Substance profile
1,4-dioxane
1,4-dioxane is a colorless liquid or solid (below 53 degrees F) with a faint pleasant odor.
01 · Identification
What 1,4-dioxane is
1,4-dioxane is a colorless liquid or solid (below 53 degrees F) with a faint pleasant odor. Its molecular formula is C4H8O2 and its molecular weight is 88.11 g/mol. It boils at 101 °C, melts at 11.8 °C.
Under the GHS it carries the signal word Danger. It is classed as hazardous Air Pollutants (HAPs).
02 · Identifiers
1,4-dioxane identifiers and molecular data
1,4-dioxane CAS number and EC number
1,4-dioxane molecular formula and molecular weight
Other names for 1,4-dioxane
- dioxane
- Di(Ethylene Oxide)
- Diethylene Dioxide
- 1,4-Diethylene Dioxide
- Diethylene Ether
- Diethylene Oxide
- Diokan
- 1,4-Dioxacyclohexane
- Dioxan
- 1,4-Dioxan
- Dioxane-1,4
- 1, 4-Dioxane
- 1,4-Dioxin, Tetrahydro-
03 · GHS classification
1,4-dioxane hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
1,4-dioxane pictograms and signal word
1,4-dioxane hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Flammable liquids GHS chapter 2.6 | Category 2 | H225 | GHS02 |
| Serious eye damage/eye irritation GHS chapter 3.3 | Category 2A | H319 | GHS07 |
| 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.
1,4-dioxane hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H225 | Highly 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>. |
| H335 | May cause respiratory irritation. |
| H319 | Causes serious eye irritation. |
1,4-dioxane supplemental EU statements (EUH)
| Code | Statement |
|---|---|
| EUH019 | May form explosive peroxides. |
| EUH066 | Repeated exposure may cause skin dryness or cracking. |
This page lists only the codes assigned to 1,4-dioxane. 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 1,4-dioxane
Our own 1,4-dioxane 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
1,4-dioxane precautionary statements
CLP Annex VI assigns 13 precautionary statements to 1,4-dioxane. 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
1,4-dioxane 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 | 1,4-диоксан |
| Spanish español | 1,4-Dioxano |
| Czech čeština | 1,4-dioxan |
| Danish dansk | 1,4-dioxan |
| German Deutsch | 1,4-Dioxan |
| Estonian eesti | 1,4-dioksaan |
| Greek ελληνικά | 1,4-διοξάνιο |
| English English | 1,4-dioxane |
| French français | 1,4-dioxane |
| Croatian hrvatski | 1,4-dioksan |
| Italian italiano | 1,4-diossano |
| Latvian latviešu | 1,4-dioksāns |
| Lithuanian lietuvių | 1,4-dioksanas |
| Hungarian magyar | 1,4-dioxán |
| Maltese Malti | 1,4-diossan |
| Dutch Nederlands | 1,4-dioxaan |
| Polish polski | 1,4-dioksan |
| Portuguese português | 1,4-dioxano |
| Romanian română | 1,4-dioxan |
| Slovak slovenčina | 1,4-dioxán |
| Slovenian slovenščina | 1,4-dioksan |
| Finnish suomi | 1,4-dioksaani |
| Swedish svenska | 1,4-dioxan |
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
1,4-dioxane GHS label elements
Everything CLP Annex VI fixes for 1,4-dioxane, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
1,4-dioxane
- Highly 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 respiratory irritation.
- Causes serious eye irritation.
- May form explosive peroxides.
- Repeated exposure may cause skin dryness or cracking.
- 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.
- Wash … thoroughly after handling.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF IN EYES:
- IF exposed or concerned:
- Get medical advice/attention.
- If eye irritation persists:
- Remove contact lenses, if present and easy to do. Continue rinsing.
