Paul A. Reneke

Defining flashover for fire hazard calculations

As the use of performance-based methods for evaluating the fire behavior of materials and systems becomes more widespread, objective criteria to judge fire behavior become more important. This paper reviews techniques for predicting the most common of these criteria, the onset of flashover. The experimental basis for working definitions of flashover is reviewed. Comparisons of available calculational procedures ranging from simple correlations to computer-based fire models that can be used to estimate flashover are presented. Although the techniques range in complexity and results, the various predictions give estimates commensurate with the precision of available experimental data.

Quantifying Fire Model Evaluation Using Functional Analysis

Comparisons of predictive fire models with each other or with experimental data have been largely qualitative. By treating these time series curves as infinite-dimensional vectors, a branch of mathematics called functional analysis defines geometrically meaningful operations on the curves. This allows lengths, angles, and distance between two arbitrary curves to be defined and quantified. An introduction to the theory and tools provided by functional analysis is presented. Examples of the application of these tools to fire model evaluation are presented.

Defining flashover for fire hazard calculations: Part II

Abstract Comparison of available correlations and predictive models used to predict the minimum heat release rate (HRR) necessary to cause flashover show consistent trends for a range of empirical data. Nonetheless, available experimental data for HRR at flashover in compartments of similar geometry and venting show substantial scatter. Both the experimental data and theoretical predictions based on computer modeling indicate that a significant portion of the variability can be accounted for by the time period involved in the flashover. Although typically ignored in the available correlations, qualitatively a clear trend emerges—shorter exposure times increase the needed minimum HRR at flashover, due at least in part to the effects of heat transfer to the compartment surfaces. Additional measurement needs are suggested to facilitate better understanding of conditions leading to flashover.

FIRE SAFETY OF PASSENGER TRAINS: A REVIEW OF CURRENT APPROACHES AND OF NEW CONCEPTS

New alternative technologies have been developed which can be used to increase intercity passenger train operating speeds. These technologies include steel-wheel-on-rail and magnetic levitation (maglev) systems. Fire safety is an area of particular interest for these technologies, as well as for conventional intercity and commuter trains. While the historical fire record has been very good and few serious passenger train fires have occurred, minor incidents could develop into potential life-threatening events. The report presents a detailed comparison of the fire safety approaches used in the United States, France, and Germany. The strengths and weaknesses of current methods for measuring the fire performance of rail transportation systems are evaluated. An optimum systems approach to fire safety which addresses typical passenger train fire scenarios is analyzed and recommendations are presented to address the current state-of-the-art in materials testing.

Issues in Evaluation of Complex Fire Models

Several methods of evaluation of the predictive capability have been applied to fire models, but with limited utility. These range from explicit evaluation of the equations used in simple models such as ASET to pointwise evaluation of complex models from numerous computer runs of a model. This paper presents a discussion of the issues involved in conducting an analysis of a complex room fire model. Examples using currently available room fire models are presented. For the models and test cases examined, heat release rate and heat transfer effects dominate the behavior of the models. For simple models like the ASET model, analytical techniques can be readily applied. For more complex fire models, obtaining an overall assessment of the model increases in complexity with the complexity of the model, requiring evaluation of numerous model inputs and outputs. Thus, more directed local investigations are currently the only tractable means of evaluation. Areas for additional research are identified.

Risk perception in fire evacuation behavior revisited: definitions, related concepts, and empirical evidence

Risk perception (RP) is studied in many research disciplines (e.g., safety engineering, psychology, and sociology). Definitions of RP can be broadly divided into expectancy-value and risk-as-feeling approaches. In the present review, RP is seen as the personalization of the risk related to a current event, such as an ongoing fire emergency; it is influenced by emotions and prone to cognitive biases. We differentiate RP from other related concepts (e.g., situation awareness) and introduce theoretical frameworks relevant to RP in fire evacuation (e.g., Protective Action Decision Model and Heuristic-Systematic approaches). Furthermore, we review studies on RP during evacuation with a focus on the World Trade Center evacuation on September 11, 2001 and present factors modulating RP as well as the relation between perceived risk and protective actions. We summarize the factors that influence perception risk and discuss the direction of these relationships (i.e., positive or negative influence, or inconsequential) and conclude with presenting limitations of this review and an outlook on future research.

Characteristics of Fire Scenarios in Which Sublethal Effects of Smoke are Important

A number of simulations were performed using the CFAST zone fire model to predict the relative times at which smoke inhalation and heat exposure would result in incapacitation. Fires in three building types were modeled: a ranch house, a hotel, and an office building. Gas species yields and rates of heat release for these design fires were derived from a review of real-scale fire test data. The incapacitation equations were taken from draft 14 of ISO document 13571. Sublethal effects of smoke were deemed important when incapacitation from smoke inhalation occurred before harm from thermal effects occurred. Real-scale HCl yield data were incorporated as available; the modeling indicated that the yield would need to be 5 to 10 times higher for incapacitation from HCl to precede incapacitation from narcotic gases, including CO CO2, HCN and reduce O2.The results suggest that occupancies in which sublethal effects from open fires could affect escape and survival include multi-room residences, medical facilities, schools, and correctional facilities. In addition, fires originating in concealed spaces in any occupancy pose such a threat. Sublethal effects of smoke are not likely to be of prime concern for open fires in single- or two-compartment occupancies (e.g., small apartments and transportation vehicles) themselves, although sublethal effects may be important in adjacent spaces; buildings with high ceilings and large rooms (e.g., warehouses, mercantile); and occupancies in which fires will be detected promptly and from which escape or rescue will occur within a few minutes.

Federal Investigation of the Evacuation of the World Trade Center on September 11, 2001.

This paper presents the findings of the NIST World Trade Center Investigation describing the occupant evacuation of WTC 1 and WTC 2 on September 11, 2001. The egress system, including stairwells and elevators, is described along with the evacuation procedures. The population in WTC 1 and WTC 2 on September 11, 2001 at 8:46 a.m. is enumerated and described, where the background of the population was relevant to the subsequent evacuation, including training, experience, mobility status, among others. The progress of the evacuation of both towers is described in a quasi-chronological manner. A decedent analysis explores where occupants were located when each tower was attacked. Multiple regression models were built to explore the sources of evacuation initiation delay (why people did not immediately start to leave the building), as well as stairwell evacuation time (how long the average occupant spent in the stairwells per floor). Issues identified as contributing to either slowing or aiding the evacuation process were explored. Egress simulations provided context for estimating how long WTC 1 and WTC 2 would have taken to evacuate with different populations, using three different models, and subject to different assumptions of damage to the building.

New Concepts for Fire Protection of Passenger Rail Transportation Vehicles

Recent advances in guided group transportation, fire test methods, and hazard analysis necessitate re-examination of requirements for fire safety. Several studies have indicated nearly random ability of current tests to predict actual fire behavior. A comparison of the approaches used in the United States, Germany, and France is presented. With the strengths and weaknesses of current methods for measuring the fire performance of materials used in rail transit systems reviewed, a direction is suggested in which most fire science-oriented organizations in the world are clearly headed - fire hazard and fire risk assessment methods supported by measurement methods based on heat release rate.

FASTLite :: engineering gools for estimating fire growth and smoke transport

FASTLite is a collection of procedures which builds on the core routines of FIREFORM and the computer model CFAST to provide engineering calculations of fire phenomena for the building designer, code official, fire protection engineer and fire-safety related practitioner. This manual provides documentation and examples for using FASTLite. It describes how to install the software on a computer and provides a guide for the use of FASTLite using an example.