SFPE Handbook of Fire Protection Engineering

In this section, a number of fluid properties are defined. An implicit assumption in the classical fluid mechanics is the ‘continuum hypothesis’, implying that we treat fluids as continuous media, not as an ensemble of individual molecules [1]. This is justified in ‘normal’ circumstances. This way, the fluid and flow quantities are continuous and local quantities to be interpreted as averages over a volume V

*

which is very small (but still very large when compared to distances between molecules). This assumption allows to define local fluid and flow properties (e.g. velocity vectors). The continuum hypothesis is adopted here.

Heat transfer is an area of thermal engineering the focuses on the transport, exchange, and redistribution of thermal energy. The three modes or ways that heat can be transferred have been termed conduction, convection, and radiation. In this chapter, the basic physics associated with conduction heat transfer will be elaborated, and it will be shown through examples how the tools and analysis typically used for conduction problems can be applied to design and analysis when fire occurs.

There are only two fundamental physical modes of energy transfer, conduction and radiation. In conduction, energy slowly diffuses through a

medium

from a point of higher temperature to a point of lower temperature, whereas in radiation, energy is transmitted with the speed of light by electromagnetic waves (or photons), and a transmitting medium is not required. Thus from a conceptual viewpoint, convection is not a basic mode of heat transfer. Instead, it occurs by a combined effect of conduction (and/or radiation) and the motion of the transmitting medium.

Thermal radiation is the dominant mode of heat transfer in flames with characteristic lengths exceeding approximately 0.2 m. It is for this reason that quantitative analysis of fire dynamics requires a working knowledge of thermal radiation. This chapter will introduce the fundamentals of thermal radiation and offer several methods for calculating radiant heat transfer in fires. Basic thermal radiation concepts are presented with an emphasis on application to fire phenomena; the reader is referred the literature for specialized topics [1–4].

Thermochemistry is the branch of physical chemistry that is concerned with the amounts of energy released or absorbed when a chemical change (reaction) takes place [1–3]. Inasmuch as fire is fundamentally a manifestation of a particular type of chemical reaction, viz., combustion, thermochemistry provides methods by which the energy released during fire processes can be calculated from data available in the scientific and technical literature.

The temperature of a flame must be known in order to calculate convective and radiative heat transfer rates, which control pool-fire burning rates, flame spread rates, remote ignitions, damage to exposed items (e.g., structural steel, wiring), and response of thermal fire detectors or automatic sprinklers.

Most of unwanted fires are fuelled by polymeric materials, ranging from natural polymers found in wood, cotton or wool, to synthetic polymers (“plastics”) derived from crude oil, showing much greater flammability. Polymer molecules are too large to be volatile, but break down thermally, by chain scission and chain stripping, to release fuel to the vapour phase prior to ignition. Experimental and numerical methods for investigating polymer decomposition are reviewed, followed by a description of the chemical decomposition of individual polymers. In order to use flammable synthetic polymers in high risk applications, fire retardants are frequently added to meet regulatory requirements. The range of available fire retardants is described in relation to their different modes of action. This is followed by a description of the more common test methods used to assess the flammability of polymeric materials, including ignitability, flame spread and heat release rate, together with a summary of the importance of physical properties and char formation on their burning behaviour.

Structural mechanics, sometimes called ‘solid mechanics’ or ‘mechanics of materials’ is concerned with describing the behavior of structural members under loading, as occurs in all buildings and other structures due to the effects of gravity and other forces (e.g. wind, earthquake, etc.). A detailed understanding of structural mechanics is essential for anyone seeking to competently perform structural fire engineering analysis or design.

Building components are to be designed to satisfy the requirements of serviceability and safety limit states. One of the major safety requirements in building design is the provision of appropriate fire resistance to various building components. The basis for this requirement can be attributed to the fact that, when other measures of containing the fire fail, structural integrity is the last line of defense. In this chapter, the term

structural member

is used to refer to both load-bearing (e.g., columns, beams, slabs) and non-load-bearing (e.g., partition walls, floors) building components.

The purpose of this chapter is to set out the principles of chemical kinetics as they apply to combustion in flames and fires. Chemical equilibrium, which was discussed in a previous chapter, deals with the final preferred state of a given set of reactants after an infinite time has passed. In contrast, chemical kinetics deals with the rate at which the system proceeds to the equilibrium state, i.e., the specific participating chemical reactions and their rates. Chemical equilibrium and chemical kinetics are related in that the thermodynamic, equilibrium state provides the driving force for chemical reaction. The material in this chapter is covered briefly; more detailed descriptions can be found in chemistry [1] and combustion [2–4] text books, upon which much of the material is based.

Fires involve reactants, usually fuel and air, not intimately mixed at a molecular level before combustion. Usually, the fuel is in the solid or liquid state so transfer of material across a phase boundary (phase change) must also occur. The vaporized fuel must combine with oxygen from air to form a flammable mixture, which when ignited forms the flame zone. In most fire problems, this mixing of fuel vapor and oxygen takes place mostly by diffusion and takes orders of magnitude longer time compared with that of a chemical reaction. Therefore, diffusion of species is the primary controlling process during such burning behavior. A fundamental understanding of diffusion flames then involves exploring the

mechanisms

associated with the transport of the reactants and the resulting flame structure.

Lavoisier, Berthollet and Dalton were pioneers in the understanding of the mixture composition needed for a flame existence, and in the early 1800s, Sir Humphry Davy created a miner’s lamp with a fine meshed net that improved the safety for mine workers, as the mesh was finer than the quenching distance and hence reduced the number of accidental explosions. When Bunsen created the burner associated with his name in 1855 [1], the premixed flame was ‘understood’. However, as the following will show, there was, in the words of Richard Feynman, plenty of room at the bottom.

