Design for Escape from Fire
Providing safe means of escape from fire requires more than just having a designated route out of a building. It is shown that the conditions relating to the fire, the building characteristics and the number, distribution and activities of the occupants all have a bearing on the requirements for escape. Safe escape from fire in buildings is required by the New Zealand Building Act. The Building Industry Authority (BIA) Handbook of Acceptable Solutions provides a set of prescriptive design rules for the means of escape from buildings. Compliance with these rules is deemed to comply with the legal requirements of the Building Act. The necessity of considering the BIA Acceptable Solutions as an integrated solution is discussed. The Building Act allows for the specific design of means of escape where the Acceptable Solutions are inappropriate or where an alternative solution is desired. Alternative solutions must show, to the approval of the Territorial Authority, that compliance with the requirements of the Building Act for safe escape is provided. The action of the occupants in the act of escape from an evolving fire requires consideration of both time and space; the solution becomes an exercise in four dimensions. These aspects are discussed in some detail, and design criteria. The necessity of relating the development of a fire and the products of combustion with the progression of occupants escaping to a place of safety is demonstrated. It is shown that design for safe means of escape may be effected by a variety of inter-related factors. Variation from the BIA Acceptable Solutions requires consideration of all aspects of the design process. The design is a specific solution and must be at least as effective and efficient as the requirements of the Building Act. The design of safe means of escape requires construction of 'time lines' for the fire, including tenability conditions, and the egress movement of occupants. The necessity to include margins for safety and the reliability of systems is briefly discussed. This report shows the steps necessary to provide safe means of escape for compliance with the Building Act. Comparison is made of occupancy densities as found in NZ, as noted in design guides and overseas reference literature.