I , NSS

'Reference^^

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SIR 82-2480

.ne-Based Capabilities of

Occupants to Escape Fires in

Public Buildings: A Review of

Code Provisions and Technical

Literature

NAT'L INST. OF STAND & TECH

AlllOb EST715

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

April 1982

Prepared for: —QC

100

.056

ci2-2460

1902

Home and Public Building Safety Division

U.S. Fire Administration

Federal Emergency Management Agency

Washington, DC 20472

NBSIR 82-2480

TIME-BASED CAPABILITIES OF

OCCUPANTS TO ESCAPE FIRES IN

PUBLIC BUILDINGS: A REVIEW OF

CODE PROVISIONS AND TECHNICAL

LITERATURE

JIA.T10MA1. BUKBAb

<Ur tTAKDABVI

UBMAXT

MAY 17 1982

Ho t Clcc -

! . ,/

Fred I. Stahl

James J. Crosson

Stephen T. Margulis

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

April 1982

Prepared for; Home and Public Building Safety Division

U.S. Fire Administration

Federal Emergency Management Agency

Washington, DC 20472

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

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

TABLE OF CONTENTS

Page

ABSTRACT vii

ACKNOWLEDGEMENTS viii

EXECUTIVE SUMMARY lx

1. INTRODUCTION I 1.1 Problem 1 1.2 Objective and Scope 2 1.3 Organization of the Report 3 1.4 Technical Approach 4

1.4.1 Study Design and Task Organization 4

1.4.2 Literature Review 5 1.4.3 Behavioral Assumptions Peer Review Procedures 5

1 . 5 Summary 6

2. PROVISIONS AFFECTING PRE-EMERGENCY TRAINING AND PREPARATION 7 2.1 Applicable Code Provisions 7 2.2 Underlying Behavioral Assumptions 7

2.2.2

Assumptions Relating to the Transfer of Responses

Learned During Drills to Actual Fire Situations B 2.3 Commentary 8

2.3.1 Problem 8

2.3.2 Underlying Behavioral Models 9

2.3.3 Assessment of Behavioral Assumptions Based on the

Technical Literature 13

2.4 Summary of Gaps In the Technical Literature 18

2.4.1 Research on the Predictions of Occupants' Responses

During Real Fires 18

2.4.2 Research on the Transfer of Training 19

2.4.3 Research on Occupants' Attitudes Toward Exit Drills .... 19

2.4.4 Research on the Accommodation of Training Programs

to Specific Occupancy Requirements 19

2.5 Summary 20

3. PROVISIONS AFFECTING THE PERCEPTION OF THE EMERGENCY

ENVIRONMENT AND THE RECOGNITION OF EGRESS FACILITIES 21

3.1 Applicable Code Provisions 21

3.2 Underlying Behavioral Assumptions 22

3.2.1 Assumptions Relating to the Effect of Door and

Window Design Upon Egress Route Perception 22

3.2.2 Assumptions Relating to the Affect of Illumination

Level Upon Egress Route Identification 23

3.2.3 Assumption Relating to the Role of Visual Signage and

Directional Information In Egress Route Recognition

and the Formation of Emergency Egress Strategies 23

ill
TABLE OF CONTENTS

Page 3.2.4

Assumptions Relating to the Ability of Audible and

Visual Alarm Signals to Effectively Alert Building

Occupants to a Fire Threat 24

3.3 Commentary 24

3.3.1 Problem 24

3.3.2 Underlying Behavioral Models 24

3.3.3 Assessment of Behavioral Assumptions Based on the

Technical Literature 31

3 .4 Summary of Gaps in the Technical Literature 38

3.4.1 Research on the Effects of Door and Window Design 38

3.4.2 Research on Illumination Required for Egress Route

Identification 38

3.4.3 Research on Directional Signage 39

3.4.4 Research on Alarm Signals 39

3.5 Summary 39

4. PROVISIONS AFFECTING EGRESS STRATEGY FORMATION 40

4.1 Applicable Code Provisions 40

4.2 Underlying Behavioral Assumptions 40

4.2.2

Assumptions Relating to Occupants' Abilities to

Determine the Safest and Most Accessible Escape

Route Under Potentially Stressful Conditions 40

4.3 Commentary 41

4.3.1 Problem 41

4.3.2 Underlying Behavioral Models 41

4.3.3 Assessment of Behavioral Assumptions Based on the

Technical Literature 46

4.4 Summary of Gaps in the Technical Literature 52

4.5 Summary 54

5. PROVISIONS AFFECTING DISCIPLINED EGRESS BEHAVIOR AND CROWD

MOVEMENT 55

5.1 Applicable Code Provisions 55

5.2 Underlying Behavioral Assumptions 56

5.2.1 Assumptions Concerning the Influence of Designated

Leaders Upon Egress Time During Fire Emergencies 56

5.2.2 Assumptions Concerning Pedestrian Movement Under

High Density Occupancy Conditions 56

5.2.3 Assumptions Concerning the Effects of Building

Configuration and Architectural Obstructions on Efficient Crowd Movement 56

5.3 Commentary 56

5.3.1 Problem 56

5.3.2 Underlying Behavioral Models 57

5.3.3 Assessment of Behavioral Assumptions Based on the

Technical Literature 61

iv
TABLE OF CONTENTS

Page

5 .4 Summary of Gaps in the Technical Literature 66

5.4.1 Research on the Effectiveness of Trained Leaders in

Facilitating Rapid Emergency Escape and in

Avoiding "Panic" 66

5.4.2 Research on the Effects of Occupant Loading and

Discharge Behavior on Successful Crowd Movement 67

5.4.3 Research on the Effects of Architectural Impediments

and Physical Obstacles Upon Crowd Behavior and

Disciplined Movement 67

5 .5 Summary 68

6. PROVISIONS ACCOMMODATING OCCUPANT’S CAPABILITIES TO SAFELY AND

RAPIDLY NEGOTIATE EGRESS WAYS 69

6.1 Applicable Code Provisions 69

6.2 Underlying Behavioral Assumptions 71

6.2.1 Assumptions Relating to the Effects of Stair and

Ramp Design on Occupants' Capabilities to Safely

and Rapidly Negotiate Egress Ways 71

6.2.2 Assumptions Relating to the Effects of

Physiological and Psychological Stress Upon

Occupants' Capabilities to Safely and Rapidly

Negotiate Egress Ways 72

6.2.3 Assumptions Relating to the Biomechanics of Exit

Door Operation 72

6.3 Commentary 73

6.3.1 Problem 73

6.3.2 Underlying Behavioral Models 73

6.3.3 Assessment of the Behavioral Assumptions Based Upon

the Technical Literature 78

6.4 Summary of Gaps in the Technical Literature 86

6.4.1 Research on the Affect of Stair and Ramp Design on Occupants' Capabilities to Safely and Rapidly

Negotiate Egressways 86

6.4.2 Research on the Affect of Stress and Fatigue on Occupants' Capabilities to Safely and Rapidly

Negotiate Egressways 87

6.4.3 Research on the Effects of Doorway and Door Hardware

on Occupants' Capabilities to Safely and Rapidly

Negotiate Egressways 88

6.5 Summary 88

7. PROVISIONS GOVERNING THE CAPACITY OF MEANS OF EGRESS 90

7.1 Applicable Code Provisions 90

7.2 Underlying Behavioral Assumptions 92

7.2.1

Assumptions Pertaining to the Influence of

Architectural Barriers and Other Obstructions to

Egress Flow 92

V
TABLE OF CONTENTS

Page

7 .3 Commentary 93

7.3.1 Problem 93

7.3.2 Underlying Behavioral Models 9A

7.3.3 Assessment of Behavioral Assumptions Based on the

Technical Literature 98

7.4 Summary of Gaps in the Technical Literature Ill

7.4.1 Research on the Influence of Architectural Barriers

and Other Potential Obstructions to Egress Flow ........ Ill

7.4.2 Research on the Flow Capacity of Egress Channels 112

7.5 Summary 112

8. SUMMARY AND CONCLUSIONS 113

8.1 Selection of Code Provisions 113

8.2 Underlying Behavioral Assumptions 114

8.3 Technical Commentaries 115

8.3.1 Problem Statements 115

8.3.2 Behavioral Models 117

8.3.3 Assessment of Behavioral Assumptions Based on the

Technical Literature 119

8.4 Summary of Gaps in the Technical Literature 128

8.4.1 Overview 128

8.4.2 Pre-emergency Training and Preparation 128

8.4.3 Perception of the Emergency Environment, and

Recognition of Egress Facilities 129

8.4.4 Egress Strategy Formation 130

8.4.5 Disciplined Egress Behavior and Crowd Movement 130

8.4.6 Occupants’ Capabilities to Safely and Rapidly

Negotiate Egress Ways 131

8.4.7 The Capacity of Means of Egress 131

8.5 Conclusions 132

8.5.1 Overview 132

8.5.2 Provisions Affecting Pre-emergency Training and

Preparation 132

8.5.3 Provisions Affecting Perception of the Emergency

Environment, and Recognition of Egress Facilities 133

8.5.4 Provisions Affecting Egress Strategy Formation 133

8.5.5 Provisions Affecting Disciplined Egress Behavior and

Crowd Movement 133

8.5.6 Provisions Accommodating Occupants' Capabilities to

Safely and Rapidly Negotiate Egress Ways 134

8.5.7 Provisions Governing the Capacity of Means of

Egress 134

REFERENCES 135

APPENDIX A: MEMBERS OF PEER REVIEW PANEL A-1

APPENDIX B: INSTRUCTIONS TO REVIEWERS B-1

vi
ABSTRACT

This document reviews available technical literature pertaining to exit facility

design and emergency escape provisions of the National Fire Protection Association's Life Safety Code (1976 Edition) in order to determine the technical support for such provisions. The report focuses on the time-based capabilities of

building occupants to effect rapid evacuations, in relation to evacuation time

available during fires, A number of functional criteria are examined in relation to Code provisions influencing the design of means of egress and fire protection and protective signalling systems for places of assembly, residential

occupancies, mercantile occupancies, and business occupancies. Provisions

affecting fire exit drill and building management practices are also considered.

The technical literature bearing on applicable Code provisions is reviewed, the

validity and generalizability of findings presented in the literature are discussed, and the degree of technical support currently available for egress

provisions of the Code are evaluated. In addition, gaps in the technical literature are identified, and recommendations regarding future research are offered.

Finally, preliminary conclusions about the supportability of Code provisions

are presented.

vii
ACKNOWLEDGEMENTS

The successful completion of so large an undertaking necessarily involves

contributions by many capable people The authors particular express their

gratitude to the following individuals, whose technical assistance and insight were of Immeasurable value during the early stages of the project: Mr. Harold

Nelson and Dr. Bernard Levin of the National Bureau of Standards Center for

Fire Research (NBS CFR) , Mr. Irwin Benjamin and Dr. Norman Groner, formerly

with the NBS CFR, Mr. John Ferguson and Mr. John Fannin, both formerly with

the United States Fire Administration, Federal Emergency Management Agency,

and the members of the peer review panel (see appendix A of the report for a complete listing of panel members). The authors gratefully acknowledge the

assistance of Dr. Belinda Collins and Dr. Arthur Rubin of the NBS Center for

Building Technology (CBT) who critically reviewed drafts of the report.

Finally, the authors thank the staff of the CBT Word Processing Center.

vill
EXECUTIVE SUMMARY

1 . OVERVIEW

1 . 1 PROBLEM

This report reviews available technical research pertaining to the exit facility

design and emergency escape provisions of the National Fire Protection Association's Life Safety Code (1976 Edition, hereafter referred to as the Code ) , in

order to determine the technical support for such provisions. The central

foci of the investigation are the time-based capabilities of building occupants

to effect rapid evacuations, in relation to evacuation time available during

fires. A number of functional criteria (e.g. maximum travel distance, building

configuration, remoteness of exits, and barlers to egress flow) are examined in

relation to Code provisions Influencing the design of means of egress and fire

protection and protective signalling systems for places of assembly, residential occupancies, mercantile occupancies, and business occupancies. Provisions

affecting fire exit drill and building management practices are also considered.

1.2 TECHNICAL APPROACH

To effectively treat this broad problem, the current report organizes Code

provisions and related technical discussions in relation to areas of potential

impact, including provisions affecting: (1) pre-emergency training and prepa?

ation (Chapter 2 of the report), (2) the perception of the emergency environment and recognition of egress facilities (Chapter 3), (3) egress strategy formation (Chapter 4), (4) disciplined egress behavior and crowd movement (Chapter

5), (5) occupants' capabilities to safely and rapidly negotiate egress ways

(Chapter 6), and (6) the capacity of means of egress (Chapter 7).

Within each chapter of the report, provisions of the Code which have a common

area of potential Impact, and human behavioral assumptions underlying these

provisions, are enumerated. The technical literature bearing on these provisions and assumptions is presented, including references to applicable theories

and models, pertinent empirical data from published experiments and field

studies, and where appropriate, anecdotal accounts of actual fire events. The

validity and generallzability of findings presented in the literature are discussed, and the degree of technical support currently available for egress provisions of the Code is evaluated. In addition, each chapter provides a summary

of gaps in the technical literature, recommending specific areas for future

research. Finally, preliminary conclusions regarding the supportability of

Code provisions in each impact area are offered. A summary of the major

conclusions presented in the report follows.

ix
2.1 SUMMARY OF MAJOR CONCLUSIONS PRESENTED IN THE REPORT

A CAUTIONARY NOTE

The intention of NBS researchers is not to pass judgment on the validity and

usefulness of Code provisions. Indeed, where technical support for individual

provisions, or more precisely human behavioral assumptions underlying these

provisions, is either weak or unavailable, the authors do not recommend eliminating or otherwise modifying these provisions. In such Instances, rather, the

authors suggest that code-writers approach the task of revision with caution,

and that further technical Investigations be conducted.

2.2

PROVISIONS AFFECTING PRE-EMERGENCY TRAINING AND PREPARATION

Behavioral assumptions underlying code provisions affecting pre-emergency

training and preparation are evaluated by reference to psychological models of

learning, experimental data reported in the psychological literature, and the

growing body of evidence from post-incident fire investigations. To date,

experimental and post-incident investigations provide mixed conclusions con- cerning the supportability of these assumptions. Moreover, available evidence

does not often permit direct inferences to be drawn between research findings

and the specific questions raised by code provisions. Future modifications to

provisions affecting pre-emergency training appear to require additional

research on the role of training and its relation to emergency behavior.

2.3

PROVISIONS AFFECTING PERCEPTION OF THE EMERGENCY ENVIRONMENT, AND

RECOGNITION OF EMERGENCY FACILITIES

A number of human behavioral assumptions about the perception of emergency

environments and the recognition of egress facilities underlie various provisions of the Life Safety Code . These assumptions are evaluated by reference to

several models of perception, to limited data from experiments on visibility,

and to a small body of evidence from post-incident fire investigations. Taken

as a whole, available data neither support nor refute behavioral assumptions

about occupants' emergency perceptions at a level technically sufficient to

permit a thorough evaluation of pertinent Code provisions. Where data are available in sufficient quantity, however, it has been suggested that behavioral

assumptions underlying alarm provisions of the Code tend not to be supported.

