The harmful compound that I identified is carbon monoxide. It is formed by covalent bonding.
Carbon monoxide is produced from the partial oxidation of carbon-containing compounds; it forms when there is not enough oxygen to produce carbon dioxide (CO2), such as when operating a stove or an internal combustion engine in an enclosed space.Carbon monoxide is produced from the partial oxidation of carbon-containing compounds; it forms when there is not enough oxygen to produce carbon dioxide (CO2), such as when operating a stove or an internal combustion engine in an enclosed space.
Carbon is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds.Oxygen is a member of the chalcogen group on the periodic table, and is a highly reactive nonmetallic element that readily forms compounds (notably oxides) with almost all other elements.

http://wiki.answers.com/Q/How_is_carbon_monoxide_formed_and_what_is_it_used_for

http://en.wikipedia.org/wiki/Carbon_monoxide