Hydrogen chloride

May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

CAS number: 7647–01–0

NIOSH REL: 5 ppm (7 mg/m3) CEILING

Current OSHA PEL: 5 ppm (7 mg/m3) CEILING

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 5 ppm (7.5 mg/m3) CEILING

Description of Substance: Colorless to slightly yellow gas with a pungent, irritating odor.

LEL:. . Nonflammable Gas

Original (SCP) IDLH: 100 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statements by Patty [1963] that according to Matt [1889] as cited in Flury and Zernik [1931], work is impossible when one inhales air containing hydrogen chloride in concentrations of 75 to 150 mg/m3 (50 to 100 ppm); work is difficult but possible when the air contains concentrations of 15 to 75 mg/m3 (10 to 50 ppm); and work is undisturbed at the concentration of 15 mg/m3 (10 ppm).

Existing short-term exposure guidelines: National Research Council [NRC 1987] Emergency Exposure Guidance Levels (EEGLs) and Short-term Public Emergency Guidance Levels (SPEGLs):

10-minute EEGL: 100 ppm

1-hour EEGL: 20 ppm

24-hour EEGL: 20 ppm

1-hour SPEGL: 1 ppm

24-hour SPEGL: 1 ppm


Lethal concentration data:






Adjusted 0.5-hr

LC (CF*)






G. pig



Lefaux 1968

MacEwen and Vernot 1974

Machle et al. 1942

Machle et al. 1942

Tab Biol Per 1933

Wohlslagel et al. 1976













30 min

1 hr

30 min

30 min

5 min

1 hr

1,300 ppm (1.0)

6,248 ppm (2.0)

4,416 ppm (1.0)

4,416 ppm (1.0)

500 ppm (0.17)

2,216 ppm (2.0)

130 ppm

625 ppm

442 ppm

442 ppm

50 ppm

222 ppm

*Note: Conversion factor (CF) was determined with "n" = 1.0 [ten Berge et al. 1986].

Other animal data: RD50 (mouse), 309 ppm [Alarie 1981].

Other human data: It has been reported that 50 to 100 ppm for 1 hour is barely tolerable and that 35 ppm causes irritation of the throat [Henderson and Haggard 1943]. It has also been reported that work is impossible at 50 to 100 ppm but is difficult but possible at 10 to 50 ppm [Flury and Zernik 1931].

Revised IDLH: 50 ppm

Basis for revised IDLH: The revised IDLH for hydrogen chloride is 50 ppm based on acute inhalation toxicity data in humans [Flury and Zernik 1931; Henderson and Haggard 1943; Tab Biol Per 1933].



1. Alarie Y [1981]. Dose-response analysis in animal studies: prediction of human responses. Environ Health Perspect 42:9-13.

2. Flury F, Zernik F [1931]. Schädliche gase dämpfe, nebel, rauch- und staubarten. Berlin, Germany: Verlag von Julius Springer, p. 128 (in German).

3. Henderson Y, Haggard HW [1943]. Noxious gases. 2nd ed. New York, NY: Reinhold Publishing Co., p. 126.

4. Lefaux R [1968]. Practical toxicology of plastics. Cleveland, OH: Chemical Rubber Co., p. 207.

5. MacEwen JD, Vernot EH [1974]. Toxic Hazards Research Unit annual report: 1974. Wright-Patterson Air Force Base, OH: Air Force Systems Command, Aerospace Medical Division, Aerospace Medical Research Laboratory Report, AMRL-TR-74-78.

6. Machle W, Kitzmiller KV, Scott EW, Treon JF [1942]. The effect of the inhalation of hydrogen chloride. J Ind Hyg Toxicol 24:222-225.

7. Matt L [1889]. Doctoral dissertation. Wurzburg, Germany: Julius Maximillian University (in German). [From Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 851.]

8. NRC [1987]. Emergency and continuous exposure guidance levels for selected airborne contaminants. Vol. 7. Ammonia, hydrogen chloride, lithium bromide, and toluene. Washington, DC: National Academy Press, Committee on Toxicology, Board on Toxicology and Environmental Health Hazards, Commission on Life Sciences, National Research Council, pp. 17-30.

9. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 851.

10. Tab Biol Per [1933]; 3:231 (in German).

11. ten Berge WF, Zwart A, Appelman LM [1986]. Concentration-time mortality response relationship of irritant and systematically acting vapours and gases. J Haz Mat 13:301-309.

12. Wohlslagel J, Dipasquale LC, Vernot EH [1976]. Toxicity of solid rocket motor exhaust: effects of Hcl, HF, and alumina on rodents. J Combustion Toxicol 3:61-70.

Page last reviewed: December 4, 2014