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iSIBSIR 83-2748

Smoke Movement in Rooms of

Fire Involvement and Adjacent

Spaces

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Washington, DC 20234

July 1983

QC—

100

U56

83-2748

1983

C ,2

U S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 83-2748

’> f SMOKE MOVEMENT IN ROOMS OF

FIRE INVOLVEMENT AND ADJACENT

SPACES

VATIOrtAI. BUHEACJ OK STANIjAJUW

AUG 1 2 196:

.(-i

Leonard Y. Cooper

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Washington, DC 20234

July 1983

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

TABLE OF CONTENTS

Page

LIST OF FIGURES iv

Abstract 1

1. INTRODUCTION 2

1.1 Purpose 2 1.2 The General Problem of Establishing Facility Fire Safe Designs. 2

2. THE DEVELOPMENT OF FIRE ENVIRONMENTS IN COMPARTMENTS OF FIRE

INVOLVEMENT 4

3. THE ROOM OF FIRE INVOLVEMENT 5

3.1 Fire Growth in the Combustible of Fire Origin 5

3.2 Development of the Plume 7 3.3 The Plume-Ceiling Interaction 8

3.4 The Ceiling Jet-Wall Interaction 9

3.5 Development and Growth of the Upper Layer - "Smoke Filling" . . 10

3.6 The Transition Stage of Fire Development 14

4. SMOKE SPREAD FROM THE ROOM OF FIRE INVOLVEMENT AND AN ADJACENT

SPACE 14

4.1 Smoke and Fresh Air Exchange Between a Room of Fire

Involvement and an Adjacent Space 14

4.2 Door Plume, Ceiling Jet and Smoke Filling of the Adjacent

Space 16

4.3 Multiroom and Multilevel Fire/Smoke Compartment 18

4.4 Some Special Classes of Multiroom Fire Scenarios 18

5. SOME AVAILABLE MATHEMATICAL MODELS/COMPUTER CODES FOR PREDICTING

DYNAMIC ENCLOSURE FIRE ENVIRONMENTS 20

6. SMOKE SPREAD OUTSIDE THE SMOKE COMPARTMENT OF FIRE INVOLVEMENT ... 21

7. ACKNOWLEDGEMENTS 22

8. REFERENCES 23

-iii-
LIST OF FIGURES

Page

Figure 1. Events immediately after ignition 26

Figure 2. Development of the plume 27

Figure 3. The plume-ceiling interaction 28

Figure 4. Ceiling jet-wall interaction 29

Figure 5. Fully enclosed space with developed growing upper layer ... 30

Figure 6. Further "smoke filling" 31

Figure 7. Smoke and fresh air exchange between a room of fire

involvement and an adjacent space 32

Figure 8. Figure 7 with sketches of pressure distributions 33

Figure 9. A concept for modeling smoke spread throughout complex

facilities 34

-iv-
SMOKE MOVEMENT IN ROOMS OF FIRE INVOLVEMENT AND ADJACENT SPACES

Leonard Y. Cooper

Abstract

Key to the solution of fire safety design problems is the capability to

predict the dynamics of enclosure fire environments. This paper presents a detailed qualitative description of the generic phenomena which occur during

typical fire scenarios. The focus of attention is on effects within building

compartments of fire involvement, i.e., compartments made up of a single

enclosed space or a space of two or more rooms interconnected by significant

penetrations such as open doors or windows. Throughout the discussion reference is made to quantitative methods for predicting some of the most significant of these effects. Reference is also made to available mathematical/

computer models which use these latter methods to quantitatively predict the

overall fire environment.

The basic topics that are covered are: fire growth in combustibles of

fire origin; development of the fire plume and interaction of the plume with

the ceiling surface; generation of ceiling jet flows which lead to actuation

of detection/intervention hardware; interaction of ceiling jets and wall

surfaces; growth of the smoke layer; development of wall flows which can be

instrumental in drawing smoke down from the upper smoke layer into the relatively uncontaminated, shrinking lower ambient environment; downward radiation

from the high temperature smoke layer and upper enclosure surfaces which can

ultimately lead to flashover; onset of conditions which are untenable for

human occupancy or property survivability.

Topics related to fire generated environments in multiroom fire/ smoke

compartments include: dynamics of the smoke and fresh air exchange between

the room of fire involvement and the adjacent spaces; dynamics of door/ window

plumes, ceiling jets, smoke filling and wall flows within adjacent spaces;

actuation of adjacent space fire detection/intervention hardware; and onset of

adjacent space untenability

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The paper concludes with a brief discussion on the relationship between

fire compartment smoke dynamics and smoke movement throughout the rest of a building.

1. INTRODUCTION

1.1 Purpose

This paper has a threefold purpose. The first is to describe the significant physical phenomena that lead to smoke (product of combustion) spread in rooms of fire involvement and in freely connected (e.g., open connected

doorways) adjacent spaces. The second is to indicate how it is possible to

predict the dynamic fire-generated environment within such spaces. The final

purpose is to indicate how such predictions can be used to design for life or property fire safety.

The following introductory comments are presented in order to place the

presentation of subsequent sections into the perspective of the generalized

fire safety problem.

1.2 The General Problem of Establishing Facility Fire Safe Designs

The present discussion is concerned with aspects of past and ongoing

developments of fire science and technology which relate to the general

problem of establishing fire safety in enclosed spaces. The problem can be

stated as follows:

How is it possible to characterize the fire risk of facilities, and

to establish criteria for safe design, by using traditional engineering methodology ?

In order to handle this problem successfully, three types of tasks need

to be carried out. First, it is necessary to define and establish measures of

life or property safety - measures that can be expressed in concise, quantitative terms. Second, it is necessary to formulate tractable problems.

Tractable problems, here, refer to specific quantitative problem formulations

which adequately model the real engineering problems and which can be solved

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with methods of mathematical analysis (e.g., graphs, equations, and/or user- friendly computer codes) ultimately available to professional fire protection

practitioners. The final type of task would be to actually solve the

problem( s) , that is, to generate procedures for evaluating or designing

adequate life or property safety relative to potentially hazardous fires.

