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Compressed Gas: Toxic and Hazardous Gas Classifications

Learn the hazard class of toxic and hazardous gases.

Find everything you wanted to know about compressed gases including hazard class, description and hazards, CHUA Hazard Control Plan, regulator information, signs and symptoms of exposure, and more on the Toxic and Hazardous Gas Classifications Chart below (or download the entire Toxic and Hazardous Gas Classifications Chart). Always follow Hazard Class Requirements and Safety Requirements for your material, based on hazard class.

Toxic and Hazardous Gas Classifications Chart 

Gas Molecular Formula CAS Physical State & Description CHUA Hazard Control Plan Description Hazards CGSL Hazard Class
Acetylene C2H2 74-86-2 Dissolved gas - Colorless, odorless Compressed gas Colorless, odorless Flammable, unstable, reactive IV
Ammonia NH3 7664-41-7 Liquefied gas Compressed gas Colorless, strong pungent odor Corrosive, non-flammable III
[Threshold Limit Values ppm: 25; Permissible Exposure Limit  ppm: 50; Lethal Dose ppm: 7338; Immediately Dangerous to Life or Health ppm: 500]
Argon Ar 7440–37–1 Compressed gas Compressed gas Colorless, odorless Simple asphyxiant IV
Arsine AsH3 7784–42–1 Compressed gas Arsine Colorless, garlic or fish-like scent Highly toxic, flammable, pyrophoric I
[Threshold Limit Values ppm: 0.05; Permissible Exposure Limit  ppm: 0.05; Lethal Dose ppm: 178; Immediately Dangerous to Life or Health ppm: 3]
Boron tribromide BBr3 10294–33–4 Liquid Compressed gas Colorless Toxic, corrosive II
[Threshold Limit Values ppm: 1; Permissible Exposure Limit  ppm: 1; Lethal Dose ppm: 380; Immediately Dangerous to Life or Health ppm: 50]
Boron trichloride BCl3 10294–34–5 Compressed gas Compressed gas Colorless Corrosive III
[Threshold Limit Values ppm: 5; Permissible Exposure Limit  ppm: 5; Lethal Dose ppm: 2541; Immediately Dangerous to Life or Health ppm: 25]
Boron trifluoride BF3 7637–07–2 Compressed gas Compressed gas Colorless, strong irritating pungent odor Toxic, corrosive II
[Threshold Limit Values ppm: 1; Permissible Exposure Limit  ppm: 1; Lethal Dose ppm: 864; Immediately Dangerous to Life or Health ppm: 25]
Bromine Br2 7726–95–6 Liquid Bromine Brownish red liquid, suffocating odor Highly toxic, corrosive, oxidizer I
[Threshold Limit Values ppm: 0.1; Permissible Exposure Limit  ppm: 0.1; Lethal Dose ppm: 113; Immediately Dangerous to Life or Health ppm: 3]
Carbon dioxide CO2 124-38-9 Compressed gas Compressed gas Colorless, odorless, tasteless Simple asphyxiant IV
[Threshold Limit Values ppm: 5000; Permissible Exposure Limit  ppm: 5000; Immediately Dangerous to Life or Health ppm: 40000]
Carbon monoxide CO 630–08–0 Compressed gas Carbon monoxide Colorless, odorless, tasteless Toxic, flammable III
[Threshold Limit Values ppm: 25; Permissible Exposure Limit  ppm: 25; Lethal Dose ppm: 3760; Immediately Dangerous to Life or Health ppm: 1200]
Chlorine Cl2 7782–50–5 Compressed gas Chlorine Greenish-yellow, pungent odor similar to bleach Toxic, corrosive, oxidizer II
[Threshold Limit Values ppm: 0.5; Permissible Exposure Limit  ppm: 1; Lethal Dose ppm: 293; Immediately Dangerous to Life or Health ppm: 10]
Chlorine dioxide ClO2 10049–04–4 Gas Compressed gas Chlorine-like odor Toxic, oxidizer II
[Threshold Limit Values ppm: 0.1; Permissible Exposure Limit  ppm: 0.1; Lethal Dose ppm: 250; Immediately Dangerous to Life or Health ppm: 5]
Chlorine trifluoride ClF3 7790–91–2 Liquefied gas Compressed gas Colorless, strong irritating odor Toxic, oxidizer, corrosive II
[Threshold Limit Values ppm: 0.1; Permissible Exposure Limit  ppm: 0.1; Lethal Dose ppm: 299; Immediately Dangerous to Life or Health ppm: 20]
