To limit the probability that smoke and toxic gases will accumulate in a fire situation, which could lead to delays or inefficiencies in emergency response operations [e.g. poor visibility], which could lead to the spread of fire to other parts of the building, which could lead to damage to the building.
To limit the probability that smoke will accumulate in a fire situation, which could lead to the spread of smoke to other parts of the building, which could lead to damage to the building.