Richard D. Peacock

Heat release rate: The single most important variable in fire hazard☆

Abstract Heat release rate measurements are sometimes seen by manufacturers and product users as just another piece of data to gather. It is the purpose of this paper to explain why heat release rate is, in fact, the single most important variable in characterizing the ‘flammability’ of products and their consequent fire hazard. Examples of typical fire histories are given which illustrate that even though fire deaths are primarily caused by toxic gases, the heat release rate is the best predictor of fire hazard. Conversely, the relative toxicity of the combustion gases plays a smaller role. The delays in ignition time, as measured by various Bunsen burner type tests, also have only a minor effect on the development of fire hazard.

Verification of a model of fire and smoke transport

Abstract A set of comparison between a comprehensive room fire model and a range of real-scale fire experiments is presented. For these comparisons, a zone-based model, CFAST (‘consolidated fire and smoke transport’ model) is used. The model predicts the evolution of a fire in a room and the subsequent transport of the smoke and toxic gases which result from this fire. These comparisons serve two purposes: to determine, within limits, the accuracy of the predictions for those quantities of interest to the users of the models (usually those extensive variables related to hazard), and to highlight the strengths and weaknesses of the underlying algorithms in the models to guide future improvements in this and other models. The predicted variables selected for comparison deal with both of these purposes. Although differences between the model and the experiments were clear, they can be explained by limitations of the model and of the experiments.

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.

A methodology for obtaining and using toxic potency data for fire hazard analysis

A comprehensive methodology has been developed for obtaining and using smoke toxicity data for fire hazard analysis. This description of the methodology comprises (1) determination that the post-flashover fire is the proper focus of smoke inhalation deaths; criteria for a useful bench-scale toxic potency (LC50) measurement method; (2) a method which meets these criteria, especially validation against real-scale fires; (3) a computational procedure for correcting the results from the bench-scale test for the CO levels observed in real-scale post-flashover fires; (4) procedures for reducing the usage of animals and broadening the applicability of data by interpreting gas measurement data using the N-Gas Model; and (5) a procedure for identifying whether a product produces smoke within the ordinary range of toxic potency for postflashover fires.

Toxic potency measurement for fire hazard analysis

SummaryThis report is the principal product of a long-term research program to provide a technically sound methodology for obtaining and using smoke toxicity data for hazard analysis. It establishes:(a)an improved bench-scale toxic potency1 measurement, one which represents the important combustion conditions of real fires; and(b)a design and analysis framework which will allow the toxic potency data to be used in a rational, consistent, appropriate, and adequate way.nThis establishment of proper bench-scale test conditions, validation of the output against real-scale fire measurements, and development of a consistent framework for the inclusion of toxic potency in fire hazard2 analysis is unique and represents a successful, usable implementation of the state of the art.This method focuses on post-flashover fires. The U.S. fire statistics show that 69% of all fire deaths are associated with post-flashover fires, with the preponderance of deaths due to smoke inhalation and occurring outside the room of fire origin. These fires are characterized by:• primarily radiant heating, with heat fluxes from about 20 to 150 kW/m2 throughout the room;• many items simultaneously on fire; and• vitiated combustion air for some, but not all, burning items.

Pedestrian and evacuation dynamics

Preface.- Dedication.- Pedestrian and Evacuation Dynamics Awards.- Five Grand Challenges in Pedestrian and Evacuation Dynamics.- Data Collection (Evacuation).- Data Collection (Pedestrian).- Data Collection (Vulnerable Groups).- Data Collection (Transport).- Data Collection Methods.- Theory for Models.- General Model Development.- Large-scale Modeling.- Transport Modeling.- Modeling Methods.- Model Calibration / Validation.- Vertical Egress.- Regulations / Engineering Guidance.- Posters

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.

Stairwell Evacuation from Buildings: What We Know We Don’t Know

Occupant descent down stairwells during building evacuations is typically described by measurable engineering variables such as stairwell geometry, speed, density, and pre-evacuation delay. In turn, predictive models of building evacuation use these variables to predict the performance of egress systems for building design, emergency planning, or event reconstruction. This paper provides a summary of literature values for movement speeds and compares these to several new fire drill evacuations. Movement speeds in the current study are observed to be quite similar to the range of literature values. Perhaps most importantly though, the typical engineering parameters are seen to explain only a small fraction of the observed variance in occupant movement speeds. This suggests that traditional measures form an incomplete theory of people movement in stairs. Additional research to better understand the physiological and behavioral aspects of the evacuation process and the difference between fire drill evacuations and real fire emergencies are needed.