 Chronic exposure to relatively low levels of carbon monoxide may cause persistent headaches , lightheadedness , depression , confusion , memory loss , nausea and vomiting . It is unknown whether low @-@ level chronic exposure may cause permanent neurological damage . Typically , upon removal from exposure to carbon monoxide , symptoms usually resolve themselves , unless there has been an episode of severe acute poisoning . However , one case noted permanent memory loss and learning problems after a 3 @-@ year exposure to relatively low levels of carbon monoxide from a faulty furnace . Chronic exposure may worsen cardiovascular symptoms in some people . Chronic carbon monoxide exposure might increase the risk of developing atherosclerosis . Long @-@ term exposures to carbon monoxide present the greatest risk to persons with coronary heart disease and in females who are pregnant . 
