Jose L. Torero

SFPE handbook of fire protection engineering

Revised and significantly expanded, the fifth edition of this classic work offers both new and substantially updated information. As the definitive reference on fire protection engineering, this book provides thorough treatment of the current best practices in fire protection engineering and performance-based fire safety. Over 130 eminent fire engineers andresearchers contributed chapters to the book, representing universities and professional organizations around the world. It remains the indispensible source for reliable coverage of fire safety engineering fundamentals, fire dynamics, hazard calculations, fire risk analysis, modeling and more. With seventeen new chapters and over 1,800 figures, the this new editioncontains: • Step-by-step equations that explain engineering calculations • Comprehensive revision of the coverage of human behavior in fire, including several new chapters on egress system design, occupant evacuation scenarios, combustion toxicity and data for human behavior analysis • Revised fundamental chapters for a stronger sense of context • Added chapters on fire protection system selection and design, including selection of fire safety systems, system activation and controls and CO2 extinguishing systems • Recent advances in fire resistance design • Addition of new chapters on industrial fire protection, including vapor clouds, effects of thermal radiation on people, BLEVEs, dust explosions and gas and vapor explosions • New chapters on fire load density, curtain walls, wildland fires and vehicle tunnels • Essential reference appendices on conversion factors, thermophysical property data, fuel properties and combustion data, configuration factors and piping properties.

How did the WTC towers collapse: a new theory

Abstract This paper uses a finite-element model to investigate the stability of the Twin-Towers of the World Trade Center, New York for a number of different fire scenarios. This investigation does not take into account the structural damage caused by the terrorist attack. However, the fire scenarios included are based upon the likely fires that could have occurred as a result of the attack. A number of different explanations of how and why the Towers collapsed have appeared since the event. None of these however have adequately focused on the most important issue, namely ‘what structural mechanisms led to the state which triggered the collapse’. Also, quite predictably, there are significant and fundamental differences in the explanations of the WTC collapses on offer so far. A complete consensus on any detailed explanation of the definitive causes and mechanisms of the collapse of these structures is well nigh impossible given the enormous uncertainties in key data (nature of the fires, damage to fire protection, heat transfer to structural members and nature and extent of structural damage for instance). There is, however, a consensus of sorts that the fires that burned in the structures after the attack had a big part to play in this collapse. The question is how big? Taking this to the extreme, this paper poses the hypothetical question, “had there been no structural damage would the structure have survived fires of a similar magnitude”? A robust but simple computational and theoretical analysis has been carried out to answer this question. Robust because no gross assumptions have been made and varying important parameters over a wide range shows consistent behaviour supporting the overall conclusions. Simple because all results presented can be checked by any structural engineer either theoretically or using widely available structural analysis software tools. The results are illuminating and show that the structural system adopted for the Twin-Towers may have been unusually vulnerable to a major fire. The analysis results show a simple but unmistakable collapse mechanism that owes as much (or more) to the geometric thermal expansion effects as it does to the material effects of loss of strength and stiffness. The collapse mechanism discovered is a simple stability failure directly related to the effect of heating (fire). Additionally, the mechanism is not dependent upon failure of structural connections.

Kinetic and Fuel Property Effects on Forward Smoldering Combustion

In this paper, we present the results from a one-dimensional transient model of forward smoldering. Fuel oxidation and pyrolysis reactions as well as a char oxidation reaction are included in the model. The solid energy, solid species, gas energy, oxygen species (bulk gas and surface), and overall mass conservation equations were discretized in space using finite-difference techniques and were solved using VODE, an ordinary differential equation integrator designed for stiff equations. Local thermal and chemical nonequilibrium are allowed in this model and transfer coefficients are derived from a Nusselt number correlation. A base case is chosen to represent experimental conditions reported in the literature. The effects of inlet gas velocity, kinetic frequency factors, inlet oxygen concentration, and fuel properties such as specific heat, density, conductivity, and pore diameter were studied using this model.