The Code provision specifying a maximum (10 second) switchover delay between

standard and emergency lighting, on the other hand, tends to be supported by

available technical data. Initial emergency perceptions are important, and

their relationship to rapid escape has been shown. Consequently, future

research which leads to more effective perceptions of the fire environment by

victims is recommended.

2.4

PROVISIONS AFFECTING EGRESS STRATEGY FORMATION

A number of assumptions about human Information processing and decisionmaking

behavior during fire emergencies underlie several provisions of the Life Safety

Code . Such assumptions are evaluated by reference to models of cognitive

behavior, as well as to data from recent psychological research on way-finding

X
behavior, environmental cue processing, disaster response, and stress. Few

directly relevant technical data were found within the field of fire research

Itself. Taken as a whole, available technical knowledge Is not sufficient to

warrant statements specifically supporting or refuting Code provisions which

may Influence egress strategy formation. However, the literature generally

supports the notion that the demands of occupying a burning building require

Individuals to efficiently extract Information from the fire environment, and

to formulate effective and timely decisions about what to do. Depending upon

the design and layout of a building, and upon the nature of given fire conditions, these processes will consume some proportion of the time within which

occupants must escape. Errors In judgment and decisionmaking will frequently

consume even more time. However, crucial gaps in current knowledge about the

time-based capabilities of building occupants to effect rapid emergency escape

continue to center about questions of emergency Information processing and

strategy formation,

2.5 PROVISIONS AFFECTING DISCIPLINED EGRESS BEHAVIOR AND CROWD MOVEMENT

A number of human behavioral assumptions about crowd movement and disciplined

group behavior underlie selected provisions of the Code . These assumptions are evaluated by reference to several models of human collective behavior, data

from research In experimental social psychology, field research on natural

disasters, and post-incident fire investigations. In general, the technical

literature suggest support only for those assumptions pertaining to leadership

and direction-taking behavior. Behavioral assumptions pertaining to the

effects of occupant loading and physical obstacles upon orderly and rapid

crowd movement appear to be neither supported nor refuted by available technical literature. To the extent that Impediments to crowd movement result In

maladaptive collective behavior and panic, future research on the role of

building design in facilitating crowd movement seems an essential percursor to

Code revision.

2.6 PROVISIONS ACCOMODATING OCCUPANTS’ CAPABILITY TO SAFELY AND RAPIDLY

NEGOTIATE EGRESS WAYS

Human behavioral assumptions which underlie Code provisions relating to

occupants' capability to safely and rapidly negotiate means of egress are evaluated by reference to biomechanical models of human movement, toxicological

research, stair and ramp use field studies, physiological measurements, and

anecdotal evidence from actual fire incidents. At present, much of the evidence reported In the experimental and nonexperimental literature on occupants'

capabilities presents contradictions and mixed opinions, and does not permit

specific conclusions or Inferences to be drawn. As a result, there appears to

be no analytical basis upon which to unequivocally support or refute applicable

Code provisions. It is left for future research to determine the specific

domains (i.e., occupancies and fire scenarios) under which particular data are valid and useful in this context.

xi
2.7 PROVISIONS GOVERNING THE CAPACITY OF MEANS OF EGRESS

A number of human behavioral assumptions underlying Code provisions which govern

the capacity of means of egress are presented. These assumptions are evaluated

by reference to several models of pedestrian movement, data from laboratory and

field studies of walking behavior during normal occupancy conditions, and

observations of stair use during fire exit drills in high-rise office buildings.

With regard to Code provisions affecting the design of doors, available technical literature support only those assumptions concerning the deleterious effects

of particularly severe constrictions or obstructions. However, behavioral

assumptions underlying provisions governing the design of corridors and stairs

find challenge within the technical literature. This is especially true of

provisions depending on the validity of assumptions about the linearity of

pedestrian movement and the 22 inch (0.56 m) unit width standard. Because

there remain differences in reported data describing pedestrian behavior on stair and level surfaces, inconsistent definitions of important variables, and

nonstandardized techniques for measuring the performance of means of egress,

it is not now possible to either support or refute exisitng provisions and

their underlying behavioral assumptions on the basis of the available technical

literature. The most important objectives for future research on the subject

of the capacity of means of egress are; (1) the development and validation of

standardized measures and measurement methods, and (2) the systematic analysis

of complete egress systems, emphasizing transitions between means of egress

elements

xii
1 . INTRODUCTION

A predominant motivating factor behind America Burning (National Commission on Fire Prevention and Control, 1973) was the potential for multifatality fire

tragedies in buildings. Accordingly, a primary goal of the Home and Public

Building Safety Program of the United States Fire Administration is to ensure

that up-to-date and feasible criteria are implemented to provide for life

safety in public occupancy buildings, including multifamily residential

occupancies, places of assembly, mercantile occupancies, and business facilities. The three most obvious alternative approaches to providing life safety

from fire in buildings involve rapid emergency escape, protection of occupants

in place, and rescue. The study reported here focusses only on the problem of

rapid emergency escape.

Many building code provisions influencing emergency escape have remained

virtually unchanged since important research was reported by the National

Bureau of Standards (NBS) in 1935. In general, these provisions govern the

design and capacity of means of egress (or, egressways), and are based upon

empirically derived relationships between pedestrian flow, egressway capacity,

and escape time. Since then, several of these relationships have been called

into question. For example, it has become more widely believed that occupants

usually do not move through stairways and other egress channels in regemented

fashion at constant speeds (although the computation of egress way capacity

often requires this assumption), that fire products can move into and thereby

contaminate exit stairwells not carefully designed to prevent smoke infiltration, and that many buildings of substantial size or population cannot be com- pletely evacuated rapidly. Moreover, researchers and life safety design professionals have learned that early warning devices, pre-emergency training, and

various social, psychological and organizational factors each play an important—although not fully understood—role in rapid emergency egress.

Finally, it has also become more widely accepted during recent years that functional variations between occupancy categories, and the differing needs of

people with varying escape capabilities, both affect emergency readiness and the

ability to evacuate buildings efficiently. Many of these problems were first

discussed by Stahl and Archea (1977) of the Center for Building Technology, NBS,

in their original assessment of the technical literature on emergency egress

from buildings. Since that time, various issues have been expanded and investigated by numerous other investigators at NBS and elsewhere^.

1.1 PROBLEM

The principal lessons to be learned from research conducted during the last 10

years on human responses to fires are that individual design provisions, which

^ A substantial portion of the research on emergency egress and human

behavioral aspects of life safety from fire is discussed later in this

report. Consequently, individual investigators are not listed here.

1
usually embody professional engineering judgment and responses to specific

disasters, and (1) are not consistently applicable under all conditions or circumstances, or (2) are not consistently supportable by reference to the

technical literature. Thus, analyses of means of egress design provisions

(e.g. Rivers and Bickman, 1979; Stahl and Archea, 1977) reveal that underlying

behavioral assumptions are often expected to hold under a relatively broad

range of conditions, and that empirical support for the validity of these

assumtions is frequently difficult to identify. The problems of identifying

relevant technical literature and of applying it to the verification of current

means of egree design provisions are key issues addressed by the present study,

1,2 OBJECTIVES AND SCOPE

The primary objective of the present investigation is to assess available

research pertaining to exit facility design and emergency escape criteria of

the National Fire Protection Association's (NFPA) Life Safety Code (1976 Edition, hereafter referred to as the Code ) , in order to determine the technical

support for such criteria, A secondary working goal is to Identify human

behavioral assumptions believed to underlie egress and related provisions of

the Code , By gaining an understanding of occupant behavior patterns implicit

in compliance with various Code provisions, the project staff felt better able

to evaluate individual provisions against state-of-the-art technical data, and

thereby better able to verify currently promulgated egress requirements. The

purpose of these activities is to provide a technical foundation from which

substantive modifications to egress provisions may eventually be made,^ in

preparing this report, the intention of NBS researchers is not to pass judgment

on the validity of the Code , Where technical support for given provisions is

either weak or unavailable, the authors do not recommend eliminating or otherwise modifying these provisions. In such instances, rather, the authors suggest that code-writers approach their task with caution, and that further

technical investigations be conducted.

The central foci of the investigation are the time-based capabilities of

building occupants to effect rapid evacuations, in relation to evacuation time

available during fires. Numerous functional criteria were studied, including:

(a) maximum travel distance; (b) building configuration; (c) remoteness of

exits; (d) barriers to egress flow (e,g,, railings, security devices, doorways); (e) illumination of means of egress and of directional signs; (f) egress

channel carrying capacity; (g) the ability to totally evacuate a building, in

terms of competition for available space, and in terms of physiological and

psychological fatigue.

Such functional criteria are specifically treated within various chapters of

the Code , and provisions from the following Code chapters were selected for

evaluation: Chapter 5, Means of Egress; Chapter 6, Features of Fire Protection

(specifically, provisions concerning protective signaling systems); Chapter 8,

Places of Assembly; Chapter 11, Residential Occupancies; Chapter 12, Mercantile

2 Recommendations for modifying provisions of the Code lie outside the scope of

the present report.

2
Occupancies; Chapter 13, Business Occupancies; and Chapter 17, Operating Features

(specifically, provisions concerning fire exit drills and building management

practices)

1.3 ORGANIZATION OF THE REPORT

During the course of the project an attempt was made to posit a model of

emergency escape behavior, and to functionally relate provisions of the Code to

such a model. Principal components of this time-based model included; sensa- tion and perception of emergency environmental cues, interpretation of emergency

cues, strategy formation and decisionmaking, action initiation, and action com- pletion (generally after models suggested elsewhere by Bickman, Edelman and

McDaniel, 1977; Stahl, 1978a, 1979, 1980; and others). However, organizations

based upon a time-based model of human response were found incapable of accom- modating numerous Important code provisions. For example, provisions governing

the management of fire exit drills, or the carrying capacity of stairs, could

not easily be addressed by reference to a model of human perceptual and cognitive behavior. Moreover, useful models of human response to fires are neces- sarily dynaniic: environmental cues are received and assessed not once at the

outset of an event but continuously; action strategies are not rigidly adhered

to but change as events unfold and as new information becomes available to

occupants. Indeed, the task of relating existing design provisions to emer- gency egress dynamics is one of enormous complexity (especially since available

models are largely hypothetical) and was judged to lie outside the immediate

scope of the study.

Egress provisions and their underlying behavioral assumptions were, however,

found to cluster with respect to more or less naturally occurring categories

within the Code , including provisions: affecting pre-emergency training and

preparation (Chapter 2 of the current report); affecting the perception of the

emergency environment, and recognition of egress facilities (Chapter 3); affecting egress strategy formation (Chapter 4); affecting disciplined egress behavior

and crowd movement (Chapter 5); accommodating occupants’ capabilities to safety

and rapidly negotiate egress ways (Chapter 6) ; governing the capacity of means

of egress (Chapter 7). In order to simplify the presentation of egress provisions, underlying behavioral issues, and supporting technical material,

therefore, the report is organized about these categories.

Each of the six technical Chapters (Chapters 2 through 7) provides a complete

analysis of a single class of Code provisions. These Chapters are organized

as Illustrated below with reference to hypothetical Chapter n:

n.l APPLICABLE CODE PROVISIONS

This section lists provisions of the Code pertaining to the technical

issue treated by the Chapter.

n.2 UNDERLYING BEHAVIORAL ASSUMPTIONS

This section presents a set of human behavioral assumptions hypothesized

to underlie Code provisions enumerated in section n.l.

3
n.3 COMMENTARY

n.3.1 Problem. A succinct description of the problem or class of problems

addressed by applicable provisions of the Code .

n.3. 2 Underlying behavioral models. Theories and models selected from the

behavioral science (and other related) literature to provide a framework for understanding emergency events, and for guiding the development

of design solutions.

n.3. 3 Assessment of behavioral assumptions based on the technical literature.

(1) literature review; (2) discussion of strengths and weaknesses of the

technical literature.

n.4 SUMMARY OF GAPS IN THE TECHNICAL LITERATURE

This section reviews areas for future research, and summarizes the

usefulness of available studies in analyzing provisions of the Code .

n.5 SUMMARY

This section provides an overall review of the Chapter, and highlights

specific conclusions.

1.4 TECHNICAL APPROACH

1.4.1 Study Design and Task Organization

The study was designed to analyze egress related design requirements of the

Code , from the standpoint of occupants’ abilities to rapidly escape buildings

during fires. The goal of the analysis was to determine the extent to which

Code provisions Influencing the escape potential of buildings can be technically supported on the basis of state-of-the-art knowledge of time-based human

capabilities during fire emergencies. It was recognized at the outset that in

many cases the needed technical data are either not available, or else inconclusive. Therefore, another important objective of the research design was to

identify gaps in the available technical base, and to recommend areas for

further empirical investigation. The investigation reported here is a continuation and expansion of preliminary work on human behavioral aspects of the Code

funded by the NBS Center for Fire Research and conducted by Loyola University

of Chicago (Rivers and Blckman, 1979).

To effect the goals of the study, the following tasks were undertaken: (1) The

Code was reviewed and escape related provisions were identified. (2) Human

behavioral assumptions seen as potentially underlying egress provisions were hypothesized by the project staff. (3) An initial set of hypothetical behavioral assumptions was distributed among members of a peer review panel for

detailed comment, and on the basis of this review, initial hypotheses about

behavioral assumptions were modified and refined. (4) A comprehensive review

of technical literature pertaining to human behavior during fires and other

emergencies, and to other salient problems in the behavioral sciences was conducted

4
(5) Egress provisions and related behavioral assumptions were organized into

logical categories, and the extent to which provisions and assumptions are supported by evidence in the technical literature was assessed. The literature

review and peer review tasks are discussed in more detail below.

1.4.2 Literature Review

Rivers and Bickman (1979), in their assessment of behavioral assumptions

underlying Code provisions, relied almost entirely upon technical literature on human behavior during fires. Referring to the newness of this field of study

and to various methodological shortcomings, these investigators cautioned that

indeed few conclusive inferences could be drawn from available data in this

impoverished area. Ongoing objectives of the current investigators in discussing behavioral aspects of egress provisions, therefore, have been to draw upon

salient theoretical concepts from various areas of the behavioral sciences, and

to cite pertinent empirical data from the nonfire related psychological

literature, in order to amke inferences about probable behavior in fires.

1.4.3 Behavioral Assumptions Peer Review Procedure

The project sought to determine the degree to which emergency exiting

provisions of the Code may be supported by reference to state-of-the-art

knowledge about the time-based escape capabilities of building occupants.

Implicit in this goal is the notion that "hidden" expectations, or assumptions,

about human behavior during fire emergencies, and about the abilities of occupants to perform as expected, underlie many design provisions. In the current

context behavioral assumptions refer to those patterns of occupant response

that a building designer or code official might reasonably assume will occur,

(implicitly or explicitly) under prescribed design conditions, in the event of

a fire. For example, if an "EXIT" sign of particular characteristics is specified, the designer or code official may be thought to assume that, in general:

(1) during fires many occupants in fact look for and use "EXIT" signs, and (2)

the specified design characteristics Influence the utilization of such signs in some positive fashion.

