Question

Why are we advised never to sleep in a room with a burning or smoldering coal fire in it

Answer 1

because carbon monoxide is released which combines with haemoglobin to form carbaminohaemoglobin and reduces the supply of oxygen

Answer 2

Hello friend.

We are advised not to sleep in a room with a burning or smoldering coal fire because combustion of coal gives out carbon monoxide gas which is very harmful if inhaled.
Carbon monoxide mixes with heamoglobin to form a stable compound namely carbaminohaemoglobin which cannot be broken down easily. This formation reduces the capacity of the RBC to transport oxygen and carbon dioxide to different parts of the body. Persistent exposure may result in death.

Hope this helps