To supersede the requirements of Sentence 3.6.2.1.(5), which would otherwise require a minimum 1 h fire separation, and require a higher minimum rated separation, on the basis that vaults pose a higher risk of fire or explosion.
To limit the probability that fire will spread from the vault to other parts of the building, which could lead to damage to the building.
To limit the probability that a fire originating in a location outside a vault will spread into the vault, which could lead to the disruption and discontinuation of service from equipment located in the vault, which could lead to an undue fire hazard in the building, which could lead to damage to the building.