Historically an acceptable standard of fire safety in buildings has been achieved by reference to prescriptive codes that provide standard solutions for a given set of building parameters. For many buildings that are of simple and straightforward design, layout and use, prescriptive codes and standards will probably provide the designer with an acceptable solution.
The Technical Standards for Scotland and Approved Document B in England and Wales are examples of prescriptive guidance.
However, unlike the Technical Standards the recommendations of Approved Document B and Technical Booklet E (Northern Ireland) are not mandatory and designers are not required to adopt any particular solution contained in them providing that it is explicitly demonstrated that the functional requirements of the regulations can be met in some other way.
Fire safety engineering techniques can be adopted as a means of demonstrating compliance with functional requirements of the Building Regulations in England and Wales and specific relaxations of the Scottish Technical Standards can be achieved.
In many large and complex buildings fire safety engineering may be the only practical way of achieving and demonstrating a satisfactory standard of fire safety.
As the traditional prescriptive codes have to account for an almost infinite range of building designs they will rarely provide the optimum solution in terms of:
- life safety
- property protection
- cost effective fire protection
- operational requirements
The prescriptive approach will often not meet the needs of building owners, designers or approvals bodies, particularly for more complex buildings or processes, or in instances where there is a potential for substantial financial loss arising from a relatively small fire.
A particular weakness in the prescriptive approach was recognised in the conclusions of the Cullen report into the Piper Alpha offshore platform disaster, which stated that:
“Many regulations are unduly restrictive in that they are of a type that impose ‘solutions’ rather than ‘objectives’ and are out of date in relation to technological advances. There is a danger that compliance takes precedence over wider safety considerations...”
This conclusion is equally applicable to building design and BS 7974 (Application of fire safety engineering principles to the design of buildings) has been developed to provide an objectives based approach to the achievement of fire safety in buildings (Note. BS 7974 was originally issued as a draft for development BS DD 240).
The main objectives of BS 7974 are to:
a) provide a structured framework for assessing the interaction between buildings, people and fire.
b) enable an objective assessment of the fire safety measures required to achieve defined objectives.
c) assist in developing alternatives to prescriptive codes and enable the effect of these to be evaluated.
The British Standard divides the fire safety engineering design process into three main stages:
- Qualitative design review
- Quantitative analysis
- Assessment against criteria
Note: For further information please refer to BS 7974
Structure of Fire Engineering Methodology Given in BS 7974
