List of highly toxic gases explained

Many gases have toxic properties, which are often assessed using the LC₅₀ (median lethal concentration) measure. In the United States, many of these gases have been assigned an NFPA 704 health rating of 4 (may be fatal) or 3 (may cause serious or permanent injury), and/or exposure limits (TLV, TWA/PEL, STEL, or REL) determined by the ACGIH professional association. Some, but by no means all, toxic gases are detectable by odor, which can serve as a warning. Among the best known toxic gases are carbon monoxide, chlorine, nitrogen dioxide and phosgene.

Definitions

• Toxic: a chemical that has a median lethal concentration (LC₅₀) in air of more than 200 parts per million (ppm) but not more than 2,000 parts per million by volume of gas or vapor, or more than 2 milligrams per liter but not more than 20 milligrams per liter of mist, fume or dust, when administered by continuous inhalation for 1 hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each.^{[1] [2]}
• Highly Toxic: a gas that has a LC₅₀ in air of 200 ppm or less.
• NFPA 704

Materials that, under emergency conditions, can cause serious or permanent injury are given a Health Hazard rating of 3. Their acute inhalation toxicity corresponds to those vapors or gases having LC₅₀ values greater than 1,000 ppm but less than or equal to 3,000 ppm. Materials that, under emergency conditions, can be lethal are given a Health Hazard rating of 4. Their acute inhalation toxicity corresponds to those vapors or gases having LC₅₀ values less than or equal to 1,000 ppm.

List

Chemical name[3]	Chemical formula	CAS number	NIOSH IDLH (ppm)	OSHA PEL / NIOSH REL / ACGIH TLV[4]	NFPA 704 Ratings		LC50 (ppm)[5]	Odor threshold (ppm)
					Health	Special Hazard
Arsenic pentafluoride	AsF5	7784-36-3	5		4
Arsine	AsH3	7784-42-1	3		4
Bis(trifluoromethyl)peroxide	C2F6O2	927-84-4	10
Boron tribromide[6]	BBr3	10294-33-4	50		3	W
Boron trichloride[7]	BCl3	10294-34-5	25		4	W	[8]
Boron trifluoride	BF3	7637-07-2	25	OSHA, ACGIH (1962) 1 ppm ceiling	4
Bromine	Br2	7726-95-6	3		3	OX		<0.01
Bromine chloride	BrCl	13863-41-7		1500 (TQ)	3	OX
Bromomethane	CH3Br	74-83-9	250	NIOSH PEL 20 ppm	3		[9]
Carbon monoxide	CO	630-08-0	1,200 (moderately toxic)		3		[10]
Chlorine	Cl2	7782-50-5	10	ACGIH (1986) STEL-TLV 1 ppm	3	OX		1
Chlorine pentafluoride	ClF5	13637-63-3
Chlorine trifluoride	ClF3	7790-91-2	12	ACGIH (1979) Ceiling limit 0.1 ppm	4	W+OX		Inadequate odor
Chloropicrin[11]	CCl3NO2	76-06-2	2	ACGIH (1990) TWA-TLV 0.1 ppm	4
Cyanogen	C2N2	460-19-5		ACGIH (1966) TWA-TLV 10 ppm	4
Cyanogen chloride	CNCl	506-77-4		ACGIH (1977) ceiling limit 0.3 ppm	4
Diazomethane	CH2N2	334-88-3	2	ACGIH (1970) TWA-TLV 0.2 ppm	4
Diborane	B2H6	19287-45-7	15	ACGIH (1990) TWA-TLV 0.1 ppm	4	W		Inadequate odor
Dichloroacetylene[12]	C2Cl2	7572-29-4		NIOSH REL 0.1 ppm Ceiling
Dichlorosilane	H2Cl2Si	4109-96-0		2500 (TQ)	4	W	1785-2092
Dimethylmercury	HgC2H6	593-74-8			4
Ethylene oxide (anhydrous)	C2H4O	75-21-8	800	REL TWA <0.1 ppm, 5 ppm Ceiling	3
Fluorine	F2	7782-41-4		ACGIH (1970) STEL-TLV 2 ppm	4	OX		20 ppb
Formaldehyde (anhydrous)	CH2O	50-00-0	20	NIOSH REL 0.016 ppm, Ceiling limit 0.1 ppm	3
Germane	GeH4	7782-65-2		NIOSH REL 0.2 ppm	4
Hydrogen azide	HN3	7782-79-8		NIOSH REL: 0.1 ppm Ceiling	4
Hydrogen cyanide	HCN	74-90-8	50		4
Hydrogen fluoride	HF	7664-39-3	30		4	POI
Hydrogen selenide	H2Se	7783-07-5	1	ACGIH (1990) TWA-TLV 0.05 ppm	4
Hydrogen sulfide	H2S	7783-06-4	100		4			0.3
Hydrogen telluride	H2Te	7783-09-7			4
Nickel tetracarbonyl	Ni(CO)4	13463-39-3	2		4		9.642[13]
Nitrogen dioxide	NO2	10102-44-0	13		3	OX		4
Osmium tetroxide	OsO4	20816-12-0	0.001		3	OX		0.0019
Oxygen difluoride	OF2	7783-41-7	0.5		4	OX		0.5
Perchloryl fluoride	ClFO3	7616-94-6	100		3	OX
Perfluoroisobutylene	C4F8	382-21-8		1.2 ppm
Phosgene	CCl2O	75-44-5	2		4
Phosphine	PH3	7803-51-2	50		4
Phosphorus pentafluoride[14]	PF5	7647-19-0	25	TLV - TWA 0.25 ppm ACGIH & OSHA	4
Selenium hexafluoride	SeF6	7783-79-1	2	OSHA PEL, NIOSH REL, ACGIH (1992) TWA-TLV 0.05 ppm	3
Silicon tetrachloride[15]	SiCl4	10026-04-7			3	W
Silicon tetrafluoride	SiF4	7783-61-1			3	W
Stibine[16]	H3Sb	7803-52-3	5	OSHA PEL/NIOSH REL/ACGIH TLV: 0.1 ppm	4
Disulfur decafluoride	S2F10	5714-22-7	1	ACGIH (1962) ceiling limit 0.01 ppm	4	OX
Sulfur tetrafluoride	SF4	7783-60-0		OSHA PEL/NIOSH REL/ACGIH (1992) ceiling limit 0.1 ppm[17]	3	W
Tellurium hexafluoride	TeF6	7783-80-4	1	NIOSH REL/ACGIH (1992) TWA-TLV 0.02 ppm
Tetraethyl pyrophosphate	C8H20O7P2	107-49-3	5	ACGIH (2006) TWA-TLV 0.01 mg/m3	4
Sulfotep	C8H20O5P2S2	3689-24-5	10	NIOSH PEL TWA 0.2 ppm	4
Trifluoroacetyl chloride	C2ClF3O	354-32-5
Tungsten hexafluoride[18]	WF6	7783-82-6			3	W

