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

CAS number: 334–88–3

NIOSH REL: 0.2 ppm (0.4 mg/m3) TWA

Current OSHA PEL: 0.2 ppm (0.4 mg/m3) TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.2 ppm (0.34 mg/m3) TWA

Description of Substance: Yellow gas with a musty odor.

LEL:. . Unknown

Original (SCP) IDLH: 2 ppm

Basis for original (SCP) IDLH: The only available acute inhalation toxicity data concerning diazomethane is the statement by Patty [1963] that a 10-minute exposure to 175 ppm was lethal for cats [Flury and Zernik 1931]. This concentration is obviously too high for an IDLH. ACGIH [1971] reported that the toxicity of diazomethane seems comparable to that of phosgene. Therefore, the chosen IDLH is based on an analogy with phosgene, which has an IDLH of 2 ppm.

Short-term exposure guidelines: None developed


Lethal concentration data:






Adjusted 0.5-hr




Cat Marhold 1986 175 ----- 10 min 121 ppm (0.69) 12 ppm

Other animal data: It has been suggested that the toxicity of diazomethane is comparable to that of phosgene, possibly because diazomethane is a strong methylating agent [Potts et al. 1949].

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

Revised IDLH: 2 ppm [Unchanged]

Basis for revised IDLH: Based on an analogy to phosgene [Potts et al. 1949] which has an IDLH of 2 ppm, the original IDLH for diazomethane of 2 ppm is not being revised at this time.



1. ACGIH [1971]. Diazomethane. In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 71-72.

2. Flury F, Zernik F [1931]. Schädliche gase dämpfe, nebel, rauch- und staubarten. Berlin, Germany: Verlag von Julius Springer, p. 420 (in German).

3. Marhold J [1986]. Prehled Prumyslove Toxikologie, Organicke Latky. Prague, Czechoslovakia: Avicenum, p. 496 (in Czechoslovakian).

4. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., pp. 940, 2214.

5. Potts AM, Simon FP, Gerard RW [1949]. The mechanism of action of phosgene and diphosgene. Arch Biochem 24:329-337.

Page last reviewed: December 4, 2014