Why is it dangerous to burn coal in a closed room?

It is dangerous to burn coal in a closed room because:

i. Carbon burns in air to form carbon dioxide, but in the absence of enough oxygen, carbon burns to form carbon monoxide.

ii. Carbon monoxide is a very poisonous gas, inhaling which can cause death.

iii. There is an absence of enough oxygen in a closed room because it is used during respiration by living beings.

iv. Thus carbon monoxide is formed in a closed room which is very dangerous.