See also

• List of Schedule 1 substances (CWC)
• EPA list of extremely hazardous substances
• List of gases

External links

• OSHA Limits for Air Contaminants
• OSHA Permissible Exposure Limits
• California Department of Industrial Relations Permissible Exposure Limits for Chemicals

Notes and References

1. Web site: California Fire Code California Code of Regulations,Title 24, Part 9, Chapter 2 - Definitions.
2. Web site: Environmental Health and Radiation Safety Department at the University of Pennsylvania.
3. Web site: Chemical Name Search. 2021-11-10. webbook.nist.gov.
4. Web site: CDC - NIOSH Pocket Guide to Chemical Hazards - Arsenic (inorganic compounds, as As). 2021-11-10. www.cdc.gov.
5. Web site: 2011-07-16 . Principles for the safe handling and distribution of highly toxic gases and mixtures . AIGA 026/06 . Asia Industrial Gases Association . 2021-09-22 . https://web.archive.org/web/20110716144944/http://www.asiaiga.org/docs/AIGA%20026_06%20Principles%20for%20safe%20handling%20&%20distribution%20of%20h.pdf . 2011-07-16.
6. Web site: 2020-02-25. 1988 OSHA PEL Project - Boron Tribromide NIOSH CDC. 2021-11-10. www.cdc.gov. en-us.
7. Web site: PubChem. Boron trichloride. 2021-11-10. pubchem.ncbi.nlm.nih.gov. en.
8. Book: Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 17 . Boron Tribromide . 2014. 10.17226/18796. 978-0-309-30476-4. en.
9. Methyl bromide - OECD HPVMETHYL BROMIDE CAS N°: 74-83-9
10. Levin. B. C.. Paabo. M.. Gurman. J. L.. Harris. S. E.. Braun. E.. 1987-12-01. Toxicological interactions between carbon monoxide and carbon dioxide. Toxicology. 47. 1–2. 135–164. 10.1016/0300-483x(87)90165-x. 0300-483X. 3120355.
11. Decomposes in gaseous form.
12. Explodes in gaseous form.
13. Book: Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 6 . . 2007 . 978-0-309-11214-7.
14. Web site: January 6, 2023 . Phosphorus(V) fluoride Safety Data Sheet . ThermoFisher Scientific.
15. Web site: October 2010 . Silicon Tetrachloride Hazardous Substance Fact Sheet . New Jersey Department of Health.
16. Web site: August 2001 . Stibine Hazardous Substance Fact Sheet . New Jersey Department of Health and Senior Services.
17. Web site: Sulfur Tetrafluoride Safety Data Sheet . Airgas.
18. Web site: Tungsten Hexafluoride Safety Data Sheet . Airgas.