Substance profile
Chloroprene
Chloroprene is a colorless liquid with a pungent, ether-like odor.
01 · Identification
What Chloroprene is
Chloroprene is a colorless liquid with a pungent, ether-like odor. It boils at 59.4 °C, melts at -130 °C, is soluble in water.
Under the GHS it carries the signal word Danger. It is classed as hazardous Air Pollutants (HAPs).
02 · Identifiers
Chloroprene identifiers and molecular data
Chloroprene CAS number and EC number
Chloroprene molecular formula and molecular weight
Other names for Chloroprene
- chloroprene (stabilised)
- 2-chlorobuta-1,3-diene (stabilised)
03 · GHS classification
Chloroprene hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Chloroprene pictograms and signal word
Chloroprene 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 4 | H302 | GHS07 |
| Acute toxicity - inhalation GHS chapter 3.1 | Category 4 | H332 | GHS07 |
| Skin corrosion/irritation GHS chapter 3.2 | Category 2 | H315 | GHS07 |
| 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 |
| Specific target organ toxicity - repeated exposure GHS chapter 3.9 | Category 2 | H373 | GHS08 |
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.
Chloroprene 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>. |
| H332 | Harmful if inhaled. |
| H302 | Harmful if swallowed. |
| H335 | May cause respiratory irritation. |
| H373 | May cause 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>. |
| H315 | Causes skin irritation. |
| H319 | Causes serious eye irritation. |
This page lists only the codes assigned to Chloroprene. 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 Chloroprene
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 Chloroprene 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
Chloroprene precautionary statements
CLP Annex VI assigns 24 precautionary statements to Chloroprene. 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
Chloroprene 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 | хлоропрен (стабилизиран) 2-хлоробута-1,3-диен (стабилизиран) |
| Spanish español | Cloropreno (estabilizado) 2-clorobuta-1,3-dieno (estabilizado) |
| Czech čeština | chloropren (stabilizovaný) 2-chlorbuta-1,3-dien (stabilizovaný) |
| Danish dansk | chloropren (stabiliseret) 2-chlor-1,3-butadien (stabiliseret) |
| German Deutsch | Chloropren (stabilisiert) 2-Chlorbuta-1,3-dien (stabilisiert) |
| Estonian eesti | kloropreen (stabiliseeritud) 2-klorobuta-1,3-dieen (stabiliseeritud) |
| Greek ελληνικά | χλωροπρένιο (σταθεροποιημένο) 2-χλωροβουτα-1,3-διένιο (σταθεροποιημένο) |
| English English | chloroprene (stabilised) 2-chlorobuta-1,3-diene (stabilised) |
| French français | chloroprène (stabilisé) 2-chlorobuta-1,3-diène (stabilisé) |
| Croatian hrvatski | kloropren (stabilizirani) 2-klorbuta-1,3-dien (stabilizirani) |
| Italian italiano | cloroprene (stabilizzato) 2-clorobuta-1,3-diene (stabilizzato) |
| Latvian latviešu | hloroprēns (stabilizēts) 2-hlorbuta-1,3-diēns (stabilizēts) |
| Lithuanian lietuvių | chloroprenas (stabilizuotas) 2-chlorbuta-1,3-dienas (stabilizuotas) |
| Hungarian magyar | kloroprén (stabilizált) 2-klórbuta-1,3-dién (stabilizált) |
| Maltese Malti | kloropren (stabbilizzat) 2-klorobuta-1,3-djen (stabilizzat) |
| Dutch Nederlands | chloropreen (gestabiliseerd) 2-chloorbuta-1,3-dieen (gestabiliseerd) |
| Polish polski | chloropren (stabilizowany) 2-chlorobuta-1,3-dien (stabilizowany) |
| Portuguese português | cloropreno (estabilizado) 2-cloro-1,3-butadieno (estabilizado) |
| Romanian română | cloropren (stabilizat) 2-clorobuta-1,3-dienă (stabilizat) |
| Slovak slovenčina | chloroprén (stabilizovaný) 2-chlórbuta-1,3-dién (stabilizovaný) |
| Slovenian slovenščina | kloropren (stabiliziran) 2-klorobuta-1,3-dien (stabiliziran) |
| Finnish suomi | kloropreeni (stabiloitu) 2-klooributa-1,3-dieeni (stabiloitu) |
| Swedish svenska | kloropren (stabiliserad) 2-klorbuta-1,3-dien (stabiliserad) |
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
Chloroprene GHS label elements
Everything CLP Annex VI fixes for Chloroprene, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Chloroprene
- 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>.
- Harmful if inhaled.
- Harmful if swallowed.
- May cause respiratory irritation.
- May cause 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>.
- Causes skin 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:
- Call a POISON CENTER/doctor/… if you feel unwell.
- Get medical advice/attention.
- Get medical advice/attention if you feel unwell.
- Rinse mouth.
- If skin irritation occurs:
- 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 Chloroprene in the GHS label constructor →
07 · Health hazards
Chloroprene health hazards and exposure limits
Chloroprene hazard summary
Symptoms reported from acute (short-term) human exposure to high concentrations of chloroprene include giddiness, headache, irritability, dizziness, insomnia, fatigue, respiratory irritation, cardiac palpitations, chest pains, nausea, gastrointestinal disorders, dermatitis, temporary hair loss, conjunctivitis, and corneal necrosis. Symptoms of chronic (long-term) exposure in workers were fatigue, chest pains, giddiness, irritability, dermatitis, and hair loss. Chronic occupational exposure to chloroprene vapor may contribute to liver function abnormalities, disorders of the cardiovascular system, and depression of the immune system. Occupational studies have found that exposure to chloroprene increases the risk of liver cancer. Studies in animals have found an increased risk of tumors in multiple organs. The EPA has classified chloroprene as likely to be carcinogenic to humans.
Source: EPA Hazardous Air Pollutants
Chloroprene carcinogenicity classification
Under the conditions of these 2-year inhalation studies, there was clear evidence of carcinogenic activity of chloroprene in male F344/N rats based on increased incidences of neoplasms of the oral cavity; increased incidences of neoplasms of the thyroid gland, lung, and kidney were also attributed to chloroprene exposure. There was clear evidence of carcinogenic activity of chloroprene in female F344/N rats based on increased incidences of neoplasms of the oral cavity; increased incidences of neoplasms of the thyroid gland, mammary gland, and kidney were also attributed to exposure to chloroprene. Low incidences of urinary bladder neoplasms in male and female rats and lung neoplasms in female rats may also have been related to exposure to chloroprene.
Source: US National Toxicology Program · TR-467: Toxicology and Carcinogenesis Studies of Chloroprene (CASRN 126-99-8) in F344/N Rats and B6C3F1 Mice (Inhalation Studies) (1998 )
Evaluation: There is inadequate in humans for the carcinogenicity of chloroprene. There is sufficient evidence in experimental animals for the carcinogenicity of chloroprene. Overall evaluation: Chloroprene is possibly carcinogenic to humans (Group 2B).
Source: Hazardous Substances Data Bank (HSDB)
Chloroprene: reasonably anticipated to be a human carcinogen.
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.
Chloroprene occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 25.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 25 ppm (90 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 25 ppm (90 mg/m3) [skin] See Appendix G | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | 1 ppm (3.6 mg/m³) [15 minute] | Occupational Safety and Health Administration (OSHA) |
| REL | Ca C 1 ppm (3.6 mg/m3) [15-minute] See Appendix A | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 300 ppm ; A potential occupational carcinogen. (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 300.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | NIOSH considers beta-chloroprene 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
Chloroprene 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.