Practically all fires go through an important, initial stage in which a coherent, buoyant gas stream rises above a localized volume undergoing combustion into surrounding space of essentially uncontaminated air. This stage begins at ignition, continues through a possible smoldering interval, into a flaming interval, and may be said to end prior to flashover. The buoyant gas stream is generally turbulent, except when the fire source is very small. The buoyant flow, including any flames, is referred to as a fire plume.

Most devices associated with measures to detect and suppress fires in the built environment (e.g., commercial or modern residential buildings) are located near ceiling surfaces. The gas flow induced by an accidental fire tends to form a shallow layer beneath the ceiling surface that carries heat and smoke to areas remote from the fire position. Such a flow, known as a Ceiling Jet, can activate fire detection and suppression devices that are properly positioned in the shallow layer but can also cause damage eventually by heating the ceiling surface or structure. In this chapter, important characteristics of the ceiling jet, such as layer thickness, gas temperature or velocity and heat transfer rate for unconfined and confined ceiling configurations and for both steady and transient fires are discussed. Algebraic formulas are presented in all cases discussed to allow for rapid and reasonably accurate calculation of ceiling jet characteristics that can be used to verify aspects of more detailed numerical models. These formulas have also been embedded in comprehensive zone fire models and in design standards or codes.

Fire releases a great amount of heat that causes the heated gas to expand. The expansion produced by a fire in a room drives some of the gas out of the room. Any opening through which gas can flow out of the fire room is called a

vent.

A complete compartment fire hazard assessment requires a knowledge of toxic chemical species production. Although combustion products include a vast number of chemical species, in practical circumstances the bulk of the product gas mixture can be characterized by less than 10 species. Of these, carbon monoxide (CO) represents the most common fire toxicant (see Chap.

63

). Over half of all fire fatalities have been attributed to CO inhalation [1, 2]. Concentrations as low as 4000 ppm (0.4 % by volume) can be fatal in less than an hour, and carbon monoxide levels of several percent have been observed in full-scale compartment fires. A complete toxicity assessment should not only include the toxicity of CO but also include the synergistic effects of other combustion products, such as elevated CO

2

and deficient O

2

levels.

It is well known that not all fuel/oxidant/diluent mixtures can propagate flame. Normal flame-type combustion cannot be sustained outside certain limits definable in terms of fuel/oxidant/diluent composition. Definition of these limits has received a great deal of attention in premixed combustion conditions, that is, in systems where the fuel and oxidant are mixed prior to combustion. Despite scientific interest in the subject dating back to the nineteenth century, the mechanism responsible for flammable limits is not yet understood. Nonetheless, a great deal has been learned that has practical application.

The purpose of this chapter is to discuss the ignition characteristics of combustible liquids that are in widespread use as fuels and solvents and are encountered as process fluids in the chemical and process industries. Ignition leads to flaming combustion in which the fuel undergoes a change of state and is converted from liquid to vapor.

Smoldering combustion is the slow, low temperature, flameless burning of porous fuels and is the most persistent type of combustion phenomena. It is especially common in porous fuels which form a char on heating, like cellulosic insulation, polyurethane foam or peat. Smoldering combustion is among the leading causes of residential fires, and it is a source of safety concerns in industrial premises as well as in commercial and space flights. Smoldering is also the dominant combustion phenomena in megafires in natural deposits of peat and coal which are the largest and longest burning fires on Eartht.

The term

spontaneous combustion

will be used here to refer to the general phenomenon of an unstable (usually oxidizable) material reacting and evolving heat, which to a considerable extent is retained inside the material itself by virtue of poor thermal conductivity of either the material or its container. Under some circumstances this process can lead to flaming combustion and overt fire, in which case it is properly called

spontaneous ignition,

which here is regarded as a special case of spontaneous combustion. This has been responsible for significant losses of life and enormous losses of property. Fire loss statistics from many sources show that spontaneous ignition is quoted as the cause in a much greater proportion of cases with multimillion-dollar losses than in smaller fires. Of course, one should also note that the proportion of “cause unknown” results follows a similar trend, probably due to the greater degree of destruction, and hence evidence loss, in larger fires.

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.

An electrical fire is generally understood to be a fire that is caused by the flow of an electric current or by a discharge of static electricity. It is not defined as a fire involving an electrical device or appliance. For example, a fire on an electric range that occurs due to overheating and ignition of the oil in a deep-fry pan is not classed as an electrical fire, even though it involves an electrical appliance. Conversely, an electrical device or appliance is not always needed for an electrical fire to occur. Lightning-caused fires are a form of electrical fires and these can ignite, for example, a dry bush, which is not an electrical device.

Surface flame spread is a process of a moving flame in the vicinity of a pyrolyzing region on the surface of a solid or liquid that acts as a fuel source. It is distinct from flame propagation in a premixed fuel and oxygen system in that the surface spread of flame occurs as a result of the heating of the surface due to the direct or remote heating by the flame generated from the burning surface. The surface flame spread is very often critical to the destiny of fires in natural and built environments. This spread applies whether the fire is an urban conflagration or is the first growth after ignition of a room’s draperies. This chapter provides fire safety engineers with an overview of surface flame spread during the growth of a fire and the modeling of different modes of flame spread to improve understanding of their effects on the outcomes of fires.

Smoke is a mixture of (1) particulates consisting of soot, semi-volatile organic compounds (SVOC), and solid inorganic compounds; and (2) non-particulates consisting of very volatile organic compounds, volatile organic compounds, and liquid and gaseous inorganic compounds. Soot creates bridging between electrical conductors and conveys corrosive products, resulting in damage to electronics and electrical circuits through leakage current and corrosion, while SVOC and non-particulates stain and impart malodor to surfaces. Soot is also a very effective adsorbent and transport mechanism for SVOC, non-particulates and inorganic compounds.