The Effects of Different Airflows on the Formation of Pollutants During Waste Incineration

An experimental study has been conducted with a fixed bed reactor to simulate, in a laboratory scale, industrial municipal waste incineration using moving grates. Carbon monoxide, nitrogen oxide and temperature measurements have been used to establish the importance of the operating parameters of a municipal waste incinerator in the characteristics of the combustion process. The observation of the different combustion regimes established has served to show the potential impact of the operating conditions on the yields of carbon monoxide and nitrogen oxide. Two different regimes have been identified and that are controlled by the airflow through the fuel (primary airflow). For primary airflows below the stoichiometric requirement an oxygen deficient combustion regime is established within the porous matrix. This regime is characterized by low reaction temperatures, favors endothermic pyrolysis and greatly enhances the production of CO. Within this regime, an increase in primary airflow will result in a decrease in CO yield. For airflows above the stoichiometric requirement the reaction establishes above the fuel, the temperature increases and the CO yield increases weakly with the total airflow rate. The introduction of a secondary airflow downstream of the fuel degradation region results in better mixing and an increase in the reaction temperature. As the secondary air increases the enhancement of mixing becomes less important and fuel dilution leads to a reduction of the temperature. The present experimental results show that the production of NO seems to be controlled only by the oxygen concentration in the secondary zone of combustion. An increase in total airflow, thus, results in an increase in the yield of NO.

Oxidizer Flow Effects on the Flammability of Solid Combustibles

A study is presented on the effect of oxidizer flow characteristics on the piloted ignition and opposed flame spread of a slab of PMMA heated by an external radiant flux. The objective is to establish the basis for a potential new lest method that may be used to determine the flammability performance of solid materials in terms of their ignition delay, critical heat flux for ignition, and flame-spread rate, for varied oxidizer flow conditions. The proposed Forced-flow Ignition and flame-Spread Test (FIST) follows the concepts of the LIFT (ASTM E 1321-93), and thus consists of a combination of ignition delay and flame spread experiments as a function of an externally applied radiant flux, but incorporates controlled forced convection as the predominant mechanism for the gas-phase transport of heat and mass. PMMA slabs were tested to assess the applicability of the methodology, and results are presented for radiant fluxes ranging from 0 to 35 kW/m2, forced oxidizer flow velocities of 1.0, 1.75, and 2.5 m/s. and natural convection. Results of the variation of ignition delay as a function of free stream oxygen concentration (18 to 45%) are also presented. Following the LIFT methodology, the ignition delay and flame spread data are used to assemble flammability diagrams for PMMA at different oxidizer flow velocities. Additional natural convection tests were performed in the LIFT apparatus with the purpose of establishing a base line for comparison of results. It is shown that the resulting FIST and LIFT flammability diagrams are similar. However, the diagrams as well as the parameters extracted from them depend on the oxidizer flow velocity, resulting in families of flow-dependent flammability diagrams. As a result of the use of forced convection, it is considered that the FIST is suitable for characterizing solid material flammability in mixed regimes ranging from natural to predominantly forced convection, and at different oxygen concentrations. This could provide a means to more accurately rank the relative flammability of solid combustible materials that would be used in environments where the oxidizer flow differs from air in natural convection, such as areas with significant air currents, vitiated environments, or microgravity applications (space based facilities).

FireGrid: An e-infrastructure for next-generation emergency response support

The FireGrid project aims to harness the potential of advanced forms of computation to support the response to large-scale emergencies (with an initial focus on the response to fires in the built environment). Computational models of physical phenomena are developed, and then deployed and computed on High Performance Computing resources to infer incident conditions by assimilating live sensor data from an emergency in real time-or, in the case of predictive models, faster-than-real time. The results of these models are then interpreted by a knowledge-based reasoning scheme to provide decision support information in appropriate terms for the emergency responder. These models are accessed over a Grid from an agent-based system, of which the human responders form an integral part. This paper proposes a novel FireGrid architecture, and describes the rationale behind this architecture and the research results of its application to a large-scale fire experiment.

Flaming Ignition of Solid Fuels

This chapter will describe how heating of a solid fuel leads to flaming ignition. The discussion will be centred on flaming ignition of solid fuels but will not address smouldering or spontaneous ignition since these subjects will be covered in Chaps. 19 and 20 respectively. Thus, the presence of a source of heat decoupled from the solid and fuel gasification will be assumed throughout the chapter.