Much of the work at the National Bureau of Standards is directed toward

life safety aspects of fire technology. With regard to measures of life

safety which can be used as focal points for any one of a number of problem

formulations , we have identified one straightforward measure which has the

desired characteristics. This measure of life safety is successful or safe

egress . Thus, for fires in buildings, even if extensive provisions have been

made for prevention, detection and suppression of potential threats, the

ultimate condition of life safety may be identified as the ability of

occupants to egress safely from all threatened spaces. Such an ability is

equivalent to a condition of life safety.

The application of this equivalence principle leads to the concept that

safe egress, and, therefore, life safety, can be achieved in buildings

designed to have a balance between the Available Safe Egress Time (ASET) and

Required Safe Egress Time (RSET). Here, ASET is defined as the length of time

interval between fire detection/(successf ul) alarm, t^g^, and the time of

onset of hazardous conditions, tg^g. RSET is defined as the length of time,

subsequent to alarm, which is actually required for safe occupant egress from

threatened spaces to places of safe refuge.

The concept of balance between ASET and RSET leads to a quantitative test or criterion for safe building design, the Designed Safe Egress Criterion,

viz .

,

Relative to a potential hazardous (to life) fire, a building is of

safe design if ASET = tg^g - tgET > RSET.

This formulation can be viewed as an algorithm for evaluating or determining the adequacy of a specific building design vis-a-vis life safety in

fires. To apply the algorithm one would be required to estimate the ASET and

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RSET associated with potential hazardous fires in specific buildings whose

designs are under evaluation.

An estimate of ASET requires estimates of and t^z

* t DET depends on

the characteristics of available detection and alarm devices, and, in general,

on the interactions of these with fire generated environments which develop

around them. If fire or smoke control intervention strategies and hardware

are involved, then predictions of the intervention times, tj^'pER* the

hardware would, again, require knowledge of the nearby fire environment.

Besides depending on the physiological characteristics of occupants, also

depends on the fire environment. It is therefore evident that estimates of

t DET» t INTER» anc* t HAZ» an<^> therefore of ASET, require predictions of the

dynamic environment which develops in buildings during fire conditions.

If property rather than life safety was the significant fire safety

problem, then the successful egress measure of life safety would be replaced

by a measure of property protection which could be related, say, to some unacceptable level of property loss. Then, a possible criterion of safe

building design, a Designed Property Safety Criterion, might be,

Relative to a potential hazardous (to property) fire, a building is

of safe design if (on account of building construction, fire intervention, smoke control, etc.) the fire environment is never likely

to develop to a state where unacceptable property loss would occur.

Just as predictions of fire environments are required to invoke the

Designed Safe Egress Criterion, so would such predictions be required to

invoke a Designed Property Safety Criterion. The next section will describe

generic characteristics of dynamic fire environment as they develop in com- partments of fire involvement.

2. THE DEVELOPMENT OF FIRE ENVIRONMENTS IN COMPARTMENTS OF FIRE INVOLVEMENT

In terms of the above discussion, the following is the generic problem

that must be solved if one is to be able to establish the fire safety of

building designs:

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Given: initiation of a fire in an enclosed space

Predict (i.e., obtain a mathematical simulation of): the environment which develops at locations of likely occupancy;

locations of likely detection devices; locations of likely

fire/ smoke intervention sensor hardware; and locations

along likely egress paths

Compute (from above predictions and from known response characteristics of people and hardware): the time of fire detection; the time of intervention sensor response; the time of

onset of hazardous conditions untenable to life and/or

property

In general, the above is only a simple sketch of the overall problem that

is likely to be associated with the interesting details of many real fire

scenarios. It is the long-term challenge of fire science and technology to

solve the above type of problem, even when it is formulated in elaborate

detail.

However, for the present and even for the future, the simple description

is/will be adequate for treating important fire safety problems. In line with

such a simple problem description this paper will mainly discuss the significant phenomena that occur during the development of fire environments in rooms

of fire origin and in freely-connected (e.g., by open doors) adjacent spaces.

3. THE ROOM OF FIRE INVOLVEMENT

3.1 Fire Growth in the Combustible of Fire Origin

An unwanted ignition rapidly leading to flaming is assumed to occur within an enclosed space. This ignition is depicted in Figure 1 as occurring

on the cushion of a couch in, say, a residential-type of occupancy. It is,

however, important to realize that all of the discussion to follow, and Figure

1 itself, is also relevant to fire scenarios which may develop in other kinds

-5 -
of occupancies, e.g. , as a result of ignitions in stacked commodity warehouse

enclosures, places of assembly, etc.

Within a few seconds of ignition, early flame spread quickly leads to a flaming fire with a power output of the order of a few tens of kW (a power

level characteristic of a small wastepaper basket fire). The fire continues

to grow. Besides releasing energy, the combustion process also yields a variety of other products including toxic and nontoxic gases and solids.

Together all of these products are referred to as the "smoke" produced by the

f ire.

With an adequate description of the ignition source and the involved

combustible (e.g., ignited paper match on the corner of a couch whose frame,

cushioning and finishing materials and construction were well defined) , one would hope that fire science and technology would provide methods to predict

the fire spread and growth process from the onset of ignition. Toward this

end, ongoing research on flame spread and combustion is under way in a variety

of different fire research institutions throughout the world. (Examples of

such research include boundary layer analyses and experiments of flame spread

on idealized materials and geometries; and flame spread tests and rate of heat

release tests on small samples of real material composites.) However, for the

present and for the foreseeable future, it is beyond the state of the art of

fire technology to make the required fire growth predictions with any generality. This situation leads to a dilemma for the modeler of enclosure fire

environments since the physical and chemical mechanisms, which govern the

dynamics of the combustion zone, drive the basic inter- and intra-compartment

smoke migration phenomena whose simulation is being sought.

A practical engineering solution to the above dilemma, proposed and

supported in references 1 and 2, lies in the following compromise in

simulation accuracy. Prior to the time of potential flashover, it is reasonable to neglect the effect of the enclosure on flame spread and to assume that

from the time of ignition to the time shortly before potential flashover the

combustion zone in a particular grouping of combustibles develops as it would

in a free burn situation. [Free burn here is defined as a burn of the combustibles in a large (compared to the combustion zone), ventilated space with

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relatively quiescent atmosphere.] To implement these ideas one simply uses empirical, free burn test data (which may or may not be presently available)

to describe the combustion physics of a fire whose hazard is being

evaluated. This compromise would, in the course of time, be supplanted by

analytic models of flame spread and fire growth to the extent that future

results of research lead to satisfactory methods for predicting such

phenomena.