Deuterium H2 7782-39-0 Compressed gas Compressed gas Colorless Flammable IV
Diborane B2H6 19278–45–7 Liquefied gas Diborane Colorless, repulsively sweet odor Highly toxic, flammable, pyrophoric I
[Threshold Limit Values ppm: 0.1; Permissible Exposure Limit  ppm: 0.1; Lethal Dose ppm: 80; Immediately Dangerous to Life or Health ppm: 15]
Dichlorosilane SiH2Cl2 (HCl) 4109–96–0 Liquefied gas Compressed gas Colorless Toxic, corrosive, flammable II
[Threshold Limit Values ppm: 2; Permissible Exposure Limit  ppm: 5; Lethal Dose ppm: 314; Immediately Dangerous to Life or Health ppm: 50]
Ethane C2H6 74-84-0 Compressed gas Compressed gas Colorless, odorless Flammable IV
Ethylene C2H4 74-85-1 Compressed gas Compressed gas Colorless, sweet musky odor Flammable IV
Ethylene oxide C2H40 75–21–8 Liquefied gas Ethylene oxide Colorless, faintly sweet odor Toxic, flammable III
[Threshold Limit Values ppm: 1; Permissible Exposure Limit  ppm: 1; Lethal Dose ppm: 2900; Immediately Dangerous to Life or Health ppm: 800]
Fluorine F2 7782–41–4 Compressed gas Hydrogen fluoride Pale yellow, strong, irritating, pungent Highly toxic, corrosive, oxidizer I
[Threshold Limit Values ppm: 0.1; Permissible Exposure Limit  ppm: 0.1; Lethal Dose ppm: 185; Immediately Dangerous to Life or Health ppm: 25]
Germane GeH4 7782–65–2 Liquefied gas Germane Colorless Highly toxic, flammable, pyrophoric II
[Threshold Limit Values ppm: 0.2; Permissible Exposure Limit  ppm: 0.2; Lethal Dose ppm: 620]
Helium He 7440-59-7 Compressed or Liquefied gas Compressed gas Colorless, odorless, tasteless Simple asphyxiant IV
Hydrogen H2 1333-74-0 Compressed gas Compressed gas Colorless, odorless, tasteless Flammable IV
Hydrogen bromide HBr 10035–10–6 Compressed gas Compressed gas Colorless, sharp, unpleasant, pungent odor Toxic, corrosive III
[Threshold Limit Values ppm: 3; Permissible Exposure Limit  ppm: 3; Lethal Dose ppm: 2860; Immediately Dangerous to Life or Health ppm: 30]
Hydrogen chloride HCl 7647–01–0 Compressed gas Compressed gas Colorless, strongly irritating Toxic, corrosive III
[Threshold Limit Values ppm: 5; Permissible Exposure Limit  ppm: 5; Lethal Dose ppm: 2810; Immediately Dangerous to Life or Health ppm: 50]
Hydrogen cyanide HCN 74–90–8 Liquid Hydrogen cyanide Colorless, faint almond-like odor Highly toxic, flammable I
[Permissible Exposure Limit  ppm: 4.7; Lethal Dose ppm: 40; Immediately Dangerous to Life or Health ppm: 50]
Hydrogen fluoride HF 7664–39–3 Liquefied gas Hydrogen fluoride Colorless, strong irritating odor Toxic, corrosive II
[Threshold Limit Values ppm: 0.5; Permissible Exposure Limit  ppm: 3; Lethal Dose ppm: 1300; Immediately Dangerous to Life or Health ppm: 30]
Hydrogen iodide HI 10034-85-2 Liquefied gas Compressed gas Colorless, pungent odor Toxic, corrosive III
[Lethal Dose ppm: 2860]
Hydrogen selenide H2Se 7783–07–5 Compressed gas Hydrogen selenide Colorless, very irritating odor like rotten eggs Highly toxic, flammable I
[Threshold Limit Values ppm: 0.05; Permissible Exposure Limit  ppm: 0.05; Lethal Dose ppm: 51; Immediately Dangerous to Life or Health ppm: 1]
Hydrogen sulfide H2S 7783–06–4 Liquefied gas Compressed gas Colorless, foul odor like rotten eggs Toxic, flammable, corrosive II
[Threshold Limit Values ppm: 10; Permissible Exposure Limit  ppm: 10; Lethal Dose ppm: 712; Immediately Dangerous to Life or Health ppm: 100]
Krypton Kr 7439-90-9 Compressed gas Compressed gas Colorless, odorless, tasteless Simple asphyxiant IV
Methane CH3 74-82-8 Compressed gas Compressed gas Colorless, odorless Flammable IV
Methyl bromide CH3Br 74–83–9 Compressed gas Compressed gas Colorless, odorless, nonflammable Toxic, flammable II
[Threshold Limit Values ppm: 1; Permissible Exposure Limit  ppm: 1; Lethal Dose ppm: 850; Immediately Dangerous to Life or Health ppm: 250]
