
40 CFR 84.54 — Restrictions on the use of hydrofluorocarbons. eCFR (Office of the Federal Register). up to date as of 9/29/2026. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-84/subpart-B/section-84.54 (accessed October 2, 2026)
[4]
2017 Guideline for Assignment of Refrigerant Container Colors (AHRI Guideline N-2017). AHRI. 2017. https://www.ahrinet.org/system/files/2023-06/AHRI_Guideline_N_2017.pdf (accessed October 2, 2026)
[5]
Technology Transitions GWP Reference Table. US EPA. updated April 2, 2026. https://www.epa.gov/hfcs/technology-transitions-gwp-reference-table (accessed October 2, 2026)
[6]
Understanding Global Warming Potentials. US EPA. last updated December 29, 2025. https://www.epa.gov/ghgemissions/understanding-global-warming-potentials (accessed October 2, 2026)
[7]
Substitutes in Typical Supermarket Systems. US EPA (SNAP). last updated March 20, 2026. https://www.epa.gov/snap/substitutes-typical-supermarket-systems (accessed October 5, 2026)
[8]
Substitutes in Cold Storage Warehouses. US EPA (SNAP). last updated March 19, 2026. https://www.epa.gov/snap/substitutes-cold-storage-warehouses (accessed October 5, 2026)
[9]
ASHRAE Refrigerant Designations. ASHRAE. web page, updated May 25, 2021. https://www.ashrae.org/technical-resources/standards-and-guidelines/ashrae-refrigerant-designations (accessed October 2, 2026)
[10]
Acceptable Refrigerants and their Impacts (motor vehicle A/C). US EPA. last updated April 28, 2026. https://www.epa.gov/mvac/acceptable-refrigerants-and-their-impacts (accessed October 2, 2026)
[11]
42 U.S.C. 7675 — American Innovation and Manufacturing Act. US Code (via Cornell LII). current. https://www.law.cornell.edu/uscode/text/42/7675 (accessed October 2, 2026)
[12]
Refrigerants and lubricants approved for use in Copeland compressors. Copeland. Form 93-11 R41 (5/24). https://webapps.copeland.com/online-product-information/Publication/LaunchPDF?Index=AEB&PDF=93-11 (accessed October 2, 2026)
[13]
NIST Chemistry WebBook (SRD 69) saturation data for carbon dioxide (R-744). NIST. https://webbook.nist.gov/cgi/fluid.cgi?TLow=-40&THigh=80&TInc=10&Digits=6&ID=C124389&Action=Load&Type=SatT&TUnit=F&PUnit=psia&DUnit=lbm%2Fft3&HUnit=Btu%2Flbm&WUnit=ft%2Fs&VisUnit=uPa*s&STUnit=lb%2Fin&RefState=DEF (accessed October 5, 2026)
[14]
NIOSH Pocket Guide to Chemical Hazards — Carbon dioxide. CDC/NIOSH. web page. https://www.cdc.gov/niosh/npg/npgd0103.html (accessed October 5, 2026)