Carbon monoxide (CO) is a colorless, odorless, and tasteless gas resulting from incomplete combustion of carbon-containing fuels. It consists of one carbon atom and one oxygen atom connected by a strong triple bond. Its sources include unvented heaters, leaking chimneys, gas stoves, generators, automobile exhaust, and tobacco smoke. CO is highly toxic because it binds with hemoglobin in the blood, forming carboxyhemoglobin, which prevents oxygen transport. Exposure to low levels causes fatigue and chest pain in heart disease patients, while higher levels impair vision, coordination, cause headaches, dizziness, confusion, and nausea. Very high concentrations can be fatal. CO poisoning is a significant indoor air quality concern and requires prevention measures like CO alarms and proper ventilation of fuel-burning appliances.

Physically, CO has a molar mass of 28.0 and is slightly less dense than air. It has a bond length of about 112.8 pm with a strong triple bond. The molecule has a small dipole moment, and carbon monoxide plays roles in industrial chemistry and biological systems, but high concentrations are acutely toxic.

In summary, carbon monoxide is a dangerous gas from incomplete combustion that can cause serious health effects and death by depriving the body of oxygen. Prevention includes ensuring adequate ventilation, maintaining appliances, and installing CO detectors indoors.