Methyl chloride CH3Cl 74-87-3 Compressed gas Compressed gas Colorless, mildly sweet odor Flammable IV
[Threshold Limit Values ppm: 50; Permissible Exposure Limit  ppm: 50;  Immediately Dangerous to Life or Health ppm: 2000]
Methyl isocyanate CH3NCO 624-83-9 Liquid Methylisocyanate Colorless Highly toxic, flammable I
[Threshold Limit Values ppm: 0.02; Permissible Exposure Limit  ppm: 0.02; Lethal Dose ppm: 22; Immediately Dangerous to Life or Health ppm: 3]
Methyl mercaptan CH3SH 74–93–1 Liquefied gas Compressed gas Colorless, cabbage-like odor Toxic, flammable II
[Threshold Limit Values ppm: 0.5; Permissible Exposure Limit  ppm: 0.5; Lethal Dose ppm: 1350; Immediately Dangerous to Life or Health ppm: 150]
Neon Ne 1/9/7440 Compressed gas Compressed gas Colorless, odorless, tasteless Simple asphyxiant IV
Nickel carbonyl Ni(CO)4 13463–39–3 Liquid Forbidden at UCSD Musty or sooty odor Highly toxic, flammable I
[Threshold Limit Values ppm: 0.001; Permissible Exposure Limit  ppm: 0.001; Lethal Dose ppm: 18; Immediately Dangerous to Life or Health ppm: 2]
Nitric oxide NO 10102–43–9 Compressed gas Nitric oxide Colorless, irritating odor Highly toxic, oxidizer, corrosive I
[Threshold Limit Values ppm: 25; Permissible Exposure Limit  ppm: 25; Lethal Dose ppm: 115; Immediately Dangerous to Life or Health ppm: 100]
Nitrogen N2 7727-37-9 Compressed or Liquefied gas Compressed gas Colorless, odorless, tasteless Simple asphyxiant IV
Nitrogen dioxide NO2 10102–44–0 Liquefied gas Nitrogen dioxide Reddish-brown color, irritating odor Highly toxic, oxidizer, corrosive I
[Threshold Limit Values ppm: 3; Permissible Exposure Limit  ppm: 5; Lethal Dose ppm: 115; Immediately Dangerous to Life or Health ppm: 20]
Nitrous oxide N2O 10024-97-2 Compressed gas Compressed gas Colorless, faint sweet odor Oxidizer IV
[Threshold Limit Values ppm: 50; Permissible Exposure Limit  ppm: 50]
Oxygen O2 7782-44-7 Compressed gas Compressed gas Colorless, odorless, tasteless Oxidizer IV
Ozone O3 10028-15-6 In situ, dissolved gas Ozone Colorless, sharp odor Highly toxic, oxidizer I
[Threshold Limit Values ppm: 0.05; Permissible Exposure Limit  ppm: 0.1; Lethal Dose ppm: 9; Immediately Dangerous to Life or Health ppm: 5]
Phosgene COCl2 75–44–5 Liquefied gas Phosgene Colorless, odor like freshly cut hay or grass Highly toxic I
[Threshold Limit Values ppm: 0.1; Permissible Exposure Limit  ppm: 0.1; Lethal Dose ppm: 5; Immediately Dangerous to Life or Health ppm: 2]
Phosphine PH3 7803–51–2 Liquefied gas Phosphine Colorless, odorless Highly toxic, flammable, pyrophoric I
[Threshold Limit Values ppm: 0.3; Permissible Exposure Limit  ppm: 0.3; Lethal Dose ppm: 20; Immediately Dangerous to Life or Health ppm: 50]
Phosphorus oxychloride POCl3 10025–87–3 Liquid Phosphorus oxychloride Colorless Highly toxic I
[Threshold Limit Values ppm: 0.1]
Phosphorus pentafluoride PF5 7647-19-0 Liquefied gas Compressed gas Colorless, strong, irritating, pungent odor Toxic, oxidizer, corrosive II
[Permissible Exposure Limit  ppm: 261]
Phosphorus trichloride PCl3 12/2/7719 Liquid Compressed gas Colorless fuming liquid, pungent odor Toxic, corrosive II
[Threshold Limit Values ppm: 0.2; Permissible Exposure Limit  ppm: 0.2; Lethal Dose ppm: 208; Immediately Dangerous to Life or Health ppm: 25]
Propane C3H8 74-98-6 Liquefied gas Compressed gas Colorless Flammable IV
[Permissible Exposure Limit  ppm: 1000]
Selenium hexafluoride SeF6 7783–79–1 Compressed gas Selenium hexafluoride Colorless, strong, irritating, repulsive odor Highly toxic, corrosive I
[Threshold Limit Values ppm: 0.05; Permissible Exposure Limit  ppm: 0.05; Lethal Dose ppm: 50; Immediately Dangerous to Life or Health ppm: 2]
