It is common home appliances, such as gas or oil furnaces, gas refrigerators, gas clothes dryers, gas ranges, gas water heaters or space heaters, fireplaces, charcoal grills, and wood burning stoves
In bacteria, carbon monoxide is produced via the reduction of carbon dioxide by the enzyme carbon monoxide dehydrogenase, an Fe-Ni-S -containing protein. CooA is a carbon monoxide sensor protein. The scope of its biological role is still unknown; it may be part of a signaling pathway in bacteria and archaea. Some processes in modern technology, such as iron smelting, still produce carbon monoxide as a byproduct. Worldwide, the largest source of carbon monoxide is natural in origin, due to photochemical reactions in the troposphere that generate about 5 × 10 kilograms per year. Carbon monoxide consists of one carbon atom and one oxygen atom, connected by a triple bond that consists of two covalent bonds as well as one dative covalent bond. It is the simplest oxocarbon and is isoelectronic with the cyanide anion, the nitrosonium cation and molecular nitrogen. Some processes in modern technology, such as iron smelting, still produce carbon monoxide as a byproduct. Worldwide, the largest source of carbon monoxide is natural in origin, due to photochemical reactions in the troposphere that generate about 5 × 10 kilograms per year. In biology, carbon monoxide is naturally produced by the action of heme oxygenase 1 and 2 on the heme from hemoglobin breakdown. This process produces a certain amount of carboxyhemoglobin in normal persons, even if they do not breathe any carbon monoxide. Some processes in modern technology, such as iron smelting, still produce carbon monoxide as a byproduct. Worldwide, the largest source of carbon monoxide is natural in origin, due to photochemical reactions in the troposphere that generate about 5 × 10 kilograms per year. Risk for carbon monoxide poisoning. Carbon monoxide is produced by the incomplete combustion of carbon-containing fuels. All combustion engines produce exhaust emissions that can contain harmful levels of carbon monoxide. In Washington State, the most common source of carbon monoxide poisoning is fuel-driven forklifts.  Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect. Carbon monoxide is a product of incomplete combustion of organic matter due to insufficient oxygen supply to enable complete oxidation to carbon dioxide (CO 2). Carbon monoxide is produced naturally by the body as a byproduct of converting protoporphyrin into bilirubin. This carbon monoxide also combines with hemoglobin to make carboxyhemoglobin, but not at toxic levels. Small amounts of CO are beneficial and enzymes exist that produce it at times of oxidative stress. Carbon monoxide is a by-product of combustion, present whenever fuel is burned. It is produced by common home appliances, such as gas or oil furnaces, gas refrigerators, gas clothes dryers, gas ranges, gas water heaters or space heaters, fireplaces, charcoal grills, and wood burning stoves.  Carbon Monoxide (CO) Poisoning in Your Home. Carbon monoxide (CO) is an odorless, colorless gas often formed in the process of incomplete combustion of organic substances, including fuels. It is dangerous because it interferes with normal oxygen uptake for humans and other living organisms needing oxygen to liv It is produced by the incomplete burning of various fuels, including coal, wood, charcoal, oil, kerosene, propane, and natural gas. Products and equipment powered by internal combustion engines such as portable generators, cars, lawn mowers, and power washers also produce CO.  1 Carbon monoxide (CO) is commonly confused with carbon dioxide (CO2). 2  CO2 is a gas used in carbonated drinks and is also the same gas breathed out by humans. 3  CO poisoning is not caused by faulty appliances, but by lack of air movement.  Dangerous concentrations of CO may also be produced by burning fossil-fuel appliances, such gas stoves or charcoal grills in any enclosed space including campers, tents, and ice fishing houses. Finally, inhalation of paint removers containing methylene chloride can also result in carbon monoxide poisoning. Carbon monoxide (CO) is an odorless, colorless gas often formed in the process of incomplete combustion of organic substances, including fuels.
https://en.wikipedia.org/wiki/Carbon_monoxide https://en.wikipedia.org/wiki/Carbon_monoxide https://en.wikipedia.org/wiki/Carbon_monoxide http://www.lni.wa.gov/Safety/Research/HazardousChem/CarbonMonoxide/Default.asp https://en.wikipedia.org/wiki/Carbon_monoxide_poisoning http://www.extension.iastate.edu/Pages/communications/CO/co1.html http://www.health.state.mn.us/divs/eh/indoorair/co/ http://www.cpsc.gov/en/Safety-Education/Safety-Education-Centers/Carbon-Monoxide-Information-Center/Carbon-Monoxide-Questions-and-Answers-/ http://www.safefiredirect.co.uk/Page/27/what-is-carbon-monoxide.aspx http://www.health.state.mn.us/divs/eh/indoorair/co/
most carbon monoxide is produced by