To limit the probability that cooking vapours or residue will accumulate and subsequently be ignited, which could lead to a fire or explosion, 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 fire protection systems for commercial cooking equipment exhaust will not properly operate in a fire situation, which could lead to the spread of fire to other parts of the building, which could lead to damage to the building.