The heat transfer from fires to adjacent surfaces is an important consideration in many fire analyses. Some example applications that may require knowledge of the heat transfer from a flame include heating and failure of structural beams, heat transfer through walls and ceilings, and the ignition and flame spread along combustible surfaces.

Calculations of fire behavior in buildings are not possible unless the heat release rate of the fire is known. This chapter on heat release rates provides both theoretical and empirical information. The chapter is organized so that theory and basic effects are considered first, then a compendium of product data is provided, which is arranged in alphabetic order.

Heat release rate is the single most important variable in fire hazard assessment [1]. Various test methods for measuring the heat release rate of materials and products under different conditions have therefore been developed. This chapter is dedicated to these test methods. An apparatus used for measuring heat release rate is referred to as a

calorimeter

and the measurement of heat release rate is called

calorimetry.

Chapter

27

describes the history and development of techniques for measuring heat release rate (HRR). This chapter outlines features and details of today’s preferred instrument for measuring bench-scale HRR—the cone calorimeter. Other cone calorimeter measuring functions are

An approach for predicting various aspects of fire phenomena in compartments has been called

zone

modeling. Based on a conceptual representation for the compartment fire process, it is an approximation to reality. Any radical departure by the fire system from the basic concept of the zone model can seriously affect the accuracy and validity of the approach. The zone model represents the system simply as two distinct compartment gas zones: an upper volume and a lower volume resulting from thermal stratification due to buoyancy. Conservation equations are applied to each zone and serve to embrace the various transport and combustion processes that apply. The fire is represented as a source of energy and mass manifested as a plume, which acts as a pump for the mass from the lower zone to the upper zone through a process called

entrainment.

The ability to predict temperatures developed in compartment fires is of great significance to the fire protection professional for protection of human life and property. There are many uses for a knowledge of compartment fire temperatures, including the prediction of (1) the onset of hazardous conditions, (2) property and structural damage, (3) changes in burning rate, pyrolysis rate and heat (energy) release rate, (4) ignition of objects,(5) the onset of flashover and so on.

Understanding the behavior of fire in compartments is of interest to the fire protection engineer for both fire safety design and postfire reconstruction. Such understanding may be obtained by examining experimental fires (full or reduced scale) or by

fire models

using mathematical techniques to represent the processes encountered in compartment fires by interrelated expressions based on physics and chemistry. The two major classes of fire models for analyzing enclosure fire development are stochastic and deterministic.

It was in the early 1920s that Lewis Richardson first demonstrated the feasibility of solving, using numerical methods, the governing equations of fluid flow [1] for the purpose of weather prediction. It was not for another 50 years that what is now known as computational fluid dynamics (CFD) emerged as a general analysis tool for the full breadth of fluid flow problems including those associated with fire.

Fires in buildings and other structures are distinguished from outdoor fires by the confinement effects associated with enclosure boundaries and by the ventilation effects associated with openings in these boundaries. The confinement of heat and smoke released by a fire in an enclosure gives rise to the evolution of fire-generated environmental conditions that can threaten life safety and cause thermal and nonthermal damage to the structure and its contents. For performance-based building fire safety analysis and design, it is important to be able to calculate the environmental conditions generated by fires in enclosures in order to evaluate the threat levels posed by anticipated fire scenarios. This chapter addresses the enclosure smoke-filling process and the fire-generated environmental conditions that develop within an enclosure during this process.

The fire resistance of structural elements is traditionally determined by standard fire endurance tests. However, there is also a need to be able to predict the response of structures of various designs when exposed to alternative design fire conditions. Accurate and robust analytical methods are then needed. Such methods may also be used for predicting standard tests of, for example, structural elements that cannot be tested due to their size or for extending test results to modified structures.

The fire load has a strong influence on the fire development during a compartment fire and is a significant parameter in fire safety design methods. The assessment of the fire load is therefore an important task in fire safety engineering. This chapter reviews the methods to survey the fire load, discusses how variation during the life time of the building can be represented and how to derive design fire loads. An overview of past fire load surveys and a summary of fire load data for specific building types is provided as well.

Hazards associated with fire are characterized by the generation of calorific energy and products, per unit of time, as a result of the chemical reactions of surfaces and material vapors with oxygen from air. Thermal hazards constitute those scenarios where the release of heat is of major concern. On the other hand, nonthermal hazards are characterized by fire products (smoke, toxic, corrosive, and odorous compounds.) Generation rates of heat and fire products (and their nature) are governed by (1) fire initiation (ignition); (2) fire propagation rate beyond the ignition zone; (3) fire ventilation; (4) external heat sources; (5) presence or absence of fire suppression/extinguishing agents; and (6) materials: (a) their shapes, sizes, and arrangements; (b) their chemical natures; (c) types of additives mixed in; and (d) presence of other materials. In this handbook most of these areas have been discussed from fundamental as well as applied views. For example, the mechanisms of thermal decomposition of polymers, which govern the generation rates of material vapors, are discussed in Chap.

7

, generation rate of heat (or heat release rate) from the viewpoint of thermochemistry is discussed in Chap.

5

, Flaming ignition of the mixture of material vapors and air is discussed in Chap.

21

, and surface flame spread in Chap.

23

.

The

SFPE Engineering Guide to Performance-Based Fire Protection

[1] defines performance-based design as “an engineering approach to fire protection design based on (1) agreed upon fire safety goals and objectives, (2) deterministic and/or probabilistic analysis of fire scenarios, and (3) quantitative assessment of design alternatives against the fire safety goals and objectives using accepted engineering tools, methodologies, and performance criteria.”

The engineering approach to fire safety design requires the selection and evaluation of fire scenarios that may occur in a building. Each fire scenario represents a unique combination of events and circumstances that influence the outcome of a fire in a building, including the impact of fire safety measures. The

SFPE Engineering Guide to Performance-Based Fire Protection

[1] refers to fire scenarios as “a set of conditions that defines the development of fire and the spread of combustion products throughout a building or part of a building.”