Silane SiH4 7803-62-5 Compressed gas Silane Colorless, sharp repulsive odor Pyrophoric I
[Threshold Limit Values ppm: 5; Permissible Exposure Limit  ppm: 5]
Silicon tetrachloride SiCl4 10026–04–7 Liquid Compressed gas Colorless fuming liquid, irritating odor Toxic, corrosive II
[Threshold Limit Values ppm: 2; Permissible Exposure Limit  ppm: 5; Lethal Dose ppm: 750; Immediately Dangerous to Life or Health ppm: 100]
Silicon tetrafluoride SiF4 (HF) 7783–61–1 Compressed gas Compressed gas Colorless, strong irritating disagreeable odor Toxic, corrosive II
[Threshold Limit Values ppm: 3.2; Permissible Exposure Limit  ppm: 3.2; Lethal Dose ppm: 922; Immediately Dangerous to Life or Health ppm: 30]
Stibine SbH3 7803–52–3 Compressed gas Stibine Colorless, odor like rotten eggs Highly toxic, flammable I
[Threshold Limit Values ppm: 0.1; Permissible Exposure Limit  ppm: 0.1; Lethal Dose ppm: 178; Immediately Dangerous to Life or Health ppm: 5]
Sulfur dioxide SO2 7446–09–5 Liquefied gas Compressed gas Colorless, pungent odor Toxic, corrosive III
[Threshold Limit Values ppm: 2; Permissible Exposure Limit  ppm: 5; Lethal Dose ppm: 2520; Immediately Dangerous to Life or Health ppm: 100]
Sulfur hexafluoride SF6 2551-62-4 Liquefied gas Compressed gas colorless, odorless, tasteless Simple asphyxiant IV
Sulfuryl fluoride SO 2F2 2699–79–8 Liquefied gas Compressed gas Colorless, odorless, strong irritating Toxic, corrosive III
[Threshold Limit Values ppm: 5; Permissible Exposure Limit  ppm: 5; Lethal Dose ppm: 3020; Immediately Dangerous to Life or Health ppm: 1000]
Tellurium hexafluoride TeF6 7783–80–4 Compressed gas Tellurium hexafluoride Colorless gas, repulsive odor, strong irritating Highly toxic, corrosive I
[Threshold Limit Values ppm: 0.02; Permissible Exposure Limit  ppm: 0.02; Lethal Dose ppm: 25; Immediately Dangerous to Life or Health ppm: 1]
Titanium tetrachloride TiCl4 7550–45–0 Liquid Titanium tetrachloride Colorless, yellow or reddish brown Highly toxic, corrosive I
[Permissible Exposure Limit  ppm: 1.3; Lethal Dose ppm: 119; Immediately Dangerous to Life or Health ppm: 1.3]
Tungsten hexafluoride WF6 (HF) 7783–82–6 Compressed gas Compressed gas Colorless, strong irritating Toxic, corrosive II
[Permissible Exposure Limit  ppm: 30; Lethal Dose ppm: 218; Immediately Dangerous to Life or Health ppm: 30]
Vinyl bromide C2H3Br 593-60-2 Liquefied gas Compressed gas Colorless, sweet odor Toxic, flammable IV
[Permissible Exposure Limit  ppm: .01; Lethal Dose ppm: >40,000]
Vinyl chloride C2H3Cl 75-01-4 Liquefied gas Compressed gas Colorless, sweet odor Toxic, flammable IV
[Lethal Dose ppm: 150.000]
Xenon Xe 7440-63-3 Compressed gas Compressed gas Colorless, odorless, tasteless Simple asphyxiant IV

Definition: Liquefied gas

Liquefied gas means a gas which when packaged under pressure, is partially liquid at temperatures above-50°C. A distinction is made between:

(i) High pressure liquefied gas: a gas with a
critical temperature between -50°C and+65°C; and

(ii) Low pressure liquefied gas: a gas with a
critical temperature above +65°C.

Compressed Gas Safety Level (CGSL) defined as ppm:

  • Class I = < 200 LC50
  • Class II = 201–2000 LC50
  • Class III >= 2001–5000 LC50
  • Class IV >= 5000

Class as defined in 2010 Fire Code:

  • Highly toxic = < 200 LC50
  • Toxic = 201–2000 LC50

Table references and resources:

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Important: This chart is intended for use by University of California, San Diego (UCSD) employees only. Standards and requirements may differ at other institutions and businesses.

Important: This chart is intended for use by University of California, San Diego (UCSD) employees only. Standards and requirements may differ at other institutions and businesses.