Self-Sustaining Smoldering Combustion for NAPL Remediation: Laboratory Evaluation of Process Sensitivity to Key Parameters

Smoldering combustion has been introduced recently as a potential remediation strategy for soil contaminated by nonaqueous phase liquids (NAPLs). Published proof-of-concept experiments demonstrated that the process can be self-sustaining (i.e., requires energy input only to start the process) and achieve essentially complete remediation of the contaminated soil. Those initial experiments indicated that the process may be applicable across a broad range of NAPLs and soils. This work presents the results of a series of bench-scale experiments that examine in detail the sensitivity of the process to a range of key parameters, including contaminant concentration, water saturation, soil type, and air flow rates for two contaminants, coal tar and crude oil. Smoldering combustion was observed to be self-sustaining in the range 28,400 to 142,000 mg/kg for coal tar and in the range 31,200 to 104,000 mg/kg for crude oil, for the base case air flux. The process remained self-sustaining and achieved effective remediation across a range of initial water concentrations (0 to 177,000 mg/kg water) despite extended ignition times and decreased temperatures and velocities of the reaction front. The process also exhibited self-sustaining and effective remediation behavior across a range of fine to coarse sand grain sizes up to a threshold maximum value between 6 mm and 10 mm. Propagation velocity is observed to be highly dependent on air flux, and smoldering was observed to be self-sustaining down to an air Darcy flux of at least 0.5 cm/s for both contaminants. The extent of remediation in these cases was determined to be at least 99.5% and 99.9% for crude oil and coal tar, respectively. Moreover, no physical evidence of contamination was detected in the treatment zone for any case where a self-sustaining reaction was achieved. Lateral heat losses to the external environment were observed to significantly affect the smoldering process at the bench scale, suggesting that the field-scale lower bounds on concentration and air flux and upper bound on grain size were not achieved; larger scale experiments and field trials where lateral heat losses are much less significant are necessary to define these process limits for the purposes of field application. This work provides valuable design data for pilot field trials of both in situ and ex situ smoldering remediation applications.

The Effect of Buoyancy on Opposed smoldering

An experimental investigation on the effects of buoyancy on opposed-flow smolder is presented. Tests were conducted on cylindrical samples of open-cell, unretarded polyurethane foams at a range of ambient pressures using the Microgravity Smoldering Combustion (MSC) experimental apparatus. The samples were tested in the opposed configuration, in which the flow of oxidizer is induced in the opposite direction of the propagation of the smolder front. These data were compared with opposed-forced-flow tests conducted aboard STS-69, STS-77, and STS-105 and their ground-based simulations. Thermal measurements were made of the smolder reaction to obtain peak reaction temperatures and smolder velocities as a function of the ambient pressure in the MSC chamber. The smolder reaction was also observed using high-frequency ultrasound pulses as part of the ultrasound imaging system (UIS). The UIS measurements were used as a second means of providing smolder propagation velocities as well as to obtain permeabilities of the reacting samples. Results of forced-flow testing in normal gravity were compared to results in microgravity at a range of ambient pressures and forced flows. Results indicate that a critical oxidizer mass flux of roughly 0.5 to 0.8 g/m2s is required in normal gravity for a self-sustaining propagation in this configuration. In microgravity tests, self-sustained smolder propagation was observed at a significantly lower oxidizer mass flux of 0.30 g/m2s. Analysis suggests that the removal of buoyancy-induced heat losses in microgravity allows for self-sustained propagation at an oxidizer mass flux below the critical value observed in normal-gravity testing. Normal-gravity tests also show that the smolder propagation velocity is linearly dependent on the total oxidizer mass flux in an oxidizer-limited regime. Pressure effects on the chemical kinetics of a smolder reaction are inferred by comparison of normal-gravity and microgravity tests and believed to be only weakly dependent on pressure (∼P 1/3).

The Effect of Model Parameters on the Simulation of Fire Dynamics

Peer-reviewed article published in the Proceedings of the 9th International Symposium on Fire Safety Science, Karlsruhe, 2008.