A fundamental responsibility of an engineer is the design of systems that satisfy the overall goals and objectives for a given facility. When it comes to fire and life safety, the fire protection engineer (FPE) is called upon to design those systems deemed necessary to meet the performance objectives for the project. However, before specific protection systems can be designed, decisions must be made regarding what systems are most appropriate and necessary in light of the fire events of concern, and the overall outcomes to be achieved at the conclusion of these events.

Fire detection and alarm systems are recognized as key features of a building’s fire prevention and protection strategy. This chapter presents a systematic technique to be used by fire protection engineers in the design and analysis of detection and alarm systems. The majority of discussion is directed toward systems used in buildings. However, many of the techniques and procedures also apply to systems used to protect planes, ships, outside storage yards, and other nonbuilding environments.

Hydraulics may be regarded as the application of knowledge about how liquids behave in static and flowing conditions to solve practical fluid related problems. It is generally held to describe the behavior and effects of water in motion in both closed conduits and open channels. In the field of fire protection we are concerned primarily with the closed conduit flow regime. In this chapter we will restrict our discussion to the behavior and properties of water flowing in pipes as the phenomenon of paramount interest, although other fluids such as antifreezes at room temperature and foam/water solutions are similar enough to water that the discussion will be applicable to them as well. Additionally some of the principles presented here also apply to system designs utilizing other fluids such as foam concentrate or antifreeze at low temperatures.

Water is the most commonly used fire fighting agent, mainly due to the fact that it is widely available and inexpensive. It also has very desirable fire extinguishing characteristics such as a high specific heat and high latent heat of vaporization. A single gallon of water can absorb 9280 Btus (2586.5 kJ) of heat as it increases from a 70 °F (21 °C) room temperature to become steam at 212 °F (100 °C).

Fire protection systems using halogenated extinguishing agents provide a classic example of a fire protection technology with a comprehensive evolutionary lifespan. These systems are a relatively recent innovation in fire protection, but, despite this, they already face extinction. As of January 1, 1994, the production of fire protection halons in most countries ceased, based on international treaties.

Total flooding clean agents and systems were developed in response to the regulation of Halon 1301 under the Montreal Protocol and its amendments culminated in the phase-out of production of halons in the developed countries on December 31, 1993. This regulation engendered tremendous research and development efforts across the world in a search for replacements and alternatives. Since that time on the order of 15 total flooding, clean agent alternatives to Halon 1301 have been commercialized, and development continues on others. In addition to cleanagent total flooding gaseous alternatives, new technologies, such as water mist and fine solid particulate, are being introduced. This chapter focuses on total flooding clean agent halon replacements.

Carbon dioxide (CO

2

) fire extinguishing systems have been in use continuously since the early 1900s. The National Fire Protection Association (NFPA) first published its design standard on carbon dioxide extinguishing systems in 1929. Since this time, carbon dioxide extinguishing systems have gained wide acceptance around the world, and have successfully protected fire hazards in a large variety of configurations and locales, including in land-based industrial environments, and on ships and mobile drilling platforms at sea. Carbon dioxide is electrically non-conductive and, when used at concentrations recommended in design standards, extinguishes fires relatively quickly leaving no residue.

This chapter addresses the engineering of fixed fire suppression systems that discharge water mist. The term

water mist,

as currently understood in the fire protection field, relates to fine water sprays with no drops larger than 1.0 mm, or 1000 μm (micrometers or microns) [1, 2]. Such sprays are not true mists, however. A

mist

in the scientific sense consists of drops somewhere on a continuum between

aerosol

(particles with diameter approximately 5 μm) and

fog

(droplet diameters ranging between 10 and 100 μm). Particles less than 20 μm in diameter take a long time to settle out and, hence, create what is recognized in both literature and science as a “mist.” A water mist as intended for fire protection purposes is a fine water spray consisting of a range of droplet sizes, many of which are in the range of true mist particles and some of which are considerably larger. Water mist nozzles produce sprays that have a higher fraction of very fine droplets, in the range of mist, than is typical of standard sprinklers or water spray nozzles.

Foams have been developed almost entirely from experimental work. Although the technologies are rather mature, no fundamental explanations of foam extinguishment performance have been developed based on first principles. As a result, foams are characterized by (1) fire tests for which there is no general international agreement and (2) physical and chemical properties that may or may not correlate with empirical results. This chapter reviews the important parameters associated with foam agents, test methods used to evaluate foams, and relevant data in the literature that can be used to evaluate foam system designs. Because of their superior performance in extinguishing certain types of hydrocarbon liquid fuel fires, the emphasis is on film-forming foams and thin pool fires (e.g., from spills). Situations involving fuels “in depth” are limited to a discussion on foam modeling and small-scale tests to assess oil and petrochemical industry hazards.

Foam is a stable aggregation of gas-filled bubbles formed from a homogeneous mixture of water and foam concentrate in predetermined proportions. Foam fire protection is well suited for the control and extinguishment of specific types of fires especially those involving certain arrangements of flammable and combustible liquids. Foam is generally lighter than flammable/combustible liquids; therefore it floats on the liquid surface producing a layer which has multiple advantageous effects. These effects include vapor-sealing of the liquid, cooling of the liquid surface, and limitation of oxygen to the liquid surface.

Fire protection and life safety strategies for modern buildings and facilities are developed to accomplish specific goals and objectives as agreed to by the relevant stakeholders. Effective implementation of such strategies requires not only sound design and installation of the relevant building systems and features, but also the proper integration and coordination of such systems and features. The overall process for properly integrating and coordinating the applicable systems often requires significant effort and focus as the various systems are often designed and installed by different engineering and contracting disciplines, and approved by different enforcement agencies. As such, it is critical that the building system integration and coordination process be appropriately considered throughout the project. This chapter overviews the systems integration and coordination process throughout design, installation,

commissioning

(

Cx

), and acceptance testing.

