The purpose of fire safety design in a building is to allow people to escape before being overcome by the effects of fire.
Traditional Approach: The move to the performance based building code in New Zealand in 1991 changed the emphasis from following sets of rules to designing for building performance. As in many countries a large number of different prescriptive rules had been developed that related to fire safety in buildings. The kinds of provisions that were specified included:
- The number of emergency exits from a building
- Where the exits must be located
- Signs required at exits
- Systems required to detect fires
- Alarms required to warn people of fire
- Sprinkler systems to extinguish fires
- Materials to be used in the construction of the building to slow fire growth
- Construction to limit fire spread from one area to another
- Structural elements to stand up for long enough to get people out and enable firefighters to mount an attack.
Performance-Based Approach: Since 1991 the traditional prescriptive approach to building design in New Zealand has been embodied in the Approved Documents to the building code. These have the status of a guideline. The code itself now contains performance requirements. The Approved Documents are one way of satisfying the performance requirements, but a designer can put forward alternative solutions for approval.
The use of an alternative solution allows the designer to design fire safety into the building using fire engineering rather than relying on prescriptive rules. Fire engineering relies on the principles of fire science, human behaviour and risk management. This process requires the designer to think through the issues of:
- fire ignition growth and spread
- the location of people in the building and their state
- how people will become aware of a fire and what they might do
- how quickly people can get out
- how the fire might develop
- how smoke will be generated and could spread
- how the smoke and fire might affect people
- how the building materials will respond to the fire.
These considerations allow a fire safety solution to de developed that suits the particular building and its use.