Note the bright "cherry red" or bright pink lividity to the hand. Carbon monoxide (CO) poisoning is a form of asphyxia that results when CO is inhaled, diffuses across alveoli, and binds tightly to hemoglobin. Poorly ventilated houses with faulty heaters, housefires, and motor vehicle exhaust are the most common sources. Even small atmospheric concentrations of CO are dangerous, because CO binds to hemoglobin 200 times more avidly than oxygen. Drowsiness and headache occur at carboxyhemoglobin concentrations between 10 and 20%. Levels from 20 to 30% can be fatal to persons with pre-existing cardiac or respiratory disease. Levels above 30 to 40% can be fatal to anyone. Similar lividity could be the result of cyanide poisoning or monofluoroacetate poisoning.