To evalute Code provisions on the basis of human capabilities, therefore, seemed

to require a thorough identification and assessment of underlying behavioral

assumptions. It became apparent to the project staff, moreover, that evaluating

the technical support for behavioral assumptions believed to underpin Individual

provisions or sets of provisions, yielded the most direct and effective means of

evaluating behavioral aspects of Code provisions themselves.

As indicated earlier, the project staff hypothesized a set of assumptions it

believed underlie selected provisions of the Code . To avoid the liklihood that

these assumptions reflected only the biases and experience of the project staff,

to ascertain that the Code itself was not being misunderstood, and to elicit

useful ideas from other life safety professionals, a peer review procedure was developed. This procedure involved distributing a specially designed review

package among more than 20 professionals in government, industry, and academia.

The review package displayed all provisions of the Code included in the study,

5
along with various hypothesized behavioral assumptions pertaining to each^.

Respondents were instructed to review the sets of provisions and assumptions,

noting any changes, corrections, additions, or new ideas. Statements of

behavioral assumptions appearing later in this report reflect the recommendations of the peer review panel. Members of the panel are listed in Appendix A

instructions distributed with peer review packages are provided in Appendix B.

1 . 5 SUMMARY

This report addresses the time-based capabilities of building occupants to

effect rapid emergency escape during fire situations, and in particular, documents the availability of technical support for egress related provisions of

the NFPA Code (1976 edition). These provisions were noted to cluster with

respect to six distinct categories, and each category is treated within a separate chapter of the report.

3 In some instances, several assumptions were listed for a single provision.

In other cases, a single assumption pertained to a set of provisions.

6
2. PROVISIONS AFFECTING PRE-EMERGENCY TRAINING AND PREPARATION

2.1 APPLICABLE CODE PROVISIONS

17-1.2.1.1^ Every required exit access and exit discharge shall be continuously

maintained free of all obstructions or impediments to full instant use in the case of fire or other emergency.

17-1.4.1 Fire exit drills conforming to the provisions of this chapter of the

Code shall be regularly conducted in occupancies where specified by the provisions of this chapter, or by appropriate action of the enforcing authority

having jurisdiction, but with any necessary modifications in detail of procedures to make the drills most effective for their intended purpose in any

individual building.

17-1.4.2 Fire exit drills, where required by the authority having jurisdiction

shall be held with sufficient frequency to familarlze all occupants with the

drill procedure and to have the conduct of the drill a matter of established

routine.

17-1.4.3 Drills shall Include suitable procedures to make sure that all persons

in the building, or all persons subject to the drill, actually participate.

17.1.4.4 Drills shall be held at unexpected times and under varying conditions

to simulate the unusual conditions obtaining in case of fire.

2.2 UNDERLYING BEHAVIORAL ASSUMPTIONS

2.2.1 Assumptions Relating to the Ability to Predict Occupant Responses During

Real Fires

(1) The likelihood that people will panic, behave maladaptively and increase

the risk to themselves and others is a clear and constant threat (17-1.4)^.

(2) During Fire emergencies, people are often confused or lack disipline, and

hence may require lengthy time periods for evacuation; properly conducted fire

exit drills result in more orderly and disciplined behavior during real emer- gencies , and thereby help to reduce needed evacuation time (17-1.4).

(3) Disciplined and orderly behavior during fire emergencies are more important

than the actual speed with which people evacuate themselves (17-1.4.4).

^ Numbers refer to provisions of the NFPA Life Safety Code , 1976 Edition.

5 Numbers refer to Code provisions enumerated in the previous section of this

chapter

7
2.2.2 Assumptions Relating to the Transfer of Responses Learned During Drills

to Actual Fire Situations

(1) People are more likely to exit rapidly, and are less likely to panic or respond maladaptively during actual fires, when fire exit drills are practiced

frequently (17-1.4).

(2) People respond appropriately and effectively during real fires when they

have participated in properly conducted fire exit drills (17-1.4).

(3) Effective emergency behavior becomes habituated through frequent

participation in properly conducted fire exit drills (17-1.4.2).

(4) Occupant's responses during particular emergencies will be most rapid and

effective if drill training accurately simulates a variety of potential fire

scenarios (17-1.4.6).

2.2.3 Assumptions Relating to Occupants' Attitudes About Drills

(1) If occupants do not take drill participation seriously, they may not

behave effectively during actual fire emergencies (17-1.4.4).

(2) Some individuals may not take drill procedures seriously if other persons

are excused from participation (17-1.4.5).

2.2.4 Assumptions Relating to the Accommodation of Training Procedures to the

Diversity of Potential Fire Scenarios

(1) Occupants will be better prepared by fire exit drills and similar training

in occupancies in which controlled discipline is present (as in schools or hospitals) (17-1.4).

(2) Behaviors learned and practiced during drills designed for one type of

occupancy may not be effective in emergencies in other occupancies (17-1.4.1).

2 . 3 COMMENTARY

2.3.1 Problem

Code provisions affecting pre-emergency training and preparation are Intended

to prepare people for actual emergencies, reduce the probability of maladaptive

behavior during fires, and increase the likelihood of effective egress or movement to refuge areas. The general notion underlying many of these provisions

is that behavior patterns learned during training situations transfer to actual

fire events. Following from this supposition, behavioral assumptions underlying

these provisions address four principal areas of concern: (1) the ability to

predict occupant responses during actual fire emergencies; (2) the relevance and

transferability of responses learned during fire exit drills to actual fire situations; (3) occupants' attitudes toward the value of fire exit drills and other

forms of pre-emergency training and preparation; (4) the ability of fire exit

drill procedures and management to predict and accommodate the diversity of

potential fire scenarios in various occupancies. Several established models

8
of human learning within the behavioral sciences offer useful perspectives on

the role of training in promoting adaptive emergency behavior. Three important

models are considered below.

2.3.2 Underlying Behavioral Models

Three approaches to learning which offer useful insights into the problem of

pre-emergency training are the instrumental conditioning or reinforcement

approach, the social learning approach, and the cognitive approach. The most

basic and best known of these is the instrumental conditioning approach. This

approach assumes that, with learning, the individual acquires a connection

between a specific environmental stimulus and a particular behavioral response.

The person has an active role in creating the environmental conditions which

strengthen the stimulus-response connection. When an individual provides the

proper response under certain stimulus conditions, the result is a "reward"

(or relnforcer) of some kind. The reinforcer, which can be either learned or unlearned, strengthens the association between the stimulus and the response.

It is this strengthening to which the term "learning" refers in instrumental

conditioning.

Numerous experiments on the conditioning of laboratory animals and human

subjects have demonstrated that: (1) learning may generalize, i.e., a particular learned connection may transfer to other stimuli or responses; (2) subjects may be taught to discriminate stimuli and thereby limit learned connections to very specific situations; (3) learning may be lost, or extinguished,

if the connection between stimulus and response is weakened by discontinuing

reinforcement

The first category of assumptions addresses the ability to predict occupant

responses during real fires. One theory of instrumental conditioning that

has implications for this category is Clark Hull's systematic behavior

theory (Hllgard and Bower, 1966). In Hull's view, learning a response and

performing it are distinguished. Moreover, motivational factors, such as physiological needs, anxiety, and fear, play a central role in learning.

To Illustrate an application of these ideas: If a fire in a building creates

high levels of anxiety or fear among occupants, these occupants are likely to

have difficulties learning new and appropriate behaviors with which to deal

with the emergency. Habitual ways of responding, under the pressure of

motivational factors, are likely to be performed and could result in inappropriate activity. However, if occupants were well-drilled in fire emergency

procedures, that is, had a well-learned response or habit associated with fire

emergency situations, then the motivational factors created by the fire are likely to result in the vigorous performance of the learned emergency procedure

(Hilgard and Bower, 1966).

The second category of behavioral assumptions addresses the expectation that

fire exit drills prepare occupants to respond effectively during actual fire

events. For example, fire exit drills in elementary schools have been based

upon an Instrumental conditioning approach: students are conditioned to

respond to an alarm stimulus (e.g, a bell or buzzer), and when the stimulus is

presented the students respond by performing a prescribed sequence of actions

9
designed to result in rapid egress from the school building. Reward for

successful performance during drills may take the form of praise from the

teacher, early dismissal from class, etc. Generalization also is illustrated

in the school exit drill. Should the alarm bell malfunction on one occasion,

for example, a teacher’s call of "FIRE" is likely to elicit the appropriate

sequence because the alarm bell and the teacher's call share the same meaning

for students. From an instrumental conditioning viewpoint, the overall objective of exit drill training is to establish behavior sequences which lead to

rapid and orderly evacuation. It is generally assumed that if such patterns

can be established through a program of exit drills, then the learned behaviors

will transfer to actual fire events in schools and other occupancies so long as the different settings share conditions associated with the learned activity.

Another category of behavioral assumptions considers the ability of fire exit

drill planners and emergency managers to predict and accommodate the diversity

of potential scenarios in various occupancies. The instrumental conditioning

approach, for example, suggests that if persons are trained only to behave in

a particular manner within a given building, they may respond adaptively during

fires in that building (or within very similar buildings) only. On the other

hand, this approach suggests that training can also be specially designed to

permit the generalization of learning to other building types, or alarm modes,

and other fire scenarios.

Social learning approaches to understanding behavior are often built on instrumental conditioning concepts. Social learning approaches emphasize the

role that other persons play, as individuals or groups, as sources of reward

or of punishment. These approaches are predicated on the assumption that as social animals, humans depend on others for help in achieving rewarding goals

and in avoiding punishing ones. Therefore, what others say and do can influence an individual's behavior. That is, people are effective sources of reward

and punishment for one another. These concepts are often used by social psychologists to explain the relations among individuals and the operation of

groups (see Shaw and Costanzo, 1970, chapters 2-4). Thus, people learn to

follow an instruction from a person in authority because of the rewards that

compliance may bring and to avoid the punishments or costs of noncompliance.

The rewards (and costs) come from both the authority and from the achievement

(or nonachievement) of desired goals. With regard to group effects, groups

offer Interaction with other members and aid in meeting shared goals that can

be sources of rewards and costs. The rewarding effects of group membership

make one member a source of satisfaction to other members, make the group

attractive, and encourage members to remain in the group (Shaw and Costanzo,

1970, chapter 4).

Imitative learning is another important feature of social learning (McLaughlin,

1971). By observing other people, individuals learn both how and when to

respond. Imitative behavior may be directly rewarded by other persons, who

approve of how a given individual has responded. It may also be rewarded

vicariously, as when an individual observes the rewards or costs another person

received for a given response. Imitation has also been referred to as observational learning and modeling. It applies to the learning of emotional

responses and motor behavior, both of which are Important elements in fire

10
emergency situations. Some explanations of observational learning are based on instrumental conditioning principles (e.g. Gewlrtz and Stingle, 1968). Others

explained observational learning in terms of verbal and visual skills, and the

performance of such responses in terms of instrumental conditioning and motivational factors (e.g. Bandura, 1965). Thus, if a person is seen to be rewarded

for an action, the observer is more likely to perform this action than if the

person was punished for that action. Studies suggest that people tend to

imitate others who control resources (i.e. have power), such as people high in

status or in positions of authority.

Social learning principles apply to the transfer of responses learned during

drills to actual fire situations. If the individual has been rewarded for fire

drill performance as part of a group, and if the Individual wishes to maintain

the rewards (e.g., praise, esteem) that come from group membership, then during

other drills or an actual emergency the person is likely to do what has been

taught. This behavior is even more likely if others are also doing what they

have been taught. This is because doing what others are doing is an activity

that could lead to escape (which is rewarding), and which is rewarded for

helping the group by not performing disruptive (e.g. maladaptive) actions for

others (McLaughlin, 1971).

Social learning principles also apply to the ways in which attitudes toward

drills are learned. A learning-theory approach to social behavior developed

by Homans (1961) considers the role of distributive justice in this context.

Simply stated, people expect a fair exchange in their dealings with other individuals. The more a person puts into a given social interaction (referred to as the costs of Interaction) , the more the individual expects to get out of

the transaction (referred to as the rewards of interaction). Thus, if all the

people asked to participate in a fire exit drill are called away from an activity perceived to be more preferable than the drill, the drill is likely to

represent a cost. If one person does not attend the drill, those who do attend,

by comparison, may have Incurred proportionately greater costs. According to

Homans (1961), persons who are disadvantaged in an exchange will become angry.

This effort can be reflected as disinterest in future drills ("why should I^ attend if others don’t?”). It could also be reflected in anger toward those

responsible for enforcing drill attendance or toward those individuals who

would not attend.

Pre-emergency training based upon social learning concepts might take advantage

of relationships between occupants and leaders or legitimate authority figures,

and would emphasize the training of these leaders. Such leaders, once trained,

could serve as models for observational learning of emergency egress procedures,

among other techniques for Instruction. The availability of such individuals,

and the likelihood that appropriate relationships will exist within a given

building, depends considerably upon the nature of the occupancy. The proper

personnel and conditions may exist with an elementary school or nursing home,

for example, but not within an apartment building, hotel, or shopping mall.

In contrast with conditioning concepts and social learning approaches (which

are also rooted in conditioning principles), the cognitive approaches to

learning tend to underplay the role of conditioning, specific stimulus-response

11
connections, and physiologically-based motives. Instead, they emphasize types

of learning that result in an individual’s understanding of social and environmental events (Shaw and Costanzo, 1970, chapter 7). Tolman, a major learning

theorist, conducted research suggesting that people learn about their environment through repeated exposure to (l.e., familiarization with) it, even in the

absence of explicit reward systems (Hilgard and Bower, 1966).

Much more recently the cognitive approach has been applied to understanding the

ways people learn to understand and negotiate the architectural environment

(Ittelson, Proshansky, Rivlln, and Winkel, 1974, chapters 4 and 5; Evans,

Fellows, Zom, and Doty, 1980). In this view, the process of learning is frequently linked with human Information processing which involves: (1) perception and information gathering; (2) mediation or "filtering" of environmental

stimuli stimuli in accordance with a person's goals and traits; (3) allocation

and retention of environmental information in short- and long-term memory; (4)

formulation and implementation of specific action strategies as required by

current environmental events, (5) evaluation of actions against goals. These

cognitive activities form and reform mental images, or "cognitive maps" of

environmental situations, within people’s minds. As people are required to

respond to specific events, they test their cognitive maps against the reality

of the event. As more experience with a particular class of events is gained,

individuals’ cognitive maps more accurately reflect reality and provide better

preparation for adaptive behavior. Learning, then, is viewed within cognitive

theory as the development of processes by which information is assimilated,

processed and utilized, and by which the environment is effectively accommodated. Training programs based on this view frequently stress the need to

expose individuals to relevant sets of experiences, and to match these experiences to individuals’ level of development. Children, or adults with developmental disabilities, for example, may extract considerably less (or different)

information from a given environmental event (whether an actual fire emergency

or a drill simulation) than might average adults.

