Prolonged exposure to carbon monoxide levels of one to 70 parts per million does not cause any symptoms for most people, according to the United States Consumer Product Safety Commission. However, people who are heart patients or have a history of cardiac problems may experience chest pain.
The effects of carbon monoxide differ depending on the concentration levels and the health of affected individuals. When CO levels reach 70 ppm and above, symptoms such as headache, fatigue and nausea may occur. Disorientation, unconsciousness and death are possible with prolonged exposure to levels of CO between 150 ppm and 200 ppm.