The implementation of the above compromise is, in principle, relatively

simple. But for general use, it must be supported by an extensive data base

acquired from a series of actual full-scale free burn tests. This kind of

data is being acquired with some regularity at fire test laboratories such as those of the National Bureau of Standards and the Factory Mutual Research

Corporation, and much has already been published (e.g., Tables 3.2 of reference 3, Tables 4-1 and 4-2 of reference 4, Figure G. 2 and Table G. 2 of reference 5, Table 3 of reference 6, and much data reported in reference 7 all

provide information on energy release rates, Q(t), of fires in a variety of

practical, full-scale assemblies of combustibles).

3.2 Development of the Plume

As depicted in Figure 2, a large fraction, X^, of the rate of energy

released in the high temperature combustion zone is transferred away by radiation. The transferred energy, X^Q(t), irradiates nearby surfaces of the

combustible and far-away wall, ceiling, etc., surfaces which are in the lineof-sight of the combustion zone. The actual value of X^_ associated with the

free burn of a specific array of combustibles is often deduced from data

acquired during the aforementioned type of free burn tests. For practical

hazardous flaming fires, X^ is typically of the order of 0.35.

Because of the elevated temperature of the products of combustion,

buoyancy forces drive them out of the growing combustion zone and up toward

the ceiling. In this way a plume of upward moving elevated temperature gases

is formed above the fire. For the full height of the plume and at its periphery relatively quiescent and cool gases are laterally entrained and mixed with

the plume gases as they continue their ascent to the ceiling. As a result of

- 7 -
this entrainment the total mass flow in the plume continuously increases and

the average temperature and average concentration of products of combustion in

the plume continuously decrease with increasing height. Hie plume dynamics at

any instant of time can, with reasonable accuracy, be quantitatively described

by a function of the rate of energy convected up from the combustion zone,

C 1 —

r )Q( t) . A description of the concentration of combustion products in the

plume would require, in addition, the combustion zone's rate of product

generation. With regard to predictions of the dynamics of the plume, references 8-10 provide results in a variety of different levels of detail. Thus,

reference 9 provides the formula in Figure 2 as an estimate of the mass flux

in the plume, m , at a distance Z above the combustion zone.

P

3.3 The Plume-Ceiling Interaction

As depicted in Figure 3, when the hot plume gases impinge on the ceiling,

they spread across it forming a relatively thin radial jet. This jet of hot

gases contains all of the smoke generated from the combustion zone, and all

the ambient air which was entrained along the length of the plume.

As the hot jet moves outward under the ceiling surface it entrains

ambient air from below; it transfers energy by conduction to the relatively

cool adjacent ceiling surface, and by convection to the entrained air; and it

is retarded by frictional forces from the ceiling surface above, and by turbulent momentum transfer to the entrained air from below. As a result of all

this flow and heat transfer activity, the ceiling jet continuously decreases

in temperature, smoke concentration, and velocity; and increases in thickness

with increasing radius.

Research reported in the literature (e.g., references 11-18) has led to

results for predicting the quantitative aspects of ceiling jet dynamics that can be used for selecting and locating smoke detectors and fusible link

IQ on sprinkler head actuators ’, and for the mathematical modeling of overall

enclosure fire environments.

With regard to detectors and fusible links, it is evident that knowledge

of the properties of the ceiling jet, which hopefully engulfs these devices in

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real fire scenarios, is key to the prediction of their response. With regard

to the overall modeling of enclosure fire environments, the basic information

that must be extracted from the ceiling jet properties is the overall rate of

heat transfer to the ceiling surface. Experiments have shown that this heat

transfer will be significant, of the order of several tens of percent of the

total energy released by the combustion zone, and, as a result, it is key to

predicting the temperature of the smoke which ultimately spreads throughout

the enclosure. Also, a reasonable estimate of this rate of heat transfer is

required for estimating temperatures of the ceiling surface material itself.

3.4 The Ceiling Jet - Wall Interaction

The ceiling jet continues to move radially outward under the ceiling

surface, and it eventually reaches the bounding walls of the enclosure. As

depicted in Figure 4, the ceiling jet (now somewhat reduced in temperature

from its highest levels near the plume) impinges and turns downward at the

ceiling-wall juncture, thereby initiating a downward directed wall jet.

The downward wall jet is of higher temperature and lower density than the

ambient into which it is being driven. The jet is, therefore, retarded by

buoyancy in its downward descent, and at some distance below the ceiling the

downward motion of the smokey jet is eventually halted. The wall jet is also

retarded (probably to a lesser degree) by frictional forces at the wall

surface, and it is cooled by conductive/convective heat transfer to relatively

cool wall surfaces. Momentum and heat transfer from the jet occur away from

the wall as its outer flow is sheared off and driven back upward on account of

buoyancy. In its turn, the now upward-moving flow entrains ambient air in a manner which is reminiscent of entrainment into the original fire plume.

Eventually a relatively quiescent upper gas layer is formed below the continuing ceiling jet flow activity.

The strength of the wall-jet flow activity will be determined by the

strength of the ceiling jet at the position of its impingement with the wall.

In particular, the closer the wall surfaces are to the fire, the larger will

be the momentum and temperature of the ceiling jet at the ceiling-wall

juncture; and the more important will be the details of the wall-jet flow

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activity to mi understanding of the overall enclosure fire environment. Thus,

for fire scenarios where the proximity of the walls to the fire is no greater

than a room height, or so, It is reasonable to speculate that rates of conductive/convective heat transfer to wall surfaces can be significant, of the

order of tens of percent of the fire's energy release, and that entrainment to

the upward moving, reverse portion of the wall flow can lead to significant

variations of the early rate of thickening of the upper gas layer. On the

other hand, if walls are several room heights from the fire then the ceiling

Jet will be relatively weak by the time it reaches the walls. Under these

latter circumstances the ceiling jet-wall interactions will themselves be

weak, and it is not likely that they will play an important role in the

dynamics of the overall fire environment.

Besides being important in the prediction of the overall fire environment, knowledge of the flow and temperature environments local to vigorous

ceiling Jet-wall interaction zones would be key to predicting the response of

wall mounted smoke detectors, fusible links, etc.

