Skip directly to local search Skip directly to A to Z list Skip directly to navigation Skip directly to site content Skip directly to page options
CDC Home
May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

Carbon dioxide

CAS number: 124–38–9

NIOSH REL: 5,000 ppm (9,000 mg/m3) TWA,

30,000 ppm (54,000 mg/m3) STEL

Current OSHA PEL: 5,000 ppm (9,000 mg/m3) TWA

1989 OSHA PEL: 10,000 ppm (18,000 mg/m3) TWA,

30,000 ppm (54,000 mg/m3) STEL

1993-1994 ACGIH TLV: 5,000 ppm (9,000 mg/m3) TWA,

30,000 ppm (54,000 mg/m3) STEL

Description of Substance: Colorless, odorless gas.

LEL: . . Nonflammable Gas

Original (SCP) IDLH: 50,000 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statements by ACGIH [1971] that a 30-minute exposure at 50,000 ppm produces signs of intoxication, and a few minutes of exposure at 70,000 ppm and 100,000 ppm produces unconsciousness [Flury and Zernik 1931]. AIHA [1971] reported that 100,000 ppm is the atmospheric concentration immediately dangerous to life. In addition, Hunter [1975] noted that exposure to 100,000 ppm for only a few minutes can cause loss of consciousness.

Short-term exposure guidelines: None developed


Lethal concentration data:







Adjusted 0.5-hr




HumanTab Biol Per 1933-----90,0005 min49,500 ppm (0.55)4,950 ppm

Other human data: Signs of intoxication have been produced by a 30-minute exposure at 50,000 ppm [Aero 1953], and a few minutes exposure at 70,000 to 100,000 ppm produces unconsciousness [Flury and Zernik 1931]. It has been reported that submarine personnel exposed continuously at 30,000 ppm were only slightly affected, provided the oxygen content of the air was maintained at normal concentrations [Schaefer 1951]. It has been reported that 100,000 ppm is the atmospheric concentration immediately dangerous to life [AIHA 1971] and that exposure to 100,000 ppm for only a few minutes can cause loss of consciousness [Hunter 1975].


Revised IDLH: 40,000 ppm

Basis for revised IDLH: The revised IDLH for carbon dioxide is 40,000 ppm based on acute inhalation toxicity data in humans [Aero 1953; Flury and Zernik 1931; Schaefer 1951].


1. ACGIH [1971]. Carbon dioxide. In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 39.

2. Aero Medical Association [1953]. Committee on Aviation Toxicology, Blakiston, New York.

3. AIHA [1964]. Carbon dioxide. In: Hygienic guide series. Am Ind Hyg Assoc J 25:519-521.

4. Flury F, Zernik F [1931]. Schädliche gase dämpfe, nebel, rauch- und staubarten. Berlin, Germany: Verlag von Julius Springer, pp. 218-219 (in German).

5. Hunter D [1975]. The diseases of occupations. 5th ed. London, England: Hodder and Stoughton, p. 618.

6. Schaefer KE [1951]. Studies of carbon dioxide toxicity. New London, CT: Navy Department, Bureau of Medicine and Surgery, Medical Research Laboratory, U.S. Naval Submarine Base, Vol. 10, Report No. 181, pp. 156-189.

7. Tab Biol Per [1933]; 3:231 (in German).

Contact Us: The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Road Atlanta, GA 30329-4027, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC–INFO