Why can inhaling of carbon monoxide become fatal?

Explanation

Carbon monoxide is a highly poisonous gas and can cause death even if air containing 0.5% carbon monoxide by volume is inhaled because it combines with the haemoglobin present in the red blood cells of our body to form a stable compound called Carboxy-haemoglobin. This stable compound does not allow haemoglobin to absorb or carry oxygen, thus depriving our body cells of oxygen.