This means that the unborn or newborns may suffer more serious effects than adults, even at the same levels of exposure. At low levels, CO exposure causes no obvious symptoms, although people exposed to low CO levels may experience decreased exercise tolerance and shortness of breath during exertion. Tightness across the forehead, flushed skin and slightly impaired motor skills also may occur. The first and most obvious symptom is usually a headache with throbbing temples. Symptoms of mild to moderate CO poisoning may resemble winter flu or gastroenteritis, particularly in children, and include nausea, lethargy and malaise.
Higher levels cause fainting upon exertion, marked confusion and collapse.
If exposure continues, coma, convulsion and death from respiratory arrest can result. When unexplained symptoms persist and affect more than one person in a home or workplace where a source of combustion is present, CO poisoning should be considered. This is especially true during heating season. CO poisoning survivors may continue to suffer both severe and subtle neurological effects. These symptoms most often appear within two to four weeks after exposure, even after apparent recovery.