Low-Oxygen Burning

• Carbon monoxide (CO), a lighter-than-air odorless gas that is deadly to humans and animals, is made up of a single atom of carbon together with 1 of oxygen. CO is created when carbon-based materials (including all fossil fuels) are burned in an atmosphere lacking sufficient oxygen to yield carbon dioxide (CO2, 1 carbon atom to 2 of oxygen) instead. Once created, carbon monoxide can wreak havoc on the bloodstream, due to its tendency to bond with hemoglobin and inhibit the blood's absorption of oxygen. If those overcome by severe carbon monoxide poisoning are not rescued in time, asphyxiation and death are certain. Because of the strong presence of CO in automobile exhaust, anyone starting a car in an unopened garage will suffer this fate in minutes.
  
  

High Temperature Combustion

• Carbon monoxide can and does routinely form in nature, such as in forest fires. However, industrial and other human-caused burning present a much more serious and ongoing threat for CO creation. Burning coal, natural gas, oil, gasoline and cigarettes gives off varying degrees of carbon monoxide. So-called "complete combustion" results in carbon dioxide, a gas infamous for its contribution to the greenhouse effect in global warming but lacking the poisonous character of CO. Carbon monoxide is generated not only in a situation of "incomplete combustion," where oxygen is in short supply, but also when CO2 decomposes at high temperatures.
  
  

Health Effects of CO

• While most of the publicity about health effects of carbon monoxide centers on the dire consequences of sudden exposure to heavy concentrations, lower levels of exposure also have noticeable ill effects. Symptoms of low-level exposure can appear to be flu-like, including shortness of breath, general weariness and persistent headache. Chest pain, blurred vision and vertigo can indicate an increased level of exposure. The nightmare scenario of home CO exposure occurs when a leaky furnace or other malfunctioning combustion system in the house (such as a gas-powered water heater) suddenly begins producing a high level of carbon monoxide with the windows closed while the house's occupants are asleep. Persons overcome by CO poisoning can slip into a coma and die without ever having perceived the threat. The only response for those who suspect they are suffering from CO exposure is to rush outside to fresh air and make a 911 call to emergency response authorities. The risk posed to sleeping persons has been the subject of a public awareness campaign that encourages the installation of carbon monoxide detectors in homes to alert or awaken people while levels of CO are still manageably low.