3.5 Development and Growth of the Upper Layer - "Smoke Filling"

The gases in the ceiling and wall jets redistribute themselves across the

upper volume of the room. Eventually a relatively quiescent, uniform thickness, elevated temperature upper smoke layer is formed below the continuing

ceiling jet flow activity. As the thickness of this layer grows, it would

also eventually submerge any flow zones generated by vigorous ceiling jet-wall

interactions. The bottom of the layer is defined by a distinctive material

interface which separates the lower ambient air from the upper, heated, smokeladen gases. With increasing time the level of the smoke layer interface

continues to drop, and the temperature and smoke concentration of the upper

layer continues to rise.

In general, one would hope that fire detection, successful occupant

alarm, and, if appropriate, successful intervention hardware response would

occur during the stage of fire growth described so far in this and in the

previous two paragraphs. As suggested earlier, rationally engineered design

in this regard would be possible with predictions of the dynamic fire
environments local to deployed devices, and with predictions of the resulting

response of such devices.

For reasons already mentioned, some detail in the description of plume,

ceiling jet and ceiling jet-wall flow dynamics is required. However, for the

purpose of understanding the implications of the overall fire environment on

life and property safety, simplified descriptions compatible with the aforementioned detail, would suffice, and, for a variety of practical reasons,

would actually be preferable. For this reason, available predictive models of

enclosure fire environments commonly describe the bulk of the upper layer

environment in terms of its spacially averaged properties. Actual full scale

testing of enclosure fire environments has indicated that such a simple means

of describing the smoke layer represents a reasonable compromise between

accuracy in simulation and practicality in implementation.

Figure 5 is a generic depiction of the enclosure fire environment at the

stage of fire development under discussion. At this stage, whether or not the

space of fire involvement is fully enclosed (i.e., all doors and windows are closed and only limited leakage occurs at bounding partitions) or is freely

communicating with adjacent space(s) (e.g., open or broken windows or open

doors to the outside environment or to an adjacent enclosed space of virtually

unlimited extent; and/or open doorways to adjacent spaces of limited extent)

becomes very important in the subsequent development of the fire environment.

In the sense that the upper layer thickness and temperature would grow most

rapidly, the fully enclosed space with most leakage near the floor would lead

to the most rapid development of potentially life and property threatening

conditions.

Referring again to the depiction in Figure 5, the fire plume below the

smoke layer interface continues to entrain ambient air as it rises to the

ceiling. However, as the hot plume gases penetrate the layer interface and

continue their ascent, additional entrainment is from an elevated temperature,

smoke environment. Also, once the plume gases enter the smoke, they are less

buoyant relative to this layer than they were relative to the cool lower layer

of ambient air. Thus, the continued ascent of plume gases is less vigorous

than it would otherwise be in the absence of the upper layer.

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The new and more complex two-layer state of the enclosure environment

requires that some modification of the earlier-referenced quantitative

descriptions of the plume, ceiling jet, and ceiling jet-wall flow dynamics be

introduced. Reference 21 has proposed some modifications along these lines.

As depicted in figure 6, a new and potentially significant wall flow can develop during the present stage of fire development. This flow, which is

distinct from the previously described upper wall Jet, develops on account of

the condition of relatively cool upper wall surfaces which bound the elevated

temperature upper smoke layer. The smoke which is adjacent to these wall

surfaces is relatively cool and, therefore, more dense than its surroundings.

As a result of this density difference, a continuous, downward-directed wall

flow develops which is injected at the smoke interface into the lower, relatively smoke-free layer. Once in the lower layer, the smoke-laden wall flow, now of higher temperature than its surroundings, will be buoyed back upward to

either mix with and contaminate the lower layer or to entrain additional

(i.e., in addition to the fire plume) lower layer air into the upper layer.

It is noteworthy that the wall effect just described has been observed in

full and reduced scale fire tests, and that it appears to be particularly

significant in enclosures with relatively large ratios of perimeter to ceiling

height (e.g., in corridors) .

As a result of its elevated temperature the smoky upper layer transfers

energy by radiation to the ceiling and upper wall surfaces which contain it.

As depicted in Figures 4 and 5 by the downward directed arrows, the layer also

radiates to the lower surfaces of the enclosure and its contents. Initially,

the only significant role of this downward radiation is its effect on human

tissue. Indeed, only after seriously life-threatening levels of downwarddirected radiant energy (characterized by smoke layer temperature levels on

the order of 200°C, or by radiant flux levels of the order of 2.5 kW/m^) would

the radiant energy feedback to enclosure surfaces and combustibles have a significant impact on fire growth and spread, and on the overall fire environment^ .

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Once radiation feedback becomes of general significance, say when the

average upper layer temperature reaches 300-400°C, it is likely that the

potential for flashover will develop within a relatively short time interval

(compared to the time interval between ignition and the onset of a lifethreatening environment). The events which develop during this time interval

will be referred to here as the transition stage of fire development.

The onset of life threatening conditions, which could be instigated for

any one of a number of reasons, would occur prior to the transition stage of

fire development. Before this event can be predicted, quantitative criteria

defining a "life threatening environment" must be established. These criteria

must be defined in terms of those physical parameters for which predictive

models of enclosure fire environments can provide reasonable estimates.

Consistent with earlier discussion, such parameters would include the smoke

layer thickness (or vertical position of its interface), and temperature. The

concentration of potentially hazardous components of the smoke in the upper

layer would also be key. Criteria for the onset of a life threatening

2 3 environment could, for example, be based on the following considerations

(which would neglect the effect of lower layer contamination due to wall

flows )

When the smoke layer interface is above some specified, characteristic,

face-elevation, an untenable environment would occur if and when a hazardous

radiation exposure from the upper layer is attained. Such an exposure could

be defined by a specified, upper layer, critical temperature. If the interface is below face-elevation, then untenability would occur if and when a second, critical, smoke layer temperature is attained. However, the latter

temperature would be lower than the former one, and untenable conditions would

be initiated as a result of direct burns or inhalation of hot gases. Once the

interface dropped below face elevation, untenability would also occur if and

when a specified, critical concentration (or a specified exposure dosage) of

some hazardous product of combustion was attained.

