NBSIR 87-3675

Analytical Methods for Fire Safety

Design

James G. Quintiere

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

November 1987

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 87-3675

ANALYTICAL METHODS FOR FIRE SAFETY

DESIGN

James G. Quintiere

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

November 1987

U.S. DEPARTMENT OF COMMERCE, C. William Verity, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

TABLE OF CONTENTS

Page

ABSTRACT . iii

1. INTRODUCTION 1

2. ANALYTICAL APPROACH TO FIRE PREDICTION 5

2 . 1 Discrete Phenomena 5

2 . 2 Systems 5

2.3 Exact Solution of the Basic Laws 6

2 . 4 Scale Models 7

3 . STATE OF THE ART FOR DESIGN 7

3.1 Fire Source 8

3.2 Effect of Surroundings on the Fire 9

3.3 Effect of Fire on the Surroundings 11

3.4 Fire Conditions in a Room 13

3.4.1 Fire in a Closed Room 13

3.4.2 Vented Compartments 15

3.5 Fire Conditions in a Building 17

3.6 Effect of Fire on the Structure 18

3.7 Effect of Fire on People 19

4. APPLICATIONS 21

5. FACTORS AFFECTING THE USE OF ANALYTICAL METHODS 22

6 . FUTURE PROSPECTS 24

7. REFERENCES 26

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ANALYTICAL METHODS FOR FIRE SAFETY DESIGN

James Quintiere

ABSTRACT

The ability to predict aspects of fire and its impact on a building's

structure, contents and people is discussed in terms of its application to

safety design. It is presented from the perspective of how research has

addressed the prediction of fire phenomena. A review of the state of the art

on the capability for predicting the fire, its impact and response, is given.

Examples are cited to illustrate the scope and accuracy of predictive methods

and how they are being incorporated into some codes and standards.

Keywords: buildings; deterministic models; fire growth; people;

review; structures

1 . INTRODUCTION

By analytical methods for design, we mean the ability to perform

calculations to assess the correctness of the design in terms of scientific

principles. Once a design is conceived, we can use an analytical method to

select the size, shape and nature of its materials and component parts. In

the design of a complex system, it is usually not possible to have a method to

predict all the interactions of the component parts. But by having an understanding of the system in terms of parameters -- properties and variables --

consistent with requirements of the analytical methods, complex systems can be

1
designed. This understanding allows us to break the problem into tractable

pieces, whose solutions in the end provide the system design. As we learn

more about the system, we can integrate the analysis to couple more and more

of its elements together, or we can justify single - element approaches with

more certainty.

Fire itself is a complex physical and chemical system so that the

inclusion of its effect on structure and people make the situation more

difficult to address. This is the realm of fire safety engineering and its

application to fire safety design. It has only been over the last twenty-five

years that a more quantitative understanding of fire and its impact has led to

analytical methods for its prediction. It is therefore not surprising that

the current prevailing design practice is not based on analytical methods.

The current practice of fire safety design is based on meeting specific

requirements in building codes and regulations that do not necessarily require

any scientific analysis to achieve. The requirements are expressed for

specific components of the system, and the methods for evaluating the

performance of the component are given in terms of standards and test methods.

For the most part, performance rankings by a specific test have been

established by consensus and are applied to indicate implied performance in a

particular design application or use; and in other cases, specifications are

given without any scientific justification for the specific system under

consideration. For example, the requirement that a wall lining material in a

corridor must have a rating of less than 75 by a specific flammability test is

an expression of performance. For an analytical method to be applicable, an

alternative statement for the performance must be developed such as: the

2
material must not allow sustained flamespread in the specific corridor in a

given time for a given ignition intensity. The exact values of the

performance parameters are not important here, but they must be given in

scientific terms. Of course the numeric values do become important when we

wish to establish levels of equivalent performance with current notions of

safety

.

Therefore, the ability to assess the applicability of analytical methods

for fire safety design depends on two factors. The first is the adequacy of

the knowledge base to allow suitable and sufficiently accurate predictions.

The second is the ease of recognizing the relationship between predictive

capabilities, and the practices and issues that arise in applying fire safety

codes and standards. This discussion will address the first factor in some

detail, and attempt to give some examples which illustrate the second factor.

The process of developing the knowledge-base for fire has emerged from the

agenda set by the research community. This agenda has been determined by a

desire to understand all aspects of fire and its effects. Over the last

fifteen years, this research has been oriented to the issues of fire growth in

buildings. Fifteen years ago our knowledge was very sparse, so that a

discussion on the prospect of using scientific analysis in fire safety design

would have been premature. The ability to predict aspects of fire had to

first gain credibility among scientists. In 1959, the International Symposium

on the Use of Models in Fire Research was held [1]. Its focus was on

fundamental knowledge and not its use, but the papers presented demonstrated

the feasibility of fire prediction and quantification. In the mid-70's the

3
term "fire modeling" was coined to describe the various methods, mainly

computer models, to predict the development of fire in a room. A review of

compartment fire modeling, its nature, accuracies, and needs, was given by

this author in 1984 [2]. In 1986, Emmons [3] reviewed the needs of "fire

science" in terms of research needs, but with a view to solving practical

problems. In this review, he cites 141 references which give some support to

an emerging ordered-set of information -- a science of fire. A recent book,

intended for educational purposes, by Drysdale [4] on ways to compute aspects

of fire is a further demonstration of progress in the development of the

knowledge base. The demand to assimilate this knowledge has been high. I

believe Drysdale 's book is now in its third printing. Several years ago I saw

the new Japanese Fire Protection Handbook. It was very different from its

previous editions because the first few hundred pages dealt with the science

of fire and quantitative methods. Those sections reminded me more of the

handbooks available to other engineering professions. It is noteworthy that

in the USA, the Society of Fire Protection Engineers is now attempting to

develop a handbook that will contain much new information from research.

