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Engineering ToolBox > Health Effects of Carbon Monoxide
Carbon monoxide is a odorless, tasteless, colorless, and toxic gas.
Carbon monoxide is produced as a by-product of combustion. Any combustion process, fuel burning appliance, vehicle or other device has the potential to produce carbon monoxide gas.
Carbon monoxide is dangerous because it inhibits the blood's ability to carry oxygen to vital organs such as the heart and brain. Inhaled CO combines with the oxygen carrying hemoglobin of the blood and forms carboxyhemoglobin (COHb) which is unusable for transporting oxygen.
Health effects of various concentration of carbon monoxide:
| Exposure (hours) | CO Concentration (ppm)1 | ||
| Perceptible | Sickness3) | Deadly4) | |
| 0.5 | 600 | 1000 | 2000 |
| 1 | 200 | 600 | 1600 |
| 2 | 100 | 300 | 1000 |
| 4 | 50 | 150 | 400 |
| 6 | 25 | 120 | 200 |
| 8 | 252) | 100 | 150 |
1) ppm - parts per million - is defined as the mass of the component in solution divided by the total mass of the solution multiplied by 106 (one million)
2) The maximum exposure allowed by OSHA in the workplace over an eight hour period is 35 ppm.
3) Typical sickness symptoms are mild headache, fatigue, nausea and dizziness.
4) A CO concentration of 12-13.000 ppm is deadly after 1-3 minutes. A CO concentration of 1600 ppm is deadly after one hour.
| Concentration of CO in the air (ppm) | Inhalation Time | Toxic Symptoms |
| 9 | Short term exposure | ASHRAE recommended maximum allowable concentration in living area. |
| 35 | 8 hours | The maximum exposure allowed by OSHA in the workplace over an eight hour period. |
| 200 | 2-3 hours | Slight headache, tiredness, fatigue, nausea and dizziness. |
| 400 | 1-2 hours | Serious headache-other symptoms intensify. Life threatening after 3 hours. |
| 800 | 45 minutes | Dizziness, nausea and convulsions. Unconscious within 2 hours. Death after 2-3 hours. |
| 1,600 | 20 minutes | Headache, dizziness and nausea. Death within 1 hour. |
| 3,200 | 5-10 minutes | Headache, dizziness, nausea. Death within 1 hour. |
| 6,400 | 1-2 minutes | Headache, dizziness, nausea. Death within 25-30 minutes. |
| 12,800 | 1-3 minutes | Death within 1-3 minutes |