Chloroprene boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 59.4 °C (138.9 °F) | HSDB | |
| 59.44 °C (139 °F) | NIOSH | ||
| 59.39 °C (138.9 °F) | at 760 mmHg | CAMEO |
Chloroprene melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -130 °C (-202 °F) | HSDB | |
| -102.78 °C (-153 °F) | NIOSH |
Chloroprene density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.96 g/cm³ | NIOSH | |
| 0.956 g/cm³ | at 20 °C | HSDB | |
| 0.9583 g/cm³ | at 20 °C | CAMEO |
Chloroprene solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Miscible in ethyl ether, acetone, and benzene; slightly soluble in water. | HSDB | |
| Soluble in alcohol, diethyl ether | HSDB | ||
| Slight | NIOSH |
Chloroprene vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 188 mmHg | NIOSH | |
| 174.014 mmHg | at 20 °C | ICSC | |
| 215 mmHg | at 25 °C | HSDB |
Chloroprene flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | -20 °C (-4 °F) | OPEN CUP | HSDB |
| -20 °C (-4 °F) | NIOSH |
Chloroprene autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 440 °C (824 °F) | ICSC |
Chloroprene lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | 4 % by volume | HSDB | |
| 1.9 % by volume | NIOSH |
Chloroprene upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | 20 % by volume | HSDB | |
| 11.3 % by volume | NIOSH |
Chloroprene vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 3 (air = 1) | HSDB | |
| 3.1 (air = 1) | ICSC |
Chloroprene odor threshold
| Property | Value | Conditions | Source |
|---|---|---|---|
| Odor threshold | Odor Threshold Low: 0.11 [ppm] | Haz-Map | |
| Odor Threshold High: 138.0 [ppm] | Haz-Map | ||
| Odor threshold from AIHA | Haz-Map |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Chloroprene 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.
Chloroprene fire potential
A very dangerous fire hazard when exposed to heat or flame.
Source: Hazardous Substances Data Bank (HSDB)
10 · Handling and storage
Chloroprene storage and handling
Chloroprene peroxide formation
A: Compounds that form explosive levels of peroxides without concentration
Source: Lab and Research Safety, University of Minnesota
Chloroprene safe storage
Fireproof. Separated from food and feedstuffs and incompatible materials. See Chemical Dangers. Cool. Keep in the dark. Well closed. Store only if stabilized. Store in an area without drain or sewer access.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Chloroprene storage conditions
/OXIDATION/...INHIBITED BY STORAGE AT LESS THAN -15 °C AND/OR BY THE ADDN OF ANTIOXIDANTS TO THE FRESH DISTILLATE.
Source: Hazardous Substances Data Bank (HSDB)
Chloroprene incompatible materials
Peroxides & other oxidizers [Note: Polymerizes at room temperature unless inhibited with antioxidants].
Source: Hazardous Substances Data Bank (HSDB)
Chloroprene reactivity
CHLOROPRENE emits highly toxic fumes of chlorine gas when heated to decomposition. Autooxidizes very rapidly with air and, even at 0 °C, produces unstable peroxides that catalyze exothermic polymerization [Bretherick, 5th ed., 1995, p. 507]. This reactivity is greatly slowed by presence of an inhibitor.
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Chloroprene in the storage compatibility matrix →
11 · Transport
Chloroprene 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.
Chloroprene under UN 1991 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| CHLOROPRENE, STABILIZED | 3 | FT1 | 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) |
|---|---|---|---|
| Chloroprene, stabilized | 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
Chloroprene — frequently asked questions
What is the CAS number of Chloroprene?
The CAS number of Chloroprene is 126-99-8. Its EC number is 204-818-0.
What does a Chloroprene label have to show?
Under CLP Annex VI the label for Chloroprene carries the pictograms Flame, Health hazard and Exclamation mark and the signal word is Danger.
Is Chloroprene flammable?
Yes. CLP Annex VI assigns Chloroprene H225 — highly flammable liquid and vapour. The flash point reported for it is -20 °C (-4 °F), OPEN CUP (HSDB).
Is Chloroprene a carcinogen?
Yes. CLP Annex VI classifies Chloroprene 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 Chloroprene?
The US occupational exposure limit reported for Chloroprene is 25.0 [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 Chloroprene?
The boiling point reported for Chloroprene is 59.4 °C (138.9 °F) (HSDB).
What is the melting point of Chloroprene?
The melting point reported for Chloroprene is -130 °C (-202 °F) (HSDB).
How should Chloroprene be stored?
CLP Annex VI assigns Chloroprene the storage statement P403. /OXIDATION/...INHIBITED BY STORAGE AT LESS THAN -15 °C AND/OR BY THE ADDN OF ANTIOXIDANTS TO THE FRESH DISTILLATE. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Chloroprene
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