Acetylene

1Identification

Name

Acetylene

IUPAC name

acetylene

CAS number

74-86-2

EC number

200-816-9

Molecular formula

C2H2

Molecular weight

26.04 g/mol

InChIKey

HSFWRNGVRCDJHI-UHFFFAOYSA-N

SMILES

C#C

PubChem CID

6326

Synonyms

Ethyne, Narcylen, Ethine, Acetylen, Vinylene, acetylene;ethyne, RefChem:109145, Azetylen, C2H2, Ethin, CH#CH, HC#CH, ACETYLENE (1,2-13C2), ACETYLENE (D1)

Recommended uses

• A compressed gas used in the welding and cutting of metals; Was used as a general anesthetic in the 1920's; [ACGIH]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Gas Welding and Cutting [Category: Weld]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Smoking cigarettes [Category: Food & Drugs]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Intermediate Fuel Heat transferring agent Fuel agents Monomers Other
  EPA Chemical Data Reporting (CDR)
• Intermediate Not Known or Reasonably Ascertainable Fuel Other
  EPA Chemical Data Reporting (CDR)

Description

• Acetylene appears as a colorless gas with a faint garlic-like odor. Easily ignited and burns with a sooty flame. Gas is lighter than air. Flame may flash back to the source of a leak very easily. Under prolonged exposure to fire or heat the containers may rupture violently and rocket.
  CAMEO Chemicals
• Acetylene is a gas molecular entity, an alkyne and a terminal acetylenic compound.
  ChEBI
• The simplest two carbon alkyne with the formula HCCH.
  Medical Subject Headings (MeSH)

2Hazard identification

Signal word

Danger

Pictograms

GHS02, GHS04

Classification source

Regulation (EC) No 1272/2008 of the European Parliament and of the Council

Precautionary statements

Other reported classifications

4 classification records exist across sources. Differences usually reflect purity, physical form or impurities.

NFPA 704 rating

• 0 - Materials that, under emergency conditions, would offer no hazard beyond that of ordinary combustible materials.
  Hazardous Substances Data Bank (HSDB)
• 4 - Materials that rapidly or completely vaporize at atmospheric pressure and normal ambient temperature or that are readily dispersed in air and burn readily.
  Hazardous Substances Data Bank (HSDB)
• 2 - Materials that readily undergo violent chemical changes at elevated temperatures and pressures.
  Hazardous Substances Data Bank (HSDB)

Health hazards

• Headache, dizziness and loss of consciousness may occur. Death from "smothering" may occur if oxygen content of the air is severely reduced by dilution with acetylene. (USCG, 1999)
  CAMEO Chemicals
• · Vapors may cause dizziness or asphyxiation without warning, especially when in closed or confined areas. · Some may be toxic if inhaled at high concentrations. · Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. · Fire may produce irritating and/or toxic gases.
  Emergency Response Guidebook (ERG)

Fire hazards

• Behavior in Fire: May explode in fire (USCG, 1999)
  CAMEO Chemicals
• · EXTREMELY FLAMMABLE. · Will be easily ignited by heat, sparks or flames. · Will form explosive mixtures with air. Acetylene (UN1001, UN3374) may react explosively even in the absence of air. · Disilane (UN3553) and Silane (UN2203) will ignite spontaneously in air and may re-ignite. · Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. · Vapors from liquefied gas are initially heavier than air and spread along ground. · Vapors may travel to source of ignition and flash back. · Cylinders exposed to fire may vent and release flammable gas through pressure relief devices. · Containers may explode when heated. · Ruptured cylinders may rocket.
  Emergency Response Guidebook (ERG)
• Extremely flammable. Gas/air mixtures are explosive.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• Acetylene is an explosive hazard and simple asphyxiant. [LaDou, p. 558] Possible frostbite from contact with liquid; [NIOSH] Acetylene is in the list of Some volatile substances which may be abused by inhalation published on the web site of the U.N. International Drug Control Programme, indicating its potential to cause narcosis in workers. [Reference #1]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases

3Composition / information on ingredients

This page describes the pure substance. Commercial products may be solutions or mixtures. Check Section 3 of your supplier's SDS for concentrations and other ingredients.

4First-aid measures

• Excerpt from NIOSH Pocket Guide for Acetylene: Eye: FROSTBITE - If eye tissue is frozen, seek medical attention immediately; if tissue is not frozen, immediately and thoroughly flush the eyes with large amounts of water for at least 15 minutes, occasionally lifting the lower and upper eyelids. If irritation, pain, swelling, lacrimation, or photophobia persist, get medical attention as soon as possible. Skin: FROSTBITE - If frostbite has occurred, seek medical attention immediately; do NOT rub the affected areas or flush them with water. In order to prevent further tissue damage, do NOT attempt to remove frozen clothing from frostbitten areas.
  CAMEO Chemicals
• General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped with a one-way valve or other device).
  Emergency Response Guidebook (ERG)
• (General first aid procedures) Eye: Frostbite - If eye tissue is frozen, seek medical attention immediately; if tissue is not frozen, immediately and thoroughly flush the eyes with large amounts of water for at least 15 minutes, occasionally lifting the lower and upper eyelids. If irritation, pain, swelling, lacrimation, or photophobia persist, get medical attention as soon as possible. Skin: Frostbite - Compressed gases may create low temperatures when they expand rapidly. Leaks and uses that allow rapid expansion may cause a frostbite hazard. Wear appropriate personal protective clothing to prevent the skin from becoming frozen. Breathing: Fresh air
  The National Institute for Occupational Safety and Health (NIOSH)