Thus, we see an evolution of the development of fire knowledge of sufficient

scope and depth to now allow its orderly description for practitioners to

learn and use. This is a significant milestone, but: recognize that it has

taken 15 to 25 years to achieve. Moreover, the depth of knowledge in

particular areas is shallow and in some cases we have holes. Also, prediction

capability on fundamental aspects of fire research do not always yield

analytical tools for design.

4
2. ANALYTICAL APPROACH TO FIRE PREDICTION

Here I use the term analytical methods to mean any technique that will

allow quantitative predictions. The technique could involve approximate or

exact mathematical solutions, numerical solutions using computers, or analog

and scaling techniques. Often scaling techniques have allowed formulas which

have a wide range of applicability to be developed from experimental data.

2.1 Discrete Phenomena

Part of the progress made in fire prediction has been the ability to

identify important features of the fire processes. This has come about due to

experimental observations, conceptualization into a defined element for study,

and then the development into a validated predictive result. For example, in

a room fire, we identify the fire plume, a ceiling jet, a hot upper layer and

flows at vents. Features associated with these elements have been studied and

predictive prescriptions developed. In many cases, correlations have been

developed from experimental data so that algebraic formulas comprise the

nature of the results. Examples of reports which describe computational

techniques for discrete phenomena have been given by Lawson and Quintiere [5],

and Nelson [ 6 ]

.

2.2 Systems

Typically a fire problem will involve many processes, and it could be

viewed as a set of interacting discrete elements. The degree to which we

5
couple these elements depends on our knowledge and understanding of them. For

example, the evacuation of people in a fire will be affected by the fire

conditions. Thus a complete analytical method for evacuation should take the

relevant fire conditions into account. The temperature in a beam heated by .a

fire will affect its structural properties and determine the likelihood of

failure. The beam temperature arises from the thermal state of the exposing

fire, and all of this depends on the conservation of energy.

A particular approach to predicting fire conditions in compartments has

been to mathematically couple together regions of distinct physical character.

This relies on the application of the conservation laws, assumptions of the

property distributions within the regions, and the predictive ability to

describe the transfer of mass and energy at the boundaries of the regions.

This has come to be called "zone modeling". The solution of this system

mainly involves the solution of nonlinear algebraic and ordinary differential

equations in time. The solution to partial differential equations could also

arise. Thus, a small (PC) to medium-sized (mini) computer is necessary in its

solution.

2.3 Exact Solution of the Basic Laws

It is possible to write the governing equations, based on mass, momentum

and energy conservation for reacting fluid systems. In principle, their

solution achieved by numerical methods on computers can lead to a complete

description of the variables over space and time. However models need to be

assumed for turbulence and for chemical reaction so that even these solutions

6
based on the exact differential equations are approximations. The models for

turbulence and chemistry come from applications other than fire, so questions

of their appropriateness are still not resolved. But a careful application of

this approach to fire problems can lead to proper results, and this has been

demonstrated in a number of applications. Fire researchers have come to call

this approach "field modeling".

2.4 Scale Models

The analytical methods we are discussing are mathematical in nature. But

we could utilize scaling techniques based on the laws of physics to develop

physical scale models to generate quantitative information for fire safety

design. This has its counterpart in wind tunnel testing of aircraft. For

example, it has been demonstrated that the thermal and flow conditions in

rooms adjoining the fire room can be reasonably predicted in full scale

systems by using scale models [7,8].

3. STATE OF THE ART FOR DESIGN

I would like to review the capabilities for making predictions for various

aspects of fire, its development and interactions as they relate to design.

Where available, examples of their use in standards will be given.

7
3.1 Fire Source

No general predictive method exists for the generation rate of fuel mass,

energy and combustion products for materials and products that make up the

contents of buildings. But for many design applications, the initial fire

source conditions might be specified in terms of a plausible or maximum

credible fire condition for the problem under investigation. A suitable

database of information on fuel packages, or a means to obtain the information

must then be available. This is possible by measuring the combustion product

concentrations in a collection hood above the freely burning fuel package [9].

Many research laboratories have such devices so that examples of results can

be found in the literature.

For simple solid fuel systems, namely flat surfaces, burning rate theories

and correlations exist to predict the steady rate of mass loss. From

collection hood apparatuses, energy and combustion product yield data can be

generated on a per unit mass loss basis [10]. The availability of these data

provide a way to estimate steady generation rates for simple systems of

arbitrary size.

The ability to predict ignition and flame spread only applies to flat

solid fuels also, and requires particular data for the material. For example,

these models use the concept of an ignition temperature so it must be

appropriately determined for the material. A practical measurement technique

to estimate such properties is available [11].