- Store in a well-ventilated place.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open 1,4-dioxane in the GHS label constructor →
07 · Health hazards
1,4-dioxane health hazards and exposure limits
1,4-dioxane hazard summary
1,4-Dioxane is a clear liquid that easily dissolves in water. It is used primarily as a solvent in the manufacture of chemicals and as a laboratory reagent; 1,4-dioxane also has various other uses that take advantage of its solvent properties. 1,4-Dioxane is a trace contaminant of some chemicals used in cosmetics, detergents, and shampoos. However, manufacturers now reduce 1,4-dioxane from these chemicals to low levels before these chemicals are made into products used in the home.
Source: Agency for Toxic Substances and Disease Registry (ATSDR)
1,4-dioxane carcinogenicity classification
Studied by the US National Toxicology Program: TR-080: Bioassay of 1,4-Dioxane for Possible Carcinogenicity (CASRN 123-91-1) (1978 )
Evaluation: There is inadequate evidence in humans for the carcinogenicity of 1,4-dioxane. There is sufficient evidence in experimental animals for the carcinogenicity of 1,4-dioxane. Overall evaluation: 1,4-Dioxane is possibly carcinogenic to humans (Group 2B).
Source: Hazardous Substances Data Bank (HSDB)
1,4-dioxane is characterized as "likely to be carcinogenic to humans." This characterization is based on the following findings: (1) inadequate evidence of carcinogenicity in humans, and (2) sufficient evidence in animals (i.e., hepatic tumors in multiple species [three strains of rats, two strains of mouse, and in guinea pigs] mesotheliomas of the peritoneum, mammary, and nasal tumors have also been observed in rats following 2 years of oral exposure to 1,4- dioxane).
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.
1,4-dioxane occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 100.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 100 ppm (360 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 100 ppm (360 mg/m3) [skin] See Appendix G | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | 1 ppm (3.6 mg/m³) [30 minutes] | Occupational Safety and Health Administration (OSHA) |
| REL | Ca C 1 ppm (3.6 mg/m3) [30-minute] See Appendix A | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 500 ppm ; A potential occupational carcinogen. (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 500.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | NIOSH considers 1,4-dioxane to be potential occupational carcinogen. [500 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
1,4-dioxane 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.
1,4-dioxane boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 101.2 °C (214.2 °F) | HSDB | |
| 101.11 °C (214 °F) | NIOSH | ||
| 101.11 °C (214 °F) | at 760 mmHg | CAMEO |
1,4-dioxane melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | 11.75 °C (53.2 °F) | HSDB | |
| 11.67 °C (53 °F) | NIOSH | ||
| 11.78 °C (53.2 °F) | CAMEO |
1,4-dioxane density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 1.03 g/cm³ | NIOSH | |
| 1.0337 g/cm³ | at 20 °C | HSDB | |
| 1.036 g/cm³ | at 20 °C | CAMEO |
1,4-dioxane solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Miscible with most organic solvents | HSDB | |
| Miscible with aromatic hydrocarbons and oils. | HSDB | ||
| In water, >800 g/L at 25 °C | at 25 °C | HSDB |
1,4-dioxane vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 29 mmHg | NIOSH | |
| 29 mmHg | at 20 °C | CAMEO | |
| 38.1 mmHg | at 25 °C | HSDB |
1,4-dioxane flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | 18.33 °C (65 °F) | HSDB | |
| 12.78 °C (55 °F) | NIOSH | ||
| 12.22 °C (54 °F) | CAMEO |
1,4-dioxane autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 180 °C (356 °F) | HSDB |
1,4-dioxane lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | 2 % by volume | HSDB |
1,4-dioxane upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | 22 % by volume | HSDB |
1,4-dioxane vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 3.03 (air = 1) | HSDB | |
| 3 (air = 1) | ICSC |
1,4-dioxane odor threshold
| Property | Value | Conditions | Source |
|---|---|---|---|
| Odor threshold | ...Air threshold of recognition at 170 ppm. This odor recognition threshold allows for dioxane to be detected before acute toxic effects occur. | HSDB | |
| Odor Threshold Low: 0.8 [ppm] | Haz-Map | ||
| Odor Threshold High: 172.0 [ppm] | Haz-Map |
1,4-dioxane critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | 312 °C (593.6 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
1,4-dioxane 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.
