Substance profile
Methyl Isocyanate
Methyl Isocyanate is a colorless liquid with a sharp, unpleasant odor.
01 · Identification
What Methyl Isocyanate is
Methyl Isocyanate is a colorless liquid with a sharp, unpleasant odor. Its molecular formula is C2H3NO and its molecular weight is 57.05 g/mol. It boils at 39.5 °C, melts at -45 °C.
Under the GHS it carries the signal word Danger. It is classed as hazardous Air Pollutants (HAPs).
02 · Identifiers
Methyl Isocyanate identifiers and molecular data
Methyl Isocyanate CAS number and EC number
Methyl Isocyanate molecular formula and molecular weight
03 · GHS classification
Methyl Isocyanate hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Methyl Isocyanate pictograms and signal word
Methyl Isocyanate hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Flammable liquids GHS chapter 2.6 | Category 2 | H225 | GHS02 |
| Acute toxicity - oral GHS chapter 3.1 | Category 3 | H301 | GHS06 |
| Acute toxicity - dermal GHS chapter 3.1 | Category 3 | H311 | GHS06 |
| Acute toxicity - inhalation GHS chapter 3.1 | Category 1 or 2 | H330 | GHS06 |
| Skin corrosion/irritation GHS chapter 3.2 | Category 2 | H315 | GHS07 |
| Serious eye damage/eye irritation GHS chapter 3.3 | Category 1 | H318 | GHS05 |
| Respiratory sensitisation GHS chapter 3.4 | Category 1 or 1A or 1B | H334 | GHS08 |
| Skin sensitisation GHS chapter 3.4 | Category 1 or 1A or 1B | H317 | GHS07 |
| Specific target organ toxicity - single exposure GHS chapter 3.8 | Category 3 | H335 | GHS07 |
Where two values are shown with “or”, the hazard statement is shared by more than one category or by more than one class, and the code alone does not say which. H272, for example, belongs to oxidising liquids and to oxidising solids — the physical state decides. The binding answer for a specific entry is in the CLP Annex VI table itself.
Methyl Isocyanate hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H225 | Highly flammable liquid and vapour. |
| H361d | Suspected of damaging the unborn child. |
| H330 | Fatal if inhaled. |
| H311 | Toxic in contact with skin. |
| H301 | Toxic if swallowed. |
| H335 | May cause respiratory irritation. |
| H315 | Causes skin irritation. |
| H318 | Causes serious eye damage. |
| H334 | May cause allergy or asthma symptoms or breathing difficulties if inhaled. |
| H317 | May cause an allergic skin reaction. |
This page lists only the codes assigned to Methyl Isocyanate. 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 Methyl Isocyanate
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 Methyl Isocyanate 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
Methyl Isocyanate precautionary statements
CLP Annex VI assigns 23 precautionary statements to Methyl Isocyanate. 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
Methyl Isocyanate 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 | метилов изоцианат |
| Spanish español | Isocianato de metilo |
| Czech čeština | methyl-isokyanát |
| Danish dansk | methylisocyanat |
| German Deutsch | Methylisocyanat |
| Estonian eesti | metüülisotsüanaat |
| Greek ελληνικά | ισοκυανικό μεθύλιο ισοκυανικός μεθυλεστέρας |
| English English | methyl isocyanate |
| French français | isocyanate de méthyle |
| Croatian hrvatski | metil izocijanat |
| Italian italiano | isocianato di metile metilisocianato |
| Latvian latviešu | metilizocianāts |
| Lithuanian lietuvių | metilizocianatas |
| Hungarian magyar | metil-izocianát |
| Maltese Malti | isoċjanat tal-metil |
| Dutch Nederlands | methylisocyanaat |
| Polish polski | izocyjanian metylu |
| Portuguese português | isocianato de metilo |
| Romanian română | izocianant de metil |
| Slovak slovenčina | metylizokyanát |
| Slovenian slovenščina | metil izocianat |
| Finnish suomi | metyyli-isosyanaatti |
| Swedish svenska | metylisocyanat |
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
Methyl Isocyanate GHS label elements
Everything CLP Annex VI fixes for Methyl Isocyanate, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Methyl Isocyanate
- Highly flammable liquid and vapour.
