Substance profile
Oxygen
Oxygen is a colorless gas and is odorless.
01 · Identification
What Oxygen is
Oxygen is a colorless gas and is odorless. It boils at -183 °C, melts at -218 °C.
Under the GHS it carries the signal word Danger.
02 · Identifiers
Oxygen identifiers and molecular data
Oxygen CAS number and EC number
Other names for Oxygen
- compressed oxygen
- liquid oxygen
- O2
- Lox
- Oxygen, (Liquid)
- Dioxygen
- Molecular Oxygen
- Oxygen Molecule
03 · GHS classification
Oxygen hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Oxygen pictograms and signal word
Oxygen hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Oxidising gases GHS chapter 2.4 | Category 1 | H270 | GHS03 |
Oxygen hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H270 | May cause or intensify fire; oxidiser. |
This page lists only the codes assigned to Oxygen. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
Safety Data Sheet
Getting an SDS for Oxygen
Our own Oxygen safety data sheet walks through all sixteen sections of the published data. What it is not is the document an inspector asks for: an SDS is issued for a product by its supplier, so the sheet covering the grade actually standing in your store exists only in that supplier’s version. Collecting those and keeping them current as suppliers revise them is a separate job.
04 · Precautionary statements
Oxygen precautionary statements
CLP Annex VI assigns 4 precautionary statements to Oxygen. They are grouped the way a label groups them: what to do before handling, what to do when something has already happened, how to store it and how to dispose of it.
Prevention
What to do before and during handling so the hazard never happens.
Response
What to do once exposure, spillage or fire has already happened.
Reading the notation. … is a blank the supplier fills in — not a truncated sentence.· [square brackets] mark a part printed only when it applies.
05 · Names in the regulation
Oxygen name in 23 EU languages
CLP Annex VI Part 3 is published in every language edition of the regulation, and the identification column is written out in each of them. Nothing below is translated by us: each line is the name as that edition prints it. Under Art. 18(2) the substance name from Annex VI is a lawful product identifier, so this is the wording to put on a label going to that market — and where the cell lists several designations, any one of them qualifies.
| Language | Name in CLP Annex VI Part 3 |
|---|---|
| Bulgarian български | кислород |
| Spanish español | Oxigeno |
| Czech čeština | kyslík |
| Danish dansk | ilt |
| German Deutsch | Sauerstoff |
| Estonian eesti | hapnik |
| Greek ελληνικά | οξυγόνo |
| English English | oxygen |
| French français | oxygène |
| Croatian hrvatski | kisik |
| Italian italiano | ossigeno |
| Latvian latviešu | skābeklis |
| Lithuanian lietuvių | deguonis |
| Hungarian magyar | oxigén |
| Maltese Malti | ossiġenu |
| Dutch Nederlands | zuurstof |
| Polish polski | tlen |
| Portuguese português | oxigénio |
| Romanian română | oxigen |
| Slovak slovenčina | kyslík |
| Slovenian slovenščina | kisik |
| Finnish suomi | happi |
| Swedish svenska | syre |
All 23 language editions of Annex VI carry this entry. Irish is the twenty-fourth official EU language and has no line here for a different reason: no consolidated CLP text has ever been published in Irish, so there is no Irish edition of Annex VI to quote a name from. Source: consolidated CLP, CELEX 02008R1272, language editions. © European Union, https://eur-lex.europa.eu — only the electronic Official Journal of the European Union is authentic.
06 · Label elements
Oxygen GHS label elements
Everything CLP Annex VI fixes for Oxygen, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Oxygen
- May cause or intensify fire; oxidiser.
- Keep away from clothing and other combustible materials.
- Keep valves and fittings free from oil and grease.
- In case of fire:
- Stop leak if safe to do so.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Oxygen in the GHS label constructor →
07 · Health hazards
Oxygen health hazards and exposure limits
Oxygen hazard summary
A powerful oxidizer and explosion hazard; Liquid may cause frostbite; Inhalation of 100% oxygen for 24 hours can cause pulmonary edema; Chronic exposure to high concentrations of oxygen can cause lung scarring; [CHEMINFO] Oxygen toxicity is observed in mechanically ventilated patients treated for hypoxic respiratory failure. Exposures to oxygen at FIO2 of 50 to 60% for more than 6 hours can cause lung injury including alveolar edema, formation of hyaline membranes, hypoxemia, and progressive fibrosis. [Cecil, p. 582]
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
08 · Physical and chemical properties
Oxygen properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
Oxygen boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | -182.96 °C (-297.3 °F) | HSDB | |
| -182.94 °C (-297.3 °F) | at 760 mmHg | CAMEO | |
| -183 °C (-297.4 °F) | ICSC |
Oxygen melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -218.4 °C (-361.1 °F) | HSDB | |
| -218.33 °C (-361 °F) | CAMEO |
Oxygen density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.0014 g/cm³ | at 0 °C | HSDB |
| 1.14 g/cm³ | at -183 °C | CAMEO |
Oxygen solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | 1 vol gas dissolves in 32 vol water at 20 °C, in 7 vol alcohol at 20 °C; sol in other organic liquids and usually to a greater extent than in water | at 20 °C | HSDB |
| Solubility in water, ml/100ml at 20 °C: 3.1 | at 20 °C | ICSC |
Oxygen vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 7.5006 mmHg | at -211.9 °C | HSDB |
| 38100 mmHg | at -118 °C | ICSC |
Oxygen lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | Not flammable in air. | Liquid oxygen | HSDB |
| The substance is a strong oxidant and reacts with combustible and reducing materials, causing fire and explosion hazard. | HSDB |
Oxygen vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 1.43 (air = 1) | HSDB | |
| 1.1 (air = 1) | ICSC |
Oxygen critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | -118.95 °C (-182.1 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Oxygen fire and explosion behaviour
These are descriptions rather than measured values, so they are kept out of the table above and quoted here with the source that reported them.
