Substance profile
Carbon Monoxide
Carbon Monoxide is a colorless gas and is odorless.
01 · Identification
What Carbon Monoxide is
Carbon Monoxide is a colorless gas and is odorless. It boils at -191 °C, melts at -205 °C, is soluble in water.
Under the GHS it carries the signal word Danger. It is classed as teratogens.
02 · Identifiers
Carbon Monoxide identifiers and molecular data
Carbon Monoxide CAS number and EC number
Carbon Monoxide molecular formula and molecular weight
03 · GHS classification
Carbon Monoxide hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Carbon Monoxide pictograms and signal word
Carbon Monoxide hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Flammable gases GHS chapter 2.2 | Category 1A | H220 | GHS02 |
| Acute toxicity - inhalation GHS chapter 3.1 | Category 3 | H331 | GHS06 |
| Specific target organ toxicity - repeated exposure GHS chapter 3.9 | Category 1 | H372 | GHS08 |
Carbon Monoxide hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H220 | Extremely flammable gas. |
| H360D | May damage the unborn child. |
| H331 | Toxic if inhaled. |
| H372 | Causes damage to organs <or state all organs affected, if known> through prolonged or repeated exposure <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
This page lists only the codes assigned to Carbon Monoxide. 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 Carbon Monoxide
A Safety Data Sheet is written for a product, not for a substance: the supplier of the grade you actually buy issues it, so two suppliers of Carbon Monoxide issue two different sheets. That is why there is no single authoritative SDS for a substance to download — what there is, is the job of collecting the sheets for the products you hold and keeping them current as suppliers revise them.
04 · Precautionary statements
Carbon Monoxide precautionary statements
CLP Annex VI assigns 9 precautionary statements to Carbon Monoxide. 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
Carbon Monoxide 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 | въглероден моноксид |
| Spanish español | Monóxido de carbono |
| Czech čeština | oxid uhelnatý |
| Danish dansk | carbonmonoxid |
| German Deutsch | Kohlenstoffmonoxid KohlenmonoxidKohlenoxid |
| Estonian eesti | süsinikmonooksiid |
| Greek ελληνικά | μονοξείδιο του άνθρακα |
| English English | carbon monoxide |
| French français | monoxyde de carbone |
| Croatian hrvatski | ugljikov monoksid |
| Italian italiano | monossido di carbonio |
| Latvian latviešu | oglekļa monoksīds |
| Lithuanian lietuvių | anglies monoksidas |
| Hungarian magyar | szén-monoxid |
| Maltese Malti | monossidu tal-karbonju |
| Dutch Nederlands | koolstofmonoxide |
| Polish polski | tlenek węgla |
| Portuguese português | monóxido de carbono |
| Romanian română | monoxid de carbon |
| Slovak slovenčina | oxid uhoľnatý |
| Slovenian slovenščina | ogljikov monoksid |
| Finnish suomi | hiilimonoksidi |
| Swedish svenska | kolmonoxid |
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
Carbon Monoxide GHS label elements
Everything CLP Annex VI fixes for Carbon Monoxide, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Carbon Monoxide
- Extremely flammable gas.
- May damage the unborn child.
- Toxic if inhaled.
- Causes damage to organs <or state all organs affected, if known> through prolonged or repeated exposure <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
- Keep container tightly closed.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Do not eat, drink or smoke when using this product.
- Use only outdoors or in a well-ventilated area.
- IF INHALED:
- Immediately call a POISON CENTER/doctor/…
- Get medical advice/attention if you feel unwell.
- Store in a well-ventilated place.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Carbon Monoxide in the GHS label constructor →
07 · Health hazards
Carbon Monoxide health hazards and exposure limits
Carbon Monoxide hazard summary
Carbon monoxide is a colorless, nonirritating, odorless, and tasteless gas. It is found in both outdoor and indoor air.
Source: Agency for Toxic Substances and Disease Registry (ATSDR)
Carbon Monoxide occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 50.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 50 ppm (55 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 50 ppm (55 mg/m3) See Appendix G | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | 35 ppm (40 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| REL | 200 ppm (229 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| REL | TWA 35 ppm (40 mg/m3) C 200 ppm (229 mg/m3) | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 1200 ppm (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 1200.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 1200 ppm | Hazardous Substances Data Bank (HSDB) |
These are United States values. The European Union sets its own indicative and binding limits, and the figure that applies at a given workplace is the one in the local regulation — not the one shown here.
08 · Physical and chemical properties
Carbon Monoxide 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.