In building fires, smoke often flows to locations remote from the fire, threatening life and damaging property. Research has shown that smoke is the major killer in building fires (Harland and Woolley 1979; [4]).

Smoke management in large-volume spaces, such as atria and covered malls, poses separate and distinct challenges from well-compartmented spaces. In particular, smoke control strategies using pressure differences and physical barriers described by Klote in Chap.

50

, and NFPA 92,

Standard for Smoke-Control Systems

[1], are infeasible. Without physical barriers, smoke propagation is unimpeded, spreading easily throughout the entire space. The tall ceiling heights in many large-volume spaces pose additional challenges because of the production of substantial quantities of smoke and delayed detection times. However, on the positive side, the combination of large-volume space and tall ceiling height permit the smoke to become diluted and cooled as it spreads vertically and horizontally, thereby reducing the level of hazard posed by the smoke. Even so, there is still a need to ensure that dangerous concentrations of smoke are prevented in large-volume spaces.

Use of the temperature-dependent thermophysical material properties, shape geometry, and fundamental heat transfer and structural principles, in combination with available fire test data, can enable several distinct levels of engineering/calculation methods of fire resistance. The simpler computational methods, such as those in ASCE/SFPE 29-05 [1], are semi empirically based on standard fire test results. They provide fire resistance ratings for members and assemblies that do not directly match listed assemblies to meet prescriptive code requirements. Higher-order fire simulations and structural analyses can be used as performance-based design alternatives to achieve a solution to overall fire safety.

Traditionally, fire resistance has been evaluated by subjecting a structural member to a standard test for a specified duration [1]. All members performing acceptably are rated and listed for the duration period of the test (e.g., 1 h, 2 h). Assemblies not listed are assumed to be unable to meet the test criteria and thus have no rating, unless proven otherwise. Providing proof of acceptable performance can be accomplished in one of three manners:

Concrete structures have a reputation for excellent behavior in fires. Many reinforced concrete buildings that have experienced severe fires have been repaired and put back into use. Concrete is by nature noncombustible and has a low thermal conductivity. Concrete tends to remain in place during a fire, protecting the reinforcing steel, with the cool inner core continuing to carry the load. Catastrophic failures of reinforced concrete structures in fires are rare, but some occasionally occur [1].

The fire resistance ratings of wood members and assemblies, as with other materials, have traditionally been obtained by testing the assembly in a furnace in accordance with ASTM International (ASTM) Standard E119 “Standard test methods for fire tests of building construction and materials”, International Organization for Standardization (ISO) Standard 834 “Fire-resistance tests-Elements of building construction”, and similar standards. In the U.S., these ratings are published in listings, such as Underwriters Laboratories

Fire Resistance Directory

, Gypsum Association’s

Fire Resistance Design Manual

, American Wood Council’s

Design for Code Acceptance

publications, and those in building codes. The ratings listed are limited to the actual assembly tested and normally do not permit modifications such as adding insulation, changing member size, changing interior finish, or increasing the spacing between members. Code interpretation of test results sometimes allows the substitution of larger members, thicker or deeper assemblies, smaller member spacing, and thicker protection layers, without reducing the listed rating.

Among the most important concepts in fire safety in buildings is to manage those potentially exposed to the fire and its effects, either by protecting them in place or by moving them to a place of safety. Protected spaces and paths of travel needed to accomplish this are the egress components, systems and procedures that are discussed in this chapter. The chapter presents an overview of considerations, concepts, methods, and strategies utilized globally for emergency egress system design. Approaches to full or partial evacuation using stairs or elevators, egress for people with disabilities, protect-in-place strategies, and alternatives to evacuation, are presented. Prescriptive and performance-based approaches are discussed and strategies for selecting specific systems are summarized.

In many cases, the principle goal of a fire safety engineering (FSE) design is the life safety of the users of a structure. There are, however, other potential fire safety goals to consider, e.g., property protection, continuity of operations, protection of the environment and protection of cultural heritage [1]. Whatever the goal, users of the building, both building managers and occupants, will have a role in its achievement.

Human behavior in fire is at the core of all life safety projects completed by fire safety or fire protection engineers. A better understanding of how people respond to building emergencies can aid in safer building design; improved use or development of calculation tools used to ensure the level of safety afforded by these designs; and more effective emergency procedures, emergency communication systems, and pre-event emergency training for buildings and communities. The purpose of this chapter is to provide a basic understanding of human behavior in fire concepts and theory for use by engineers. The chapter contains the following aspects of human behavior in fire and other emergencies: a definition of human behavior in fire, including a discussion of the types of disciplines employed in the study of people in fires; a presentation on what human behavior in fire is

not

, including examples of disaster myths; an overview of the disaster-based decision-making process in fires and other emergencies; a discussion relating theory to practice (highlighting studies from fire events that support the decision-making theory); the identification of important factors that influence the decision-making process; and a conclusion highlighting what is missing in the field of human behavior in fire. Each section of this chapter will include an implications section that outlines the reasons why these ideas or theories are important for engineers to understand and incorporate.

This chapter provides the engineer with a model to quantify egress performance. This model is formed from a set of numerical tools that vary in their scope and sophistication. Guidance is provided on the capabilities of these tools and on when they should be employed, making reference to the data on which these tools are based. Detailed examples are presented to clarify the application of these tools, along with a description of how the use of these tools fits in with other fire engineering calculations. This chapter will, therefore, allow the engineer to assess egress performance in a responsible and informed manner.

