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Copyright International Fire Protection 2016
Airport terminals are typical places where a Performance Based Design Approach is necessary.

Fire engineering vs. prescribed fire protection

The title seems to suggest that there are two ways to deal with fire safety on projects, a Fire Engineering approach or a Prescriptive approach. Before exploring that any further there is a need to understand how the two concepts are used and when, and maybe there are other problems related to these two approaches as well.

Prescribed fire protection, or a prescriptive approach, is a design approach that will allow the building to meet a pre-set standard when it comes to fire safety. Applying already deemed to satisfy solutions to the design the building will inherently be “safe”, it is a “code compliant” building. So from a societal point of view a building that is designed in accordance with the code is considered to be an acceptable building from a fire risk perspective. It is relatively easy to use a prescriptive approach, the code contains the prescriptive requirements and it is a matter of incorporating those into the building design. There is not really any need to understand specific fire engineering concepts (smoke control design, evacuation analysis, etc.) to be able to apply the prescriptive requirements, it is a matter of correctly interpret the code. So why not always use such an approach? A prescriptive approach is limited in such a way that when a building, its architectural design (the vision of the architect), deviates too much from a “standard” building it is very difficult to impossible to apply the standard set of rules set out in the code. This of course does not necessarily mean that the building is unsafe it just mean that it cannot comply with the deemed to satisfy solutions. This is where Fire Engineering, rightly or wrongly, comes in as a “savior”.

Fire Engineering, or a Performance Based Design approach, works with objectives (safety goals) instead of pre-set rules. It is necessary to show that a certain deviation (non-compliance) from the code is acceptable i.e. that the “performance” of the proposed design solution is as safe as a code solution would have been. Fire engineering is normally only applied to specific areas where the deviation from the code is necessary for the project, the overall design approach is normally a mixture of fire engineering and prescribed fire protection. A good example is an airport terminal, a terminal is normally a large open space with a high amount of occupants. A prescriptive approach could have difficulties to show compliance with for example; size/volume requirements for the fire sector, travel distance requirements, exit width requirements, structural requirements for the roof (non-protected steel), etc. A performance based design is an engineering approach to fire protection design [1], it can be said to comprise of three steps: 1/ agree on and set up the safety goals and objectives to be used (for example, the occupants must the able to evacuate the building safely in case of a fire, the structure of the building must be able to withstand the effects of a fire during a certain time, etc.), 2/ to perform an engineering analysis of the problem (deterministic or probabilistic analysis of fire scenarios), 3/ quantitative assessment of the design against the fire safety goals and objectives using accepted engineering tools, methodologies and performance criteria.

Hopefully the reader should now have a more or less clear idea of these two concepts and when they are used. Besides the obvious differences between the two approaches there is one major difference that cannot (or at least should not) be overlooked, namely the competence of the practitioner. To adequately be able to perform fire engineering there is a definitive need to have a fundamental understanding of the principles used and the specific skills-set needed to develop performance based designs. This is not the case when applying a prescriptive approach.

The competence level of the practitioner is the single most important issue when it comes to fire engineering. Within the fire safety engineering profession this is something that has been looked upon with concern and it is something that are now being recognized as a real problem, and different initiatives [2] are being undertaken to raise the awareness level regarding this problem. Currently, in most countries, there is a confusion regarding the needed qualifications, training requirements and experience needed to be able to practice as a fire engineer (i.e. to adequately perform fire engineering on projects). At the moment there is basically nothing implemented within the national legal systems to impede an engineer (or a non-engineer for that matter) to call himself a fire engineer and to perform fire engineering on projects. This is directly linked with poor individual awareness of competence, people tend to hold overly favorable views of their abilities and that as a consequence not only do they reach erroneous conclusions and make unfortunate choices, but their lack of competence robs them of the ability to recognize it [3] [2]. The more worrying part of this very real problem is that this could potentially lead to unsafe buildings.

CFD modeling is a good example of when the competence of the practitioner plays a significant role.

CFD modeling is a good example of when the competence of the practitioner plays a significant role.

This has now led to that specific countries are to some degree turning their backs on fire engineering by imposing certain design restrictions (for example, specific fire scenarios, specific design fires, etc.) and by that turning fire engineering into “prescribed fire engineering”. This is very clear in New Zealand where regulators now have introduced “prescribed fire engineering”, and other countries seem to be going in the same direction.

The actual key to solve this seem to be quite straightforward but how to implement it in practice is unfortunately not as clear. Fire safety engineering must evolve in the right direction and with some fundamental changes taking place: 1/ this evolution must start with the educational systems providing the market with engineers. We must have educational programs (teaching faculties) which have the necessary characteristics to produce very competent engineers with the right skills set, see also [4] [5] [6]. 2/ strong competency awareness must be encouraged and fostered within the fire safety engineering profession and the educational systems, see also [3] [2].

So by going back to the title again, Fire Engineering vs. Prescribed Fire Protection, it seems like there is a clear picture of how and when to use these two fire safety concepts. Unfortunately there are greater concerns affecting the actual foundations of fire engineering and how fire safety engineering as a profession and a discipline will evolve.

For more information, go to www.jvvafire.com

References

  1. SFPE Engineering Guide to Performance Based Fire Protection, 2nd Edition
  2. SFPE ECCG: White paper for Professional Recognition for Fire Safety Engineering, 2014
  3. Dunning, D., et al. Why people fail to recognize their own incompetence. Current Directions in Psychological Science, 2003. 12(3): p. 83-87
  4. Johnson, P. Fire Safety Engineering – Part of and Accreditation Framework, in Fire Australia Conference. 2011
  5. Woodrow, M., Bisby, L., and Torero, J., A nascent educational framework for fire safety engineering. Fire Safety Journal, 2013 (58): p. 180-194
  6. Johnson, P. Fire Safety Engineering Education – Part of a Certification Framework, Fire Protection Engineering (SFPE), Q4 Issue, 2012

Top image:- Airport terminals are typical places where a Performance Based Design Approach is necessary.

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Jimmy Jönsson is a Director with JVVA Fire & Risk in Madrid. He has worked on a wide range of fire/life safety projects internationally over the last 15 years and has extensive experience in developing performance based fire engineering design and analysis. Jimmy has specific knowledge and experience regarding Fire Engineering, Performance Based Design and Risk Management. He has led fire engineering design and implementation across a varied range of international building and infrastructure projects.  

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