Frequently a person will leave the house for work or school and feel better, but then get sick again upon returning home. If the car exhaust is bad, a person is ill when driving for distances, especially if the windows are closed. Once they get out of the car and into fresh air, they start to feel better again. Other sources include structural fires, car exhaust and cigarette smoke. People who smoke already have measurable amounts of carbon monoxide in their blood.
Smokers develop problems with smaller exposures to carbon monoxide.
The initial symptoms are much like the flu and include headache, dizziness, drowsiness, fatigue, shortness of breath, nausea and vomiting. Symptoms may progress to fainting, unconsciousness, heart problems and even death. Many people die in their sleep, never realizing that carbon monoxide levels have risen to a dangerous level. The severity of the symptoms depends on the concentration of the carbon monoxide, the duration of the exposure and the size of the area. If a person is in a small, enclosed area without ventilation, they are more likely to have a more severe case.