With the rapid increase in computer capability and the increase in egress model development, there is a need for guidance on evacuation modeling, specifically the process involved and the models available. This chapter provides general guidance to users on the first three steps of the evacuation modeling process, namely, (1) identifying project requirements, (2) selecting the appropriate model (including a review of 26 current building evacuation models), and (3) configuring the model scenarios. In addition, an example of evacuation modeling configuration is provided to identify the factors to consider when configuring the building, the population, and the procedures. The chapter briefly reviews the final three steps of the evacuation modeling process, which are applying the model, obtaining output, and analyzing results. These final steps are important but only briefly mentioned due to the fact that these are often specific to the evacuation model chosen and the goals of the project. Overall, this chapter aims to provide necessary guidance that is general enough to be model independent and specific enough to be valuable to the model user.

This chapter presents the scientific basis for establishing effective safety evacuation countermeasures, that is, evacuation plans, escape signs, and so forth in case of fire. The data were obtained in Japan, but should provide more general guidance internationally. In particular, issues of physical and physiological effects of fire smoke on evacuees are addressed. The chapter consists of three sections: (1) visibility, (2) characteristics of human behavior, and (3) development of an intensive system for escape guidance in fire smoke.

The purpose of this chapter is to review experimental studies, especially those involving combustion chemistry and toxicity test methods, in order to establish the basis and validation for material toxicity and toxic hazard calculations and to obtain yield data for input to fire dynamics and toxicity calculations. The review covers several major topics, including the following:

The aims of this chapter are to provide methods for the assessment of life safety hazards in fires and an understanding of the effects of smoke, heat, and toxic fire effluents on occupants of buildings and other enclosures. Detailed discussions of the physiology and derivation of expressions suitable for a range of applications are presented in the main sections of the chapter. The assessment of toxic products from materials and the findings from studies of the toxicity of fire effluents in humans and animals from fire incident investigations, large and bench-scale fire tests and animal exposures is presented in Chap.

62

[1].

This chapter is an updated version of the previous chapter “Evacuation Timing” that appeared in the fourth edition of the

SFPE Handbook

. This new version of the chapter represents a significant change to previous versions, moving from a narrative description of important case studies that include data to a tabular representation of a broader range of data-sets. It is hoped that this approach provides a useful reference resource for readers [1, 2].

Liquid fuel spill and pool fires represent potential hazards in many applications ranging from accidents at industrial plants using combustible liquids to arson fires with flammable fuels. A pool is characterized as a confined body of fuel that typically has a depth greater than 5 mm. A pool can result due to a liquid fuel release that collects in a low spot, such as a trench, or can exist as a result of normal storage of fuels in tanks and containers. A fuel spill is generally associated with thin fuel layers resulting from an unconfined release of fuel. The nature of a spill fire is highly variable, depending on the source of the release, surface features of the substrate (e.g., concrete, ground, water) on which the fuel is released, and the point and time of ignition. The ability to characterize fuel spills and the resulting fires in a consistent and conservative manner is required for many engineering analyses. This chapter provides an overview of the most relevant factors and methodology for evaluating a liquid fuel spill or pool fire in terms of fire growth and size.

A major challenge in industrial fire protection is controlling the impact from large, open hydrocarbon fires. The primary mechanism for injury of damage from such fires is thermal radiation. Depending on the circumstances and conditions leading to such an event, a different type of open fire may result. For example, ignited releases can produce pool fires, jet flames, vapor cloud fires, or fireballs, all of which behave differently and exhibit markedly different radiation characteristics. This chapter presents detailed techniques for calculating impacts from large, open hydrocarbon fires. Examples are included throughout this chapter to illustrate the application of these expressions.

Vapor cloud explosions can be devastating events that result in significant damage to property and loss of life. Although vapor cloud explosion hazards are more common for oil and gas facilities, vapor cloud explosion incidents have occurred at other industrial facilities, such as chemical waste and water treatment plants [1, 2]. Analysis of vapor cloud explosions presents many challenges to engineers and investigators and requires an understanding of several issues. Some of these issues include the potential phase change of the source via condensation or flashing, dispersion characteristics of the vapor due to atmospheric conditions, and effects of buildings and structures on cloud dispersion and flame front propagation. The scope of this chapter is to discuss several of these key issues and present practical tools that can be used in vapor cloud explosion investigations or hazard analyses. Owing to the potentially large scale of vapor clouds, representative experimental testing is limited and often impractical. Therefore, this chapter focuses on analytical and computation methodologies that have been validated using experimental tests, and notes several standardized tests that can be used to quantify specific vapor cloud hazards. It is important to note that these methodologies only provide order of magnitude estimates and analysis, and therefore careful interpretation is required. Engineering experience often serves as the most important element to a successful vapor cloud explosion analysis.

The human body can not tolerate elevated temperatures for any long duration of time. Pain and damage to the skin, i.e. skin burns, begins to occur when the temperature at the basal layer exceeds 44 °C [1]. The amount of damage is a function of both the skin temperature and duration of time for which the temperature is elevated above 44 °C. Previous studies on the effects of thermal radiation on the skin have led to empirical models, graphical techniques, and simple algorithms to predict the temperature-time histories of the skin and the degree of damage due to a constant radiative exposure. All of the methods discussed in this chapter are limited to predicting ONLY 1st and superficial 2nd degree burns. For more severe burns engineering guidance is not currently possible due to the lack of reliable data. Although this chapter provides guidance on calculating the onset of pain from empirical studies it does not include any prediction of humane response to pain as it relates to fire safety decision.

Flammable gases and vapors can produce an explosion when they are ignited while at a concentration between their lower and upper flammable limits, usually in a confined volume. Values of the lower and upper flammable limits for a particular flammable gas or vapor depend on the oxidant and inert gas in the mixture, as well as the mixture temperature. Flammable limits for gas-air mixtures are listed in Chap.