Conditioning principles were applied with reference to assumptions regarding

the expectation that fire exit drills prepare occupants for emergency egress

during a real fire. However, certain occupancies, such as health care and

custodial care facilities, may require a cognitive approach. Such facilities

present circumstances marked by mobility or cognitive impairments of occupants,

and by the presence of a cadre of supervisory personnel. Under these conditions, emergency training often includes lectures, films and other methods of

sensitizing staff personnel in addition to practice performance during fire

exit drills (Bickman, Herz, Edelman, and Rivers, 1979). Unlike the situation

in schools, pre-emergency training in health care institutions seems to follow

the cognitive approach to learning, which emphasizes the development of skills

intended to promote effective decisionmaking in response to unique and unpredictable events. For example, the decision as to whether patients should first

be evacuated or doors should first be closed requires staff personnel to formulate an action strategy on the basis of their current evaluations of specific

conditions. Thus, training for this type of occupancy may stress the accommo- dation of emergency procedures to the demands of unpredictable fire situations.

As with conditioning, it is assumed with the cognitive approaches to training

that lessons learned during drills or from films will transfer appropriate

response patterns to actual fire crises.

12
Cognitive learning models are also useful in understanding the role of

participants* attitudes toward training. These models stress the importance of

Individuals* experiences, levels of development, goals, motivations, values,

and beliefs. Thus, a cognitive approach to pre-emergency training might attempt

to change individuals' own motivations, attitudes, and beliefs about fires and

the need for training, in addition to training specific responses.

Pre-emergency training based on a cognitive approach to learning may also lead

to both situation-specific and generalized training programs. Programs may be

specifically designed to reflect potential scenarios within a given building

type, and to take into account the capabilities of a particular class of occupants. Or programs may be designed to equip people with fundamental life

safety knowledge useful during almost any fire scenario in almost any building

type.

In summary, human behavioral assumptions believed to underlie Code provisions

affecting pre-emergency preparation and training are discussed in relation to

three general models of human learning. While each model presents a somewhat

different explanation of learning processes, each one seems useful in understanding the problems associated with fire emergency training, and in evaluating behavioral assumptions believed to underlie applicable provisions of the

Code . The next section of this chapter discusses the behavioral assumptions

in relation to data presented in the technical literature.

2.3.3 Assessment of Behavioral Assumptions Based on the Technical Literature

Literature review. Assumptions stated in section 2.2.1 assert that panic is a likely response to a fire emergency and that there is a need to prevent panic

behavior during fire emergencies. Before presenting arguments supporting these

assumptions based on the technical literature, it is important to discuss panic

as a psychological concept.

Although many investigators have addressed the topic of panic, the term "panic"

lacks a clear, widely accepted technical definition. There are at least two

views about what panic means. The more common view stresses the irrational

roots of, and maladaptive responses to panic. This view is endorsed by Melinek

and Baldwin (1975), Janis and Mann (1977), Phillips (1978), and Schultz (1967).

A second, far less common view, stresses the rational nature of what is called

panic. In this view panic is an adaptive but thoroughly self-serving attempt

to gain a desired personal outcome (i.e., escape) even at the cost of sacrificing others to the existing, oncoming danger or threat (Burstein, 1969). This

view is consistent with research on panic by Brown (1965), Mlntz (1951), and

Kelley, Contry, Dalhke, and Hill (1965). In either case, these views suggest

that if there is panic, it is more likely that there will be unncessary victims

than if there is no panic.

Arguments supporting the assumptions about panic are based primarily upon

post-incident accounts of actual fires, and find additional basis in the

experimental literature on panic behavior. For example, the 1903 Iroquois

Theater fire is frequently cited as a case in which irrational panic behavior

(including simply remaining in one’s seat throughout the fire) is believed to

13
have claimed some 602 lives, although the building itself was not completely

destroyed, Galbreath (1969) related the probability of panic (which he did not

define in behavioral terms) to available egress capacity in a building. He

suggested that panic may occur in buildings where stair enclosures have been

designed to accommodate 50 percent of the population of a given floor, as was recommended by NBS (1935).

Relationships between occupants' perceptions of their own safety, the amount of

time available for safe escape, and the likelihood of panic behavior have been

stressed by several researchers, Melinek and Baldwin (1975) suggested that

after a 2.5 minute waiting period, people are likely to panic, and engage in

maladaptive, ineffective behavior. Janis and Mann (1977), Kelley et al. (1965),

and Phillips (1978) all have emphasized the importance of actual or perceived

time on the probability of panic behavior. An examination of Janis and Mann's

(1977) argument may suggest why time plays a critical role in creating panic.

According to these investigators, panic arises when time is perceived as insufficient for finding or using a means of escape from a serious, oncoming

threat. In such instances, people tend to deal ineffectively with available

information, and their thoughts frantically focus on too narrow a range of

alternatives. Wrapped in thought, these people are likely to further underestimate available time. In this regard, studies have found that there is a decrease in the perceived duration of an event when judgments of time intervals are made while people are performing tasks which draw attention away from the

passage of time (Dember and Warm, 1979), This potentially vicious cycle is

likely to invoke actions which are counterproductive and maladaptive, unless

environmental conditions Improve.

The importance of leadership and supervision in producing adaptive responses

during fire emergencies was discussed in section 2.3,2. Experiments conducted

for the Central Intelligence Agency (Klein, 1976) found that orderly discipline

channeled through a hierarchical organizational plan was essential to successful egress, Schultz (1967) concluded from his experiments that dependent persons may tend to respond maladaptlvely to life threats when leadership or supervision is absent. Reporting on the tragic Andraus Building fire in Sao Pualo,

Brazil, Willey (1972) noted that a rescue helicopter was almost destroyed by a panicking crowd on the building's roof. A second helicopter landed successfully

when firefighters were first lowered to the rooftop to control the crowd, clear

a landing area, and assure those waiting that they would be rescued.

The concepts of leadership and social control can be put into a larger

perspective, and one consistent with social learning (particularly modeling)

principles. Kelley et al. (1965) who experimentally examined panic behavior,

found that if volunteers faced with a serious personal threat learned that some

of their peers were willing to wait their turn in a queue in order to escape,

and if these peers had experience with escape and were trustworthy sources of

guidance, then successful escape was likely and the probability of panic

decreased. These results underscore the importance of social control, and of

the disciplined response to a threat, on successful emergency escape. These

findings also suggest that there is potential uncertainty about how others will

react to an oncoming threat; Will they respond in a self-serving way, or take

their turn in a queue? If other individuals make clear their intentions to

14
behave in a disciplined fashion, then this may serve to reduce uncertainty and

thereby reduce the likelihood of panic.

A number of investigators, however, have argued against panic as a real and

likely threat. Pauls (1979), for example, has contended that contrary to

popular opinion, panic responses are rare even where people perceived the situation to be potentially or actually dangerous. In a study of fires in health

care institutions, Haber (1977) found no incidents of panic-like behavior.

Wood (1972), in his Investigation of nearly 1,000 fires noted that only about

5 percent of all persons Interviewed claimed to have engaged in behavior judged

to increase personal risk. In recent studies modeled after Wood's work, Bryan

(1977) also found little evidence to support the notion that panic is a frequent occurrence. Best (1978), Canter, Breaux, and Sime (1978), and Swartz

(1979) also presented evidence to support the view that panic is infrequent.

Assumptions enumerated in section 2.2.1 not only stress the importance of panic

as a problem, but also suggest that the threat of panic may be reduced through

fire exit drill training. No direct evidence of this relationship was found in

the technical literature. However, Bryan's (1977) post-hoc studies of actual

fires suggest that pre-emergency training in the form of exit drills did produce more disciplined egress behavior. Also, Kelley et al . (1965), in their

experiments on panic behavior, indicated that conditions such as drills, which

lead people to be self-confident in their belief that they will successfully

escape, can decrease the extent of panic behavior.

The general question of whether behavior patterns learned during drills and

other forms of pre-emergency preparation transfer to actual emergency conditions was addressed by the assumptions enumerated in section 2.2.2. This

question has been discussed in detail by a number of investigators, and in

addition, researchers also have often stressed the importance of exit drill

frequency. For example, reviewing the tragic Beverly Hills Supper Club fire.

Best (1978) similarly argued that the lack of fire emergency training was a major cause of death and injury. However, there remains no direct experimental evidence of a transfer of training from drills to performance during actual

building fire emergencies.

Rivers and Bickman (1979) analyzed selected provisions of the Life Safety Code

(1976 edition), pointing out that once a particular sequence of emergency

responses has been learned, it must be practiced. According to Bird and Nocking (1949), participation in exit drills, however, is most likely to occur in

buildings with a single, consistent occupancy. Moreover, to be predictive of

responses during actual fires, fire exit drills must simulate actual emergency

conditions as closely as possible (Rivers, 1978). This notion is supported by

Garner and Blethrow (1970), who conducted experiments simulating emergency

conditions in commercial aircraft. They argued that simulations approximating

real emergencies could in fact be conducted, and that such simulations should

prepare participants (e.g. aircraft crew personnel) to respond effectively in

the event of a crash, fire, or other catastrophe. Observations drawn from

Bryan's numerous post-hoc fire investigations suggest a similar conclusion. If

actual emergency conditions are likely to be unique, then to avoid the possible

confounding (interfering) effects of unique aspects of a fire emergency on

15
performance during fire drills, simulated fire scenarios, time of day, exit

route blocking, etc., should be varied during drill exercises. This idea is

supported by the experiments of Posner and Keele (1968) on the value of highvariety learning in minimizing the effects of interfering events on task

performance

In such occupancies as nursing homes and hospitals, staff (in contrast to

patient) drills are critical. In a review of two Pennsylvania hospital fires,

for example, Lathrop (1978) credits frequent staff drills as the most significant reason for successful patient evacuations. Moreover, instances of multiple fatalities due to fires in health care facilities often have been attributed to the fact that these emergencies occurred during night time or early

morning hours, when the smallest number of staff personnel were present.

Other arguments appear in the literature, however, which question the

relationship between exit drill training and performance during actual fires.

In their report on a fire at the National Institute of Health Nursing Horae,

Bryan and DiNenno (1979) suggested that the frequency of exit drills may have

led to the belief by building occupants that the fire alarm signaled another

drill, and not a real fire. According to Bryan and DiNenno, some occupants,

apparently "tired" of drills, ignored the alarm signal and delayed the initiation of emergency procedures. Rivers and Bickman (1979) raised the point that

people vary in their capabilities, and that what may be an effective practice

exercise for one person may not be effective for another. Thus, the frequency

of practice of a particular type of drill cannot, in and of itself, guarantee

that adequate learning has taken place, or that adequate performance will take

place during an actual fire emergency.

In summary, researchers* conclusions and opinions on the significance of exit

drill frequency and on the design of particular training programs differ. Moreover, there appears to be no universally accepted opinion regarding the degree

to which exit drills prepare building occupants to respond effectively during

actual fires.

Section 2.2.3 enumerated assumptions relating to occupants’ attitudes toward

fire exit drills, and the effects of such attitudes upon performance during

both drills and actual emergencies. Rivers and Bickman (1979) argued that

unless drills are conducted properly and are taken seriously by participants,

inappropriate behavior patterns may be rehearsed and learned. Bryan and

DiNenno (1979) indicated that maladaptive responses may have resulted from the

inconsistent participation of personnel in exit drill procedures.

Section 2.2.4 contains assumptions concerning the accomodation of training

procedures to suit diverse occupancy conditions. Experiments discussed earlier

by Schultz, Klein, and Kelley et al . all suggest that effective emergency

response requires a social organization possessing leadership and discipline.

Clearly, however, not all occupancies are characterized by organizational

structures which possess these qualities. Moreover, few technical data appear

in the literature (e.g. Lathrop, 1978) describing occupant performance during

fire drills or actual fires in which disciplined, confident leadership was present.

16
Conventional wisdom currently holds that programs for pre-emergency training

and preparation should be designed to meet the special requirements of various

occupancies, and this is reflected in the Code . Evidence supports this assumption, For example, problems associated with evacuating handicapped persons in an acceptable period of time have been reported (Baldwin, Melinek, and Appleton,

1976). Additional evidence has been reported by the Federal Aviation Administration in connection with the evacuation of handicapped persons from commercial aircraft (Blethrow, Garner, Lowrey, Busby, and Chandler, 1977), Nevertheless, no evidence was found which documents the extent to which handicapped,

incapacitated, or elderly persons avoid participation in drills, or which indicates specific consequences of their failure to participate. Thus, not only is

there no technical data available addressing the conventional wisdom on drills

with special user groups but no tests of emergency training programs have been

conducted across various building occupancies.

In summary, researchers hold a variety of positions on the relationship between

drill behavior and responses to real fires, on the significance of drill frequency, and on the design of individual training programs. Moreover, there

appear to be no universally accepted conclusions regarding the degree to which

exit drills actually prepare building occupants for potential life threats.

Strengths and weaknesses of the techical literature . Many of the behavioral

assumptions underlying Code provisions affecting pre-emergency preparation and

training deal with the notion of panic. The term "panic" lacks a widely

accepted technical definition. For example, returning to a burning building to

retrieve valuable possessions might be called panic by an observer, while

thought to be an acceptable risk based on well-planned behavior by the individual performing these action. If panic is defined to result in mass flight or behavior which Increases risk, then it is not surprising that Pauls, Bryan,

and others noted so few examples. In the absence of a common technical definition of the panic response, reliable conclusions regarding either the predictability on occurrence of this response will be extremely difficult to obtain.

Experiments on behavior during stressful events conducted by Schultz (1967),

Kelley et al, (1965) and Klein (1976) were all conducted under controlled laboratory conditions. These investigators obtained similar results under varying

experimental conditions, and this supports their conclusions regarding conditions under which panic is likely and regarding the need for supervision and

discipline. However, since Important characteristics of actual life threats,

such as fire emergencies, cannot be simulated in the laboratory, it is difficult to infer real-world emergency behavior from these studies.

The assertion that panic behavior is Infrequent is supported by experimental

findings, anecdotal accounts, and by observations reported during post-hoc

interviews with fire victims and eyewitnesses. As the body of data from such

post-hoc case studies grows, reliable statements regarding the nature and frequency of the so-called panic response may be possible. This process should be

further aided by Improvements in post-incident surveying and eyewitness interviewing technique (Loftus, 1980).

17
The literature addressing relationships between fire drill performance and

behavior during actual emergencies is primarily nonexperimental. This literature presents two important difficulties for the analyst. First, although the

frequency of exit drills is often discussed, drill frequency has not been

treated as an Independent variable in research design and data analysis. Second, no investigator has specifically measured the potential long-term effects

of drill participation as a dependent variable. Hence, while it is possible

(and potentially useful) to continue speculating about the magnitude and direction of relationships between drill performance, drill frequency, and emergency

behavior, conclusions cannot now be substantiated.

