Agent Name

Carbon monoxide

CAS Number




Major Category

Toxic Gases & Vapors


Carbon oxide; Flue gas; Monoxide; [NIOSH]


Chemical Asphyxiants


Colorless, odorless gas. [Note: Shipped as a nonliquefied or liquefied compressed gas.] [NIOSH]


An incomplete combustion product of carbon-containing materials and an emission of internal combustion engines; [ACGIH] Sewer construction workers can be poisoned by carbon monoxide migrating through the soil from nearby use of explosives. [Appl Occup Environ Hyg 2002 Mar;17(3):152-3]


Carboxyhemoglobin 1/2 life in the body = 4 hours in room air and 60-90 minutes in 100% oxygen; Nonsmoker normal = 2%; Smoker = 5-7%; Neurological symptoms = 30%; Death = 40-50%; Carbon monoxide is the most common cause of chemical asphyxia. There is limited positive data that carbon monoxide causes low birth weight and fetal death in humans. In animals, there is strong positive data that it causes birth defects and neonatal mortality and limited positive data that it causes testicular damage. [ATSDR Case Studies, #29] "Decreased exercise time to onset of angina or ischemia was observed at COHb levels as low as 3% and increased ventricular arrhythmias at COHb levels of 6%." [ACGIH] "Early on, symptoms include headache, dizziness, and disorientation. More prolonged or severe hypoxia is accompanied by a varying combination of tremor, chorea, spasticity, dystonia, rigidity, and bradykinesia. Recovery from the hypoxia may be incomplete. Residual dementia, spasticity, cortical blindness, and parkinsonian features are relatively common." [Ladou, p. 430]

Reference Link

Carbon monoxide poisoning and death after the use of explosives in a sewer construction project

Exposure Assessment

Carboxyhemoglobin in blood = 3.5% of hemoglobin at end of shift; carbon monoxide in end-exhaled air = 20 ppm at end of shift;

Skin Designation (ACGIH)

Insufficient data




25 ppm


50 ppm


30 ppm


1200 ppm

Excerpts from Documentation for IDLHs

Other human data: It has been stated that a 1hour 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 1020% will only cause slight headaches [NIOSH 1972] and a COHb of 1113% 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 30minute exposure to 1,200 ppm will produce a COHb of 1013% [NIOSH 1972].

Lethal Concentration

LC50 (rat) = 1,807 ppm/4H

Half Life

Elimination 1/2 life: 5-6 hours (shortened by administration of oxygen); [TDR, p. 283]

Adverse Effects

Parkinson's Syndrome

Reproductive Toxin


Other Poison

Chemical Asphyxiant

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information


Chemical Information

Search ChemIDplus

Biomedical References

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Related Information in HazMap

Occupational diseases associated with exposure to this agent:


Industrial Processes with risk of exposure:


Activities with risk of exposure: