Some people require years to recover while others might never fully recover. The time of exposure, the concentration of CO, the activity level of the person breathing the CO, and the person's age, sex, and general health all affect the danger level. Physical exertion, with an accompanying increase in respiration rate, shortens the time to critical levels by 2 or 3 fold. Respiratory capacity decreases and the risk of heart attack increases at levels well below 50 ppm. Flu-like symptoms decrease while away from the house.
Illness is present when gas appliances are in use.
Excess moisture on the interior of windows. In severe cases, patients are treated in a hyperbaric chamber which forces carbon monoxide from the body. Oxygen and hyperbaric chambers, can reduce CO damage, speed recovery, and reduce medical problems. Loss of consciousness suggests high levels of carbon monoxide poisoning, and patients tend to have symptoms for several weeks. They will suffer from headache, fatigue, loss of memory, difficulty in thinking clearly, irrational behavior, and irritability.