Symptoms of exposure

• Dizziness. Lethargy. Headache. Suffocation.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• headache, dizziness; asphyxia; liquid: frostbite
  The National Institute for Occupational Safety and Health (NIOSH)

5Fire-fighting measures

• Stop flow of gas before extinguishing fire. Use water spray to keep fire-exposed containers cool. Approach fire from upwind to avoid hazardous vapors and toxic decomposition products. Fight fire from protected location or maximum possible distance. Use water spray, dry chemical, form, or carbon dioxide. /Acetylene, dissolved/
  Hazardous Substances Data Bank (HSDB)
• Stop flow of gas. ... Carbon dioxide, dry chemical and water spray are not generally recommended because the discharged gas or volatile liquid may create a more serious explosion hazard.
  Hazardous Substances Data Bank (HSDB)
• If material on fire or involved in fire: Do not extinguish fire unless flow can be stopped. Use water in flooding quantities as fog. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible. /Acetylene, dissolved; Acetylene, solvent free/
  Hazardous Substances Data Bank (HSDB)

6Accidental release measures

Isolation and evacuation

• Excerpt from ERG Guide 116 [Gases - Flammable (Unstable)]: IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area for at least 100 meters (330 feet) in all directions. LARGE SPILL: Consider initial downwind evacuation for at least 800 meters (1/2 mile). FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 1600 meters (1 mile) in all directions; also, consider initial evacuation for 1600 meters (1 mile) in all directions. (ERG, 2024)
  CAMEO Chemicals
• Immediate precautionary measure · Isolate spill or leak area for at least 100 meters (330 feet) in all directions. Large Spill · Consider initial downwind evacuation for at least 800 meters (1/2 mile). Fire · If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 1600 meters (1 mile) in all directions; also, consider initial evacuation for 1600 meters (1 mile) in all directions.
  Emergency Response Guidebook (ERG)

Spill cleanup

• Remove all ignition sources. Evacuate danger area! Consult an expert! Personal protection: self-contained breathing apparatus. Ventilation.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Evacuate danger area! Consult an expert! Ventilation. Remove all ignition sources. (Extra personal protection: self-contained breathing apparatus).
  Hazardous Substances Data Bank (HSDB)
• Eliminate all ignition sources. Stop or control the leak, if this can be done without undue risk. Use water spray to cool and disperse vapors and protect personnel. /Acetylene, dissolved/
  Hazardous Substances Data Bank (HSDB)

7Handling and storage

• Fireproof. See Chemical Dangers. Cool.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Keep container in a cool, well-ventilated area. Keep container tightly closed and sealed until ready for use. Avoid all possible sources of ignition (spark or flame). Segregate from oxidizing materials. Cylinders should be stored upright, with valve protection cap in place, and firmly secured to prevent falling or being knocked over. Cylinder temperatures should not exceed 52 degC (125 degF).
  Hazardous Substances Data Bank (HSDB)
• Acetylene can be stored as a gas or in solution. Gaseous acetylene becomes highly explosive when compressed or heated and consequently it is stored under low pressure in large tanks or gasholders.
  Hazardous Substances Data Bank (HSDB)
• Outside or detached storage is preferred. Isolate from oxidizing gases, especially chlorine. Store in a cool , dry, well-ventilated location. Store cylinders upright. /Acetylene, dissolved/
  Hazardous Substances Data Bank (HSDB)

8Exposure controls / personal protection

Personal protective equipment

• Excerpt from NIOSH Pocket Guide for Acetylene: Skin: FROSTBITE - Compressed gases may create low temperatures when they expand rapidly. Leaks and uses that allow rapid expansion may cause a frostbite hazard. Wear appropriate personal protective clothing to prevent the skin from becoming frozen. Eyes: FROSTBITE - Wear appropriate eye protection to prevent eye contact with the liquid that could result in burns or tissue damage from frostbite. Wash skin: No recommendation is made specifying the need for washing the substance from the skin (either immediately or at the end of the work shift).
  CAMEO Chemicals
• Where conditions ... are such that ... impurities may constitute health hazard, composition of acetylene should be determined. Respiratory protective equipment is not normally required ... /but/ self-contained type should be available for emergency and rescue use.
  Hazardous Substances Data Bank (HSDB)
• Compressed gases may create low temperatures when they expand rapidly. Leaks and uses that allow rapid expansion may cause a frostbite hazard. Wear appropriate personal protective clothing to prevent the skin from becoming frozen.
  Hazardous Substances Data Bank (HSDB)
• Wear appropriate eye protection to prevent eye contact with the liquid that could result in burns or tissue damage from frostbite.
  Hazardous Substances Data Bank (HSDB)