1,4-dioxane fire potential
A very dangerous fire and explosion hazard when exposed to heat or flame.
Source: Hazardous Substances Data Bank (HSDB)
10 · Handling and storage
1,4-dioxane storage and handling
1,4-dioxane reactive group
CAMEO Chemicals places 1,4-dioxane in the reactive group Ethers. 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.
1,4-dioxane peroxide formation
B: Compounds that form peroxides on concentration (distillation/evaporation)
Source: Lab and Research Safety, University of Minnesota
1,4-dioxane safe storage
Fireproof. Separated from strong oxidants, strong acids and incompatible materials. Cool. Dry. Well closed. Keep in the dark. Store only if stabilized. Store in an area without drain or sewer access.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
1,4-dioxane storage conditions
Store in a cool, dry, well-ventilated location. Store away from heat, oxidizing materials, and sunlight. Outside or detached storage is preferred. Inside storage should be in a standard flammable liquids storage warehouse, room, or cabinet.
Source: Hazardous Substances Data Bank (HSDB)
1,4-dioxane incompatible materials
Pure, dry, o- and hydroperoxide-free dioxane rapidly forms hydroperoxide on contact with air.
Source: Hazardous Substances Data Bank (HSDB)
1,4-dioxane reactivity
DIOXANE is a flammable liquid; when exposed to air it undergoes autooxidation with formation of peroxides. In the distillation process peroxides will concentrate causing violent explosion. The addition complex with sulfur trioxide (1:1) sometimes decomposes violently on storing at room temperature [Sisler, H. H. et al., Inorg. Synth., 1947, 2, p. 174]. Evaporation of boron trifluoride in aqueous dioxane with nitric acid led to an explosion upon addition of perchloric acid [MCA Guide, 1972, p. 312]. Explosive reaction with Raney nickel catalyst above 210 °C {Mozingo R., Org. Synth., 1955, Coll. Vol. 3, p. 182].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check 1,4-dioxane in the storage compatibility matrix →
11 · Questions
1,4-dioxane — frequently asked questions
What is the CAS number of 1,4-dioxane?
The CAS number of 1,4-dioxane is 123-91-1. Its EC number is 204-661-8.
What is the chemical formula of 1,4-dioxane?
The molecular formula of 1,4-dioxane is C4H8O2 and its molecular weight is 88.11 g/mol.
What does a 1,4-dioxane label have to show?
Under CLP Annex VI the label for 1,4-dioxane carries the pictograms Flame, Health hazard and Exclamation mark and the signal word is Danger.
Is 1,4-dioxane flammable?
Yes. CLP Annex VI assigns 1,4-dioxane H225 — highly flammable liquid and vapour. The flash point reported for it is 18.33 °C (65 °F) (HSDB).
Is 1,4-dioxane a carcinogen?
Yes. CLP Annex VI classifies 1,4-dioxane 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 1,4-dioxane?
The US occupational exposure limit reported for 1,4-dioxane 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 1,4-dioxane?
The boiling point reported for 1,4-dioxane is 101.2 °C (214.2 °F) (HSDB).
What is the melting point of 1,4-dioxane?
The melting point reported for 1,4-dioxane is 11.75 °C (53.2 °F) (HSDB).
How should 1,4-dioxane be stored?
CLP Annex VI assigns 1,4-dioxane the storage statement P403. Store in a cool, dry, well-ventilated location. Store away from heat, oxidizing materials, and sunlight. Outside or detached storage is preferred. Inside storage should be in a standard flammable liquids storage warehouse, room, or cabinet. (Hazardous Substances Data Bank (HSDB))
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