Concerning the question of whether fire exit drills can adequately simulate

real emergency conditions, Pauls' (1974) data from drills in high rise buildings and Garner and Blethrow's (1970) evacuations from simulated plane wrecks

provide noteworthy data. These investigators learned, by analyzing questionnaires returned after the events, that a number of participants appeared to

believe the drills to be "the real thing." For these persons, at least, creating the impression of an actual life threat may have provided opportunities to

observe their own performance under actual conditions. It may be useful to test

whether these individuals are better prepared during some future emergency than are those who believed the drill to be an artificial exercise.

The paucity of research on participants' attitudes toward fire exit drills, and on the need to accomodate training to specific occupancies makes it difficult

to evaluate the strengths and weaknesses of individual studies at present.

Several investigators have suggested hypotheses regarding these issues, but

these remain to be evaluated. Specific directions for further research on pre-emergency training and preparation are discussed in Section 2,4,

2.4 SUMMARY OF GAPS IN THE TECHNICAL LITERATURE

2,4.1 Research on the Prediction of Occupants' Responses During Real Fires

Contrasting opinions appear to have emerged concerning the assumptions that

so-called panic behavior is a clear and constant threat, and that the danger of

panic can be minimized through effective pre-emergency training. Although

experimental data exist which support these assumptions, a growing body of evidence from post-incident fire investigations suggests they are not well founded.

Several important Issues, however, have not been adequately treated in either

the experimental or survey literature; (1) adoption of a standard definition

of panic; (2) identification of environmental and situational cues and stimuli

which affect the likelihood of panic (3) identification of perceptual and cognitive processes which lead to panic (e.g. time and distance-to-threat perception); (4) understanding the processes by which leadership and the channeling

of tasks and responsibilities reduces the likelihood of panic; (5) specification of the relationship between pre-emergency training and the occurrence of

panic; (6) specification of the relationship between the likelihood of panic

and the nature of the occupancy.

18
2.4.2 Research on the Transfer of Training

Assumptions that behavior learned during drills transfers to actual fire

situations remain to be empirically tested. While this problem presents complex methodological difficulties (e.g., neither trained nor untrained subjects can be randomly assigned to buildings which are later purposefully burned) , the use of rigorous drill evaluation methods and the standardization of training

procedures (as noted by Rivers and Bickman, 1979) may provide elementary controls which improve the reliability and validity of data from post-incident

investigations. Carefully designed field experiments, involving appropriate

safeguards for human participants, may ultimately be required to determine the

extent to which transfer of emergency training occurs. Pauls’ (1974) observations of evacuation drills in high-rise buildings, in which a number of participants believed actual emergencies were in progress, provide a useful model

for the design of such experiments.

2.4.3 Research on Occupants’ Attitudes Toward Exit Drills

The objectives of future research on the role of occupants’ attitudes will be

to: (1) determine correlations between attitudes toward drill participation,

performance during drills, and in rare cases, performance during actual (or

least perceived) emergencies; (2) determine ways by which adaptive behavior

patterns can be effected through attitude change. Attitudes toward the value

of pre-emergency training are complex phenomena, partly because they result

from interactions between a person’s history of experiences, physical capabilities, emotional and motivational predispositions, and personality makeup. For

example, while a healthy adult who has never experienced a building fire may

consider exit drills to be necessary and important, this person may be distressed to find other people joking and taking drills less seriously. A handicapped person working in a high-rise office building however, may view serious

participation by all during an exit drill as the difference between life and

death in the event of a real fire. Unfortunately, the psychological literature

on the relationship between attitudes and behavior, and on the potential for

effecting behavior change through attitude change, provides no sound basis for

specific conclusions in the area of life safety.

2.4.4 Research on the Accommodation of Training Programs to Specific Occupancy

Requirements

Assumptions suggesting that exit drills and training programs be designed to

recognize differences between various occupancies may be relatively easy to

test empirically. For example, studies modeled after Pauls’ drill observations

and Hertz et al’s. analysis of training methods could be extended to permit

analytical comparisons between building types, modes of occupancy and types of

organizational structure, after various training procedures have been introduced.

2 . 5 SUMMARY

Behavioral assumptions underlying Code provisions affecting pre-emergency

training and preparation may be evaluated by reference to psychological models

of learning, experimental data reported in the psychological literature, and

19
the growing body of evidence from post-incident fire investigations. To date,

experimental and post-incident investigations provide mixed conclusions con- cerning the supportabllity of these assumptions. Moreover, available evidence

does not often permit direct inferences to be drawn between research findings

and the specific issues implied by code provisions. Future modifications to

provisions affecting pre-emergency training appear to require additional

research on the role of training and its relation to emergency behavior.

20
3. PROVISIONS AFFECTING THE PERCEPTION OF THE EMERGENCY ENVIRONMENT AND THE

RECOGNITION OF EGRESS FACILITIES

3.1 APPLICABLE CODE PROVISIONS

5-2. 1.1. 1.2 Every door and every principal entrance which is required to serve

as an exit shall be so designed and constructed that the way of exit travel is

obvious and direct. Windows which because of their physical configuration or design and the materials used in their construction could be mistaken for doors

shall be made inaccessible to the occupants by barriers or railings conforming

to the requirements of 5-2. 2. 3.

5-5. 2. 2 Ways of exit access and the doors to exits to which they lead shall be

so designed and arranged as to be clearly recognizable. Hangings or draperies

shall not be placed over exit doors or otherwise so located as to conceal or obscure any exit. Mirrors shall not be placed on exit doors. Mirrors shall

not be placed in or adjacent to any exit in such a manner as to confuse the

direction of exit.

5-8. 1.3 The floor of means of egress shall be illuminated at all points

Including angles and Intersections of corridors and passageways, stairways,

landings of stairs, and exit doors to values of not less than 1.0 foot-candle

measured at the floor.

5-9. 1.2 Where maintenance of illumination depends upon changing from one energy source to another, there shall be no appreciable interruption of illumination during the changeover. Where emergency lighting is provided by a prime mover-operated electric generator, a delay of not more than 10 seconds

shall be permitted.

5-10. 1.2 Access to exits shall be marked by readily visible signs in all cases where the exit or way to reach it is not immediately visible to the occupants,

and in any case where required by the applicable provisions of Chapters 8

through 16 for individual occupancies.

5-10.1 .

Every required sign designating an exit or way of exit access shall

be so located and of such size, distinctive color, and design as to be readily

visible and shall provide contrast with decorations. Interior finish, or other

signs. No decorations, furnishings, or equipment which impair visibility of an exit sign shall be permitted, nor shall there be any brightly illuminated sign

(for other than exit purposes), display, or object in or near the line of

vision to the required exit sign of such a character as to so detract attention

from the exit sign.

5-10.3 Illumination of Signs. Every sign shall be suitably illuminated by a reliable light source giving a value of not less than 5 foot-candles on the

illuminated surface. Such illumination shall be continuous as required under

the provisions of Section 5-8, Illumination of Means of Egress, and where

emergency lighting facilities are required, exit signs shall be Illuminated

from the same source.

21
5-10»4. 1 .

A sign reading "EXIT," or similar designation, with an arrow

indicating the direction, shall be placed in every location where the direction

of travel to reach the nearest exit is not immediately apparent.

5-10 .4.1.2 Escalators, Moving Walks. A sign complying with 5-10.2 indicating

the direction of the nearest approved exit shall be placed at the point of

entrance to any escalator or moving walk that is not in a means of egress.

5-

10.4.2.1 Any door, passage, or stairway which is neither an exit nor a way

of exit access, and which is so located or arranged as to be likely to be mistaken for an exit shall be identified by a sign reading "NOT AN EXIT" or simldesignatlon or shall be identified by a sign indicating its actual character,

such as "TO BASEMENT," "STOREROOM," "LINEN CLOSET" or the like.

6-

3 .4 .

Audible alarm indicating devices shall be of such character and so distributed to be effectively heard above the maximxim noise level obtained

under normal conditions of occupancy.

6-3 .4 .2 Audible alarm indication shall produce signals which are distinctive

from audible signaling indicating devices used for other purposes in the same area.

6-3. 4.

Audible fire alarm devices as required by Chapters 8 through 16 other

than voice communication shall be used only for fire alarm system purposes.

6-3 .4 .4 Visual alarm indicating devices may be used in lieu of audible devices,

where permitted by Chapters 8 through 16.

6-3. 4.

Where a protective signaling system is required for purpose of

evacuation, it shall be so installed as to provide effective warning of fire

in any part of the building.

Exception: Where a building is divided by (1) fire walls into separate fire

sections or (2) by other means with adequate safeguards against the spread of

fire or smoke from one section to another, each section may be considered a separate building

11-3.2. 10.

Any apartment building with 26 or more living units shall have

emergency lighting in accordance with 5-9.

3.2 UNDERLYING BEHAVIORAL ASSUMPTIONS

3.2.1 Assumptions Relating to the Effect of Door and Window Design Upon

Egress Route Perception

(1) Occupants' perceptions of the obviousness and directness of the way of

exit travel may be influenced by the design of doors and entrances; the design

of these elements may affect egress time (5-2. 1 . 1 . 1 . 2)

22
(2) While seeking, identifying, or using an egress way, occupants may mistake

some Improperly designed windows for doors, and thereby delay egress

(5-2. 1.1. 1.2).

(3) Occupants' perception of proper egress route elements can be enhanced by

providing physical barriers to windows when these are not elements of exit ways.

Preventing the use of incorrect building elements during fires increases the

likelihood that egress ways will be quickly recognized and effectively used

(5-2. 1.1. 1.2).

(4) To facilitate rapid perception and recognition of egress facilities,

occupants require unobscured visual access to ways of exit access. Mirrors or wall hangings on, over, or adjacent to doors leading to means of egress may

obscure the means of egress and/or otherwise confuse occupants, and thereby

lead to excessive evacuation time (5-5. 2. 2).

3.2.2 Assumptions Relating to the Affect of Illumination Level Upon Egress

Route Identification

(1) Escaping occupants require the uniform illumination of egress way floor

surfaces. One foot-candle, measured at the floor, is sufficient for emergency

egress (5-8. 1.3).

(2) Occupants' recognition of egress facilities requires the continuous

illumination of various architectural and safety elements. Delays in the

actuation of emergency lighting facilities greater than 10 seconds may reduce

egress flow and jeopardize safe pedestrian movement (5-9, 1,2).

(3) In multifamily residential buildings which require occupants to negotiate

corridors en route to exits (as distinct from buildings which permit all occupants to exit directly to the outside), emergency lighting will facilitate

evacuation and reduce egress time (11-3.2.10.1).

3.2.3 Assumptions Relating to the Role of Visual Signage and Directional

Information in Egress Route Recognition and the Formation of Emergency

Egress Strategies

(1) During fire emergencies occupants require visual access to exits or egress

ways in order to achieve timely emergency egress. Where direct visual access

is not possible, directional signs will achieve the same result (5-10.1.2;

5-10.4.1.1; 5-10.4.1.2).

(2) Occupants will be able to see directional signs in spaces infiltrated by

smoke (5-10.1.2; 5-10.1.3).

(3) Occupants are more likely to see and use directional and exit marking signs

when such signs are properly illuminated (5-10.3).

(4) Signs denoting that a door or pathway does not lead to an exit are sufficient to keep occupants along intended egress ways, and are effective in

reducing overall egress time (5-10.4.2.1).

23
3.2.4 Assumptions Relating to the Ability of Audible and Visual Alarm Signals

to Effectively Alert Building Occupants to a Fire Threat

(1) Occupants will receive an unambiguous alert of an actual fire danger from

audible and visual alarm devices, and will take Immediate and effective action

upon hearing or seeing an alert signal (6-3.4. 1 through 6-3. 4. 5).

(2) Occupants receive sufficient information from alarm devices to enable them

to formulate effective response strategies in a timely manner (6-3.4. 1 through

6-3. 4. 5).

3.3 COMMENTARY

3.3.1 Problem

In some instances, the design and implementation of emergency egress facilities

for buildings may directly affect occupants* perceptions of the emergency

environment and their recognition and consequent use of egress facilities. In

general, provisions of the Code are intended to provide occupants with readily

Identifiable egress channels, facilitate rapid and accurate escape route determination, and confirm occupants’ overall awareness and understanding of a fire

emergency situation. These goals are based on the notion that the physical

features of buildings and of certain fire safety system components can be

designed to Influence stimulus and cue detection, situation definition, and

egress strategy formation in some positive manner, by building occupants.

Behavioral assumptions underlying Code provisions affecting occupants’

perception of the emergency environment and their recognition of egress facilities focus on four principal Issues: (1) the Impact of door and window design

on the perception of egress routes; (2) the effects of lighting level on the

recognition and perception of escape routes; (3) the degree to which occupants

depend upon visual signage and directional information while formating and

executing egress strategies; (4) the ability of visual and audible alert signals

to stimulate rapid situation definition and effective response strategy

formation.

Models of perception which provide useful insight to the role of fire safety

systems and building components in the emergency perception process are discussed below. Later in this chapter the models and supporting research

findings are considered in relation to behavioral assumptions believed to

underlie Code provisions affecting occupants’ perception of the emergency

environment and recognition of egress facilities.

3.3.2 Underlying Behavioral Models

Three models of perception offer perspectives on the process of egress

facility identification. These are perceptual field theory (also called

Gestalt Psychology), environmental Information processing theory, and signal

detection theory. Following a description of each model, its implication for one or more of the categories of assumptions enumerated in section 3.2 will

be presented.

24
Perhaps the most widely known of these is perceptual field theory, which

focuses upon the configuration or organization of sensory events (Dember and

Warm, 1979). According to perceptual field theory, individuals perceive real

world stimuli as patterns set within "fields," or backgrounds. Accordingly,

objects are always viewed against a background which may provide varying

degrees of contour, contrast and boundary to the figure. The nature of the

background is thought to determine the clarity and distinctiveness with which

a figure or object can be perceived. Figure-ground segregation, considered

to be one of the most primitive aspects of perceptual organization, is not

limited to visual phenomena but is applicable to other sensory modalities as well. In audition, for example, a melody may be perceived as a "figure"

against a "ground" of harmony.

Empirical research based upon perceptual field theory generally suggests that

physical objects, and the environment itself, can only be understood in terras of how they "appear" to the observer, rather than in terms of their actual

(or objective) physical composition. Recent research in retinal organization, for example suggests that after stimulation, sensory receptors in the

eye initiate an encoding process which requires some mediating mechanism to

decode the information before a response can be offered (Ratliff, 1972).

What is "perceived" is thus thought to be a S 3mthesis of sensory data as mediated by past experience, cognitive style, expectation and other factors.

The perceived image may not correspond precisely to the pattern of

environmental data encoded by retinal stimulation. For example, color is

frequently used for contrast in exit signage because of its attention-getting

capabilities (Dember and Warm, 1979). However, the traditional choice of red or green as opposed to other colors may lie less in the physical intensity of

these colors than in their apparent brightness. A green exit light fixture

is known to appear brighter than a blue one of equal physical intensity.