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3.6 The Transition Stage of Fire Development

Any detailed analysis and prediction of the fire environment during the

transition stage of fire development must, of necessity, take account of the

effects of upper layer and upper surface re-radiation, in general (e.g.,

significant modification to the character of the aforementioned wall flows^) , and of the complex effects of radiation-enhanced fire growth, in particular.

Such an analysis would require a mathematical model of enclosure fire phenomena which was significantly more sophisticated than would be required to

predict the fire environment prior to, and, possibly, even following the

transition stage.

Regarding the potential difficulty, uncertainty, inconvenience and/or

cost of carrying out transition stage analysis, it is noteworthy that conservative designs for life and property safety may be possible by implementing a strategy of fire environment analysis which avoided the details of transition

stage entirely. This would be done by conservatively assuming that the relatively brief time interval associated with the transition stage shrinks to a flashover jump condition at a relatively early time in the fire scenario^.

4. SMOKE SPREAD FROM THE ROOM OF FIRE INVOLVEMENT TO ADJACENT SPACES

4.1 Smoke and Fresh Air Exchange Between a Room of Fire Involvement and an Adjacent Space

This and the following paragraph will discuss smoke spread phenomena

associated with a room of fire involvement and a communicating adjacent space.

Reference here will be made to a fully enclosed, two-room space with relatively large common penetrations (e.g., open doors or windows) through which

the smoke and ambient air exchange will be so significant as to render inadequate an analysis which treats the room of fire involvement as an isolated

enclosure. Regarding the two-room spacial configuration, Figures 1-5 would

still be relevant to the early development of conditions within the fire

room. However, once the smoke layer interface drops to the level of the

soffit of the communicating doorway(s) or window(s), significant amounts of

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smoke would start to move into the adjacent space from above while significant

amounts of ambient air would be driven out of the adjacent space (and into the

fire room) from below. From that time on, as depicted in Figure 7, an interdependent smoke filling process in each of the two spaces will be

initiated, and the adjacent space will itself start to develop a two-layer

type of environment.

Throughout the course of real fire scenarios, changes in the absolute

pressures of facility spaces are at the most of the order of one percent.

Yet, dynamic, elevation-dependent pressure differences that exist between the rooms of fire involvement and adjacent spaces are large enough to drive a significant cross-door exchange of smoke and ambient air.

Toward the left side of Figure 8 is a sketch of the vertical static

pressure distribution, Pfi re (Z), of the room of fire involvement. This is the

pressure distribution that would be measured in the bulk of the relatively

quiescent-environment room, away from vigorous door and plume flows. Notice

that the rate-of-change of pressure with elevation is uniform and relatively

large between the floor and the smoke interface, and is uniform and relatively

small within the smoke layer. The reason for this is that the density

(temperature) throughout each of the two layers has been assumed to be

uniform, and the lower layer is more dense (i.e., of lower temperature) than

the upper one. The pressure at the floor is designated as Pfire(Z=°> -

P fire ,0*

Toward the right side of Figure 8 is a sketch of the vertical static

pressure, P

acjj(2), in the adjacent space. There, the change of slope occurs

at the elevation of the adjacent space smoke interface, which is above the

smoke interface in the fire room. Also, the slope of the pressure distribution above the interface is consistent with a smoke layer somewhat more dense

or cooler than the smoke layer in the fire room. Finally, the pressure at the

floor is designated as P

acjj( z ) ~ pa dj 0* two Pressure distributions can

be compared by the plot of the pressure difference, AP(Z) =

P^

re ^^-Padj » which is sketched in the doorway of Figure 8. At Z elevations below the

soffit where AP is positive, gases would be driven from the fire room into the

adjacent space. At elevations where AP is negative, gases would be driven

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from the adjacent space into the fire room. At the unique elevation, called

the neutral plane, where AP is zero, the gases would tend to remain stagnant

in both spaces. This is the elevation in the doorway which would divide

outgoing fire room smoke above from inflowing adjacent space air below.

At any given elevation it is typical in the modeling of fire generated

doorway/ window flows to use Bernoulli's equation to estimate the velocity,

V(Z), of the flow coming out of or into the fire room. The flow is assumed to

2 be accelerated from rest to a dynamic pressure, pV (Z)/2 = AP(Z), where p is

the density of the gas from which the streamlines originate. Also, at any

elevation the flow is assumed to be constricted at the vena contracta of the

inlet/outlet jet, as with an orifice, to a fraction, C, of the width, W(Z), of

the doorway. Then the total rate of mass flow across the doorway per unit

height at any elevation would be pCV(Z)w(Z) = Cw(Z)/2pAP(Z) . With some minor

variations, the Law of Conservation of Mass requires that the total rate of mass outflow (the smoke flow) from the fire room is equal to the total rate of mass inflow (the ambient-air flow) to the fire room. Imposing this conser- vation principle at any instant of time when the layer thicknesses and densities (temperatures) in the two rooms are known, leads to the instantaneous

values of AP (Z=0) and neutral plane elevation.

An indepth presentation of results for calculating total inlet and outlet

mass flows and for general application of the above considerations are presented in reference 25. Recent results on most appropriate values to use

for C have been obtained from full scale fire experiments described in reference 26.

4.2 Door Plume, Ceiling Jet and Smoke Filling of the Adjacent Space

Having been driven into the adjacent space by the cross-door pressure

differential, the doorway smoke jet is buoyed upward toward the ceiling on account of its relatively low density (high temperature). The upward buoyant

flow, depicted in Figure 7, is analogous to the previously discussed fire

plume, and, with minor modifications, can be quantitatively described by the same kinds of equations. In using these equations, the enthalpy flux of the

inflowing smoke jet would replace the strength, Q(t), of the fire plume, and

-16 -
the "smoke jet buoyancy source" elevation, taken to be at the neutral plane

elevation, would replace the elevation of the fire's combustion zone. Further

quantitative details on one possible set of door-plume flow calculations are available in reference 25.

Just as the doorway smoke jet rises up in the adjacent space, is diluted

by entrained fresh ambient air, and is mixed with the upper layer in the

manner of a fire plume; so the relatively cool and dense doorway ambient jet

enters the fire room, drops down past the upper layer, is contaminated by

entrained smoke, and is mixed with the lower layer. This mechanism of lower

layer smoke contamination in the room of fire involvement is in addition to

the previously described wall flow mechanism which was depicted in Figure 6.

