Carbon Monoxide Poisoning

Page address:

Carbon Monoxide Poisoning
Carbon monoxide (CO) is a colorless, odorless and tasteless gas that is slightly lighter than air. It is sometimes called carbonic oxide, exhaust gas or flue gas. 

Carbon monoxide is produced by the incomplete combustion of any fuel that contains carbon. This includes gasoline, natural gas, oil and propane, as well as coal and wood products. Sources of CO include gas and oil burning appliances like furnaces, dryers, water heaters, ovens, wood burning stoves, charcoal grills, gas powered forklifts and automobiles.
Carbon monoxide is a chemical asphyxiant. When CO is inhaled into the lungs, it bonds with hemoglobin in the blood—hemoglobin is responsible for carrying oxygen throughout the body. The CO replaces the oxygen molecules in hemoglobin and deprives the heart, brain and body of the oxygen it needs to function. High concentrations of CO will displace enough oxygen in your body, resulting in oxygen starvation. 

The symptoms of low level CO poisoning include headaches, nausea, weakness, dizziness and confusion. CO exposure causes a victim’s blood pressure to rise in an attempt to get more oxygen to the body. As a result, the skin may take on a reddish color. The symptoms at low levels are very similar to what a person might exhibit if affected by the flu or other common illnesses. Therefore, carbon monoxide is sometimes referred to as the “Great Imitator.”
As CO exposure increases, more serious symptoms develop; lack of coordination, chest pain, vomiting and loss of consciousness. If exposed to carbon monoxide long enough, coma and death can occur. A concentration of 1200 ppm CO is considered IDLH (Immediately Dangerous to Life or Health). The table lists common symptoms and effects on healthy adults at various carbon monoxide concentrations. 

Carbon Monoxide Level in ppm 
(Parts per Million)

Resulting Conditions/Effects on Humans


Permissible Exposure Level (PEL) for 8 hours (OSHA)


Possible mild frontal headache in 2 to 3 hours


Frontal headache and nausea after 1 to 2 hours; Occipital headache (back of head) after 2 to 3 hours


Headache, dizziness, and nausea in 45 minutes; Collapse and possible death in 2 hours


Headache, dizziness, and nausea in 20 minutes; Collapse and possible death in 1 hour


Headache and dizziness in 5 to 10 minutes; Unconsciousness and danger of death in 30 minutes


Headache and dizziness in 1 to 2 minutes; Unconsciousness and danger of death in 10 to 15 minutes


Immediate effects: unconsciousness; Danger of death in 1 to 3 minutes