To supersede the requirements for a minimum 45 min rated fire separation as stated in Sentences 9.10.9.13.(1) and 9.10.9.14.(1) and require a higher minimum rating, on the basis that moving from one storey to another in an emergency situation could lead to increased evacuation time.
This is to limit the probability that fire will spread from one dwelling unit to other parts of the building, or from a part of the building to the dwelling unit, during the time required to achieve occupant safety, which could lead to harm to persons.