Figure 7 depicts the fire environment after the adjacent space upper

layer is already well established. At earlier times, adjacent space smoke

movement phenomena are closely related to those effects described above (i.e.,

Figures 3 and 4 and associated text) for the room of fire involvement. Thus,

the doorway smoke jet plume impinges on the adjacent space ceiling, leads to

the development of a ceiling jet which interacts with wall surfaces, and

eventually redistributes itself to form a growing, uniform thickness, upper

1 aye r

As was the case in the room of fire involvement, knowledge of adjacent

space ceiling and upper wall jet properties would be key in predicting the

response of adjacent-space-deployed fire detection/intervention hardware, and

the temperatures of the adjacent space environment. Also, as discussed in

reference 22, contamination of the lower layer by smoke injection from downward directed wall flows can play a relatively more important role in adjacent

spaces than in the fire room itself.

All the above adjacent room effects must be predicted quantitatively with

reasonable accuracy, since the fire generated environments in the fire room

and in adjacent spaces are strongly coupled by cross-door mass exchanges.

Also, of key importance is the ability to predict the onset of adjacent space

environmental conditions which are untenable for life or property.

-17 -
4.3 Multiroom and Multilevel Fire/ Smoke Compartments

The discussion of the last two paragraphs was related to the two-room

illustration of Figure 7. However, the general principles of smoke migration

are no different in fire/ smoke compartments of more than two connected spaces.

In multiroom or even multilevel compartments, smoke migration occurs as smoke in successive rooms fills to the door/window soffits, and then starts to

"spill out" into the adjacent spaces. At the same time, in each room where

filling has been initiated, the phenomena related to plumes, ceiling jets,

different wall flows and upper layer-lower layer mixing are also taking place.

In each of the spaces these various phenomena are generally coupled together

through the connecting door/window flows. For this reason, all effects must

be analyzed simultaneously. For example, in a multiroom fire/ smoke compartment one needs to satisfy the principle of conservation of mass when it is

applied not just to a single doorway, but to all envelopes which completely

bound each room of the compartment. To do so, one needs to solve for the

pressure difference distributions, and the resulting inflows and outflows

across all intercompartraent penetrations.

4.4 Some Special Classes of Multiroom Fire Scenarios

Single room vented to the outside . One practical, special class of

multiroom fire scenario is the single room of fire involvement which is vented

to the outside ambient environment. One can carry out an analysis of the fire

environment in such vented spaces by bringing to bear all considerations

relevant to the Figure 7 discussion, but by assuming the adjacent space to be

arbitrarily large, i.e., large enough so that it would never be filled with

smoke to the point where such smoke would interact with the fire room

itself. The pressure distribution of the adjacent space from the floor to the

top of the door/window would be specified to be the same as that of an outside

ambient environment; dynamics of the plume, which is driven by the smoke jet

entering the adjacent space from the fire room, would not be affected by the

adjacent space ceiling or far wall surfaces; and all inflow to the fire room

would be uncontaminated, ambient air.

- 18 -
Treating the adjacent space in the above manner leads to considerable

simplifications in mathematically modeling the room fire environment. It is

noteworthy in this regard, that the only mathematical models to date for

predicting post-flashover fire environments are related to this configuration

of a single room of fire involvement vented to the outside.

Single room vented to a large space. Another important class of fire

scenario, which is directly related to the last one, is the single room of

fire involvement which is actually vented to a very large space. Such is the

configuration, for example, when a room of fire involvement is vented to a large atrium.

Under the above circumstances one could analyze the fire environment

which develops in the large containing space (the atrium) as one would analyze

the environment in a space with a single isolated fire (e.g., see Figures

4-6). Here, the energy and products of combustion release rates of the fire

would be taken to be the enthalpy and combustion products’ fluxes of the

effluent from the doorway/window jet of the fire room. As before (i.e.,

independent of changes in the large, but now finite, adjacent space), and at

least for some significant time into the fire, the development of the environment in the fire room itself, and the resulting door/window smoke jet could

hopefully be obtained analytically. Short of analytic predictions, however,

actual measurements of the door/ window effluent acquired in full scale, free

burn tests of the fire room, up to and even beyond flashover, could be used as inputs in the analysis of the (large) adjacent space problem.

The latter, combined experimental/analytic approach has been used to

predict the environment which develops in large prison cell blocks during

27 fires in single cells of different design .

Single- and freely connected multi-room fire compartments . For those

times of fire development when the compartment of fire involvement consists of

a single enclosed space, analysis of the fire environment is considerably

simplified. This is because an accounting of inflow and outflow at windows

and doors (which are presumably closed) is not required.

- 19 -
When the fire compartment is partitioned into separate but freely connected spaces, the relatively simple, single enclosed space analysis, where the area of the single space is taken to be the total area of the fire com- partment, can continue to be relevant. Here, "freely connected" refers to

fire scenarios and spacial configurations where common openings between rooms

are large enough, and/or the energy release rate of the fire is small enough

so that smoke layers remain reasonably uniform in thickness, temperature and

product concentration throughout the bulk of the compartment area.

Quantitative criteria for establishing whether a specific fire compartment is freely connected relative to a specified fire threat are not yet

available. However, the concept of the freely connected, multiroora, fire/

smoke compartment has been shown to be valid during full scale multiroom fire

experiments reported in references 2 and 28.

5. SOME AVAILABLE MATHEMATICAL MODELS/COMPUTER CODES FOR

PREDICTING DYNAMIC ENCLOSURE FIRE ENVIRONMENTS

In recent years many mathematical models and associated computer codes

for predicting dynamic enclosure fire environments have been developed in a variety of different research institutions throughout the world. To the

extent that these models/coraputer codes take account of any of the individual

fire phenomena discussed earlier, the accounting tends to be relatively

similar from model to model. Nonetheless, there is a good deal of variation

between them. Some of the significant differences tend to be in the number

and detail of the individual physical phenomena that are taken into account,

the number and complexity of interconnected fire compartment spaces that can be analyzed, the capability of the computer hardware that is required to run

the computer code, the user-friendliness of the computer code, and its available documentation.

While it is well beyond the scope of this paper to exhaustively catalogue

and describe the capabilities and special features of all currently available

fire models, it is at least appropriate to identify some of them. Attention

here will be focused on a listing of some zone-type, enclosure fire growth

models and associated computer codes which are available with some

-20-
documentation through the Center for Fire Research of the U.S. National Bureau

of Standards. It is noteworthy that these models tend to be in a continuing

state of development/ improvement. In this regard, only the capabilities of

their "user-ready" versions are identified here.