8
From a hazard point of view, it is useful to know the flame height. This

can be computed with good accuracy for design purposes from correlations that

depend only on the energy release rate of the fire and the equivalent diameter

of the fuel base [12]. The maximum velocity^ and temperature distributions

along the centerline of the fire and its noncombusting plume can be estimated

in terms of the same variables required for flame height [13]. This appears

to be successful over an extensive range of scales comparable with normal

design needs.

The inability to completely predict the radiation heat transfer from

flames in terms of practically measured properties limits models for burning

rate and spread at relevant scales of interest. However we do have some

knowledge of the range of radiant heating in some situations which can prove

useful in design estimates. Except for distances very close to the flame, the

radiant heating of the surroundings by the flame can be computed with good

accuracy provided the fraction of energy radiated is known. This quantity is

available in the literature for some materials and tends to vary from 15 to

50%. It can be deduced from the free burn fuel package experiments.

3.2 Effect of Surroundings on the Fire

We know that the temperature and oxygen concentration of the atmosphere

around the fire affect the burning and mass loss rate of the (solid) fuel.

Also radiant heat flux from the surroundings is a factor along with any

imposed wind conditions. Models for steady burning and flame spread for

simple configurations provide a means to quantitatively estimate the magnitude

9
of these environmental effects. In some cases, algebraic expressions exist

for the steady simple configurations. For the more general case of unsteady

burning of a complex fuel package, no generally acceptable procedure has been

developed. Sensible extrapolation, of the mathematical relationships governing

simple fuel configurations is certainly viable and reasonable for design use.

Again property data for the fuel package is needed; a key property is the

effective heat of gasification. In general, this property is time - dependent

,

and no standard test exists for its determination. But time-averaged values

have been determined for a number of materials [10]. The heat of gasification

is essential in determining the rate of gaseous fuel generation from the

available fuel packages as their decompositions are augmented and initiated by

heat transfer from the environment. This is a feedback process that the fire

lives and dies by. As the fire grows, environmental oxygen decreases and the

environmental heat transfer increases. If the fuel package is totally

immersed in an atmosphere of decreasing oxygen, flaming combustion will cease

at some critical value of oxygen concentration. This value is not unique, but

some data and crude methods exist for its estimation. Ten per cent or less is

a nominal rule of thumb.

In addition to the effect of the fire environment on the fuel generation

rate, it is well known that the products of combustion change with the

available oxygen supply rate. We can think of this as two streams: the fuel

stream caused by heat transfer to the solid fuel surface, and the oxygen

stream entrained into the fire plume. The entrainment rate can be calculated

[12,13]. For several fuels, Beyler [14] has determined and tabulated the

product yields as a function of the oxygen and fuel supply ratio. For water

10
vapor and carbon dioxide, estimates could be adequately made from the known

chemical composition of the fuel. But for carbon monoxide, the major toxic

fire product for most common fuels, the experimental determination procedure

described by Beyler [14] offers the only means for estimating CO in fire

problems. Thus, estimates of CO are possible over a wide range of fire growth

conditions, provided the fuel and oxygen supply rates can be determined.

Since only limited material data exist, judgement must be used to extrapolate

to other materials. Nevertheless, this approach might be perfectly valid in

design situations where an evaluation of a specific material is not at issue.

3.3 Effect of Fire on the Surroundings

A primary effect of the fire on its surroundings is the heat transfer

caused by the direct interaction of the flame and its plume with surfaces and

objects. For fires along walls there are good results available to assess

convective heat transfer [15], and a correlation has been developed to

estimate the total heat flux distribution for flames of moderate size (< 2 m)

[16]. For larger flames within the flame zone, radiation heat transfer is not

generally predictable, but some limited data exist to show its magnitude. A

similar state of knowledge exists for flames impacting ceilings; however, more

work has gone into the study of this problem than for walls. Again,

convective heat transfer is well predicted [17], and a more limited knowledge

is available for the flame impingement region [18].

Very little general predictive ability for objects in fire plumes has been

pursued, but to the extent that the velocity and temperature fields are

11
available, estimates of heat transfer to objects in these plumes can be made.

In particular, a number of studies have been made to enable the prediction of

the velocity and temperature distribution of a ceiling jet that arises due to

the interaction of a fire plume with a ceiling. It should be mentioned here

that the principle variables required to make these calculations of heat

transfer are the energy release rate of the fire and geometric variables which

describe the configuration.

An example of the use of ceiling jet research is in determining the

response of alarm and suppression devices located in the jet. The standard,

NFPA 72E on automatic fire detectors, contains supplementary information on

how to determine the spacing of thermal detectors based on the rate of growth

of a design fire, the ceiling height, and the response characteristics of the

detector to temperature [19]. Much of the research that underlies this

procedure was developed at Factory Mutual Research Corporation (FMRC) , and is

described in the Standard. This procedure has been further developed into a

series of PC compatible computer codes (DETACT) for more general application

[20]. A. necessary ingredient of this procedure, is the availability of test

data on the thermal response of the detector. Essentially the detector is

approximated as a uniformly heated object in gas stream of known temperature

and velocity. The overall convective heat transfer coefficient is determined

from this test (commonly known as the "plunge test") and then related to the

ceiling jet characteristics. This is an approximate method that has been

shown to work, and refinements can even make it better. It is significant

that it requires data for the detector or in general, the thermally responding

device. The data are realizable from a test procedure, and are compatible

12
with an analytical procedure to make general predictions of performance under

fire conditions.

