HAZARD I: Software for Fire Hazard Assessment

NIST Handbook 146, HAZARD I—Fire Hazard Assessment Method [1], represents the culmination of a long-term program aimed at placing the prediction of fire outcomes on an objective and scientific basis. In the 1970s, NIST supported Harvard University to develop numerical models that could predict the temperature in a room containing a fire. These early models were difficult to use and interpret; required large, mainframe computers that were available only in academic institutions; and were plagued with long execution times, often interrupted by software crashes. Major pieces of fire physics and most fire chemistry were not well enough understood to be included in the models, so that predictive accuracy was disappointing. As a result, these early models were little more than academic playthings which were seldom put to practical use. In 1983, NIST’s fire program established a goal to develop a tool that could evaluate the role of the fire performance of an individual material or product in the outcome of a specific fire in a specific compartment or group of compartments. The first year of the project was devoted to determining the capabilities needed to accomplish this, and the effort was somewhat daunting. Not only would it be necessary to predict the fire environment in the space resulting from the material or product burning, but it would also require understanding the movement and behavior of occupants and the physiological and psychological effects of exposure to this fire. Since the project started before the personal computer revolution, the initial plan was to develop the software to run on NIST’s mainframe and to equip a “fire simulation laboratory” at NIST with terminals and graphics equipment so that scientists and engineers could learn how to use the software to address practical problems. Once the usefulness of these models were appreciated, the larger engineering firms were expected to invest in the hardware needed to exploit the technology. It was expected that these firms would have the computers to run the software in their own offices by the end of the century. By 1986 the NIST multi-compartment model, FAST (Fire and Smoke Transport) [2] had been enhanced so that its predictions were credible when applied within specific bounds. NIST’s pioneering development of oxygen consumption calorimetry provided a means to measure the rate at which mass and energy were released from a burning item. By expressing a material’s fire performance in terms of conserved quantities, it was possible to describe burning behavior for a predictive model. A NIST psychologist was developing a unique evacuation model with embedded behavioral rules derived from interviews with fire victims. Finally, the NIST combustion toxicology program was producing data that showed toxicological effects were primarily from a small number of toxic species. Also at this time, the personal computer revolution was well underway. It became clear that a computer on every desktop would soon be a reality, so the NIST software was now targeted at that group of users. Efforts were expended on an improved user interface that would both simplify data entry at the front end and provide graphical output support to make the results more understandable and useful at the back end. The first version of the HAZARD I software and documentation [1] was released in 1989. The software was clearly focused on material and product manufacturers as a tool to assess the fire hazards of their products and a means to justify higher costs associated with better performing products. However, the manufacturers were underwhelmed because the methods required skill to apply and were unproven. Several factors soon began to change perceptions of the potential of HAZARD I. There was political pressure to regulate combustion toxicity, with one state actually promulgating a regulation. NIST produced a fire hazard analysis that showed burning rate was much more important as an indicator of fire hazard than toxicity. In addition, a well respected fire protection engineer became interested in learning these new techniques and successfully applied HAZARD I to absolve clients of liability in civil litigation involving a fire. This led to additional uses in both civil and criminal litigation and represented the first significant application of modern fire models. The publication of NIST Handbook 146 was a watershed for NIST in several ways. While NIST had developed and distributed other software products (such as DATAPLOT, a scientific graphing package), HAZARD I was an engineering analysis tool that could be used to make (literally) life and death decisions. It contained a broad range of engineering and scientific methodology that needed to be appropriately documented. Documentation consisted of a Technical Reference Guide which underpins the equations and assumptions and explains how they are coded, a set of worked examples, and a