17

and Appendix

3

. A more extensive compilation is available in the Zabetakis Bureau of Mines Report [

47

].

Fine particulates of combustible materials can pose a dust flash fire hazard when dispersed as a cloud and ignited. If the suspended dust concentration is sufficiently high, a flame will propagate through the dust cloud. The dust flash fire hazard can escalate into a dust explosion hazard when there is confinement that restrains the dust laden air flow induced ahead of the propagating flame front such that potentially damaging pressures are developed.

The storage of flammable liquids and vapors in closed vessels can lead to a catastrophic failure of the vessel during a fire. When a vessel explosion involves a flammable substance, it is usually followed by a fireball [1]. If the flammable material is stored as a pressure liquefied gas, a sudden failure of the storage vessel may result in a

B

oiling

L

iquid

E

xpanding

V

apor

E

xplosion (BLEVE). A BLEVE event will result in a sudden conversion of stored thermal energy into mechanical energy in the form of a pressure wave. Additionally, the rupture of a compressed gas storage vessel may also result in a pressure wave.

The risk assessment chapters in this section describe concepts and methods to be used in answering the three questions: What could happen? How bad would it be? How likely is it? This chapter in particular is intended to provide an overview of fire risk analysis as a whole, indicating how the subsequent chapters fit together and how a completed fire risk analysis connects to other evaluative and management activities. The purpose of this introductory chapter is threefold:

This chapter introduces the basic definitions and methods of probability and statistical analysis, which are the foundation for all work reliability and fire risk analysis, and other topics of this section. With increased availability of sizeable quantities of reliable data on a whole range of topics related to fire protection engineering, it is essential that the analysis of this data be based on sound mathematical principles from probability and statistical theory. The chapter is divided into two main sections: probability theory, and statistics.

Many engineering fields can benefit from reliability, availability, and maintainability, concepts and techniques. Fire protection engineering is not an exception. For example, fire protection engineers may be interested in estimating the number of failures of fire pumps under their watch. Other practical applications may include increasing the reliability and/or availability of a fire protection system, optimizing inspection, testing and maintenance intervals and calculating probabilistic values for a fire risk assessment. As the use of risk-informed, performance based methods increases, fire protection researchers and engineers continue to improve and apply reliability, availability, and maintainability methods and techniques in the field.

Building Fire Risk Analysis provides insight into how to enhance the design, construction and management of our built environment. Fire safety, as a concept, branches into all manner of fields. It can affect a building’s design & appearance, its capital and ongoing costs, its day-to-day functionality and above all the community or business it serves – in the event of a fire. Understanding risk is fundamental for consultants, approval organizations, Fire Brigades, insurers and regulators. Fire risk is embedded within codes and guidance – where decisions have been made about what is reasonable and practicable for buildings based on their size and use. This chapter explores what risk is and how it may be understood for future decision making throughout the fire safety industry. Risk herein is defined as the possibility of an unwanted outcome in an uncertain situation. Three key factors are: loss or harm of something; the event(s) that causes loss; and, the likelihood it will occur. The unwanted outcome generally affects life safety, property, business continuity, heritage, the environment, or a combination of these. The reality of our built environment, both now and in the future, is that unwanted outcomes are subject to a variety of active, passive and managerial systems which all contribute to improving safety and reducing risk. Risk assessment allows these systems to be fairly understood and the best decisions made to address the needs required.

To provide fire protection engineering decisions that are meaningful and defendable, the practitioner must understand and be able to characterize the impact of uncertainty on fire safety engineering calculations. This requirement is true for all fire safety engineering calculations, whether conducted to meet a performance-based code, to aid in the establishment of a prescriptive requirement; to compare a performance option to its prescriptive counterpart; or as part of a fire risk analysis used in managing a complex facility, such as a nuclear power plant. At present, however, there is no clear guidance for the treatment of uncertainty in the use of fire safety engineering calculations to support decision making. Development of such guidance will assist engineers and architects in the design process; assist code officials by increasing confidence in the acceptance of a performance calculation; aid researchers in prioritizing enhancements to both the physics and structure of fire models; and aid policy makers by incorporating scientific knowledge and technical predictive abilities in policy decisions. It is essential for the application of risk analysis in the regulation and management of complex facilities.

This chapter is devoted to some of the basic elements of decision analysis, a subject that has its roots firmly established in the area of management science, but now enjoys a much wider application. The present article, which is not intended as an exhaustive discussion paper, aims to introduce basic terminology and to illustrate some of the techniques that can be applied to situations in fire protection engineering, one of the many areas of application. The growth in application can be attributed to the significant developments that have taken place within information technology, particularly with regard to the ready availability of user-friendly decision support software. Practitioners interested in particular aspects of the subject and in software will find appropriate references listed in context. The reader should be aware at the outset that decision analysis is more general than risk analysis, which, in terms of fire protection, has its own extensive and highly specialized literature—see, for example, Castino and Harmathy [1], Gretener [2], Hall [3], Hirschler [4], Watts [5, 6].

This chapter addresses sources of input data required for deterministic (e.g., fire hazard) or probabilistic (e.g., fire risk) engineering analysis, such as performance-based design, code change analysis, product evaluation analysis, or major fire reconstruction. An overview of types of analysis engineers may perform, with a brief discussion of the kinds of engineering problems that should be addressed using those kinds of analysis, is given in the list below. Table 78.1 shows the fire-related phenomena that must be characterized and types of data required to model the phenomenon for each type of analysis listed.

In any fire risk analysis or risk-based assessment, valid measurements of the severity of the fire hazard—the consequences of fire, if it occurs—are of paramount importance. Most analyses are limited to simple outcome measures, such as numbers of deaths or injuries or direct property damage, defined as direct harm to property requiring repair or replacement.