- Suspected of damaging the unborn child.
- Fatal if inhaled.
- Toxic in contact with skin.
- Toxic if swallowed.
- May cause respiratory irritation.
- Causes skin irritation.
- Causes serious eye damage.
- May cause allergy or asthma symptoms or breathing difficulties if inhaled.
- May cause an allergic skin reaction.
- Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
- Keep container tightly closed.
- Use explosion-proof [electrical/ventilating/lighting/…] equipment.
- Use only non-sparking tools.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Avoid breathing dust/fume/gas/mist/vapours/spray.
- Wash … thoroughly after handling.
- Do not eat, drink or smoke when using this product.
- Use only outdoors or in a well-ventilated area.
- Contaminated work clothing should not be allowed out of the workplace.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- IF ON SKIN:
- IF INHALED:
- IF IN EYES:
- Immediately call a POISON CENTER/doctor/…
- Get medical advice/attention.
- Rinse mouth.
- If skin irritation occurs:
- If skin irritation or rash occurs:
- Remove contact lenses, if present and easy to do. Continue rinsing.
- Wash with plenty of water/…
- Store in a well-ventilated place.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Methyl Isocyanate in the GHS label constructor →
07 · Health hazards
Methyl Isocyanate health hazards and exposure limits
Methyl Isocyanate hazard summary
Methyl isocyanate is a colorless highly flammable liquid that evaporates quickly when exposed to the air. It has a sharp, strong odor. Methyl isocyanate is used in the production of pesticides, polyurethane foam, and plastics.
Source: Agency for Toxic Substances and Disease Registry (ATSDR)
Methyl Isocyanate occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 0.02 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 0.02 ppm (0.05 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 0.02 ppm (0.05 mg/m³) [skin] | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | 0.02 ppm (0.05 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| REL | TWA 0.02 ppm (0.05 mg/m³) [skin] | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 0.12 ppm (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 0.12 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 3 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
Methyl Isocyanate 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.
Methyl Isocyanate boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 39.5 °C (103.1 °F) | HSDB | |
| 38.89 °C (102 °F) | at 760 mmHg | CAMEO | |
| 39 °C (102.2 °F) | ICSC |
Methyl Isocyanate melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -45 °C (-49 °F) | HSDB | |
| -80 °C (-112 °F) | CAMEO |
Methyl Isocyanate density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.96 g/cm³ | NIOSH | |
| 0.9599 g/cm³ | at 20 °C | CAMEO | |
| 0.923 g/cm³ | at 27 °C | HSDB |
Methyl Isocyanate solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Solubility in water at 20 °C: reaction | at 20 °C | ICSC |
| 10 G/100 ML WATER AT 15 °C | at 15 °C | HSDB | |
| Decomposes (NTP, 1992) | decomposes | CAMEO |
Methyl Isocyanate vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 348 mmHg | NIOSH | |
| 348 mmHg | at 20 °C | HSDB |
Methyl Isocyanate flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | -7.22 °C (19 °F) | HSDB |
Methyl Isocyanate autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 534.44 °C (994 °F) | HSDB | |
| 535 °C (995 °F) | CAMEO |
Methyl Isocyanate lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | 5.3 % by volume | HSDB |
Methyl Isocyanate upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | 26 % by volume | HSDB |
Methyl Isocyanate vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 1.42 (air = 1) | HSDB | |
| 2 (air = 1) | ICSC | ||
| About twice as heavy as air (EPA, 1998) (Relative to Air) | CAMEO |
Methyl Isocyanate odor threshold
| Property | Value | Conditions | Source |
|---|---|---|---|
| Odor threshold | The odor warning when the exposure limit value is exceeded is insufficient. | HSDB | |
| Air: 2.1 uL/L; odor safety class E. E= less than 10% of attentive persons can detect the TLV. | HSDB | ||
| Odor Threshold Low: 2.1 [ppm] | Haz-Map |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Methyl Isocyanate 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.
