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May 1994

Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs)


CAS number: 7664-41-7

NIOSH REL: 25 ppm (18 mg/m3) TWA, 35 ppm (27 mg/m3) STEL

Current OSHA PEL: 50 ppm (35 mg/m3) TWA

1989 OSHA PEL: 35 ppm (27 mg/m3) STEL

1993-1994 ACGIH TLV: 25 ppm (17 mg/m3) TWA, 35 ppm (24 mg/m3) STEL

Description of substance: Colorless gas with a pungent, suffocating odor.

LEL: 15% (10% LEL, 15,000 ppm)

Original (SCP) IDLH: 500 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by AIHA [1971] that 300 to 500 ppm for 30 to 60 minutes have been reported as a maximum short exposure tolerance [Henderson and Haggard 1943]. AIHA [1971] also reported that 5,000 to 10,000 ppm are reported to be fatal [Mulder and Van der Zahm 1967] and exposures for 30 minutes to 2,500 to 6,000 ppm are considered dangerous to life [Smyth 1956].

Existing short-term exposure:
1988 American Industrial Hygiene Association (AIHA) Emergency Response Planning Guidelines (ERPGs)

  • ERPG-1: 25 ppm
  • ERPG-2: 200 ppm
  • ERPG-3: 1,000 ppm
National Research Council [NRC 1987] Emergency Exposure Guidance Levels (EEGLs)
  • 1-hour EEGL: 100 ppm
  • 24-hour EEGL: 100 ppm
U.S. Navy Standards [U.S. Bureau of Ships 1962] Maximum allowable concentrations (MACs):
  • Continuous exposure (60 days): 25 ppm
  • 1 hour: 400 ppm


Lethal concentration data:

SpeciesReferenceLC50(ppm)LCLo(ppm)TimeAdjusted 0.5-hr LC (CF)Derived Value
RatAlarie 198140,300-----10 min23,374 ppm (0.58)2,337 ppm
RatAlarie 198128,595-----20 min23,448 ppm (0.82)2,335 ppm
RatAlarie 198120,300-----40 min23,345 ppm (1.15)2,335 ppm
RatAlarie 198111,590-----1 hr16,342 ppm (1.41)1,634 ppm
RatBack et al. 19727,338-----1 hr10,347 ppm (1.41)1,035 ppm
MouseBack et al. 19724,837-----1 hr6,820 ppm (1.41)682 ppm
RabbitBoyd et al. 19449,859----- 1 hr13,901 ppm (1.41)1,309 ppm
CatBoyd et al. 19449,859----- 1 hr13,901 ppm (1.41)1,309 ppm
RatDeichmann and Gerarde 19692,000-----4 hr5,660 ppm (2.83) 566 ppm
MammalFlury 1928-----5,0005 min2,050 ppm (0.41)205 ppm
MouseKapeghian et al. 19824,230-----1 hr5,964 ppm (1.41)596 ppm
HumanTab Biol Per 1933-----5,0005 min 2,050 ppm (0.41)205 ppm
*Note: Conversion factor (CF) was determined with "n" = 2.0 [ten Berge et al. 1986].

Other animal data:RD50 (mouse), 303 ppm [Appelman et al. 1982].

Other human data: The maximum short exposure tolerance has been reported as being 300 to 500 ppm for 0.5 to 1 hour [Henderson and Haggard 1943]. A change in respiration rate and moderate to severe irritation has been reported in 7 subjects exposed to 500 ppm for 30 minutes [Silverman et al. 1946].

Revised IDLH: 300 ppm
Basis for revised IDLH: The revised IDLH for ammonia is 300 ppm based on acute inhalation toxicity data in humans [Henderson and Haggard 1943; Silverman et al. 1946].


  1. AIHA [1971]. Anhydrous ammonia. In: Hygienic guide series. Am Ind Hyg Assoc J 32:139-142.
  2. Alarie Y [1981]. Dose-response analysis in animal studies: prediction of human responses. Environ Health Perspect 42:9-13.
  3. Appelman LM, ten Barge WF, Reuzel PGJ [1982]. Acute inhalation toxicity study of ammonia in rats with variable exposure periods. Am Ind Hyg Assoc J 43:662-665.
  4. Back KC, Thomas AA, MacEwen JD [1972]. Reclassification of materials listed as transportation health hazards. Wright-Patterson Air Force Base, OH: 6570th Aerospace Medical Research Laboratory, Report No. TSA-20-72-3, pp. A-172 to A-173.
  5. Boyd EM, MacLachlan ML, Perry WF [1944]. Experimental ammonia gas poisoning in rabbits and cats. J Ind Hyg Toxicol 26:29-34.
  6. Deichmann WB, Gerarde HW [1969]. Trifluoroacetic acid (3FA). In: Toxicology of drugs and chemicals. New York, NY: Academic Press, Inc., p. 607.
  7. Flury F [1928]. Moderne gewerbliche vergiftungen in pharmakologisch-toxikologischer hinsicht (Pharmacological-toxicological aspects of intoxicants in modern industry). Arch Exp Pathol Pharmakol 138:65-82 (translated).
  8. Henderson Y, Haggard HW [1943]. Noxious gases. 2nd ed. New York, NY: Reinhold Publishing Corporation, p. 126.
  9. Kapeghian JC, Jones AB, Mincer HH, Verlangieri AJ, Waters IW [1982]. The toxicity of ammonia gas in the mouse. Fed Proc 41:1568 [Abstract #7586].
  10. Mulder JS, Van der Zahm HO [1967]. Fatal case of ammonium poisoning. Tydschrift Voor Sociale Geneeskunde (Amsterdam) 45:458-460 (translated).
  11. 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. 7-15.
  12. Silverman L, Whittenberger JL, Muller J [1946]. Physiological response of man to ammonia in low concentrations. J Ind Hyg Toxicol 31:74-78.
  13. Smyth HF Jr [1956]. Improved communication: hygienic standards for daily inhalation. Am Ind Hyg Assoc Q 17(2):129-185.
  14. Tab Biol Per [1933]; 3:231-296 (in German).
  15. 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.
  16. U.S. Bureau of Ships [1962]. Submarine atmosphere habitability data book. AVSHIPS 250-649-1. Rev. 1. Washington, DC: U.S. Department of the Navy, U.S. Bureau of Ships, p. 629.
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