Using fire engineering to create design flexibility
Fire engineering can be used alongside fire suppression, on a case-by-case basis, to solve fire conformance problems and make modern open plan layouts meet building regulations.
What is Fire Engineering?
The term fire engineering is widely misused and not well understood; there are two main types fire engineering:
Fire protection engineering: where the engineer is responsible for design of fire systems such as automatic fire suppression and fire detection systems.
Fire safety engineering: where the engineer is responsible for design of fire strategies including location and number of stairs, design of smoke control regimes and designed structural fire protection measures.
There are three main fire safety engineering approaches:
Equivalency (or comparative approach): whereby it is demonstrated that the design provides a level of safety equivalent to that which would have been obtained by applying prescriptive codes.
Deterministic approach: in which the objective is to show that on the basis of the initial (usually 'worst credible case') assumptions, some defined set of conditions will not occur. Where there is any doubt regarding the reliability of the input data a conservative approach should be adopted. This may require the use of explicit safety factors to compensate for uncertainties in the assumptions.
Probabilistic approach: the objective of which is to show that the likelihood of a given event occurring is acceptably small. This is usually expressed in terms of the annual probability of occurrence of the unwanted event (e.g. a probability of an individual death through fire of 10-6, or one per million). It must be recognised that, whatever measures are taken, risks can never be reduced to zero.
Benefits of a Fire Engineering Approach
There are two ways of demonstrating compliance with the Building Regulations. One is to follow the prescriptive guidance given in codes of practice and Approved Document B and the other is to use a fire engineering approach (which may be quite detailed or otherwise depending on the project).
Guidance documents such as Approved Document and British Standards cannot take into account the peculiarities of every single building design. The larger and more complex the design, the more difficult and more costly it is to ensure that the design meets the recommendations of the prescriptive codes. Some building designs may not even be possible to realise using prescriptive codes.
In contrast, Fire Engineering can:
- Increase design flexibility and make the impossible possible
- Reduce construction and operating costs
- Tailor the design to suit the building use
Building on the above some common benefits achieved by using fire engineering include:
- Extending travel distances in buildings – Improving flexibility and reducing cost
- Reducing and removing staircases and exit widths – Saving floor space, costs and improving design fluidity
- Maximize usable floor space – Increasing value and design aesthetic
- Improve flexibility and more open arrangements – Improving space quality and adding value
- Justifying the use of non-conventional escape routes – Reducing repetitious design and avoiding unnecessary costs
- Allowing greater freedom of choice for materials – Improving visual appearance and design quality
- Maximizing non-fire rated façade areas – Increasing design freedom and natural light whilst reducing cost
- Reduced fire protection to structures – Improving construction program and flexibility
- Justifying increased compartment sizes – Increasing layout flexibility and value
- Demonstrating alternative methods of achieving compartmentation – Releasing design aspiration and reducing cost
- Optimising fire service access facilities – Improving design coordination
- Reducing water storage requirements for fire fighting – Increasing floor space and spatial planning
- Minimising fire safety system designs, requirements and application – Reducing costs and design impact
- Optimising the application of existing fire safety facilities – Improving building performance and operational flexibility
Plumis' first research paper was recently published in the Fire Safety Journal and is available for free download. The research presented in the paper is part of a broader project to "examine how an electronically controlled nozzle system performs compared to traditional sprinkler systems and consider its impact on hazards that are not currently captured in existing standard test methods". We created "some tests for refrigerator fires which burn significantly slower and with more smoke output than the fire source used to assess suppression systems within standards." It concludes, "for the specific experiments presented in this paper, the measured activation times of a concealed sprinkler head are 2.0–13.7 times slower than those using an electronic nozzle system." The paper also provides fire engineers with the input parameters and assumptions necessary to represent these systems in performance-based assessments.