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Carbon monoxide																				Related Pages
										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-hr** **LC (CF)**
    **Derived** **Value**Rat RatHumanRatMouseG. pigHuman
    Hartzell et al. 1985 Hartzell et al. 1985Lefaux 1968Rose et al. 1970Rose et al. 1970Rose et al. 1970Tab Biol Per 1933
    8,636 5,207-----1,7842,4145,647-----
    ----- -----4,000---------------5,000
    15 min 30 min30 min4 hr4 hr4 hr5 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 ppm 521 ppm400 ppm357 ppm482 ppm1,129 ppm275 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 ppm **Basis 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).

			
							
								Page last reviewed:  December 4, 2014						Content
							source: 	National Institute for Occupational Safety and Health NIOSH Publications & Products
Immediately Dangerous To Life or Health (IDLH) Values
Table of IDLH Values
Criteria for Determining IDLH Values
Historical Documentation
Original (SCP) Values
Abbreviations for IDLH Documentation
Abbreviations for Journal Titles Follow NIOSH Facebook
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