Carbon monoxide is a odorless, colorless, and tasteless gas. It is toxic in high concentrations, and consists of one Carbon atom and one Oxygen atom. They are connected by a triple bond. It forms when there is not enough Oxygen to form Carbon dioxide, for example when you are using a stove or and internal combustion engine. It can also be produced through a normal animal metabolism, but this is in very low quantities. Carbon monoxide burns with a blue flame producing carbon dioxide. When combined with hemoglobin it forms carboxyhemoglobin, which usurps the space in hemoglobin that normally carries oxygen. Concentrations as low as 667 ppm may cause up to 50% of the body's hemoglobin to convert to carboxyhemoglobin. This may result in seizure, coma, and fatality. People exposed to it can also experiance headache, nausea, vomiting, and fatigue. Sometimes the this is mistaken for food poisoning. To get to your question, it can make breathing difficult in certain circumstances, but has no affect on the mental ability of breathing.