An official website of the United States government
Carbon monoxide
May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)
CAS number: 630–08–0
NIOSH REL: 35 ppm (40 mg/m3) TWA, 200 ppm (229 mg/m3) CEILING
Current OSHA PEL: 50 ppm (55 mg/m3) TWA
1989 OSHA PEL: 35 ppm (40 mg/m3) TWA, 200 ppm (229 mg/m3) CEILING
1993-1994 ACGIH TLV: 25 ppm (29 mg/m3) TWA
Description of Substance: Colorless, odorless gas.
LEL: . . 12.5% (10% LEL, 12,500 ppm)
Original (SCP) IDLH: 1,500 ppm
Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by Patty [1963] that a 1-hour exposure to 1,000 to 1,200 ppm would cause unpleasant, but no dangerous symptoms [Henderson et al. 1921]. Patty [1963] also reported that 1,500 to 2,000 ppm might be a dangerous concentration for an exposure of 1 hour [Henderson et al. 1921].
Existing short-term exposure guidelines: National Research Council [NRC 1987] Emergency Exposure Guidance Levels (EEGLs):
10-minute EEGL: 1,500 ppm
30-minute EEGL: 800 ppm
60-minute EEGL: 400 ppm
24-hour EEGL: 50 ppm
ACUTE TOXICITY DATA
Lethal concentration data:
| Species | Reference | LC50(ppm) | LCLo(ppm) | Time | Adjusted 0.5-hrLC (CF) | DerivedValue |
|---|---|---|---|---|---|---|
| RatRat
Human Rat Mouse G. pig Human |
Hartzell et al. 1985Hartzell et al. 1985
Lefaux 1968 Rose et al. 1970 Rose et al. 1970 Rose et al. 1970 Tab Biol Per 1933 |
8,6365,207
—– 1,784 2,414 5,647 —– |
———-
4,000 —– —– —– 5,000 |
15 min30 min
30 min 4 hr 4 hr 4 hr 5 min |
6,822 ppm (0.79)5,207 ppm (1.0)
4,000 ppm (1.0) 3,568 ppm (2.0) 4,828 ppm (2.0) 11,294 ppm (2.0) 2,750 ppm (0.55) |
682 ppm521 ppm
400 ppm 357 ppm 482 ppm 1,129 ppm 275 ppm |
Other animal data: The median effective concentrations to produce incapacitation (EC50s) in rats have been determined to be 2,667 ppm and 1,450 ppm in 15 and 30 minutes, respectively [Hartzell et al. 1985].
Other human data: It has been stated that a 1-hour exposure to 1,000 to 1,200 ppm would cause unpleasant but no dangerous symptoms, but that 1,500 to 2,000 ppm might be a dangerous concentration after 1 hour [Henderson et al. 1921a, 1921b]. In general, a carboxyhemoglobin (COHb) level of 10-20% will only cause slight headaches [NIOSH 1972] and a COHb of 11-13% will have no effect on hand and foot reaction time, hand steadiness, or coordination [Stewart and Peterson 1970]. At a COHb of 35%, manual dexterity is impaired [Stewart 1975]. At 40% COHb, mental confusion, added to increasing incoordination, precludes driving an automobile [Stewart 1975]. A 30-minute exposure to 1,200 ppm will produce a COHb of 10-13% [NIOSH 1972].
| Revised IDLH: 1,200 ppmBasis for revised IDLH: The revised IDLH for carbon monoxide is 1,200 ppm based on acute inhalation toxicity data in humans [Henderson et al. 1921a, 1921b; NIOSH 1972; Stewart and Peterson 1970]. |
REFERENCES:
1. Hartzell GE, Priest DN, Switzer WG [1985]. Modeling of toxicological effects of fire gases. II. Mathematical modeling of intoxication of rats by combined carbon monoxide and hydrogen cyanide. J Fire Sci 3:115-128.
2. Henderson Y, Haggard HW, Teague MC, Prince AL, Wunderlich RM [1921]. Physiological effects of automobile exhaust gas and standards of ventilation for brief exposures. J Ind Hyg III(3):79-92.
3. Henderson Y, Haggard HW, Teague MC, Prince AL, Wunderlich RM [1921]. Physiological effects of automobile exhaust gas and standards of ventilation for brief exposures. IV. Concordance of the standard here proposed with the observations of other investigators. J Ind Hyg III(4):137-146.
4. Lefaux R [1968]. Practical toxicology of plastics. Cleveland, OH: Chemical Rubber Co.
5. NIOSH [1972]. NIOSH criteria for a recommended standard: occupational exposure to carbon monoxide. Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. HSM 73-11000.
6. NRC [1987]. Emergency and continuous exposure guidance levels for selected airborne contaminants. Vol. 7. Ammonia, hydrogen chloride, lithium bromide, and toluene. Washington, DC: National Academy Press, Committee on Toxicology, Board on Toxicology and Environmental Health Hazards, Commission on Life Sciences, National Research Council, pp. 17-38.
7. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 930.
8. Rose CS, Jones RA, Jenkins LJ Jr, Siegel J [1970]. The acute hyperbaric toxicity of carbon monoxide. Toxicol Appl Pharmacol 17:752-760.
9. Stewart RL [1975]. The effect of carbon monoxide on humans. Am Rev Pharmacol 15:409-423.
10. Stewart RL, Peterson MR [1970]. Experimental human exposure to carbon monoxide. Arch Environ Health 12:154-164.
11. Tab Biol Per [1933]; 3:231 (in German).