Perceptual field theory has implications for the first and third categories

of assumptions in section 3.2. The first category of human behavioral

assumptions concerns Code provisions for the design of doors and windows along

egress routes, and generally presupposes some relationship between door and

window design and egress route perception. Field theory suggests that color

and form are critical factors affecting figure-ground discrimination. In an office setting, for example, in which corridors are bounded by glazed panels

of equal size, shape and color, valuable escape time may be lost if doorways

(which may or may not lead to a means of egress) consist of panels equivalent

to fixed wall panels. Similarly, doors which reflect the color, texture or design of surrounding wall surfaces may also be difficult to discern quickly.

These Instances point to the need to make elements of egress routes visually

distinct from nonegress elements.

The third category of assumptions concerns Code provisions for signage and

directional information. In general, behavioral assumptions underlying these

provisions hold that safe and rapid evacuation from public occupancy buildings

depends in some way upon the proper use of directional information displayed

on signs. The Importance of contrast and contour to easy and rapid information perception is considered by field theory. To maximize the effectiveness

25
of egress directional signs, accordingly, these signs must be designed and

located so that Information lettered on them is clearly distinguishable from

background surfaces under various lighting conditions, and so that entire signs are clearly distinguishable from walls or other surfaces to which they are applied. Contrast and contour in visual Imagery is perhaps even more critical

in connection with pictographic , or symbolic directional signs now under con- sideration by the NFPA and other standards writing bodies (see Collins and

Lerner, 1980).

Having its basis in perceptual field theory, the environmental information

processing theory of perception suggests a mechanism which processes stimulus

input by means of sequences of operations occurring in stages. These stages

involve the encoding, storage, decoding and translation of information from the

environment. But while field theory focuses upon the perception of the environment by passive individuals, environmental information processing theory suggests that observers be viewed as active participants in settings (Ittelson,

et al., 1974). The perceptual exploration of a setting by any person uses all

of the sensory systems through which the environment and the individual transact.

Frequently, environmental settings provide far more Information than can possibly be processed by a given individual on a particular occasion. Such con- ditions of "Information overload" have been shown to produce increased levels

of stress and of maladaptive behavior. To deal with Information overload, the

individual uses criteria in order to select from available information. These

selection criteria are determined by the person’s own goals, expectations, and

needs may be affected by the individual's beliefs about the probabilities of

various events and of their outcomes.

When cues from the environment contradict a person's expectations and beliefs,

the individual often must formulate some "best bet" response (Brunswlk, 1956).

For example, a brief fire in the World Trade Center in New York City produced

smoke which was carried through the building's air-handling system. Although

the fire was extinguished almost Immediately and the public address system

properly directed occupants to remain in place, the sight of smoke appears to

have caused many occupants to Ignore the verbal announcement. As a result,

floors 9 through 22 were evacuated (Glass and Rubin, 1979). In this case, one stimulus (the verbal message) contradicted another, perceptually clearer source of information (seeing actual smoke). In the absence of less ambiguous

instructions, and in view of the information actually available (the smoke

itself), the "best bet" response appears to have been to evacuate the affected

floors. Thus, perception seems to function as an integral element of the

decisionmaking process by regulating the selection of information from the

environment thereby reducing the degree of uncertainty with which an individual

negotiates a given setting.

Environmental information processing theory has implications for the second,

third, and fourth categories of assumptions in section 3.2.

The second category of assumptions concerns Code provisions addressing the level

of egress route illumination. According to environmental information processing

theory, the selection of environmental data for subsequent decisionmaking is

26
a conscious task which not only depends upon the nature of the cues themselves

but also depends on the needs, goals, expectations and previous experiences of

the participant. For example, it is quite common for an individual to feel

uneasy upon entering a darkened stairway or corridor. It is not necessary for

the person to have actually had the experience of tripping in the dark, or of

being "mugged" in the past; most people have become well aware of such potential hazards through learning of other individuals* experiences. Accordingly,

people sufficiently uneasy about entering dark passageways may simply not use

them, until or unless the prevailing life threat is judged to be the more serious risk.

The third category of assumptions concerns Code provisions for signage and

directional Information. Environmental information processing theory suggests

that individuals consciously select information from the environment in accor- dance with their unique goals and expectations. Thus, to the extent that

directional signs are identifiable, legible, unambiguous, and consistent with

occupants* expectations. Information contained on them will be effectively

Incorporated within Individuals* egress strategies. Ambiguous or inconsistent

Information may, however, also be assimilated, and it may result in inappropriate or ineffective egress movement. In addition to occupants* goals, expectations and previous experiences, stress has also been found to affect the rate

of response to information provided by signs. Smillle (1978), for example,

found that response times were faster for pictographic signs (e.g., shapes and

figures) than for verbal signals when stress was introduced as a variable.

This finding is clearly relevant to the fire emergency problem.

The fourth category of behavioral assumptions deals with Code provisions for

alarm signals. One problem is the potential for "competition" between alarm

signals and other features of the physical and social environments among which

an individual *s attention may be divided. Environmental information processing

theory provides some basis for understanding this phenomenon. This model posits

mechanisms which permit people to deal with a continual melange of potentially

redundant, ambiguous, conflicting or contradictory information. These mechanisms provide data necessary for the Interpretation of settings and events, and

to the formulation of action strategies. According to the environmental information processing model, individuals cope with Information overload by purposefully selecting those aspects of the environment which are judged to be relevant to their immediate goals, needs or expectations. Where environmental

Information is unambiguous and judged to be consistent with one*s expectations,

competition among various pieces of information will be relatively low and the

Individual is likely to attend to those environmental data most useful in

attaining Immediate objectives. Where environmental information is ambiguous or contradictory, however, it will be difficult for the individual to determine

which data are most relevant. Consequently, the person* s attention will be

distributed among the various data sources. In especially complex or ambiguous

settings, this division of attention is likely to result in reduced attention

to each information source.

While rapid egress is certainly an essential goal for building occupants during

a fire emergency, for example, it may well not be their only objective. Where

occupants must divide their attention among alarm signals or specific vocal

27
egress instructions and, say, other persons they perceive to be endangered,

perception of alarm signal or instruction content may be significantly diminished. Similarly, the competition between vocal instructions and the contradictory sight of actual smoke could result in these instructions being virtually ignored by many building occupants (as occurred in New York's World

Trade Center),

The theory of signal detection is a major recent innovation in thinking about

the way in which information is processed in psychophysical studies. These

studies have focused on the quantitative relations between changes in physical

stimulation and concomitant changes in reported aspects of sensory experience

(Dember and Warm, 1979). Early psychophysical research posited the concept of

"threshold", which requires that before a given stimulus can be perceived by an organism that stimulus must have attained a certain physical intensity. The

threshold notion implies two possible states: a detection state in which the

stimulus or signal is present and above the threshold Intensity, and a nondetection state in which the stimulus is either absent or below the threshold

Intensity, Signal detection theory diverges from this two-state notion. By

postulating a multistate approach, it entirely avoids the threshold concept.

According to the theory of signal detection, every perceptual event contains

some degree of Interference or "noise". This noise may emlnate from a number

of possible sources Including personal and environmental sources. The concept

of noise implies that the starting point for perception is a greater-than-zero

level of sensation, and that the signal to be detected must always be distinguished from the background noise. Signal detection, then, is a process

through which the stimulus of Interest can be reliably and repeatedly distinguished from the background stimuli, so long as the perceiver has the needed

sensory capacity. For signal detection to occur, it is believed that a criterion value for sensitivity to the signal of interest is set by the person.

This criterion value may vary depending upon how often the signal is expected

to occur, and on which behavior yields the greater "payoff": responding when

in fact only noise (in the form of irrelevant signals) is present or not

responding when in fact a true signal is presented against a background of

irrelevant noise. Thus, "payoff" is based upon the tradeoff of values: response

to a false alarm versus failure to respond to a true alarm.

An example of this phenomenon involves coded emergency communications

recommended for use in health care facilities. Over a long period of time, and

in an environment where vocal messages specifying Individuals' names are common

and frequent, staff members may find themselves primarily responsive to the

call of their own names. Hence, an Individual staff member may anticipate

calls paging that person by name, while treating other messages as background

noise. Yet the "payoff" in missing an encoded emergency alarm message such as "Nurse Blaze" or "Code Blue" represents a far more serious threat to life

safety than the misinterpretation of a non-emergency message and the inappropriate initiation of emergency procedures when there is in fact no fire

emergency (see Keating and Loftus, 1977). In this example, anticipation of a criterion signal (e.g., one's own name versus an encoded emergency signal) may

vary as a function of other factors. For instance, physicians who spend only

a few hours per day at a hospital may be considerably less likely to notice

encoded emergency messages than may full time nurses who have been specifically

28
trained in emergency procedures. Time of day, ambient temperature, fatigue and

personality have also been found to affect arousal in similar instances (Craig

and Colquhoun, 1975).

A somewhat related determinant of signal detection and the perception of

emergency conditions is the so-called "orienting response," a pattern of skeletal and biological changes which occurs upon the presentation of novel and

unexpected stimuli (e.g., "FIRE!"). Such stimuli disrupt ongoing activity and

prepare the individual to receive future related stimuli and to respond effectively (Sokolov, 1963). Recommendations concerning the use of a male voice for

certain portions of vocal emergency messages while using a female voice for

other portions (Loftus and Keating, 1974) is an apparent attempt to optimize

the likelihood of getting and maintaining occupants’ attention and producing

adaptive response patterns during various stages of fire emergencies.

Signal detection theory has implications for all four categories of assumptions

in section 3.2. Thus, with regard to the first category, which deals with the

effects of door and window design or egress route perception, signal detection

theory suggests that this need is most critical in situations where building

occupants are likely to be transient (and hence not familiar with the true

location of egress elements) , or where low levels of alertness may impair

occupants’ utilization of directional signs.

Another perspective on the illumination of egressways, the topic for the second

category of assumptions, is provided by signal detection theory. During fire

emergencies, most occupants of public occupancy buildings are likely to be more

vigilant, and function at increased levels of physiological arousal, than they

would during nonemergency periods. As a result. Individuals may adopt lower

visual thresholds to provide cues and stimuli necessary in the identification

or recognition of egress route elements. Hence, lower levels of illumination

may be sufficient to permit the rapid recognition or negotiation of environmental elements during a fire emergency than during periods of normal building

use, particularly in a public occupancy building where many individuals are only marginally familiar with the building’s layout and exit facilities. Thus,

vdiereas environmental information processing theory stresses the possibility

that the effect of variation in illumination level depends on individuals’

motivations, previous experience, and training, signal detection theory emphasizes maintaining Illumination levels above some sensory threshold.

Factors relating to the effective use of signage, an aspect of the third

category of assumptions, also may be explained by reference to signal detection

theory. According to this model, variability in cue detection results from

variation in both environmental and psychological parameters. The word "EXIT"

and an arrow presented on a directional sign may be thought of as visual signals which occur within visual "noise" produced by complex interior design, the

moving about of other occupants, or by such fire products as smoke. If the

information on signs can be made distinguishable from cues produced by competing environmental elements, there is a greater likelihood that signs will be

used effectively. Similarly, the manner in which building occupants anticipate

the availability of directional signage may affect the extent to which this

information is sought out from a visually complex (or "noisy") environment, the

29
threshold at which information displayed on signs will be discerned, and the

nature of resulting egress behavior patterns.

For example, an occupant who is unfamiliar with the arrangement of exits and

egress routes within a building may believe that in case of fire, "EXIT" signs

and directional arrows can be counted upon to ensure rapid egress. T^hether by

previous experience, training or cultural norm, the individual may specifically

anticipate that signs designating exits will display the term "EXIT," and hence

the person's threshold for perceiving this word will adjust to ensure the rapid

detection of such signs even in visually complex settings. While negotiating

an egress path, however, other signs marked "NO EXIT" or "NOT AN EXIT" may be

misinterpreted because of the Individual's greatly reduced threshold for the

term "EXIT" only. Under conditions of stress during which a person believes

there is extremely little time, such mistakes may occur because the individual

fails to take sufficient time to fully read and Interpret verbal signs, even though the additional time required may be considerably less than needed to

negotiate an incorrect path (i.e., a path produced by misinterpreting a sign).

As mentioned earlier, the use of graphic or S3nnbolic exit and directional

signage may be advantageous in such situations as fire emergencies, where

above-normal levels of stress can be anticipated (Smillie, 1978).

The final category of behavioral assumptions deals with Code provisions for

alarm signals. These assumptions concern the effectiveness of audible and

visual alarm signals in alerting building occupants to a fire threat, in

enabling occupants to correctly define the emergency situation, and in helping

occupants to rapidly formulate adaptive response strategies. The specific use- fulness of alarm stimuli are perhaps most simply explained by reference to

signal detection theory. If a visual or audible alarm is to effectively bring

forth a response, then this signal must be consistently and reliably differentiated with respect to other signals in the environment (i.e., noise) which may

vary considerably in substance and intensity over time. Because the purpose of

the alerting signal is to evoke within building occupants an orienting response

by communicating the occurrence of some adverse change in the environment, the

alarm signal must be dlscrlminable as well as detectable. A very loud, clanging, audible alarm in a building where false alarms are frequent, for example,

may fail to communicate the fact that an actual emergency is in progress.

In summary, perceptual field theory, environmental Information processing

theory, and signal detection theory present different but related views of

human perception. Each theory emphasizes the significance of the overall

context in which the perception of infonnatlon occurs. This context has been

called a field, an environmental setting, and background noise. Moreover, each

of these theories stresses the Importance of individual differences in perceptual organization, and the role of personality variables upon perceptual judgment. Human behavioral assumptions which underlie Code provisions affecting

occupants' perception of the emergency environment and their recognition of

egress facilities were discussed in relation to these general models of perception. One or more theoretical explanations for each of four categories of

assumptions were presented, and it was shown that while each model is useful,

no single model is capable of explaining all aspects of environmental perception during fire emergencies. The next section treats code provisions and

30
their underlying behavioral assumptions in view of data presented in the

technical literature on human behavior during fires and other stressful events.

3.3.3 Assessment of Behavioral Assumptions Based on the Technical Literature

Literature review. Assumptions enumerated in section 3.2.1 focus on the effect

of door and window design upon rapid recognition of egress routes and facilities. At the time of this writing, no technical data either supporting or refuting these assumptions were found. In general, however, the position held

by writers of the Code that doors should not be designed so as to "blend in"

with walls, and that windows should not be designed so as to be mistaken for

exit doors (note provision 5-5. 2. 2), agrees with psychological models and data

from other contexts. Mellnek (1975) recommend that designers avoid placing

mirrors or other reflective surfaces where they could mislead occupants regarding the direction of corridors and the location of exit doors. However, he

provided no data from cases alleging such confusion to have actually occurred.

In their analysis of selected provisions of the Code , Rivers and Bickman (1979)

call for future research on this topic. They emphasize the special problem of

egress route perception in the presence of smoke, and also argue that what is

obvious to alert and able-bodied individuals may appear quite differently to

fatigued or otherwise handicapped persons.

The Influence of illumination level upon the perception of egress ways is

addressed by assumptions enumerated in Section 3.2.2. In general, there is

currently a dearth of empirical knowledge about the quality of illumination

measured at floor level (provision 5-8. 1.3), and no data are now available to

confirm or refute the applicable Code provision. Rasbash (1975), in an experiment designed to evaluate visibility under various conditions, found that

where visibility was 10 meters (32.81 feet), 10 percent of all subjects could

not complete a way-finding task and instead returned to the starting location.

