The gas that causes suffocation and death when coal or coke is burnt in a closed room is

Exhaust fumes of motor cars, gases produced from coal fire in a closed room and coal gas, all contain carbon monoxide, which is the cause of their poisonous nature. When carbon monoxide is inhaled, it prevents the oxygen from combining with hemoglobin and instead combines itself with hemoglobin to form carboxyhaemoglobin, which is stable compound. This causes oxygen starvation in the body tissues and eventually causes death by suffocation.