Question

Incomplete burning of fuel produces __ (Carbon dioxide/Carbon monoxide) which is a Poisonous gas.

Answer 1

Incomplete burning of fuel happens due to insufficient supply of oxygen gas for combustion. This leads to the formation of carbon monoxide which is a poisonous gas.
On the other hand, when sufficient oxygen gas is circulated, it produces carbon dioxide gas which is non-poisonous. Carbon monoxide gas, when inhaled, combines with blood and reduces its oxygen carrying capacity thereby damaging the nervous system and even results in death.