Methyl Isocyanate fire potential
... Flammable liquid ...
Source: Hazardous Substances Data Bank (HSDB)
Corrosivity
Methyl isocyanate diffuses through polyethylene and attacks most elastomers (fluorocarbon resins are resistant). It is dangerous to use materials other than stainless steel, nickel, or glass/ceramic in contact with methyl isocyanate. In particular, do not use iron, steel, zinc, tin, copper, or their alloys.
Source: HSDB
10 · Handling and storage
Methyl Isocyanate storage and handling
Methyl Isocyanate safe storage
Fireproof. See Chemical Dangers. Cool. Dry. Store only if stabilized. Store in an area without drain or sewer access.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Methyl Isocyanate storage conditions
Fireproof ... Store only if stabilized.
Source: Hazardous Substances Data Bank (HSDB)
Methyl Isocyanate incompatible materials
Reacts with water, which may cause runaway reaction ...
Source: Hazardous Substances Data Bank (HSDB)
Methyl Isocyanate reactivity
Airborne vapors of METHYL ISOCYANATE are explosive when exposed to heat, flame or sparks. Vapor may ignite on contact with strong oxidizing agents. Emits toxic fumes of nitriles and oxides of nitrogen when heated to decomposition [Lewis, 3rd ed., 1993, p. 860]. Caused the death of thousands in 1984 in Bhopal, India when released accidentally as a vapor following an exothermic reaction caused by contamination with water [Chem. Eng. News, 1985, 63(6), p. 27]. Reacts rapidly with acids and bases (including amines). May polymerize in contact with iron, tin, copper and certain other catalysts such as triphenylarsenic oxide, triethyl phosphine and tributyltin oxide. Polymerizes at elevated temperatures. Attacks some plastics, rubbers, and coatings [NTP].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Methyl Isocyanate in the storage compatibility matrix →
11 · Transport
Methyl Isocyanate 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.
Methyl Isocyanate under UN 2480 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| METHYL ISOCYANATE | 6.1 | TF1 | I | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 6.1 is “Toxic substances” (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) |
|---|---|---|---|
| Methyl isocyanate | 6.1 | I | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 6.1 is “Poisonous materials” (49 CFR 173.2).
12 · Questions
Methyl Isocyanate — frequently asked questions
What is the CAS number of Methyl Isocyanate?
The CAS number of Methyl Isocyanate is 624-83-9. Its EC number is 210-866-3.
What is the chemical formula of Methyl Isocyanate?
The molecular formula of Methyl Isocyanate is C2H3NO and its molecular weight is 57.05 g/mol.
What does a Methyl Isocyanate label have to show?
Under CLP Annex VI the label for Methyl Isocyanate carries the pictograms Flame, Skull and crossbones, Corrosion and Health hazard and the signal word is Danger.
Is Methyl Isocyanate flammable?
Yes. CLP Annex VI assigns Methyl Isocyanate H225 — highly flammable liquid and vapour. The flash point reported for it is -7.22 °C (19 °F) (HSDB).
Is Methyl Isocyanate a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Methyl Isocyanate. 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 Methyl Isocyanate?
The US occupational exposure limit reported for Methyl Isocyanate is 0.02 [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 Methyl Isocyanate?
The boiling point reported for Methyl Isocyanate is 39.5 °C (103.1 °F) (HSDB).
What is the melting point of Methyl Isocyanate?
The melting point reported for Methyl Isocyanate is -45 °C (-49 °F) (HSDB).
How should Methyl Isocyanate be stored?
CLP Annex VI assigns Methyl Isocyanate the storage statement P403. Fireproof ... Store only if stabilized. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Methyl Isocyanate
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