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

CAS number: 302–01–2

NIOSH REL: 0.03 ppm (0.04 mg/m3) 2-hour CEILING; NIOSH considers hydrazine to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 1 ppm (1.3 mg/m3) TWA [skin]

1989 OSHA PEL: 0.1 ppm (0.1 mg/m3) TWA [skin]

1993-1994 ACGIH TLV: 0.1 ppm (0.13 mg/m3) TWA [skin], A2

Description of Substance: Colorless, fuming, oily liquid with an ammonia-like odor.

LEL:. . 2.9% (10% LEL, 2,900 ppm)

Original (SCP) IDLH: 80 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by Patty [1963] that a 4-hour exposure to 80 to 300 ppm killed 14 of 30 rats [Comstock et al. 1954].

Existing short-term exposure guidelines: National Research Council [NRC 1985] Short-term Public Emergency Exposure Guidance Levels (SPEGLs):

1-hour SPEGL: 0.12 ppm
2-hour SPEGL: 0.16 ppm
4-hour SPEGL: 0.03 ppm
8-hour SPEGL: 0.015 ppm
16-hour SPEGL: 0.008 ppm
24-hour SPEGL: 0.005 ppm


Lethal concentration data:

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






Comstock et al. 1954Comstock et al. 1954

Comstock et al. 1954

Comstock et al. 1954

Comstock et al. 1954

Jacobson et al. 1955

Jacobson et al. 1955

LC17: 190260

LC33: 270

LC83: 300










4 hr4 hr

4 hr

4 hr

1 hr

4 hr

4 hr

380 ppm (2.0)520 ppm (2.0)

540 ppm (2.0)

600 ppm (2.0)

788 ppm (1.25)

1,140 ppm (2.0)

504 ppm (2.0)

38 ppm52 ppm

54 ppm

60 ppm

79 ppm

114 ppm

50 ppm


Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derived value
RatMouse Swiecicki 1973Swiecicki 1973 oraloral 6059 ———- 316 ppm311 ppm 32 ppm31 ppm


Human data: None relevant for use in determining the revised IDLH.

Revised IDLH: 50 ppmBasis for revised IDLH: The revised IDLH for hydrazine is 50 ppm based on acute inhalation toxicity data in animals [Comstock et al. 1954; Jacobson et al. 1955]. [Note: NIOSH recommends as part of its carcinogen policy that the “most protective” respirators be worn for hydrazine at concentrations above 0.03 ppm.]



1. Comstock CC, Lawson LH, Greene EA, Oberst FW [1954]. Inhalation toxicity of hydrazine vapor. Arch Ind Hyg Occup Med 10:476-490.

2. Jacobson KH, Clem JH, Wheelwright HJ Jr, Rinehart WE, Mayes N [1955]. The acute toxicity of the vapors of some methylated hydrazine derivatives. AMA Arch Ind Health 12:609-616.

3. NRC [1985]. Emergency and continuous exposure guidance levels for selected airborne contaminants. Vol. 5. Washington, DC: National Academy Press, Committee on Toxicology, Board on Toxicology and Environmental Health Hazards, Commission on Life Sciences, National Research Council, pp. 5-21.

4. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 2224.

5. Swiecicki W [1973]. Toksykologia zwiazkow hydrazyny. Med Pr 24:71-79 (in Polish).