Building Research Institute (BRI) - Japan: Communicating multiroom

29 multilevel space vented to the outside .

California Institute of Technology: Ttoo communicating rooms, both vented

to the outside 33 >^0.

Center for Fire Research of National Bureau of Standards (CFR/NBS):

S2 SS

- Single room vented to the outside ».

- Single enclosed space ( ASET)^ ’ 3 ’ 33

. - Postflashover predictions for a single room vented to

the outside (COMPF2) 34

.

O 1 Harvard University: Single room with vents to the outside .

Illinois Institute of Technology Research Institute (IITRI): Single room with vents to the outside (RFIRES) 3

.

6. SMOKE SPREAD OUTSIDE THE SMOKE COMPARTMENT OF FIRE INVOLVEMENT

This paper has concentrated on smoke spread phenomena within smoke

compartments of fire involvement. Yet, the outline of the generic fire safety

problem which was presented above in the second section is also relevant to

the general problem of predicting smoke environments throughout an entire

facility.

Figure 9 illustrates a practical concept for modeling the development of

smoke environments both inside and outside the smoke compartment of fire

involvement. Facility spaces that would be included in the smoke compartment

(on the left of the figure) are distinguished from those included in the rest

of the building or facility (on the right) by the detail which is required to

-21 -
describe or mathematically model the fire-generated environments within them.

In the smoke compartment of fire involvement, smoke would spread within a room, and would be driven from room to room by strong buoyancy forces which

lead to layered smoke environments. These environments must be analyzed in

the context of (at least) a two-layer model with associated phenomena of plume

flow, surface flows, etc. In the "rest of the building", it is reasonable to

describe the smoke in each space as being uniformly dispersed. Here, dyna lie

changes in the distribution of the environment comes about from room-to-room

pressure differences which are generated by stack effects, wind effects and

forced ventilation, and which lead to smoke movement, mixing, and dilution.

The fire compartment is the source of smoke to the rest of the buildi ig.

The rate of introduction of this smoke depends on the pressure differences

across common partition assemblies, and on their leakage characteristics . Once the rate of smoke leakage across common partitions can be expressed

quantitatively, the "rest of the building" problem could be analyzed with a model of smoke movement similar to those presented in references 36 and 37.

An overall view of the research and development required to implement the

above concept for modeling fire environments and designing for fire safety in

complex enclosed facilities is presented in reference 38.

7. ACKNOWLEDGEMENTS

This work was supported by the U.S. Department of Health and Human

Services, and the Bureau of Mines and National Park Service of the U.S.

Department of Interior.

-22 -
8.

REFERENCES

1. Cooper, L.Y., A Concept for Estimating Available Safe Egress Time in

Fires, in Fire Safety Journal, 5, (2), pp. 1 35—1 44 , 1983.

2. Cooper, L.Y., A Mathematical Model for Estimating Available Safe Egress

Time in Fires, Fire and Materials, 6, (3/4), pp. 135-144, 1982.

3. Butcher, E.G. and Parnell, A.C., Smoke Control and Fire Safety Design, E. and F.N. Spon Ltd., London, 1979.

4. Guide for Smoke and Heat Venting, NFPA 204M, 1982.

5. Pape, R. , Waterman, T. and Eichler, T.V. , Development of a Fire in a Room

From Ignition to Full Room Involvement - RFIRES, IITRI Rpt.

NBS-GCR-81-301 for National Bureau of Standards, 1981.

6. Friedman, R. , Quantification of Threat from a Rapidly Growing Fire in

Terms of Relative Material Properties, Fire and Materials, 1, (1),

pp. 27-33, 1978.

7. Babrauskas, V. , Combustion of Mattresses Exposed to Flaming Ignition

Sources. Part I. Full-Scale Tests and Hazard Analysis, NBSIR 77-1290,

National Bureau of Standards, 1977.

8. Heskestad, G. , Engineering Relations for Fire Plumes, to appear in Fire

Safety Journal.

9. Zukoski, E.E. , Kubota, T. and Cetegen, B. , Entrainment in Fire Plumes,

Fire Safety Journal, 3, pp. 107-121, 1980/81.

10. McCaffrey, B.J. , Purely Buoyant Diffusion Flames: Some Experimental

Results, NBSIR 79-1910, National Bureau of Standards, 1979.

11. Alpert, R.L. , Turbulent Ceiling-Jet Induced by Large Scale Fires, Combustion Science and Technology, 11, pp. 197-213, 1975.

12. Heskestad, G. , Similarity Relations for the Initial Convective Flow

Generated by Fire, Paper 72-WA/HT-17, Winter Annual Mtg. ASME, 1972.

13. Heskestad, G. and Delichatsios , M.A. , Environments of Fire Detectors - I: Effect of Fire Size, Ceiling Heights, and Material. Vol. 1. Measurements, FMRC Rpt. NBS-GCR-77-86 for National Bureau of Standards, 1977.

14. Heskestad, G. and Delichatsios, M.A., Environments of Fire Detectors - I: Effect of Fire Size, Ceiling Heights, and Material. Vol. 2. Analysis,

FMRC Rpt. NBS-GCR-77-95 for National Bureau of Standards, 1977.

15. Heskestad, G. and Delichatsios, M.A. , Environments of Fire Detectors -

II: Effect of Ceiling Configuration. Vol. 1. Measurements, FMRC Rpt.

NBS-GCR-78-1 28 for National Bureau of Standards, 1978.

-23-
16. Heskestad, G. and Delicha tsios , M.A. , Environments of Fire Detectors -

II: Effect of Ceiling Configuration. Vol. 2. Analysis, FMRC Rpt.

NBS-GCR-78-1 29 for National Bureau of Standards, 1978.

17. Veldman, C.C., Kubota, T. and Zukoski, E.E., An Experimental Investigation of Heat Transfer from a Buoyant Plume to a Horizontal Ceiling - Part

I. Unobstructed Ceiling, C.I.T. Rpt. NBS-GCR-77-97 for National Bureau

of Standards, 1975.

