Substance profile
Propylene Oxide
Propylene Oxide is a colorless liquid with an odor is sweet, alcoholic, & like ether or benzene.
01 · Identification
What Propylene Oxide is
Propylene Oxide is a colorless liquid with an odor is sweet, alcoholic, & like ether or benzene. Its molecular formula is C3H6O and its molecular weight is 58.08 g/mol. It boils at 34.2 °C, melts at -112 °C.
Under the GHS it carries the signal word Danger. It is classed as hazardous Air Pollutants (HAPs).
02 · Identifiers
Propylene Oxide identifiers and molecular data
Propylene Oxide CAS number and EC number
Propylene Oxide molecular formula and molecular weight
Other names for Propylene Oxide
- 1,2-epoxypropane
- methyloxirane
03 · GHS classification
Propylene Oxide hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Propylene Oxide pictograms and signal word
Propylene Oxide hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Flammable liquids GHS chapter 2.6 | Category 1 | H224 | GHS02 |
| Acute toxicity - oral GHS chapter 3.1 | Category 4 | H302 | GHS07 |
| Acute toxicity - dermal GHS chapter 3.1 | Category 3 | H311 | GHS06 |
| Acute toxicity - inhalation GHS chapter 3.1 | Category 3 | H331 | GHS06 |
| Serious eye damage/eye irritation GHS chapter 3.3 | Category 2A | H319 | GHS07 |
| Germ cell mutagenicity GHS chapter 3.5 | Category 1A or 1B | H340 | GHS08 |
| Carcinogenicity GHS chapter 3.6 | Category 1A or 1B | H350 | GHS08 |
| 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.
Propylene Oxide hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H224 | Extremely flammable liquid and vapour. |
| H350 | May cause cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H340 | May cause genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H331 | Toxic if inhaled. |
| H311 | Toxic in contact with skin. |
| H302 | Harmful if swallowed. |
| H335 | May cause respiratory irritation. |
| H319 | Causes serious eye irritation. |
This page lists only the codes assigned to Propylene Oxide. 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 Propylene Oxide
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 Propylene Oxide 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
Propylene Oxide precautionary statements
CLP Annex VI assigns 23 precautionary statements to Propylene Oxide. 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
Propylene Oxide 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 | пропиленов оксид 1,2-епоксипропан метилоксиран |
| Spanish español | óxido de propileno 1,2-epoxipropanometiloxirano |
| Czech čeština | propylenoxid 1,2-epoxypropanmethyloxiran |
| Danish dansk | propylenoxid 1,2-epoxypropanmethyloxiran |
| German Deutsch | Propylenoxid 1,2-EpoxypropanMethyloxiran |
| Estonian eesti | propüleenoksiid 1,2-epoksüpropaanmetüüloksiraan |
| Greek ελληνικά | 1,2-προπυλενοξείδιο 1,2-εποξυπροπάνιο μεθυλοξιράνιο |
| English English | propylene oxide 1,2-epoxypropanemethyloxirane |
| French français | oxyde de propylène 1,2-époxypropaneméthyloxirane |
| Croatian hrvatski | propilen oksid 1,2-epoksipropanmetil-oksiran |
| Italian italiano | ossido di propilene 1,2-epossipropanometilossirano |
| Latvian latviešu | propilēnoksīds 1,2-epoksipropānsmetiloksirāns |
| Lithuanian lietuvių | propilenoksidas 1,2-epoksipropanasmetiloksiranas |
| Hungarian magyar | propilén-oxid 1,2-epoxipropánmetiloxirán |
| Maltese Malti | ossidu tal-propilen 1,2-epossipropanmetilossiran |
| Dutch Nederlands | propyleenoxide 1,2-epoxypropaanmethyloxiraan |
| Polish polski | tlenek propylenu 1,2-epoksypropanmetylooksiran |
| Portuguese português | óxido de propileno 1,2-epoxipropanometiloxirano |
| Romanian română | propilen oxid 1,2-epoxipropan metiloxiran |
| Slovak slovenčina | propylénoxid 1,2-epoxypropánmetyloxirán |
| Slovenian slovenščina | propilen oksid 1,2-epoksipropanmetiloksiran |
| Finnish suomi | propyleenioksidi 1,2-epoksipropaanimetyylioksiraani |
| Swedish svenska | propylenoxid 1,2-epoxipropanmetyloxiran |
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
Propylene Oxide GHS label elements
Everything CLP Annex VI fixes for Propylene Oxide, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Propylene Oxide
- Extremely flammable liquid and vapour.
- May cause cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- May cause genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Toxic if inhaled.
