VIEWPOINT

Comments on Lucht's "Changing the Way We Do Business"

Jeffrey M. Shapiro, P.E. Shapiro is coordinator of the International Fite Code Institute in Austin, Texas, publishers of the Uniform Fire Code.

I would like to express my concurrence with the concepts presented by David Lucht in his article "Changing the Way We Do Business," published in your August 1992 issue. I found the article so interesting that I decided to reprint it with permission in the International Fire Code Institute's (IFCI) Fire CodeJournaI (Vol. 2, No. 4, Fall/ Winter 1994) and to build an entire issue around it. The Fite Code Journal, IFCI's membership magazine, is distributed to approximately 1,500 fire and building officials nationwide.

Unquestionably, the scientific basis for fire protection engineering has improved dramatically in recent years. However, the fire protection community-particularly the code development community-has been slow to accept the "science" of fire protec- tion. In his article, Dr. Lucht posed some basic questions regarding the reasons for the apparent lack of acceptance of scientifically based fire and life safety designs versus our traditional prescriptive approach, and I would like to offer some comments regarding these questions.

There are at least three easily identifiable impediments to the initiation of scientifi- cally based performance codes with a holistic approach to fite and life safety based on fire modeling. These are the longstanding history of fite protection as an "art," proprietary interests, and the inability to ensure that buildings will conform to a scientifically based design throughout their lifetimes. I would like to address each of these issues.

His tory of Fire Protect ion as an A r t Over the last 100 years, fire protection engineering has established itself as a unique mix of art and science. Until the last decade, when computers began to play a role in evaluating egress, fire behavior, fire resistance, and smoke movement, the primary basis for the development of codes and standards was the consensus judgement of building and fire safety professionals. These consensus judgements were based more on professional opinion and loss experience than on scientific evaluation. As the science of fire and life safety computer modeling has begun to come of age, the

Viewpoint 279

scientific and fire protection community has made more frequent attempts to incorpo- rate the new technology into the codes, and these efforts have generally have failed.

Traditionally, code change proposals that appear as if they might reduce the level of safety in a building are rarely approved without significant justification. Consider, for example, a proposal to introduce egress modeling as a substitute for prescribed egress distances in a code. In a sprinkled building, egress modeling would almost certainly allow exit travel distances to exceed the prescriptive distances set forth in model building and fire codes. However, one must bear in mind that the computer model may assume that the sprinkler system will always operate properly and that all other aspects of the modeled scenario will occur as planned. Because this may not be true, some margin for error or a factor of safety must be considered, but there is little guidance available in this area. From the perspective of many code enforcers, there is minimal evidence to suggest that distances currently prescribed by codes are excessive, inadequate, or unsafe, even though they are generally based on consensus judgement. Consequently, allowing the use of fire modeling to determine egress requirements is an uphill battle.

A good starting point for the introduction of more scientifically based fire and life safety criteria in codes might be an evaluation of the level of s afety the codes currently prescribe. Some efforts have already been made in this regard. For instance, the iron and steel industry in Australia conducted a study that evaluated the interaction of structural fire resistance with automatic sprinklers by probabilistic modeling. An evaluation of the current level of safety prescribed by the codes would provide a basis for evaluating the cost-effectiveness of fire and life safety features, factors of safety, and equivalencies.

Unquestionably, the fire safety criteria set forth in the codes follow the rule of diminishing returns. For example, a sprinkled building will have a 95%+ chance of surviving a fire with an acceptable level of structural damage and life loss with minimal reliance on safety features other than the sprinkler system. Structural fire resistance, on-site fire hydrants, fire resistance of exit enclosures, and so on, are high- cost items that contribute only to the remaining less-than-5% probability of an uncontrolled fire in a sprinkled building.

One example of a recent code change proposal that may have benefitted from this type of analysis was a requirement introduced into the 1992 supplement of the Uniform Building Code to provide smoke control systems whose design is based on mathematical modeling. Although it was widely agreed that smoke control in buildings is a good idea and that good design methods exist, no basis was available to determine the overall effectiveness or cost-effectiveness of providing such systems. In this case, mathematically designed smoke control systems were required in high- rise buildings in an effort to incorporate a more scientific basis for smoke control design, but the overall benefit to the level of safety in a building based on providing a smoke control system was not evaluated.

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Proprietary Interest Codes represent a unique balance of nonproprietary and proprietary interests. Manu- facturers and marketers strongly promote and defend many proprietary concerns in codes, and this may act as an impediment to the adoption of new or different technologies. For example, a requirement that mandates the installation of fire sprinklers at the expense of structural fire protection benefits the sprinkler industry and has a negative impact on the manufacturers of fire-resistive materials.

Using probabilistic modeling, scenario analysis by fire modeling, and a knowledge of the current level of safety prescribed by codes, we can base decisions about fire safety and the relative benefits of comparable methods more strongly on the impact they may have on fire and life safety. These approaches present a more solid basis for decision-making when comparing various alternative approaches to providing fire and life safety.

Changes from the Original Design Assumptions Over Time Perhaps one of the greatest challenges to incorporating scientifically based ap- proaches to fire protection into the codes is the difficulty of ensuring that a building will remain consistent with its original design assumptions. For example, a warehouse originally designed to contain high-piled combustible storage classified as a Class I commodity and provided with the appropriately designed sprinkler system would be improperly protected if the commodity were changed to Class IV and the sprinkler system were not modified accordingly. One faces a similar problem when developing fire models to determine fire and life safety design features based on specific arrangements and types of contents. Ensuring that the types and arrangements of fumishings remain constant throughout the life of a building is an extremely difficult task. To accommodate the potential variation of contents, worst-reasonable-case scenarios must be developed, and acceptable levels of risk must be established.

Conclusion In conclusion, it appears that a primary missing link in the widespread adoption of

scientifically based fire and life safety design in codes is a thorough evaluation of the current level of safety the codes prescribe and of the cost-effectiveness of various features that contribute to that level of safety. Also missing is any guidance to users and reviewers of fire models about model sensitivity, limitations, selection of scenarios, and design factors of safety. Additional concerns that deserve our attention include training and perhaps certification of model users and reviewers. Finally, models should be validated by testing and independent review, and methods of preventing modifications to validated source code should be developed to keep untrained or unscrupulous users from modifying program calculations or outputs without identifying that a modification has occurred.

Proposals for code changes to allow more liberal building designs based on mathematical modeling will be difficult to accept until these issues have been addressed.