Carbon Monoxide
Carbon Monoxide (chemical formula: CO) is a colorless and odorless gas. When carbon or organic material containing carbon is burnt, carbon dioxide (CO2) is usually produced. However, if it is incompletely combusted due to insufficient Oxygen (O2), Carbon Monoxide will be produced.
CO Toxicity
Hemoglobin is contained in red blood cells that carry inhaled Oxygen to the body’s tissues. CO has a high affinity for hemoglobin (250 times greater affinity than Oxygen). If CO is inhaled, it will prevent transport of Oxygen in blood, causing CO poisoning symptoms. The symptoms can be headache, nausea, and death in the worst case.
Carboxyhemoglobin Concentration
When CO is inhaled, it easily binds to the Hemoglobin in blood to form carboxyhemoglobin (COHb) and causes CO poisoning symptoms. The poisoning symptoms vary depending on the inhaled CO concentration and the length of exposure time. The table shows the associations between Carboxyhemoglobin levels and clinical manifestations. It is important to design a CO alarm that can give an alarm or activate a ventilation fan well before CO poisoning symptoms occur.
| COHbLevel(%) | CO Poisoning Symptoms |
|---|---|
| >70% | Death |
| 50%~70% | Coma, brain damage, seizure, and death |
| 40%~50% | Confusion, unconscious, coma, and possible death |
| 35%~40% | Vomiting, collapse |
| 30% | Drowsy |
| 25% | Headache and Nausea |
| 20% | Headache |
| 15% | Slight headache |
| 10% | None |
| 5% | None |
Source: UL2034_4th edition, Standard for Single and Multiple Station Carbon Monoxide Alarms, March 2017, pp. 50; Inkster S.E. Health hazard assessment of CO poisoning associated with emissions from a portable, 5.5 Kilowatt, gasoline-powered generator. Washington, D.C.: U.S. Consumer Product Safety Commission. 2004