-> 3.4 Fire Conditions in a Room

I would now like to turn my attention to computer models that describe the

conditions that arise in a room due to the presence of a fire. There are many

computer codes available and I will not enumerate them all, but refer you to

the citations given in References 1 and 2. They differ in approach. The

field models attempt to represent all of the fire phenomena by solving the

conservation equations. The zone models tie together homogeneous

phenomenological regions and relationships which describe their interaction by

globally applying the conservation laws to these regions. The current state

of computers allows three dimensional solutions in the field models, and more

than one room is possible. The zone models differ in scope and generality,

with some including a limited amount of the known physics, or are restricted

to a specific class of problems. Few of the room models address the effect of

the surroundings on the fire, with many relying on a prescribed fire. Let us

examine two classes of problems: fire in a closed room, and fire in a vented

compartment. I will try to give some background and a measure of success and

application.

3.4.1 Fire in a Closed Room

Fire conditions in a closed room can be solved by the zone modeling

strategy to give the depth and properties of the hot upper layer formed by the

13
collected fire gases. Typical models consider no pressure rise for a room

with a leak, which is characteristic of conventional rooms in buildings. It

is possible to overcome this restriction. The basic theory was first put

forth by Zukoski [21], and later a computer version was developed by Cooper

[22] which has seen popular use. That computer model is known as ASET and is

limited to just the closed room. This zone modeling approach has yielded good

results in the prediction of the layer characteristics in time for smoldering

fires [23], and for a variety of flaming conditions in complex closed

configurations. In a series of experiments designed to test the approach, it

was found that the smoke layer descent is predicted very well in time, but the

temperature results are only approximately predicted since the actual thermal

stratification is more gradual than the square -wave approximation of the zone

model [24]. These experiments were done in a cubical room, 6 m on a side -- a

large room. Bengston and Hagglund [25] applied their model to an entire

building having a floor area of 1000 m

2 and a height of 9.5 m producing also

good agreement between the model and measured results for the layer descent

[25]. Nakamura [26], using a more sophisticated zone model than ASET,

demonstrated good predictive ability for the layer temperature and descent

rate for experiments conducted in a large exhibition hall with a domed roof -

- 2000 m

2 of floor area and 19.2 m high. Thus, this approach appears quite

valid regardless of the scale of the fire and the compartment. Of course, the

fire source must be specified and is not influenced by the conditions in the

compartment in any of these models.

Field models have also been applied to this problem with good results.

The range of predicted variables is basically the same as those of the zone

14
models; however, they can not predict the degree of stratification. Cox et

al . [27] show good results for temperature and carbon dioxide distributions in

experiments in a six-bed hospital ward. Waters [28] has used the same model

to evaluate particular fire safety issues in buildings under design. These

included the issue of safe egress time due to a fire in a large airport

terminal, and the effect of initial thermal stratification of a fire in an

atrium space.

3.4.2 Vented Compartments

Field models do a good job at predicting the velocity and temperature

distributions in compartments including the flow at door or window vents

[29,30]. These verifications have been made for relatively small fires that

only fill a small portion of the room.

The use of the zone model for vented compartments was made possible by the

ability to predict the pressure-driven vent flows using a simple hydrostatic

model with an orifice. We now have good confidence in this vent model.

Recently, this model was proven to be very accurate for fire flows between two

rooms with a fire room temperature as high as 1000 C [31]. In the application

of this hydrostatic model to the zone modeling approach, the added assumption

of uniform temperatures in the upper and lower layers is invoked. To the

extent that these uniformities occur and to the extent that the zone model can

predict the layer temperatures, the pressure-driven vent flows should be well

predicted. Where flows across vents are due to instabilities or turbulent

15
diffusion, such as the flow through a single ceiling vent in a heated

compartment, we have no generally accepted way to compute the flow.

A typical indication of the accuracy of the zone model capability has been

reported by Mitler and Rockett for the Harvard Fire Code [32]. An improved

version called FIRST has been developed for general use. In their comparisons

with two simulated bedroom fires, they obtain good predictions for layer

position, temperature and the primary combustion products (not CO)

,

vent flow,

and the burning rate of the fire. The model is also capable of predicting the

surface temperature of a target and its ignition. It also can include thermal

feedback effects to the fuel provided the fuel properties are appropriately

defined, and a compatible model is supplied for the fuel package of interest.

The Harvard model has probably accounted for the effect of the surroundings on

the fuel as much or more than any other zone model. But the capability still

needs to be improved in dealing with feedback effects on the fire and for the

case of the fuel-rich fire.

