Ethyl mercaptan

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

CAS number: 75–08–1

NIOSH REL: 0.5 ppm (1.3 mg/m3) 15-minute CEILING

Current OSHA PEL: 10 ppm (25 mg/m3) CEILING

1989 OSHA PEL: 0.5 ppm (1 mg/m3) TWA

1993-1994 ACGIH TLV: 0.5 ppm (1.3 mg/m3) TWA

Description of Substance: Colorless liquid with a strong, skunk-like odor.

LEL:. . 2.8% (10% LEL, 2,800 ppm)

Original (SCP) IDLH: 2,500 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the mouse 4-hour LC50 of 2,770 ppm [Fairchild and Stokinger 1958 cited by ACGIH 1971].

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50(ppm) LCLo(ppm) Time Adjusted 0.5-hrLC (CF) Derivedvalue
RatMouse Fairchild and Stokinger 1958Fairchild and Stokinger 1958 4,4202,770 ———- 4 hr4 hr 8,840 ppm (2.0)5,540 ppm (2.0) 884 ppm554 ppm


Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derivedvalue
Rat Fairchild and Stokinger 1958 oral 682 —– 1,849 ppm 185 ppm


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



1. ACGIH [1971]. Ethyl mercaptan (ethanethiol). In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 107.

2. Fairchild EJ II, Stokinger HE [1958]. Toxicologic studies on organic sulfur compounds. I. Acute toxicity of some aliphatic and aromatic thiols (mercaptans). Am Ind Hyg Assoc J 19:171-189.

Page last reviewed: December 4, 2014