Carbon monoxide enters red blood cells, quickly taking the place of the oxygen your body needs. Your blood then carries the CO to your organs. If you inhale small amounts of CO over a long period, the exposure might not be fatal, but it can cause permanent damage to the brain, lungs and heart. Moderate levels of CO exposure can cause burning eyes, nausea, vomiting, dizziness, severe headaches, breathing difficulties and confusion. These symptoms are easily mistaken for other common illnesses, like food poisoning or the flu. If carbon monoxide begins to fill a home while people are sleeping, the exposure can be fatal before anyone realizes something is wrong. Infants, the elderly and people with respiratory and circulatory illnesses are at an increased risk of fatal CO poisoning.