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May 1994

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


CAS number: 76–12–0

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

Description of substance: Colorless solid or liquid (above 77°F) with a slight, ether-like odor.

LEL: . . Noncombustible Solid/Noncombustible Liquid

Original (SCP) IDLH: 15,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by ACGIH [1971] that exposure to 10,000 ppm for 1.5 to 2 hours produced slight intoxication in rats but no loss of reflexes [Greenberg and Lester 1950], and on the report that a 4-hour exposure to 15,000 ppm was fatal to rats [Clayton et al. 1966].

Short-term exposure guidelines: None developed


Lethal concentration data:






TimeAdjusted 0.5-hr


Derived value



Clark & Tinston 1982

Clayton et al. 1966

Izmerov et al. 1982







15 min

4 hr

2 hr

15,800 ppm (0.79)

30,000 ppm (2.0)

23,235 ppm (1.6)

1,580 ppm

3,000 ppm

2,324 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 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 1,1,2,2-tetrachloro-1,2-difluoroethane is 2,000 ppm based on acute inhalation toxicity data in animals [Greenberg and Lester 1950] and to be consistent with the revised IDLH for the similar chlorofluorocarbon 1,1,1,2-tetrachloro-2,2-difluoroethane which has a revised IDLH of 2,000 ppm. This may be a conservative value due to the lack of relevant acute toxicity data for workers.


1. ACGIH [1971]. 1,1,2,2-Tetrachloro 1,2-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. Clark DG, Tinston DJ [1982]. Acute inhalation toxicity of some halogenated and non-halogenated hydrocarbons. Hum Toxicol 1:239-247.

3. 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.

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

5. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 54.

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