- Toxic in contact with skin.
- Harmful if swallowed.
- May cause respiratory irritation.
- Causes serious eye irritation.
- Obtain special instructions before use.
- 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.
- Wash … thoroughly after handling.
- Do not eat, drink or smoke when using this product.
- Use only outdoors or in a well-ventilated area.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- IF ON SKIN:
- IF INHALED:
- IF IN EYES:
- IF exposed or concerned:
- Immediately call a POISON CENTER/doctor/…
- Call a POISON CENTER/doctor/… if you feel unwell.
- Get medical advice/attention.
- Rinse mouth.
- If eye irritation persists:
- 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 Propylene Oxide in the GHS label constructor →
07 · Health hazards
Propylene Oxide health hazards and exposure limits
Propylene Oxide hazard summary
Propylene oxide is used in the production of polyethers (the primary component of polyurethane foams) and propylene glycol. Acute (short-term) exposure of humans and animals to propylene oxide has caused eye and respiratory tract irritation. Dermal contact, even with dilute solutions, has caused skin irritation and necrosis in humans. Propylene oxide is also a mild central nervous system (CNS) depressant in humans. Inflammatory lesions of the nasal cavity, trachea, and lungs and neurological effects have been observed in animals chronically (long-term) exposed to propylene oxide by inhalation. Propylene oxide has been observed to cause tumors at or near the site of administration in rodents, causing forestomach tumors following ingestion via gavage (experimentally placing the chemical in the stomach) and nasal tumors after inhalation exposure. EPA has classified propylene oxide as a Group B2, probable human carcinogen.
Source: EPA Hazardous Air Pollutants
Propylene Oxide carcinogenicity classification
Under the conditions of these studies, there was some evidence of carcinogenicity for F344/N rats, as indicated by increased incidences of papillary adenomas of the nasal turbinates in male and female rats exposed to propylene oxide at 400 ppm. For male and female B6C3F1 mice, there was clear evidence of carcinogenicity, as indicated by increased incidences of hemangiomas or hemangiosarcomas of the nasal turbinates at 400 ppm. In the respiratory epithelium of the nasal turbinates, propylene oxide also caused suppurative inflammation, hyperplasia, and squamous metaplasia in rats and inflammation in mice.
Source: US National Toxicology Program · TR-267: Toxicology and Carcinogenesis Studies of Propylene Oxide (CASRN 75-56-9) in F344/N Rats and B6C3F1 Mice (Inhalation Studies) (1985 )
Cancer Classification: Group B2 Probable Human Carcinogen
Source: Hazardous Substances Data Bank (HSDB)
CLASSIFICATION: B2; probable human carcinogen. BASIS FOR CLASSIFICATION: Based on inadequate human data and an increased incidence of benign and malignant tumors at the site of exposure in two species of animals, when exposed by subcutaneous injection, by inhalation, and by gavage. There was also evidence of mutagenicity in a variety of test systems. Propylene oxide is structurally similar to other chemicals that demonstrate carcinogenic activity in animals.HUMAN CARCINOGENICITY DATA: Inadequate. ANIMAL CARCINOGENICITY DATA: Sufficient.
Source: Hazardous Substances Data Bank (HSDB)
An IARC group and a CLP classification answer different questions. IARC judges whether the evidence for cancer in humans is strong enough; CLP Annex VI is the legally binding EU classification. A substance can carry one and not the other.
Propylene Oxide occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 100.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 100 ppm (240 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 100 ppm (240 mg/m3) See Appendix G | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | Ca See Appendix A | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 400 ppm ; A potential occupational carcinogen. (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 400.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | NIOSH considers propylene oxide to be a potential occupational carcinogen. /SRP: No IDLH value specified/. | 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
Propylene Oxide 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.
