Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?

Explanation

Carbon monoxide is a poisonous gas and it binds to haemoglobin of the blood more readily (about 200 times) than oxygen to form carboxy haemoglobin.
`Hb+CO iff underset("Carboxy haemoglobin ")(HbCO)`
The presence of CO, therefore, reduces the amount of haemoglobin available in the blood for the transport of oxygen to the body cells. The harmful effects of enhaling increasing amounts of CO include reduction in awarness of judgement, dizziness, weak eye sight, headache, nervousness and cardiovascular disorders. At higher concentrations of CO, suffocation, loss of consciousness or even death after several hours. However, `CO_2` does not combine with haemoglobin and hence is less harmful pollutant. `CO_2` is main contributor towards, green house effect and global warming.