Where visibility was reduced to five meters (16.40 feet) 20 percent of all subjects returned. On the basis of these data, Rasbash suggested a requirement

that the minimum visibility during emergency evacuation be 10 meters. But he

did not convert this value to illumination level measured at the floor. In a study connducted by Horiuchl (1974), emergency floor Illumination of one lux

(0.1076 foot-candles) was compared with that under normal lighting conditions.

Only a small difference in occupants' walking velocity was found. Edmondo and

Macey (1968), on the basis of their studies of emergency lighting on board

U.S. Naval vessels, concluded that standard Navy handlanterns (providing an unspecified quantity of illumination) positioned two feet above the floor and

spaced six feet apart facilitated egress route detection by ship occupants.

Perhaps Jin, who studied illumination and visibility through smoke, expressed

the state-of-the-art most succinctly noting, "It has not been made clear yet

how much visibility is needed to escape from fire (in this case, through

smoke). But it is generally believed that visibility of 15 or 25 meters (49.20

to 122.00 feet) is necessary to escape from fires in such places as department

stores, underground shopping plazas, etc., crowded with people who are unfamiliar with the Interior of the building, while three to five meters (9.84 to

16.40 feet) is enough if escape routes are well known" (Jin, 1972a, p. 138).

Jin also provided tables showing comparative smoke densities for the visibility

31
distances expressed above. In addition to the problem of illumination level,

the question of whether delays in activating emergency lighting facilities

affect egress flow (e.g., the 10 second maximum delay permitted under provision

5-9. 1.2) finds no answer—definitive or suggestive—in the technical literature

currently available.

Jin (1972) considered illumination level in corridors as an independent variable

in his study of response time in a smoke-filled environment. In a later experiment, Jin (1976) found walking speed to be only slightly affected by variations

in corridor illumination. Psychophysical experiments designed to study lightdark adaptation have indicated that visual response is delayed when a person

moves from a lighted to a totally darkened setting (Brindley, 1970). But while

perception is slowed under such conditions in the laboratory, no documented

evidence was found by the present investigators relating perceptual decrement

to impaired movement by building occupants negotiating actual settings.

In Section 3.2.3 behavioral assumptions concerning the degree to which building

occupants depend upon visual signage and directional markers were presented.

Extremely few technical data are currently available indicating that directional signs are actually considered whether in formulating initial egress

strategies or used during an emergency evacuation. Although conclusions drawn

from experiments conducted by Horiuchi (1974), Jin (1971, 1972a, 1975) Garner

and Lowery (1976) all appear to imply that signage is used by evacuees, sign use has never itself been treated as an experimental variable by these investigators. In another experiment, however, Horicuchi (1978) found that the

visibility of stairs was the most Important factor in directing occupants to

stairs. Moreover, studies by Jin (1972b, 1976) and Tadahlsa (1975) on visibility through smoke, though not definitive regarding sign use, suggest that

persons who are familiar with a building and with routes to exits are less

likely to use directional signage.

A number of researchers have discussed the visibility of overhead directional

signs under smoke conditions. In research conducted by the Federal Aviation

Administration (Garner and Lowrey et al., 1976) several types of aircraft cabin

exit signs were evaluated under smoke conditions. These investigators con- cluded that increasing the luminosity of an overhead exit sign to compensate

for smoke conditions produces, at certain levels of smoke density, a diminishing return in brightness and only marginally increases visibility. Jin (1972b)

found that the visibility of exit signs varies with the density and composition

of the smoke. Bryan (1976) cited data from an earlier study conducted by Underwriters Laboratory (1972), noting that signs placed at a distance of 7.5 feet

(2.59 m) above the floor become obscured more quickly in smoke than do those

placed at distances of 5.0 feet (1.73 m) and 2.5 feet (0.86 m) above floor

level. Rivers and Bickman (1979) concur, noting that the placement of exit

signs near ceilings may be inappropriate under smoke conditions. This notion

is further supported by Edmondo and Macey (1968), who presented U.S. Navy data

suggesting that the optimal location for illuminated directional markers is not

more than 2.0 feet (0.61 m) above floor level.

The basic theme underlying behavioral assumptions discussed in this section is

that clearly visible Instructional and directional signs tend to reduce the

32
overall time required by occupants to evacuate a building during a fire

emergency. However, few empirical data are available to support this notion.

For example, Edmondo and Macey (1968) reported no significant difference in

transit time between experienced and Inexperienced Naval personnel when both

were provided directional markers. From a somewhat different perspective,

toxicological studies appear informative. Several studies have addressed the

affects of carbon monoxide (CO), usually produced in measurable quantities

during fires, upon sensory reaction time and behavior (Laties and Merigan,

1979). Although results of research on the visual effects of low levels of CO

remain controversial, blood saturation levels as low as 5-9 percent of carboxyhemoglobin (COHb) have been shown to significantly elevate the visual light

threshold (Stewart, 1976), Moreover, even a brief exposure to high levels of

CO may result in substantially elevated COHb saturation, producing a significant decrement in the psychomotor reaction to visual stimuli (Ramsey, 1973).

Hence, smoke conditions may not only have adverse affects on sign detection,

but they may Increase reaction time (and overall egress time) as well. These

findings underscore the need to further understand the role of smoke.

The source of illumination for egress directional signs has also been the

subject of research, Edmondo and Macey (1968), for example, found the standard

battery powered sealed-beam Naval handlantern to be an effective directional

marker, while Jin (1975) concluded that the xenon lamp best Illuminated signs

in smoke. The detection of exit signs under both smoke and clean-air conditions

and under different lighting conditions was studied experimentally by Underwriters’ Laboratory (1973), Data from this research indicated that signs illuminated by an electric lamp were detected and Interpreted more rapidly than

were "self-luminous" signs.

No data are currently available specifically Indicating whether or not fixed

directional arrows produce desired pedestrian movement patterns and reduce

egress time during building evacuations. Although directional arrows were not

treated as an experimental variable per se , findings by Edmondo and Macey do

suggest that directional markers have a positive effect on egress. Janda and

Volk (1934), in experiments designed to study the effectiveness of s 3rmbols on highway directional signs, found that symbols yielded shorter driver reaction

times than did verbal directional signs. Later research by Walker, Nicolay and

Stearns (1965) corroborate this finding. Moreover, Smith and Weir (1978) and

Lerner (1981) found that arrows of unconventional design tended to be more highly visible than were conventional arrow types.

No reference to the effectiveness of verbal "NO EXIT" signs in reducing egress

time was found in the technical literature. Recent studies conducted at the

National Bureau of Standards have, however, addressed the comprehensive of

plctographlc no-exit signs. For example, Collins and Pierman (1979) and

Collins and Lerner (1980) found that the no-exit pictograph proposed by the

International Standards Organization Technical Committee 21 was judged incorrectly as meaning "EXIT" by some 70 percent of all subjects participating in an experiment.

The effectiveness of visual and audible alarm devices to provide occupants

clear alert signals and sufficient information for egress strategy formation

33
is the subject of assumptions presented in Section 3.2.4. Although the Code

gives designers little guidance regarding the quality of alarm signals, application of the Code’s alarm provisions generally assumes fire alarm systems will

enable building occupants to initiate effective emergency egress behavior with

minimal delay. Almost without exception, however, the technical literature

contradicts this notion. Pauls studied egress behavior during exit drills in

high-rise office buildings in Canada (Pauls, 1971, 1974, 1979). He noted that

in several Instances public address systems were used by an excited announcer

providing occupants with ambiguous information. On the basis of his observations, Pauls argued that a simple alarm device can confuse occupants as often

as it effectively informs them, and that even automated public address systems

utilizing prerecorded announcements may annoy and confuse occupants. Moreover,

Pauls suggested that the long-term performance capabilities of prerecorded

vocal alerting systems has not been adequately addressed, even during the

pioneering research on these systems conducted by Loftus and Keating (1974) and

Groner, Keating and Loftus (1978).

A number of investigators have reported on the problem of alarm credibility.

Breaux, Canter and Sime (1976), for example, concurs with Pauls (see above); he

suggests that alarm signals often have low credibility for building occupants

(i.e., are not regarded as signalling a real fire emergency, in contrast to a drill). Likewise, Baker and Mack (1960), who studied responses to unanticipated air raid signals, concluded that merely hearing a warning signal is

insufficient, in and of itself, to stimulate people to take immediate protective action. Haber (1977), in post-incident studies of fires in health care facilities, noted that alarm signals were sometimes disregarded as an indication that a fire is actually in progress. She described one case in which

nursing home residents and staff attributed an alarm signal to factors other

than fire, and another case in which the alarm was specifically Interpreted as signalling the onset of an exit drill. Confusion regarding the meaning of an alarm signal was also noted in a fire at a nursing facility at the National

Institutes of Health (Bryan and DiNenno, 1979b). Reporting findings from a similar incident, Bickman, Hertz, Edelman, and Rivers (1979) noted that some patients did not define the situation as an actual fire emergency until they

heard shouts of "FIRE." In view of such evidence. Rivers and Bickman (1979)

have suggested that the assumption that occupants will be effectively alerted

by means of standard audible alarm devices may not be true in all cases.

Visual alarm devices also are permitted by the Code (note provision 6-3. 4. 4).

According to Kravontka (1975), visual alarm systems usually consist of flashing

red lights working in unison with audible alarm "gongs." However, where cer- tain physiological factors are not taken into account, the health and safety

of occupants may be compromised by such systems. For example, Kravontka has

suggested that in deaf persons with epilepsy, seizures may be triggered by certain flashing rates (6-8 Hz). Ifowever, other studies question this effect

(Engle, 1974).

Regarding the sufficiency of information provided by audible and visual alarms,

Baird (1963) reported that responses elicited by manual alarm bells tended to

be ambiguous. Baker and Mack (1960) found in their research that most people

sought some sort of additional Information to validate the meaning of alarm

34
signals. Results from these studies suggest that when hearing an alarm signal,

building occupants construct their egress behavioral strategies on the basis of

available information, and, in order to reduce the degree of uncertainty under

which decisions are made, they actively seek out additional information (which

may come from simply observing the behavior of other occupants, from seeing

smoke, from persons in authority, etc.).

Several models of human behavior during fires (e.g., Bickman, Edelman, and

McDaniel, 1977) treat the sufficiency of Information provided by audible and

visual alarms as the "situation definition" stage of a fire event. Sufficient

Information, in this view, will unequivocally and unambiguously inform the occu- pant that a situation is, or is not, a fire emergency. To illustrate insufficient information, during the fire at New York's World Trade Center, the emer- gency communications system failed to provide information sufficiently effective to prevent occupant movement (the desirable objective in that case),

especially since smoke—an extremely powerful stimulus—was present (Glass and

Rubin, 1979). A somewhat related problem pointed out by Rivers and Bickman

(1979) is that audible alarm signals (e.g., gongs) may actually be too loud,

and thereby Interfere with necessary verbal communications among occupants

during emergencies. These investigators found in several nursing homes they

studied, that staff experienced considerable difficulty giving and receiving

verbal instructions due to the loud sound produced by alarm devices.

In support of the general assumption that alarm devices provide sufficient

information to effect rapid emergency egress, are occasional news media accounts

in which occupants specifically reported having seen or heard an alarm signal,

formulated an egress strategy, and successfully escaped. However, no research

has been reported evaluating the generallzability of these anecdotes in view of

such potentially confounding factors as occupants' familiarity with the buildings, previous training and experiences, and whether or not ambient social and

organizational environments supported the egress activity.

Overall, there is little technical evidence presently available which directly

supports or refutes behavioral assumptions believed to underlie Code provisions

governing the design of doors and windows, emergency illumination, and signage.

However, a growing body of evidence has begun to challenge assumptions that

alarm signals of the type currently specified by the Code are effective in

arousing egress behavior and that they provide sufficiently unambiguous

emergency Information.

Strengths and weaknesses of the technical literature . Behavioral assumptions

underlying Code provisions which affect door and window design emphasize the

Importance of these architectural elements in egress route perception by building occupants during fire emergencies. These assumptions are based primarily

on a consensus of professional opinion. The assumptions' credibility is reinforced by reference to various behavioral models and experimental data from

other contexts. However, no direct tests of the role of door and window design

have been conducted in connection with building evacuation behavior. Consequently, it is not currently possible to make definitive technical statements

regarding the validity of these design provisions on the basis of available

literature

35
Although the literature on illumination level and its effect on egress route

perception reports experimental data, shortcomings in the design of various

experiments render many of these results difficult to interpret and apply in

relation to the Code » For example, Rasbash (1975) found that within a certain

visibility range subjects returned to their starting locations rather than com- plete a way-finding task. He concluded that the ability of Individuals to com- plete the task depended upon the light-filtering qualities of smoke. He did

not discuss visibility impairment due to lacrimation or motor impairment

resulting from smoke inhalation as possible alternative explanations of such

results. In Horluchl's (1974) experiment, groups of subjects followed leaders,

and all subjects were familiar with the spatial layout under study. A reasonable hypothesis is that Horiuchi's finding (that evacuation speed under conditions of low-level emergency Illumination differed insignificantly from that

under normal lighting conditions) may not generalize to situations in which

leaders are not present or where transient occupants lack familiarity with

egress ways. Similarly, while Edmondo and Macey (1968) evaluated the effectiveness of various lighting sources and lighting fixture locations, they did

not specifically compare lighting configurations on the basis of illumination

quantity. Hence, their results are not directly applicable to validating present Code provisions regarding egress way illumination. Jin (1972a) and

Tadahisa (1975) have themselves indicated that data from their studies are not

as yet conclusive concerning minimum required emergency lighting levels.

The Code provision permitting a 10 second maximum delay in the activation of

emergency lighting is partially supported by the literature. Light-dark adaptation experiments suggest that the need for people to adapt from light to dark

(and then again to light) be minimized. However, because these data were collected under ideal laboratory conditions, they may not be directly applicable

to actual emergency settings in which the visual and other sense modalities are simultaneously stimulated, and in which visual perception is continually influenced by the individual’s motivations, experience, and by physiological

stressors

Current knowledge regarding the effectiveness of signs and visual directional

information also is based on limited experimental data. Perhaps the most

applicable data were collected by Edmondo and Macey (1968), who found that

directional markers assisted Naval personnel in way-finding, and that the

presence of these markers produced no significant difference in transit time

between experienced and less experienced sailors. A critical unanswered question, however, is whether the transit times were influenced at all by the pre- sence of the markers. That is, the research design failed to Include a comparison of two Important groups of inexperienced personnel: those performing an escape task with directional markers, and those performing the task without

markers. Moreover, since Naval personnel are likely to have undergone more extensive safety training than have most civilian building users. Inferences

from this study should be limited to those civilian situations in which occupants can be expected to be well trained and disciplined. In addition, toxicological experiments suggesting perceptual and cognitive decrement resulting

from carbon monoxide exposure are not yet sufficiently advanced to permit

inferences concerning the physiological effects of smoke upon sign effectiveness. Moreover, data from highway safety symbol studies are applicable only

36
to the degree that driving behavior transfers to pedestrian behavior

(especially during emergencies), itself an unanswered empirical question at

this time.

