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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:

Species Reference LC50(ppm) LCLo(ppm) Time Adjusted 0.5-hrLC (CF*) Derivedvalue


G. pig



Lefaux 1968MacEwen and Vernot 1974

Machle et al. 1942

Machle et al. 1942

Tab Biol Per 1933

Wohlslagel et al. 1976











30 min1 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 ppm625 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 ppmBasis 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.