18. Cooper, L.Y. , Heat Transfer from a Buoyant Plume to an Unconfined

Ceiling, J. Heat Transfer, 104, pp. 446-451, 1982.

19. Alpert, R.L. , Calculation of Response Time of Ceiling Mounted Fire Detectors, Fire Technology, 3, pp. 181-195, 1972.

20. Benjamin, I., Heskestad, G. , Bright, R. and Mayes, T. , An Analysis of the

Report on Environments of Fire Detectors, Fire Detection Inst., 1979.

21. Cooper, L.Y. , Convective Heat Transfer to Ceilings Above Enclosure Fires,

Proceedings of 19th Inter. Symp. on Comb., Haifa, 1982.

22. Cooper, L.Y. , On the Significance of a Wall Effect in Enclosures with

Growing Fires, to be presented at 22nd ASME/AIChE National Heat Transfer

Conf., Seattle, 1983.

23. Cooper, L.Y. and Stroup, D.W., Calculating Available Safe Egress Time

(ASET) - A Computer Program and User’s Guide, NBSIR 82-2578, National

Bureau of Standards, 1982.

24. Jaluria, Y. , Buoyancy-Induced Wall Flow Due to Fire in a Room, to appear

as NBSIR, National Bureau of Standards.

25. Zukoski, E.E. and Kubota, T. , Two-Layer Modeling of Smoke Movement in

Building Fires, Fire and Materials, 4, (1), pp. 17-27, 1980.

26. Steckler, K. , Quintiere, J. and Rinkinen, W. , Flow Induced by Fire in a Compartment, Proceedings of 19th Inter. Symp. on Comb., Haifa, 1982.

27. Life Safety Code, NFPA 101, A-15-3.1.3, 1981.

28. Cooper, L.Y., Harkelroad, M. , Quintiere, J. and Rinkinen, W., An Experimental Study of Upper Hot Layer Stratification in Full-Scale Multiroom

Fire Scenarios, J. Heat Transfer, 104, pp. 741-749, 1982.

29. Tanaka, T. , A Model of Multiroom Fire Spread, to appear as NBSIR,

National Bureau of Standards.

30. Zukoski, E.E. and Kubota, T. , A Computer Model for Fluid Dynamic Aspects

of a Transient Fire in a Two Room Structure, C.I.T. Rpt. prepared for

National Bureau of Standards, 1978.

31. Mitler, H.E. and Emmons, H.W., Documentation for CFC V, the Fifth Harvard

Computer Fire Code, Harvard Univ., Home Fire Proj . Rpt. 45, 1981.

-24 -
32 . Quintiere, J. , Steckler, K. and McCaffrey, B. , A Model to Predict the

Conditions in a Room Subject to Crib Fires, presented at First

Specialists Mtg. of Comb. Inst., Bordeaux, 1981.

33. Steckler, K. , A Calculation of Wall Fire Spread in an Enclosure, to

appear as NBSIR, National Bureau of Standards.

34. Babrauskas, V., C0MPF2 - A Program for Calculating Post-Flashover Fire

Temperatures, NBS TN991 , National Bureau of Standards, 1979.

35. Cooper, L.Y., The Need and Availability of Test Methods for Measuring the

Smoke Leakage Characteristics of Door Assemblies, to appear as NBSIR,

National Bureau of Standards.

36. Wakamatsu, T. , Calculation of Smoke Movement in Buildings, Research Paper

34, Building Research Inst., Tokyo, 1968.

37. Evers, E. and Waterhouse, A., A Computer Model for Analyzing Smoke Movement in Buildings, SCS Ltd. Rpt. CP 68/78 for Fire Research Station,

1978.

38. Cooper, L.Y. and Nelson, H.E., Life Safety Through Designed Safe Egress - A Framework for Research, Development and Implementation, 6th Mtg. UJNR

Panel on Fire Research and Safety, Tokyo, 1982.

-25 -
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BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 83-2748

I 2vGo*/L Accession Nol3. Reciptenfs Accession t s£ ; , 1 W

4. TITLE AND SUBTITLE

Smoke Movement in Rooms of Fire Involvement and Adjacent

Spaces

m

5. Publication Date July 1983

S. Performing Organization Code

7. AUTHOR(S)

Leonard Y. Cooper

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

10. Projoct/Task/Work Unit No.

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, city, state, zip) 13. Type of Report & Period Covered

w.

15. SUPPLEMENTARY NOTES

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

16. ABSTRACT (A 200-word or leas factual summary^ of most-si gniji cant information. If dpcximcrit Jnclujdes a significant bibliography or

literature survey, mention it here.) key to the solution of fire saTehy design problems ljf the capability to predict the dynamics of enclosure fire environments. This paper presents a detailed qualitative description of the generic phenomena which occur during typical

fire scenarios. The focus of attention is on the effects within building compartments

of fire involvement, i.e., compartments made up of a single enclosed space or a space

of two or more rooms interconnected by significant penetrations such as open doors or windows. Throughout the discussion reference is made to quantitative methods for predicting some of the most significant of these effects. Reference is also made to available mathematical /computer models which use these latter methods to quantitatively

predict the overall fire environment. The basic topics that are covered are: fire

growth in combustibles of fire origin; development of the fire plume and interaction of

the plume with the ceiling surface; generation of ceiling jet flows which lead to actuation of detection/intervention hardware; interaction of ceiling jets and wall surfaces;

growth of the smoke layer; development of wall flows which can be instrumental in drawing smoke down from the upper smoke layer into the relatively uncontaminated, shrinking

lower ambient environment; downward radiation from the high temperature smoke layer and

upper enclosure surfaces which can ultimately lead to flashover; onset of conditions

which are untenable for human occupancy or property survivability. Topics related to

fire generated environments in multiroom fire/smoke compartments include: dynamics of

the smoke and fresh air exchange between the room of fire involvement and the adjacent

spaces; dynamics of door/window plumes, ceiling jets, smoke filling and well flows withifi

adjacent spaces; actuation of adjacent space fire detection/intervention hardware; and

onset of adjacent space untenability.

17. KEY WORDS (six to twelve entries ; alphabetical order; capitalize only the first letter of the first key word unleas a proper name;

separated by semicolons) Combustion products; compartment fires; egress; enclosure fires;

fire detection; fire growth; fusible links; hazard analysis; mathematical models; room

fires; smoke movement; tenability limits.

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