### Theory:

If the burning process does not emit any flame, then it is called combustion.
Oxygen supports combustion. Even in rockets, oxygen is considerably reduced when it reaches a certain height in the atmosphere. Hence, some amount of oxygen is added along with the fuel for combustion.

A rocket
Carbon-di-oxide:
Carbon-di-oxide occupies less than $$1\%$$ of our atmosphere. Plants and animals produce carbon-di-oxide on consuming oxygen for respiration.
Carbon-di-oxide does not support combustion, but it creates suffocation. For instance, whenever fire happens inside a closed room, people trapped in it may feel suffocated. It is due to the carbon-di-oxide which is filled inside the room.

People suffocating due to fire

Also, carbon-di-oxide is used to extinguish fires. Fire extinguishers are used to put off fire by throwing a stream of carbon-di-oxide in case of fire accidents.

Firemen using fire extinguishers

The burning of dried leaves and crop remains pollutes our environment. This is due to the emission of carbon-di-oxide gas while burning.

Burning of dried leaves
Reference:
https://live.staticflickr.com/4144/5072498899_825c44fa9d_b.jpg