The problem of a roof -vented compartment fire, with a sufficient vent

below, was studied by Thomas and Hinkley nearly 25 years ago [33]. It was

based on the zone modeling approach, and was intended for the sizing of roof

vents in fire. The principles of that analytical method formed the basis for

several European venting standards, and a modified version has now become the

basis selecting the vent area in the standard, NFPA 204M [34]. A set of

design fires, described in terms of their rate of growth, is provided. Other

needed information is the height of the building and the configuration of the

curtain boards . The vent area can be computed for a particular fire

16
condition, or selected period of effective operation. A similar analytical

method has been included in another standard [35] which addresses the

recommended mechanical exhaust capacity for smoke control in a multitiered

open cell block. Thus, we see that some applications of the zone modeling

approach are finding their way into standards of recommended design practice.

3.5 Fire Conditions in a Building

The zone modeling approach appears to be the only viable way to predict

the conditions in a building due to fire. These conditions pertain to the

motion of fire gases, their temperature and combustion product concentrations,

and the speed at which spaces of the building fill with the gases. These

computations require mini-computer capacity in the least. Also they would

require judgement in the way a building geometry is approximated in terms of

the necessary model input. All aspects of a building's rooms and vents would

not be feasible to include.

A measure of the accuracy of zone models in predicting the fire conditions

in more than one room has been described by Rockett, Morita and Cooper [36].

They examined data from a relatively small fire in a series of three rooms.

The results for temperature and layer height are estimated quite well for

each of the three rooms. Nakamura [26] and Tanaka [37] have demonstrated

computations for multi-storied buildings of up to 10 stories and 50 rooms.

Stairwells or vertical shafts are currently treated as tall rooms. We know

this assumption is not satisfactory once the plume gases fill the cross

section of the shaft, but we do not have a measure of its inaccuracy or an

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alternative approach. A similar limitation applies to the motion of fire

gases through corridors, since the concept of uniform filling from the top of

the corridor is not compatible with our observations. This limitation will

cause a discrepancy when the corridor smoke transit time is long compared to

its filling time. Again we do not have a good measure of issue. While it is

possible, the zone modeling applications to buildings have not incorporated

the effects of the forced air heating and cooling system, nor have addressed

the initial and ambient conditions that pertain to "stack" (buoyancy) or wind

effects. Although small specified fires have been considered for the most

part in these applications, it is possible to consider larger fires that

become oxygen deficient [37]. Thus it is possible to predict conditions as a

fire might spread from room to room, but we do not have good experimental data

to support the assumptions needed here.

3.6 Effect of Fire on the Structure

Analytical methods for predicting the load bearing capacity of structural

elements in a fire are based on the current structural design methods and the

ability to predict the structural property data at high temperature. Much

work has been done in this area, and sufficient property data exist to

consider concrete, steel and even timber construction. A good discussion on

the state of the art was recently prepared by Pettersson [38]. This approach

considers a specified heating load to the structure, and proceeds to compute

the temperature distribution, usually in two dimensions, over time by a

finite-element method. This is primarily a heat conduction computation with

the possibility of phase change modeled for some materials. Sufficient

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confidence in this approach has led some European countries to accept a

computation to predict the failure time of concrete or steel beam or column

elements as exposed to a test fire, a time - temperature curve representative of

a standard furnace test. I have been told that Sweden, Denmark and Norway

have such provisions in their national fire safety codes, and others are

considering similar adoptions.

In some of these applications, the fire heating load to the structure is

computed from compartment fire models or correlations for fully developed fire

conditions. These give the heating time - temperature curve in terms of the

compartment size and thermal properties, vent area, and fuel load which is

usually in based on data for wood cribs. Improvements are needed here. We

need better and more complete ways to predict the post- flashover compartment

thermal conditions for other fuel types and configurations. The thermal

boundary conditions which express the transfer of energy between the fire and

the structural element need more attention. And heating effects of fire

plumes to structures need to be characterized. All of these issues fall on

the side of the fire and combustion scientist; the structural engineering

ability appears to be in good shape provided the heating conditions can be

established.

3.7 Effect of Fire on People

A major requirement of the fire safety design of buildings is the safety

of people. Their ability to safely egress the facility in a given period of

time is essential. The fire behavior in a design calculation can determine

19
the critical times required for safe egress. Most current fire safety codes

impose exit width requirements based on the type of facility and its expected

population. Time for egress is not an explicit requirement. Based on studies

of crowd movement in buildings and exit ways, correlations have been developed

which allow the computation of the people movement speeds, the number of

people per unit time, and the overall egress time of the building population.

A review of these methods and the state of the art has been given by Kendik

[39], and a book on the subject has been translated from the Russian

literature [40]

.

Kendik points out that only the building codes in the Soviet

Union require a mathematical proof of their exit width requirement. A recent

edition of the NFPA Life Safety Code 101 provides information on alternative

calculations for determining stair widths based on crowd egress time [42]

.

We are seeing more and more considerations of matching the hazard time of

the fire with a computation of egress time for the design population of the

facility. For example, the exit design of a large enclosed stadium with a

capacity of 11,500 people was evaluated by computations of the smoke movement

from a selected design fire and the traffic flow speeds of the spectators

[42]. A formal adaptation of this process is currently under consideration in

Japan as a Fire Safety Design Method to be used as an alternative to the

Building Standard Law [43]. This design method addresses computations for

smoke movement and people movement.

