List of highly toxic gases

"Toxic gas" and "Poison gas" redirect here. For the munition, see Chemical weapon. For other uses, see Poison Gas.

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.^[2]
• 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)[5]
					Health	Special Hazard
Arsenic pentafluoride	AsF5	7784-36-3	5	NIOSH PEL TWA 0.001 ppm; REL Ceiling 0.0002 ppm (15 min)	4
Arsine[4]	AsH3	7784-42-1	3	NIOSH REL (C) (15 min): 0.002 mg/m3; OSHA PEL: 0.05 ppm; ACGIH (2006) TWA-TLV 0.05 ppm	4		120 (rat, 10 min)
Bis(trifluoromethyl)peroxide	C2F6O2	927-84-4	10
Boron tribromide[6]	BBr3	10294-33-4	50	ACGIH (1990) / PEL Ceiling limit 1 ppm; AEGL-1: 0.33 ppm, AEGL-2: 1.7 ppm, AEGL-3: 5 ppm	3	W
Boron trichloride[7]	BCl3	10294-34-5	25	No exposure limits have established; 2500 (TQ)	4	W	2541 (rat, 1 h)[8]
Boron trifluoride	BF3	7637-07-2	25	OSHA, ACGIH (1962) 1 ppm ceiling	4		436 (4 h)[8]
Bromine	Br2	7726-95-6	3	OSHA PEL 8-hr TWA: 0.1 ppm; ACGIH (1991) STEL-TLV 0.3 ppm	3	OX	174 (mice)	<0.01
Bromine chloride	BrCl	13863-41-7		1500 (TQ)	3	OX
Bromomethane	CH3Br	74-83-9	250	NIOSH PEL 20 ppm	3		302 (Rat, 8 h)[9]
Carbon monoxide	CO	630-08-0	1,200 (moderately toxic)	ACGIH (1989) TWA TLV 25 ppm; NIOSH 35 ppm; NIOSH 200 ppm Ceiling limit	3		4600/5000[10]
Chlorine	Cl2	7782-50-5	10	ACGIH (1986) STEL-TLV 1 ppm	3	OX	433 (10 min), 250 (30 min)	1
Chlorine pentafluoride	ClF5	13637-63-3		AEGL-2: 0.33 ppm, AEGL-3: 2.7 ppm			194 (Rat)
Chlorine trifluoride	ClF3	7790-91-2	12	ACGIH (1979) Ceiling limit 0.1 ppm	4	W+OX	95 (Rat, 4 h)	Inadequate odor
Chloropicrin[note 1]	CCl3NO2	76-06-2	2	ACGIH (1990) TWA-TLV 0.1 ppm	4		9.7 (Mouse, 4 h)
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		175 (Cat, 10 min)
Diborane	B2H6	19287-45-7	15	ACGIH (1990) TWA-TLV 0.1 ppm	4	W	40 (Rat, 4 h)	Inadequate odor
Dichloroacetylene[note 2]	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		90 mg/L (fish, 24 h)
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		333 (mouse, 2 h)
Germane	GeH4	7782-65-2		NIOSH REL 0.2 ppm	4		440 (mice 2 h)
Hydrogen azide	HN3	7782-79-8		NIOSH REL: 0.1 ppm Ceiling	4
Hydrogen cyanide	HCN	74-90-8	50	PEL TWA 10 ppm; REL ST 4.7 ppm	4		503 (Rat, 5 min)
Hydrogen fluoride	HF	7664-39-3	30	PEL TWA 3 ppm; REL TWA 3 ppm (2.5 mg/m³); TWA 3 ppm	4	POI	LCLo 313 (rabbit, 7 hr)
Hydrogen selenide	H2Se	7783-07-5	1	ACGIH (1990) TWA-TLV 0.05 ppm	4		1.8 (G.Pig, 47 h)
Hydrogen sulfide	H2S	7783-06-4	100	NIOSH PEL: Ceiling 20 ppm; REL Ceiling 10 ppm; ACGIH (1990) STEL-TLV 15 ppm	4		444	0.3
Hydrogen telluride	H2Te	7783-09-7			4
Nickel tetracarbonyl	Ni(CO)4	13463-39-3	2	NIOSH TWA PEL 0.001 ppm; ACGIH (1980) TWA-TLV 0.05 ppm	4		9.642[11]
Nitrogen dioxide	NO2	10102-44-0	13	NIOSH PEL Ceiling 5 ppm; REL ST 1 ppm	3	OX	99 (mice, 1 h)	4
Osmium tetroxide	OsO4	20816-12-0	0.001	NIOSH PEL TWA 0.0002 ppm; REL TWA 0.0002 ppm, ST 0.0006 ppm	3	OX	40 (rat, 4 h)	0.0019
Oxygen difluoride	OF2	7783-41-7	0.5	NIOSH PEL TWA 0.05 ppm; REL Ceiling 0.05 ppm; ACGIH (1983) ceiling limit 0.05 ppm	4	OX	26.067 (Rhesus monkeys, 1 h)	0.5
Perchloryl fluoride	ClFO3	7616-94-6	100	NIOSH PEL TWA 3 ppm; REL TWA 3 ppm, ST 6 ppm; ACGIH (1962) STEL-TLV 6 ppm	3	OX	385 (Rat, 4 h)
Perfluoroisobutylene	C4F8	382-21-8		1.2 ppm			17 (Rat, 10 min)
Phosgene	CCl2O	75-44-5	2	NIOSH PEL TWA 0.1 ppm; REL TWA 0.1 ppm, Ceiling 0.2 ppm; ACGIH (1992) TWA-TLV 0.1 ppm	4			0.5 to 1.5
Phosphine	PH3	7803-51-2	50	NIOSH 0.3 ppm time weighted average; ACGIH (1992) STEL-TLV 1 ppm	4		0.44 (Rat, 4 h)
Phosphorus pentafluoride[12]	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[13]	SiCl4	10026-04-7		OSHA PEL, NIOSH REL 5 ppm; ACGIH TLV 2 ppm	3	W	8000 (Rat, 4 h)	1 - 5
Silicon tetrafluoride	SiF4	7783-61-1			3	W	922 (Rat, 1 h)
Stibine[14]	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	2 (Rat, 10 min)
Sulfur tetrafluoride	SF4	7783-60-0		OSHA PEL/NIOSH REL/ACGIH (1992) ceiling limit 0.1 ppm[15]	3	W	40 (Rat, 1 h)[15]
Tellurium hexafluoride	TeF6	7783-80-4	1	NIOSH REL/ACGIH (1992) TWA-TLV 0.02 ppm
Tetraethyl pyrophosphate[note 1]	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		38 (Rat, 4 h)
Trifluoroacetyl chloride	C2ClF3O	354-32-5
Tungsten hexafluoride[16]	WF6	7783-82-6		OSHA PEL TWA 2.5 ppm; ACGIH TLV TWA 3 ppm	3	W	218 (Rat, 1 h)

See also

• List of Schedule 1 substances (CWC)
• EPA list of extremely hazardous substances
• Chemical warfare
• Chemical weapon
• List of chemical warfare agents
• List of psychoactive drugs used by militaries
• Psychochemical warfare
• List of gases
• Toxicity class
• Toxicity label

Notes

1. Decomposes in gaseous form.
2. Explodes in gaseous form.