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  that a 1-hour exposure to 1,000 to 1,200 ppm would cause unpleasant, but no dangerous symptoms [Henderson et al. 1921]. Patty  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:
|Hartzell et al. 1985
Hartzell et al. 1985
Rose et al. 1970
Rose et al. 1970
Rose et al. 1970
Tab Biol Per 1933
|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)
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].
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3. Henderson Y, Haggard HW, Teague MC, Prince AL, Wunderlich RM . 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.
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5. NIOSH . 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 . 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.
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