For the most part the egress models referred to above are independent of

the effects of the fire on the people. A complete analysis must consider the

effects of smoke on visibility; the impairment, toleration and lethality

20
caused by the fire and its products; and the behavior of people in a fire

environment. We are limited in our ability to quantitatively address all

these effects. Human tolerance limits are not precise, and our ability to

convert these effects into mathematical models with a complete set of

variables will always be imperfect. But for design or hazard analysis, it is

possible to address some of these interactions. Methodology which is

indicative of the state of the art has recently been published and is being

evaluated by an interested group [44] . This approach, limited to residential

single - family dwellings, contains computations on the fire; critical

impairment to the people; and the motion of the people based on behavioral

decisions, smoke conditions and a simple traffic flow model.

4. APPLICATIONS

The review presented above has been qualitative in that the specific level

of the accuracy of the various methods must be assessed by an individual

examination of the literature. Another measure of accuracy is the wide spread

acceptance of an approach by the scientific developers, and its adoption by

the engineers. I have tried to show some sense of that dimension. Many of

the analytical methods are generic because of their wide use, but have been

individualized in vehicles of execution -- mostly computer codes.

The application of these analytical methods for fire safety have ranged

from assessing a particular feature of a new facility in the design stage, to

assessing conditions in an existing structure. They have been used to justify

alternatives to the specifications in building regulations, and have been even

21
included in standards as prescribed alternatives to traditional practices. I

have tried to give some noteworthy examples above, but I am sure that they

only represent a small proportion of the use of analytical methods by

consultants, and the trend in their use has increased in recent years.

A more dramatic use of analytical method in fire is in the reconstruction

of an accidental fire disaster. This is design analysis in reverse, in that

it suggests what should have been done. Moreover, it provides a more

quantitative basis for establishing remedial actions. The fact that

regulations might have been violated before a fire disaster may have nothing

to do with the consequences of the fire. There have been several fire

reconstructions of real disasters -- some due to a formal investigation,

others mostly due to litigation over damage claims. A recent analysis which

used a very simple form of analytical relationships and computer models, but

applied in a comprehensive way, was able to reconstruct the events of a fire

growth in a hotel and its consequences [45]. The accuracy of the results

appeared to be consistent with the events, but that is not as significant as

its illustration of the ability to quantitatively analyze a complex sequence

of fire growth.

5. FACTORS AFFECTING THE USE OF ANALYTICAL METHODS

I see three factors which are important to the use of analytical methods

in fire safety.

22
First, the results from scientific research suitable for design

application must be assembled into a logical description for ease in

understanding and learning. This is an educational and technology transfer

process. Because the field of fire protection engineering has relied on nonanalytical techniques, the background required for these engineers to

comprehend the analytical methods must be provided in their training and

formal education. Text books are sorely needed. The use of user-friendly

computer codes might tend to off-set the need for a complete understanding of

the particular analysis, but there is a risk of their misuse. The user must

have sufficient understanding to effectively question the computer answers,

and to apply the computer code to problems within its valid scope.

Second, research must continue to fill the gaps of knowledge needed by

analytical methods in a timely manner. If a method does not fulfil all of the

expectations and needs of the designer due to limits in its scope, it could

lose its appeal. This loss is not necessarily due to its lack of technical

quality, but due to its completeness. Speedy and plentiful progress has been

limited in developing the knowledge of fire safety by the complex nature of

the fire problem, its dependence on the maturity and analytical state of the

related scientific disciplines, and the lack of great attention to its

research. Most of the analytical capability we see emerging has had its basis

in fundamental research. That fundamental research has needed a luxury of

deliberate study and evaluation to reach a sound conclusion. Patience is a

necessity here. We have seen good progress over the last 25 years, but the

most systematic and fruitful progress with benefit to design has come when a

23
number of researchers have focused on similar research issues with resources

for long range studies.

Third, a good dialogue must exist between the researcher and the

practitioner. Design problems must be identified and formulated by the fire

safety engineer and official, and articulated effectively to the researcher.

In many cases, the research developments have motivated progress in design

applications. Fire researchers tend to pick problems of interesting

scientific challenge and logical extension of existing research. Fire safety

research needs more direction from the practicing community, especially by

those you have gained an appreciation of analytical capabilities.

6. FUTURE PROSPECTS

Based on the recent interests in analytical methods in fire safety, we are

likely to see their increasing use. The ability of accessing analytical

methods by personal computers is accelerating their use. The research

developments are not advancing as swiftly as this transfer process. This may

ultimately disappoint some.

A computer format for the transfer of analytical methods may serve to

cloud knowledge rather than transfer it. The issue of one method versus

another will always be present, and standard computer benchmark codes will

have to be rigorously developed to make these evaluations. The benchmark

codes will have to be judged by scientific peer review.

24
Analytical methods will influence the way we test components for

attributes of fire safety. Data for components will be needed in a form

required by the mathematical model. The model itself will establish the form

of the data. The more general the results, the more their use will become.

Ultimately this will change the nature of our existing fire test methods, and

influence the way we express our codes and standards. The feasibility of

predicting the fire growth and the egress of people in a large building is

possible. Its acceptance as a viable analytical method will alter the way

accepted levels of fire safety are expressed. Analytical methods have now

given us more information and more variables. Our criteria for safety must

now be couched in these new terms. This will take continual discussion and

reconciliation with current practices.

