【正文】 cupants. Table 16 summarises the occupants who are most at risk and the levels of fire safety provided by 7 the above fire safety matrix. Table 17 provides the cell key for identifying the designated cells in Table 16. This key remains the same for all cases presented. Table 16 – Levels of fire safety (buildings greater than 25m) Table 17 – Cell key Buildings greater than three storeys and less than 25m The fire safety matrix for buildings greater than three stories and less than 25m high is presented in Table 18. The justification of the remended fire safety measures is provided in Section . Table 18 – Fire safety matrix: buildings greater than three storeys and less than 25m 8 Table 19 – Levels of fire safety (buildings greater than three storeys and less than 25m) Buildings less than three storeys The fire safety matrix for buildings less than three stories is presented in Table 20. The justification of the remended fire safety measures is provided in Section . Table 20 – Fire safety matrix: buildings less than three storeys 9 Table 21 – Levels of fire safety (buildings less than three storeys) 10 14 DISCUSSION OF FIRE SAFETY MATRIX The fire safety matrix considers the building height, sprinkler protection and the emergency strategy as the primary variables. This is due to the high influence that the interactions of these variables have on other fire safety measures. In addition to this, the fire engineer can specify the emergency strategy and sprinkler protection for the building that will provide flexibility to the matrix. Therefore once the extent of these three variables has been determined the remaining fire safety systems can be selected to suit the building. The objective of the fire safety remendations is to address key issues that result from a given set of building characteristics, while providing multiple levels of protection for occupants in the event of a fire. This provides a backup or redundancy in the design in the event of one part of the system failing. For example, if the sprinkler system fails the occupants will be protected with passive protection and smoke control systems. The following sections discuss the three building height limits with respect to the fire safety measures that have been remended. The staged evacuation strategy has not been discussed separately as it is a bination of the other two strategies and the same fundamental principles apply. Buildings greater than 25m in height. Once buildings exceed 25m in height, the ability of the fire brigade to rescue occupants externally bees limited. Therefore, a higher level of fire safety needs to be provided to the stairs and escape paths. Emergency lifts are also considered an option to provide rapid access for the fire brigade and egress for disabled occupants. As buildings bee taller the level of fire protection needs to increase. This is due to: ??Further travel distances, resulting in a higher chance of exposure to fire and fire products, and longer exposure time. ??The reduced ability of the fire brigade to rescue people externally ??The increased time for the fire brigade to reach upper levels ??More occupants, resulting in a higher risk of injury and deaths ??There is a greater variability in occupant abilities and human behaviour, due to the greater number of occupants ??There are more sources of ignition and fire 11 Evacuation in buildings greater than 25m An evacuation strategy relies on the protection of egress paths, as well as the protection of occupants in their apartments before evacuation. The protection of egress paths is critical to ensure occupants are not evacuating through untenable conditions. In buildings greater than 25m high, egress distances can be consider able and therefore, the time occupants spend in escape paths can be significant. In a sprinkler protected building, protection is provided by: 1. The sprinkler system. The sprinklers will activate and extinguish or control the fire, reducing the threat to occupants. 2. Compartmentation and mechanical systems. Rooms, corridors and stair shafts are remended to have a FRR of at least 30 minutes. This will contain the fire in the room of origin and protect occupants before and during egress. Selfclosers provided on doors are to ensure the fire does not spread to the corridor. The stairs are to be pressurised to limit smoke spread, provide a partial safe egress paths and provide a smoke free area for the fire brigade. 3. The final level of protection is the fire brigade. The fire brigade’s role would be to assist any remaining occupants and extinguish the fire. A connection n to the fire brigade will be provided to achieve a faster response. In a nonsprinkler protected building the systems of protection are 2 and 3, as listed above,however the following other fire safety measures will be introduced to increase the level of protection: 1. An increased FRR to 60 minutes minimum. This is to provide additional time for occupant evacuation and fire brigade intervention. If occupants choose to stay in their apartments the increased FRR will provide a higher level of protection. 2. Connection to the fire brigade. To ensure a faster response by the brigade to a fire. 3. Emergency lifts to aid egress and fire brigade access 4. Zoned smoke control system. This is to ensure smoke spread through the building is minimised. This should include stair and corridor pressurisation to reduce the chance of smoke spread into the escape paths. 5. Lift and stair lobbies to provide an additional barrier against smoke and an area where occupants can wait for lifts or further instructions. These areas can be used as refuge areas or other pressurised refuge areas should be provided. 12 6. Emergency warning and intermunication