The causes and effects of exposure to high levels of carbon monoxide (CO) are well documented, and many countries maintain records of annual deaths arising from CO poisoning incidents. Many such incidents are associated with the use of badly installed, poorly maintained or malfunctioning domestic combustion appliances or with the use of such appliances in poorly ventilated rooms. However, the prolonged sequelae of acute CO poisoning and the chronic effects of long-term exposure to lower levels of CO are not well understood. The home environment is particularly important because of the possibility of unrecognised long-term, low-level exposure to CO. Furthermore, the common problem of missed or misdiagnosis of CO poisoning can result in exposed individuals being given inappropriate treatment and being returned to a hazardous situation.