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

CAS number: 76–11–9

NIOSH REL: 500 ppm (4,170 mg/m3) TWA

Current OSHA PEL: 500 ppm (4,170 mg/m3) TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 500 ppm (4,170 mg/m3) TWA

LEL :. . Noncombustible solid

Description of substance: Colorless solid with a slight, ether-like odor.

Original (SCP) IDLH: 15,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by Patty [1963] that rats became slightly intoxicated after being exposed for 1.5 hours to 15,000 ppm [Greenburg and Lester 1950] and on the statement by ACGIH [1971] that rats died following a 4-hour exposure to 15,000 ppm [Clayton et al. 1966].

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50




Time Adjusted 0.5-hr


Derived value


Clayton et al. 1966

Torkelson et al. 1971





4 hr

30 min

30,000 ppm (2.0)

20,000 ppm (1.0)

3,000 ppm

2,000 ppm

Other animal data: Rats exposed to 10,000 ppm for 1.5 to 2 hours showed slight signs of intoxication but no loss of reflexes, while a concentration of 20,000 to 30,000 ppm was fatal in 1.0 to 2.5 hours [Greenberg and Lester 1950].

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

Revised IDLH: 2,000 ppm

Basis for revised IDLH: The revised IDLH for 1,1,1,2-tetrachloro-2,2-difluoroethane is 2,000 ppm based on acute inhalation toxicity data in animals [Torkelson et al. 1971] and to be consistent with the revised IDLH for the similar chlorofluorocarbon 1,1,2,2-tetrachloro-1,2-difluoroethane which has a revised IDLH of 2,000 ppm. This may be a conservative value due to the lack of relevant acute inhalation toxicity data for workers.


1. ACGIH [1971]. 1,1,1,2-Tetrachloro-2,2-difluoroethane. In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 249.

2. Clayton JW Jr, Sherman H, Morrison SD, Barnes JR, Hood DB [1966]. Toxicity studies on 1,1,2,2-tetrachloro-1,2-difluoroethane and 1,1,1,2-tetrachloro-2,2-difluoroethane. Am Ind Hyg Assoc J 27(4):332-340.

3. Greenberg LA, Lester D [1950]. Toxicity of the tetrachlorodifluoroethanes. AMA Arch Ind Hyg Occup Med 2:345-347.

4. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1331.

5. Torkelson TR, Kary CD, Chenoweth MB, Larsen ER [1971]. Single exposure of rats to the vapors of trace substances in methoxyflurane. Toxicol Appl Pharmacol 19:1-9.

Page last reviewed: December 4, 2014