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|Evolution of the Fire Protection Engineering Profession Over the Last 50+ Years|
Viewpoints Evolution of the Fire Protection Engineering Profession Over the Last 50+ Years
By Harold E. Nelson, P.E., FSFPE | Fire Protection Engineering
Within the last several decades, there have been fundamental changes in the understanding and quantification of fire. The fire protection engineer now has enhanced capabilities, which enable basing conclusions on an engineering appraisal of the potential harm or risk. The profession has made a series of important advances that progressively have added to the engineers ability to predict the potential impact of fire.
Four different, often overlapping, approaches have been or are being used. These approaches are referred to as specification, component performance, scenario performance and risk appraisal. The first two of these approaches are rule bound; the last two produce a quantitative understanding of the level of risk or safety provided. The ongoing transition from design by rule to performance appraisal has had a major impact on the professional quality and value of fire protection engineering.
Fire protection engineering in 1946 was a specialty niche of engineering dedicated for the most part to the needs of the fire insurance industry. A youngster starting off in the profession would compare buildings and other facilities to a book (e.g., codes or rating schedules) to determine compliance with the prescribed document. No evaluation of the actual impact of the fire or the facility was required or normally made.
As time progressed, it became apparent that the specification approach unnecessarily constrained design. Element-by-element component performance came into use. Under this approach, any single element could be replaced by a different element, if shown to perform at least as well as the specified element. In time, a statement of required test results often replaced the original specification, producing the now common form of codes and regulations.
At the same time, designers introduced many innovative new materials, concepts and architectural treatments. Many of the tests of fire protection or fire hazard of materials attempted to imitate a fire exposure. But, the exposures used were at best only a single point on a broad spectrum of potential fire exposures. In some cases, the tests were based more on getting reproducible results than scientific validity. Test results were seldom expressed in engineering terms usable in an analytical analysis. However, there now exists a massive collection of test results, regulations and knowledgeable individuals to support the component performance approaches. Unfortunately, virtually all of the test data fail to provide quantitative information on actual fire properties.
Starting about the first decade after World War II, various research laboratories undertook serious investigations of fire phenomena and the simultaneous interrelationship of several factors, such as burning rate and ventilation. Much of the work addressed understanding and quantification of the development of fire and fire products in enclosed spaces in buildings. Some of the important outputs included the identification of the heat zones occurring in compartment fires; the phenomenon of flashover; the analytical impact of oxygen availability; fire plumes and entrainment and other quantifiable aspects of fire development.
The investigations identified a number of the physical properties important to an engineering analysis. These include values such as temperature changes in strengths of heated materials and the rate of heat release from a combustible material as a function of incident flux. In some cases, the data could be determined by using existing apparatus. In others, new apparatus such as the cone calorimeter were needed. Key in all cases is that the measurements return values of physical properties under the conditions of the exposures of interest.
Individual solution methods were assembled in a form (such as a fire model) where applying the fire property data could produce an output showing expected level of safety. The working products appear in the form of equations, models and other information needed by the engineer to describe both the facility and the initiating conditions. This approach is normally deterministic and tends to assume that all descriptions and conditions are either constant or vary in a described manner. Running multiple scenarios may be necessary to cover the full scope of the fire potential.
The scenario approach can often, depending on the selection of scenarios, provide the information needed to draw valid conclusions on the probable course and outcome of fire in a facility.
A more comprehensive set of conclusions involving both probability and potential can be derived where the input data is expressed as a distribution in terms of the environment faced. A Monte Carlo approach is often used to reduce the number of runs of the computer code needed.
The modern practicing fire protection engineer needs to have a comprehensive understanding of the phenomena-based approaches to fire hazard analysis and use the most accurate and suitable for the needs at hand. When using established models, the engineer needs to understand the phenomena being modeled and the sensitivity of the model to the data entered. The days of simple cookbook code compliance are passing.
Further information can be found in The History of Fire Protection Engineering.1