Respirator recommendations

• Important additional information about respirator selection
  The National Institute for Occupational Safety and Health (NIOSH)

9Physical and chemical properties

10Stability and reactivity

Reactivity

• ACETYLENE reacts with alkali metals, forming hydrogen gas. Acetylene can react explosively with bromine [Von Schwartz 1918. p.142]. Acetylene forms a sensitive acetylide when passed into an aqueous solution of mercuric nitrate [Mellor 4:933. 1946-47]. It reacts with silver, copper and lead to form sensitive, explosive salts. Since acetylene is endothermic and effectively a reducing agent, its reaction with oxidants can be very violent (examples: calcium hypochlorite, nitric acid, nitrogen oxide, ozone, trifluoromethyl hypofluorite, etc.).
  CAMEO Chemicals
• Highly flammable. Slightly soluble in water.
  CAMEO Chemicals

Incompatible materials and hazardous reactions

• Mixture with air containing between 3-82% gas is explosive. Contact with /bleaching powder may lead to formation of explosive chloroacetylenes. Finely divided /cobalt/ metal decomposes and polymerizes acetylene on contact, becoming incandescent. Copper metal forms explosive compounds with acetylene. If warmed in air or oxygen, or on impact, copper acetylides may explode in subsequent contact with acetylene. Interaction with /halogens/ can be violent or explosive. Contact of acetylene with concentrated nitric acid in presence of mercury forms explosive trinitromethane or tetranitromethane if sulfuric acid is subsequently added. Mixture with /nitric oxide products/ will ignite at +30-50 °C.
  Hazardous Substances Data Bank (HSDB)
• Contact of acetylene with the concn /nitric/ acid in presence of mercury (II) salts forms trinitromethane, explosive above its mp, 15 °C. Subsequent addition of sulfuric acid produces tetranitromethane, a powerful oxidant of limited stability, in high yield.
  Hazardous Substances Data Bank (HSDB)
• Care is necessary with acetylene-fed atomic absorption spectroscopy (AAS) burners to prevent air being drawn up the liquid drainage line, when explosion is likely. While setting up an AAS instrument for use with nitrous oxide-acetylene, an explosion occurred shortly after switching from compressed air to the oxide, when the flame became unstable. This was attributed to the outdoor location of the nitrous oxide cylinder (at 5 °C) and the expansion cooling (4 °C) occurring in the reducing valve, combining to reduce the oxide flow to the point of flame instability and flashback.
  Hazardous Substances Data Bank (HSDB)

Chemical stability

• Stability during transport: Stable as shipped.
  Hazardous Substances Data Bank (HSDB)

11Toxicological information

Target organs

• central nervous system, respiratory system
  The National Institute for Occupational Safety and Health (NIOSH)

Short-term exposure effects

• Asphyxiation.
  ILO-WHO International Chemical Safety Cards (ICSCs)

12Ecological information

Not available in the public sources we compile. Check Section 12 of the supplier's SDS.

13Disposal considerations

• SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal and plant life; and conformance with environmental and public health regulations.
  Hazardous Substances Data Bank (HSDB)
• SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal.
  Hazardous Substances Data Bank (HSDB)
• Gas Leakage. By forced ventilation, maintain concentration of gas below the range of explosive mixture. Remove the tank or cylinder to an open area. Leave to bleed off in the atmosphere. Disposal. Fit a pipe line into a furnace or into a pit and burn with care.
  Hazardous Substances Data Bank (HSDB)

14Transport information

UN number: UN 1001

Shipping name

• UN 1001; Acetylene, dissolved
  Hazardous Substances Data Bank (HSDB)
• IMO 2.1; Acetylene, dissolved
  Hazardous Substances Data Bank (HSDB)

DOT hazard class

• Acetylene, dissolved
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• UN1001
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• Div 2.1 Flammable gas (49 eCFR § 173.115)
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172

DOT label

• Flammable Gas
  CAMEO Chemicals

UN classification

• UN Hazard Class: 2.1
  ILO-WHO International Chemical Safety Cards (ICSCs)

Emergency Response Guidebook

• 1001 116
  Emergency Response Guidebook (ERG)

How DOT hazard classes work →

15Regulatory information

• This action promulgates standards of performance for equipment leaks of Volatile Organic Compounds (VOC) in the Synthetic Organic Chemical Manufacturing Industry (SOCMI). The intended effect of these standards is to require all newly constructed, modified, and reconstructed SOCMI process units to use the best demonstrated system of continuous emission reduction for equipment leaks of VOC, considering costs, non air quality health and environmental impact and energy requirements. Acetylene is produced, as an intermediate or a final product, by process units covered under this subpart.
  Hazardous Substances Data Bank (HSDB)

Overview of SDS regulations (OSHA HazCom, WHMIS, REACH/CLP) →

16Other information

Compiled from PubChem CID 6326 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.