Carbon Monoxide boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | -191.5 °C (-312.7 °F) | HSDB | |
| -191.67 °C (-313 °F) | NIOSH | ||
| -191.5 °C (-312.7 °F) | at 760 mmHg | CAMEO |
Carbon Monoxide melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -205.02 °C (-337 °F) | HSDB | |
| -205 °C (-337 °F) | NIOSH | ||
| -198.89 °C (-326 °F) | CAMEO |
Carbon Monoxide density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.301 g/cm³ | HSDB | |
| 0.7886 g/cm³ | HSDB | ||
| 0.929 g/cm³ | HSDB |
Carbon Monoxide solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Soluble in benzene | HSDB | |
| 2% | NIOSH |
Carbon Monoxide vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 155000000 mmHg | at 25 °C | HSDB |
| 26600 mmHg | above this value | NIOSH |
Carbon Monoxide flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | NA (Gas) | NIOSH | |
| Flammable gas | ICSC |
Carbon Monoxide autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 700 °C (1292 °F) | HSDB | |
| 608.89 °C (1128 °F) | CAMEO | ||
| 605 °C (1121 °F) | ICSC |
Carbon Monoxide lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | 12 % by volume | HSDB | |
| 12.5 % by volume | HSDB |
Carbon Monoxide upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | 75 % by volume | HSDB | |
| 74.2 % by volume | HSDB | ||
| 74 % by volume | NIOSH |
Carbon Monoxide vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 0.968 (air = 1) | HSDB | |
| 0.97 (air = 1) | CAMEO |
Carbon Monoxide critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | -139 °C (-218.2 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Carbon Monoxide 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.
Carbon Monoxide fire potential
Flammable gas.
Source: Hazardous Substances Data Bank (HSDB)
Solubility
Freely absorbed by a concentrated solution of cuprous chloride in hydrochloric acid or ammonium hydroxide; Appreciably soluble in some organic solvents, such as ethyl acetate, chloroform, acetic acid; solubility in methanol and ethanol about 7 times as great as in water.
Source: HSDB
10 · Handling and storage
Carbon Monoxide storage and handling
Carbon Monoxide safe storage
Fireproof. Cool. Keep in a well-ventilated room.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Carbon Monoxide storage conditions
Store in a cool, dry, well-ventilated location.
Source: Hazardous Substances Data Bank (HSDB)
Carbon Monoxide incompatible materials
May react vigorously with oxygen, acetylene, chlorine, fluorine, nitrous oxide.
Source: Hazardous Substances Data Bank (HSDB)
Planning storage for a mix of chemicals? Check Carbon Monoxide in the storage compatibility matrix →
11 · Transport
Carbon Monoxide 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.
Carbon Monoxide under UN 1016 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| CARBON MONOXIDE, COMPRESSED | 2 | 1TF | — | |
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) |
|---|---|---|---|
| Carbon monoxide, compressed | 2.3 | — | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 2.3 is “Poisonous gas” (49 CFR 173.2).
12 · Questions
Carbon Monoxide — frequently asked questions
What is the CAS number of Carbon Monoxide?
The CAS number of Carbon Monoxide is 630-08-0. Its EC number is 211-128-3.
What does a Carbon Monoxide label have to show?
Under CLP Annex VI the label for Carbon Monoxide carries the pictograms Flame, Gas cylinder, Skull and crossbones and Health hazard and the signal word is Danger.
Is Carbon Monoxide flammable?
Yes. CLP Annex VI assigns Carbon Monoxide H220 — extremely flammable gas. The flash point reported for it is NA (Gas) (NIOSH).
Is Carbon Monoxide a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Carbon Monoxide. 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 exposure limit for Carbon Monoxide?
The US occupational exposure limit reported for Carbon Monoxide is 50.0 [ppm] (Haz-Map, Information on Hazardous Chemicals and Occupational Diseases). Limits differ by country: the EU sets its own indicative and binding values, and the figure that applies at a given workplace is the one in the local regulation.
What is the boiling point of Carbon Monoxide?
The boiling point reported for Carbon Monoxide is -191.5 °C (-312.7 °F) (HSDB).
What is the melting point of Carbon Monoxide?
The melting point reported for Carbon Monoxide is -205.02 °C (-337 °F) (HSDB).
How should Carbon Monoxide be stored?
CLP Annex VI assigns Carbon Monoxide the storage statement P403. Store in a cool, dry, well-ventilated location. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Carbon Monoxide
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