Fire protection engineers are required to deal with complex fire scenarios that include human reactions and behavior, in addition to the physical and chemical fire processes. Operations research (OR) pioneered the application of the scientific method to the management of organized systems in which human behavior is a key element. Fire protection engineering could be defined as the application of operations research to the fire system.

Engineering economics is the application of economic techniques to the evaluation of design and engineering alternatives [1]. The role of engineering economics is to assess the appropriateness of a given project, estimate its value, and justify it from an engineering standpoint.

Fire risk indexing is a link between fire science and fire safety. As we learn more about the behavior of fire, it is important that we implement new knowledge to meet fire safety goals and objectives. One of the barriers to implementing new technology is the lack of structured fire safety decision making. Fire risk indexing is evolving as a method of evaluating fire safety that is valuable in assimilating research results. Fire safety decisions often have to be made under conditions where the data are sparse and uncertain. The technical attributes of fire risk are very complex and normally involve a network of interacting components. These interactions are generally nonlinear and multidimensional. However, complexity and sparseness of data do not preclude useful and valid approaches. Such circumstances are not unusual in decision making in business or other risk venues. (The space program illustrates how success can be achieved when there are few relevant data). However, detailed risk assessment can be an expensive and labor-intensive process, and there is considerable room for improving the presentation of results. Indexing can provide a cost-effective means of risk evaluation that is both useful and valid.

Risk-informed fire protection evaluation is a risk-based decision support tool that evaluates fire and explosion consequence likelihood and includes an analysis of fire protection system(s) performance reliability [1].

Since the late 1990s, there has been an explosion of fire risk assessment guidance documents, both in the United States and around the world. Some address the whole subject of fire risk assessment, whereas others are focused on major component tasks, such as the selection of scenarios. But nearly all of these documents are intended for assessments at the level of whole buildings or similar-sized construction projects. Almost none are intended to support design and purchase decisions at the level of products.

Quantitative risk analysis (QRA) is a very powerful tool with which the fire protection engineer systematically can analyze fire safety problems. Risk analysis methods have during the last decades become more common for analyzing fire safety problems. This is partly because of the development of fire simulation tools enabling a quantitative estimation of the consequences. The increased use of risk analysis methods can also be traced back to the development of performance-based regulations and standards [1–4]. In such regulations and standards the requirement is to verify that the proposed design solution meets the fire safety objectives but they do not necessarily state how this shall be performed. The engineer, therefore, needs some tools by which he or she can structure the relevant problems and transform them to engineering problems that can be solved. Risk analysis is such a structured method.

Exterior building fire spread occurs in three basic ways. One scenario considers fire spread from one building to an adjoining building separated by a wall or barrier. In this case the fire spread occurs when fire exposure to the wall or barrier and any protected openings has sufficient duration and intensity to negate the integrity of the fire wall/barrier or any protected openings. Additionally, flame extension (often exacerbated by wind) above the roof or around the edges the fire barrier/wall can cause the fire to spread to the adjoining building by radiation, direct flame contact or possibly burning brands. The construction of walls, physical features and the various materials and components that are used to create the weather enclosure for a building will impact how heat and flame may be transferred between buildings or along the exterior faÓade of a building. This Chapter discusses all these factors and reviews several well-known incidents of exterior building fire spread.

Wildland fires have a big impact on the environment, human life, and property and have posed significant economic losses as demonstrated by devastating wildfires that occurred over the last few years. In August 2012, the total of 1470 km

2

(3.64 million acres) burned by wildfires in the United States ranked as the highest for any August since 2000. Moreover, nearly half the entire acreage burned since January 2012 occurred within the single month of August and brought the total acreage burned in a year to the highest on record, exceeding 3100 km

2

(7.72 million acres) [1]. The ignition and corresponding spread of these fires were predominantly influenced by extreme drought and high winds. At the global scale, the impact of wildfires is expected to increase dramatically in the future because of the combined effects of the spreading of the Wildland Urban Interface (WUI) and climate changes [2, 3].

Tunnel fire safety is a complex problem with no clear solution as yet. Current knowledge of vehicle fire behaviour in tunnels has been established on the basis of a relatively small selection of experimental fire tests, each of which is described. The characteristics of vehicle fires in tunnels are highlighted and issues to be considered when defining ‘design fires’ for tunnels are discussed. The mechanisms of fire spread in the tunnel environment are presented. The most common fire protection measures used in tunnels are ventilation systems, passive thermal barriers and, increasingly, water spray systems. Each of these three system types are discussed.

Fire risk analysis for nuclear power plants, as currently performed in the U.S. and abroad, is focused on assessing the likelihood of a particular industrial accident: the loss of cooling to the reactor core and subsequent core damage.The analyses are performed using a probabilistic approach developed in the late 1970s and implemented in numerous studies.

Efforts to improve analysis realism through the refinement of analytical methods, tools, and data are underway. These efforts will support the increased use of fire risk analysis in risk-informed decision making.

For many, the concept of fire risk elicits thoughts of the built environment. Yet occupants in the built environment are also passengers on airplanes, in trains, and on ships. The number of passengers boarding scheduled commercial airlines is expected to exceed 985 million by the year 2009. Rail rapid transit systems throughout the United States (U.S.) carry almost two billion passengers annually. Ferryboats account for more than 270 million passenger miles per year [1]. In 2010, motor coaches (or buses) topped 76.1 billion passenger miles in the U.S. and Canada [2]. Every mode of transportation carries with it unique risks; the risks are dependent on a myriad of factors, including design, construction, maintenance, and operation. Understanding or comparing the risks associated with and between the various methods of transport is not always direct. It is complicated by various metrics that can be used for example, risk per distance, risk per trip, risk per passenger exposure hour. For example per mile traveled, the fatality risk in air transport is less than that for bus transport, however, per trip, the risk in air transport is on the order of 100 times greater than that of bus transport [3].