25
7 . REFERENCES

1. Berl, W.G., editor, "The Use of Models in Fire Research", Pub. 786,

National Academy of Sciences - National Research Council, Washington,

D.C., 1961.

2. Quintiere, J., "A Perspective on Compartment Fire Growth", Comb . Sci . and

Technol . . Vol. 39, pp . 11-54, 1984.

3. Emmons, H.W.

,

"The Needed Fire Science", C.E. Grant and P.J. Pagni,

editors, Fire Safety Science . Hemisphere Pub. Corp .

,

Wash. D.C., pp . 33-

53, 1986.

4. Drysdale, D „ , Fire Dynamics . John Wiley & Sons, New York, 1985.

5. Lawson, J.R., and Quintiere, J.G., "Slide Rule Estimates of Fire Growth",

Fire Technol . . Vol. 21, No. 4, pp . 267-292, Nov. 1985.

6. Nelson, H.E., "FIREFORM - A Computerized Collection of Convenient Fire

Safety Computations", NBSIR 86-3308, National Bureau of Standards,

Gaithersburg, MD, 1986.

7. Quintiere, J.G., McCaffrey, B.J., and Kashiwagi, T., "A Scaling Study of a

Corridor Subject to a Room Fire", Comb. Sci. and Technol. . Vol. 18, p. 1,

1978.

26
8. Steckler, K.D., Quintiere, J.G., and Baum, H.R., "Salt Water Modeling of

Fire Induced Flows in a Multiroom Enclosure", 21st International Symposium

on Combustion . The Combustion Institute, Pittsburgh, PA, 1986.

'"i

9. Babrauskas , V. and Walton, W.D., "A Simplified Characterization of

Upholstered Furniture Heat Release Rates", Fire Safety Journal . Vol. 11,

pp. 181-192, 1986.

10. Tewarson, A., "Physico-chemical and Combustion Pyrolysis Properties of

Polymeric Materials, NBS-GCR-80-295 , National Bureau of Standards, 1980.

11. Quintiere, J.G. and Harkleroad, M. , "New Concepts for Measuring Flame

Spread Properties", Fire Safety Science and Engineering . T.Z. Harmathy,

editor, American Society for Testing and Materials, ASTM STP 882, pp . 239-

267, 1985.

12. Zukoski, E.E., "Fluid Dynamic Aspects of Room Fires", Grant and Pagni

,

editors, loc. cit., pp . 1-30, 1986.

13. McCaffrey, B.J., "Fire Plume Dynamics - A Review", Conference on LargeScale Fire Phenomenology, National Bureau of Standards, Gaithersburg, MD .

,

September 10-13, 1984.

14. Beyler, C.L., "Major Species Production by Solid Fuels in a Two Layer

Compartment Fire Environment", Grant and Pagni, editors, loc. cit., pp

.

431-440, 1986.

27
15.

Ahmad, T. and Faeth, G.M., "Turbulent Wall Fires", 17th International

Symposium on Combustion . The Combustion Institute, Pittsburgh, PA, pp

.

1149-1159, 1979.

"5

16. Quintiere, J.G., Harkleroad, M. and Hasemi, Y. , "Wall Flames and

Implications for Upward Flame Spread", Comb. Sci. and Technol

.

. Vol . 48,

pp, 191-222, 1986.

17. Cooper, L.Y.

,

"Heat Transfer from a Buoyant Plume to an Unconfined

Ceiling", J. Heat Transfer . Vol. 104, No. 3, pp . 445-451, 1982.

18. You, H.Z. and Faeth, G.M., "Ceiling Heat Transfer during Fire Plume

Impingement", Fire and Materials . Vol. 3, No. 3, pp . 140-147, 1979.

19. NFPA 72E Automatic Fire Detectors 1984, Nat. Fire Prot. Assoc. Quincy, MA,

June 14, 1984.

20. Evans, D.D. and Stroup, D.W., "Methods to Calculate the Response Time of

Heat and Smoke Detectors Installed Below Large Unobstructed Ceilings",

Fire Technol

.

. Vol. 22, No. 1, pp . 54-66, February, 1986.

21. Zukoski, E.E., "Development of a Stratified Ceiling Layer in the Early

Stages of a Closed-room Fire", Fire and Materials , Vol. 2, No. 2, pp . 54-

62, 1978.

28
22. Cooper, L.Y. , "A Mathematical Model for Estimating Available Safe Egress

Time in Fires", Fire and Materials . Vol. 6, Nos. 3 and 4, pp . 135-144,

1982.

23. Cooper, L.Y. , "The Development of Hazardous Conditions in Enclosures with

Growing Fires", Comb. Sci. and Technol. . Vol. 33, pp . 279-297, 1983.

24. Hagglund, B., Jansson, R. , and Nireus , K. , "Smoke Filling Experiments in a 6x6x6 meter Enclosure, FOA Rept. C 20585-D6, National Defence Research

Institute, Stockholm, September, 1985.

25. Bengston, S. and Hagglund, "The Use of a Zone Model in Fire Engineering

Application", Grant and Pagni , editors, loc. cit., pp . 667-675, 1986.

26. Nakamura, K. , "Predicting Capability of a Multiroom Fire Model", Proc. 9th

Joint Panel Meeting, UJNR Panel on Fire Research and Safety, held at

Factory Mutual Research Corp., Norwood, MA, May 4-8, 1987.