Propylene Oxide boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 34.23 °C (93.6 °F) | HSDB | |
| 34.44 °C (94 °F) | NIOSH | ||
| 34.23 °C (93.6 °F) | at 760 mmHg | CAMEO |
Propylene Oxide melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -112.13 °C (-169.8 °F) | HSDB | |
| -112.22 °C (-170 °F) | NIOSH |
Propylene Oxide density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.8304 g/cm³ | HSDB | |
| 0.83 g/cm³ | NIOSH |
Propylene Oxide solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | MISCIBLE WITH ACETONE, BENZENE, CARBON TETRACHLORIDE, METHANOL, & ETHER | HSDB | |
| Solubility of water in propylene oxide is 12.8% by wt at 20 °C. | at 20 °C | HSDB | |
| 40.5 wt% water @ 20 °C | at 20 °C | HSDB |
Propylene Oxide vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 445 mmHg | NIOSH | |
| 445 mmHg | at 20 °C | CAMEO | |
| 538 mmHg | at 25 °C | HSDB |
Propylene Oxide flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | -37.22 °C (-35 °F) | HSDB |
Propylene Oxide autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 449 °C (840.2 °F) | HSDB | |
| 465 °C (869 °F) | CAMEO | ||
| 430 °C (806 °F) | ICSC |
Propylene Oxide lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | 2.3 % by volume | HSDB | |
| 2.1 % by volume | HSDB |
Propylene Oxide upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | 36 % by volume | HSDB | |
| 38.5 % by volume | HSDB |
Propylene Oxide vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 2 (air = 1) | HSDB |
Propylene Oxide odor threshold
| Property | Value | Conditions | Source |
|---|---|---|---|
| Odor threshold | Inasmuch as the detectable odor concn of propylene oxide is reported to be as high as 200 ppm, its odor cannot be reliably used as a warning. | HSDB | |
| Odor detection in air= 9.90x10+0 ppm | Purity not specified | HSDB | |
| Odor recognition in air= 3.50x10+1 ppm | Purity not specified | HSDB |
Propylene Oxide critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | 209.1 °C (408.4 °F) | HSDB |
Propylene Oxide corrosivity
| Property | Value | Conditions | Source |
|---|---|---|---|
| Corrosivity | NONCORROSIVE TO METALS | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Propylene Oxide 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.
Propylene Oxide fire potential
FLAMMABLE, DANGEROUS FIRE RISK
Source: Hazardous Substances Data Bank (HSDB)
10 · Handling and storage
Propylene Oxide storage and handling
Propylene Oxide safe storage
Fireproof. Separated from acids, bases and strong oxidants. Dry. Cool. Well closed. Keep in the dark.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Propylene Oxide storage conditions
Use glass or metal containers sealed with nitrogen.
Source: Hazardous Substances Data Bank (HSDB)
Propylene Oxide incompatible materials
No acetylide-forming metals such as copper or copper alloys should be in contact with propylene oxide.
Source: Hazardous Substances Data Bank (HSDB)
Propylene Oxide reactivity
PROPYLENE OXIDE react with oxidizing agents and strong acids (NTP, 1992). Reacts with Grignard reagents and organolithium compounds. An explosion occurred when propylene oxide was added to an epoxy resin. It was concluded that polymerization was catalyzed by an amine accelerator in the resin [Bretherick, 5th Ed., 1995]. Underwent polymerization when mixed with sodium hydroxide causing ignition and explosion of a drum of the crude product. [Combust Sci. Technol., 1983].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Propylene Oxide in the storage compatibility matrix →
11 · Transport
Propylene Oxide 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.
Propylene Oxide under UN 1280 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| PROPYLENE OXIDE | 3 | F1 | I | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 3 is “Flammable liquids” (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) |
|---|---|---|---|
| Propylene oxide | 3 | I | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 3 is “Flammable and combustible liquid” (49 CFR 173.2).
12 · Questions
Propylene Oxide — frequently asked questions
What is the CAS number of Propylene Oxide?
The CAS number of Propylene Oxide is 75-56-9. Its EC number is 200-879-2.
What is the chemical formula of Propylene Oxide?
The molecular formula of Propylene Oxide is C3H6O and its molecular weight is 58.08 g/mol.
What does a Propylene Oxide label have to show?
Under CLP Annex VI the label for Propylene Oxide carries the pictograms Flame, Health hazard and Skull and crossbones and the signal word is Danger.
Is Propylene Oxide flammable?
Yes. CLP Annex VI assigns Propylene Oxide H224 — extremely flammable liquid and vapour. The flash point reported for it is -37.22 °C (-35 °F) (HSDB).
Is Propylene Oxide a carcinogen?
Yes. CLP Annex VI classifies Propylene Oxide as a category 1A or 1B carcinogen and assigns it H350: may cause cancer. IARC places it in Group 2B: possibly carcinogenic to humans.
What is the exposure limit for Propylene Oxide?
The US occupational exposure limit reported for Propylene Oxide is 100.0 [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 Propylene Oxide?
The boiling point reported for Propylene Oxide is 34.23 °C (93.6 °F) (HSDB).
What is the melting point of Propylene Oxide?
The melting point reported for Propylene Oxide is -112.13 °C (-169.8 °F) (HSDB).
How should Propylene Oxide be stored?
CLP Annex VI assigns Propylene Oxide the storage statement P403. Use glass or metal containers sealed with nitrogen. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Propylene Oxide
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