Oxygen fire potential
Gas: moderate fire risk as oxidizing agent.
Source: Hazardous Substances Data Bank (HSDB)
Fire and explosion
Strong oxidizer ... May initiate fire/explosion in combustible materials ... A leak of liquid oxygen onto combustible material represents a severe explosion potential ... /Oxygen, liquid/
Source: HSDB
10 · Handling and storage
Oxygen storage and handling
Oxygen reactive group
CAMEO Chemicals places Oxygen in the reactive group Oxidizing Agents, Strong. Compatibility with other chemicals is worked out from the group, not from the individual substance — which is why two substances you have never seen react can still be flagged as a pair that must be separated.
A reactive group is a CAMEO Chemicals (US NOAA) grouping, not a GHS hazard class: it has no code, no category and no legal force. It is what the storage compatibility matrix on this site computes from.
Oxygen safe storage
Fireproof. Separated from combustible substances and reducing agents. Cool.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Oxygen storage conditions
GAS & LIQ: GASEOUS OXYGEN IS STORED ... IN CYLINDERS AT A PRESSURE OF 150-160 ATM, & INSULATED TANKS ARE USED FOR LIQUID OXYGEN; SMALL QUANTITIES OF LIQUID OXYGEN (2-50 L) CAN BE STORED IN DEWAR FLASKS.
Source: Hazardous Substances Data Bank (HSDB)
Oxygen incompatible materials
Liq: Heat of water will vigorously vaporize liquid oxygen.
Source: Hazardous Substances Data Bank (HSDB)
Oxygen reactivity
Propellant; ignites upon contact with alcohols, alkali metals, amines, ammonia, beryllium alkyls, boranes, dicyanogen, hydrazines, hydrocarbons, hydrogen, nitroalkanes, powdered metals, silanes, or thiols [Bretherick 1979. p.174]. Heat of water will vigorously vaporize liquid oxygen, pressures may build to dangerous levels if this occurs in a closed container. Liquid oxygen gives a detonable mixture when combined with powdered aluminum [NFPA 491M. 1991].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Oxygen in the storage compatibility matrix →
11 · Transport
Oxygen UN number and transport classification
Transport classification is a separate system from the GHS classification above. It decides how a package is marked and how a load may be carried; it does not follow from the workplace label, and the workplace label does not follow from it. The entries below are linked by CAS number, never by name.
The same CAS number is shipped under more than one UN number. Which entry applies follows from the form and the concentration of the consignment — read the proper shipping name, not the CAS.
Oxygen under UN 1072 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| OXYGEN, COMPRESSED | 2 | 1O | — | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 2 is “Gases” (ADR 2.1.1.1).
United States · 49 CFR 172.101 Hazardous Materials Table
| Proper shipping name (column 2) | Class or division | PG | Labels (column 6) |
|---|---|---|---|
| Oxygen, compressed | 2.2 | — | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 2.2 is “Non-flammable compressed gas” (49 CFR 173.2).
Oxygen under UN 1073 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| OXYGEN, REFRIGERATED LIQUID | 2 | 3O | — | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 2 is “Gases” (ADR 2.1.1.1).
United States · 49 CFR 172.101 Hazardous Materials Table
| Proper shipping name (column 2) | Class or division | PG | Labels (column 6) |
|---|---|---|---|
| Oxygen, refrigerated liquid (cryogenic liquid) | 2.2 | — | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 2.2 is “Non-flammable compressed gas” (49 CFR 173.2).
12 · Questions
Oxygen — frequently asked questions
What is the CAS number of Oxygen?
The CAS number of Oxygen is 7782-44-7. Its EC number is 231-956-9.
What does a Oxygen label have to show?
Under CLP Annex VI the label for Oxygen carries the pictograms Flame over circle and Gas cylinder and the signal word is Danger.
Is Oxygen flammable?
CLP Annex VI assigns Oxygen no flammability hazard class. That is not a statement that it cannot burn: the harmonised list only records the hazards that were assessed for it.
Is Oxygen a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Oxygen. Annex VI is a list of agreed classifications, not a list of substances found safe, so this is an absence of a classification rather than a clean bill of health.
What is the boiling point of Oxygen?
The boiling point reported for Oxygen is -182.96 °C (-297.3 °F) (HSDB).
What is the melting point of Oxygen?
The melting point reported for Oxygen is -218.4 °C (-361.1 °F) (HSDB).
How should Oxygen be stored?
GAS & LIQ: GASEOUS OXYGEN IS STORED ... IN CYLINDERS AT A PRESSURE OF 150-160 ATM, & INSULATED TANKS ARE USED FOR LIQUID OXYGEN; SMALL QUANTITIES OF LIQUID OXYGEN (2-50 L) CAN BE STORED IN DEWAR FLASKS. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Oxygen
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