27. Cox, G. , Kumar, S, and Markatos, N.C., "Some Field Model Validation

Studies", Grant and Pagni, editors, loc. cit., pp „ 159-171, 1986.

28. Waters, R. , "The Stansted Terminal Building and Early Atrium Studies",

Annual Meeting of the Soc. Fire Protection Engineers, Cincinnati, OH,

1987.

29
29. Markatos , N.C. and Pericleous, K.A. , "An Investigation of ThreeDimensional Fires in Enclosures", Fire Dynamics and Heat Transfer, HTDVol. 25, 21st National Heat Transfer Conf . , ASME, Seattle, WA, July 24-

28, 1983, pp. 115-124.

30. Bagnaro , M. , Laouisset, M and Lockwood, F.C., "Field Model Prediction of

Some Room Fires: Steady and Transient", Ibid, pp . 107-114.

31. Nakaya, I., Tanaka, T., Yoshida, M. , and Steckler, K. , "Doorway Flow

Induced by a Propane Fire", Fire Safety Journal . Vol. 10, pp . 185-195,

1986.

32. Mitler, H.E., and Rockett, J.A., "How Accurate is Mathematical Fire

Modeling?", NBSIR 86-3459, National Bureau of Standards, Gaithersburg, MD

,

December, 1986.

33. Thomas, P.H., and Hinkley, P.L., "Design of Roof Venting Systems for

Single-Story Buildings", Fire Research Technology Paper, No. 10, Dept, of

Scientific and Industrial Research and Fire Offices' Committee, Joint Fire

Res. Org.

,

London: H.M. Stationery Office, 1963.

34. NFPA 204M Smoke and Heat Venting, 1985, National Fire Protection

Association, Quincy, MA, June 6, 1985.

30
35. NFPA 101 Code for Safety to Life from Fire in Buildings and Structures,

Chapt. 15 Existing Detention and Correction Occupancies, 15-3.1.3, A-15-

3.1.3, National Fire Protection Association, Quincy, MA, 1985.

36. Rockett, J., Morita, M. , and Cooper, L.Y. , "Comparisons of NBS/Harvard VI

Simulations and Full-Scale, Multi-Room Fire Test Data", NBSIR 87-3567,

National Bureau of Standards, Gaithersburg, MD , July, 1987.

37. Tanaka, T., "A Model of Multiroom Fire Spread", NBSIR 83-2718, National

Bureau of Standards, Gaithersburg, MD , August, 1983.

38. Pettersson, 0., "Structural Fire Behavior - Development Trends", Grant an

Pagni, editors, loc. cit., pp . 229-247, 1986.

39. Kendik, E., "Methods of Design for Means of Egress: Towards a

Quantitative Comparison of National Code Requirements", Grant and Pagni,

editors, loc. cit., pp . 497-511, 1986.

40. Predtechenskii , V.M.

,

and Milinskii, A. I., Planning for Foot Traffic Flow

in Buildings . (English) Amerind Publishing Co. Pvt. Ltd., New Delhi, 1978.

41. NFPA 101, loc. cit., Appendix D Alternative Calculations for Stairs Width.

42. Sato, H. and Ouchi, T., Computer Simulations for Total Firesafety Design

of the New Japanese Sumo Wrestling Headquarters and Stadium (Kokugikan)

,

Grant and Pagni, editors, loc. cit., pp . 541-550, 1986.

31
43. Tanaka, T., "Basic Structure of the Evacuation Safety Design Method",

Proc . 9th Joint Panel Mtg. , UJNR, loc . cit.

44. Bukowski , R.W.

,

Jones, W.W.

,

Levin, B.M., Forney, C.L., Stiefel, S.W.,

Babrauskas , V. , Braum, E. , and Fowell, A.J., "Hazard I. Volume 1: Fire

Hazard Assessment Method", NBSIR 87-3602, National Bureau of Standards,

Gaithersburg, MD, July, 1987.

45. Nelson, H.E., "An Engineering Analysis of the Early Stages of Fire

Development - The Fire at the Dupont Plaza Hotel and Casino - December 31,

1986", NBSIR 87-3560, National Bureau of Standards, April, 1987.

32
NBS»1 14A (rev. 2 -ec) U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBS I R- 87/3675

2. Performing Organ. Report No. 3. Publication Date

November 1987

4. TITLE AND SUBTITLE

ANALYTICAL METHODS FOR FIRE SAFETY DESIGN

5. AUTHOR(S)

James G. Quintiere

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

NATIONAL BUREAU OF STANDARDS

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City . State. ZIP)

10. SUPPLEMENTARY NOTES

J

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

The ability to predict aspects of fire and its impact on a building's

structure, contents and people is discussed in terms of its application to

safety design. It is presented from the perspective of how research has

addressed the prediction of fire phenomena. A review of the state of the art

on the capability for predicting the fire, its impact and response, is given.

Examples are cited to illustrate the scope and accuracy of predictive methods

and how they are being incorporated into some codes and standards.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s)

bibliographies; buildings; fire growth; fire models; literature reviews

zone models

13. AVAILABILITY

Unlimited

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