A brief digression into the nature of experimental design in fire research

seems useful at this point. Laboratory experimentation has traditionally

afforded researchers the greatest opportunities to obtain highly reliable data.

Many problems, however, are extremely complex, making laboratory experiments

difficult to design and experimental data difficult to apply. Where experiments

cannot be designed to accommodate (and control) the full range and complexity

of environmental factors, the data obtained will often lack external validity

(that is, data may not be generalizable across time frames, settings, or groups

of persons). When studies do not cover the range of factors accounting for a phenomenon, then external validity is threatened (Cook and Campbell 1976).

The study of human behavior in fire situations is an obvious case in point. For

example, experimental data on directional sign perception in a smoke simulation study may yield important psychophysical information about the effects of

variation in smoke density on visual perception. But where experimental subjects performed a visual task in relative safety, neither actually being exposed

to a life threat, nor believing their lives were otherwise endangered, the

potential effects of fear, stress, and other pertinent factors remain indeterminate. How then is the analyst to draw conclusions about sign perception and

its effect on behavior during actual fires? Clearly, researchers must not

expose human subjects to real or imagined life threats for experimental purposes. Consequently, researchers may never advance beyond the limits of validity attainable through simulations such as those reviewed above. Considerable

additional work may well be needed, however, merely to approach these limits.

In contrast to the quasi-experimental nature of the technical literature on llltjmlnatlon and sign perception, the literature on alarm effectiveness reports

primarily nonexperlmental post-incident case study data. Post-incident surveys

conducted after air raid drills, natural disasters, and fires in commercial,

educational, health care, and residential buildings provide a growing body of

evidence contradicting the general notion that alarm devices, once activated,

will yield unambiguous emergency Information. However, conclusions based on available post-incident investigations are by no means unequivocal. Consequently, specific recommendations concerning the value of present Code provisions for alarms are open to varying opinions. Nonetheless, the post-incident

case study is expected to remain a valuable source of field data necessary in

validating findings from laboratory simulations.

3.4 SUMMARY OF GAPS IN THE TECHNICAL LITERATURE

3.4.1 Research on the Effects of Door and Window Design

No data currently exist either supporting or refuting Code provisions governing

the design of doors and windows within egress ways, or dealing with assumptions

about occupants' behaviors with respect to these building elements. Questions

raised by these provisions and assumptions are nevertheless important ones requiring empirical Investigation. For example. Code provision 5-5. 2. 2 requires

37
that doors along egress paths not be designed so as to "blend in" with

surrounding walls or decor, on the assumption that doors which visually con- trast with surrounding surfaces are more likely to be quickly detected. However, the designer is provided no guidelines by which to determine the adequacy

of any given door/wall combination, nor any range or region of acceptability

for various design solutions. Similarly, while such additional factors as illumination and occupants’ visual capabilities are believed to Influence

individuals’ perception of egress route elements, the effects of variation in

these parameters upon door/wall contrast and door detection is not now known.

Most Important, no data currently exist describing the impact of door/wall

contrast variation and other design features upon egress time.

As a point of departure, laboratory experiments should be designed to evaluate

way-finding and exiting time performance for individuals of varying visual ability under different conditions of door design and door/wall contrast. Similar

experiments may also be designed to assess the extent to which doors are distinguishable from windows under various environmental conditions. Where proper

controls and safeguards are feasible, moreover, future experiments on door and

window perception should be designed to evaluate the effects of smoke (a laboratory procedure for optically simulating characteristics of smoke and its effects

on visibility is currently under development by Drs, Lerner and Collins of the

Center for Building Technology, NBS),

3, A, 2 Research on Illumination Required for Egress Route Identification

Findings from recent research on the role of illumination in emergency egress

are ambiguous and difficult to apply when evaluating Code provisions. Although

such factors as the presence of smoke and the degree of familiarity with egress

ways have been treated to a limited extent as variables by previous investigators, other important factors including stress, motivation, and visual acuity

have not. Although studies such as those conducted in Japan by Jin and Tashida

have been somewhat successful in simulating smoke conditions safely, the introduction of other stressful and more dangerous aspects of fires into experimental

settings may be too costly—especially in human terms—to be feasible. Future

research directed toward building a more reliable data base under "safe" laboratory conditions, and then validating these data against victims’ experiences

reported during post-incident case studies, appears the best approach to obtaining a quantitative basis for emergency illumination standards,

3,4,3 Research on Directional Signage

Previous research on directional signage has focused primarily on the visibility

of signs under varying conditions of illumination for people varying in their

familiarity with egress ways. In some instances, particularly in the Japanese

studies, effects of smoke were considered. Work in progress at the National

Bureau of Standards (Collins and Pierman, 1979; Collins and Lerner, 1980;

Lerner, 1981) is evaluating the extent to which various pictographlc s)rmbols are interpreted correctly under experimental conditions. In these studies,

subjects were specifically instructed to look at signs. Consequently, one cannot infer from the data that the mere presence of directional signs assures their detection and proper use in real buildings under emergency conditions.

38
The degree to which signs are in fact used by building occupants as an aid to

egress route perception, and the manner in which information derived from

signs is integrated with occupants* goals, experiences, and other environmental

information, have not been addressed to date. Future research on directional

signage (verbal, plctographic, or their combination) must be specifically

designed to assess the contribution of signs to way-finding performance and

escape time. Moreover, researchers must examine the influences of sign location, lettering and graphic design, and of variations in human visual acuity,

building familiarity, smoke density, and illumination, all of which may interact to reduce the positive and useful aspects of directional signs.

3.4.4 Research on Alarm Signals

The ability of alarm signals to alert building occupants to act effectively

during fire emergencies cannot readily be determined from the technical literature currently available. This is primarily due to the lack of data useful in

understanding the role of several key parameters, especially for nonlnstltutional public occupancies. Among the critical parameters are (1) mode of

signal or message delivery, (2) clarity of the alerting message and the extent

to which message content is consistent with occupants' perceptions, (3) emer- gency training, and the degree of consistency between previous training and

messages provided in any given building, (4) occupants' familiarity with

building layouts, and (5) occupants' physical and psychological characteristics.

Controlled field experiments in actual buildings during simulated exit drills,

such as iihose recommended by Stahl (1978b), may provide data useful in assessing

the role of such parameters in alarm effectiveness, and contribute to the

improvement of alarm system design. Similar experiments evaluating deaf individuals' responses to various types of visual alerting devices, and blind

persons* responses to audible alarms (especially in relation to other parameters

noted above) are also required,

3.5 SUMMARY

A number of human behavioral assumptions about the perception of emergency

environments and the recognition of egress facilities underlie various provisions of the Code . These assumptions were evaluated by reference to several

models of perception, to limited data from experiments on visibility, and to a small body of evidence from post-incident fire investigations. Taken as a whole, available data neither support nor refute behavioral assumptions about

occupants' emergency perceptions at a level technically sufficient to permit

a thorough evaluation of related Code provisions. To the extent that initial

emergency perceptions (as developed by alarm systems, for example) can be

linked to confusion resulting in increased evacuation time, however, research

on the role of emergency perception and its relation to egress behavior will

remain a necessary precursor to effective codes and standards.

39
4. PROVISIONS AFFECTING EGRESS STRATEGY FORMATION

4.1 APPLICABLE CODE PROVISIONS

5-2.2.2.12 Stairs and other exits shall be so arranged as to make clear the

direction of egress to the street. Exit stairs that continue beyond the floor

of discharge shall be interrupted at the floor of discharge by partitions,

doors, or other effective means.

5-2. 4. 1.2.1 Every fire section for which credit is allowed in connection with

a horizontal exit shall have in addition to the horizontal exit or exits at

least one stairway, doorway leading outside, or other standard exit. Any fire

section not having a stairway or doorway leading outside shall be considered

as part of an adjoining section with stairway.

5-4 .1.2 Exits shall be so located and exit access shall be so arranged that

exits are readily accessible at all times (see 5-5, 1,1), Where exits are not

immediately accessible from an open floor area, safe and continuous passageways

aisles, or corridors shall be maintained leading directly to every exit, and

shall be so arranged as to provide convenient access for each occupant to at

least 2 exits by separate ways of travel.

Exception: Where a single exit or limited dead ends are permitted by other

provisions of this Code,

5-5. 1.2 When more than one exit is required from a story, at least two of the

exits shall be remote from each other and so arranged and constructed as to

minimize any possibility that both may be blocked by any one fire or other

emergency condition.

4.2 UNDERLYING BEHAVIORAL ASSUMPTIONS

4.2.1 Assumptions Relating to Occupants' Capacity to Process Information About

the Location and Function of Egressways.

(1) Occupants generally expect stairs to discharge to the street, and lacking

information to the contrary, they might assume that exit discharge occurs at

the lowest level of the building (5-2.2.2.12).

(2) Building occupants understand the purpose of horizontal exits (5-2.4. 1.2.1)

(3) Routes leading from horizontal exits to stairways or other means of

reaching the outside are known to building occupants (5-2. 4.1. 2. 1)

4.2.2 Assumptions Relating to Occupants' Abilities to Determine the Safest and

Most Accessible Escape Route Under Potentially Stressful Conditions

(1) Where exits are not immediately accessible from an open floor area,

alternate routes to exits will be perceived and understood by occupants

(including occupants not otherwise familiar with the building), even under

conditions of stress posed by a fire emergency. The formation of egress

40
strategies in situations where exits are not immediately accessible will not

require so much time as to significantly increase occupants' exposure to fire

products or to other dangerous conditions (5-4,1, 2).

(2) When access to one exit is blocked by fire products, occupants will adjust

their egress strategies to seek an alternative egress route. Any additional

time required for these adjustments (and to traverse the newly selected route)

will not pose additional dangers to occupants (5-5, 1,2),

4,3 COMMENTARY

4.3.1 Problem

Several provisions of the Code are intended to ensure to a reasonable degree

that occupants will not be trapped because any single egress way is blocked

that the occupants will not become unnecessarily confused if exits are not

Immediately accessible, and that they will not "overshoot" the discharge point

when moving through stairways and other exits during fire emergencies. Each

of these conditions requires that occupants make decisions about egress routes

during various stages of the exiting event. Accordingly, Code provisions

affecting the availability of choices (e,g,, at a corridor intersection or stair landing) influence occupants' emergency egress strategy formation,

A broad-based assumption underlying these provisions appears to be that the

physical and social environments provide building occupants with Information

necessary for situation definition and strategy formation during a fire event.

More specifically, human behavioral assumptions underpinning choice related

design provisions seem to address two important concerns; (1) occupants' capacity to process Information about the location and function of egressways; and

(2) occupants' ability to determine the safest and most accessible escape route

under potentially stressful conditions.

Strategy formation leading to effective emergency egress behavior may be best

understood in terms of the cognitive processes—most specifically information

processing—which govern this activity. Models of information selection and

decisionmaking processes are considered below in relation to behavioral assumptions believed to underlie Code provisions affecting egress strategy formation,

4.3.2 Underlying Behavioral Models

In general, the environmental information processing model (Ittelson et al,,

1974) holds that sociophysical settings usually supply participants with more information about current and ongoing events than can be processed by any

individual. People obtain information about the current state of a setting

directly through personal experience with an actual event, and indirectly

through media accounts of the event and from conversations with other individuals who may or may not have had direct experience with the event. This

information is transferred to so-called "short term memory," where it is available for Immediate use, and may be transferred to "long term memory," to be

made available for future use. Long term memory refers to what an individual

41
"knows" but is not currently attend to (l.e., thinking about) at the moment,

A person can know and be capable of retrieving information about an enormous number of things (i.e., can have stored billions of items of information in

long term memory), but can retrieve, decode, and use only an extremely small

number of items at any one time.

People formulate decisions by comparing present information about an event

against information previously stored and available. This stored information

is continually affected by information gained from more recent experiences.

For example, a person who never experienced a building fire but who has

participated in numerous exit drills will have stored a "mental picture"

(structure of information) about fire events and effective behavior during such

events. This mental picture comprises the individual's expectations about fire

events. Should this person become involved in an actual fire which matches

these expectations, the Individual's mental picture of fires and of appropriate

responses to fires may not substantially change. Moreover, new information

that conforms to current expectations is assimilated so as to enrich the individual's knowledge of fires and of effective means of responding to them. If,

however, the person becomes involved in an actual fire which creates conditions

differing substantially from expectations based upon fire drills, the individual is likely to alter or adjust the mental picture of fire events and his or her opinions about the value of fire drills as well. The alteration may result

in a new conception of fire events and of proper responses to the events, which

might be an adapative solution to the extent that it matches future fire events,

or it may result in confusion about the nature of fire events and of the proper response to fire emergencies, which could prove to be dlsfunctional during

an actual fire emergency.

When negotiating an egress route, frequent decisions may be required which

necessitate the evaluation of current environmental Information, For example,

when receiving an alarm signal, hearing shouts of "fire", or seeing other occu- pants engage in behavior suggesting a fire drill or fire emergency, an individual will decide on an initial course of action. Proceeding along an egress

route, the individual can reach corridor intersections, doorways, stair landings, or other choice points, each requiring additional decisions to be made.

On what basis is an initial egress strategy formulated? How does this strategy

enable subsequent decisions to be made? What is the effect of subsequent strategy change upon egress time and success? What is the role of architectural

design and building configuration in egress strategy formation?

According to the environmental information processing model. Initial emergency

strategies result from "first cut" comparisons between Incoming information and

information retrieved from memory. Upon receiving an emergency alert, the person's initial strategy may simply be to "get out of the building," If the individual is familiar with the building's layout and safety features (i,e,, this

information is stored in long term memory) , enacting the initial strategy should

not require much additional Information, If the occupant lacks such familiarity,

or if the initial strategy is rendered ineffective because of unexpected events

(e,g,, a blocked exit or the presence of another person needing Immediate assistance), considerably more information may be required; Where is the fire?

42
Where are exits? Is enough time available to assist another person and still

assure one's own safety? Acting on the initial strategy, then, creates conditions that favor seeking specific information about the environment. Many

subsequent decisions may derive from the need to obtain necessary information,

and may not appear to lead directly to escape. For example, upon receiving an ambiguous alert from an audible gong, occupants might either continue their

routine activities or attempt to verify the existence or emergency conditions.

As a person proceeds through the fire event, more information about its nature

is obtained and stored in memory. This information stems from direct experience and indirectly from rumors, persons in authority, and (where available)

from public address messages. When a choice point concerning the egress route

is reached, information pertaining to the needed decision is compared with

information obtained and stored during the fire event. If the current situation could not have been predicted from earlier experiences (i.e., if the

Initial egress strategy cannot handle a new problem such as a blocked exit),

the individual might react adaptively by formulating a new strategy which

accommodates the current understanding of the situation. Alternatively, the

individual may react maladaptively by continuing to pursue the original

strategy, ignoring new information, and otherwise failing to deal rationally

with unanticipated changes in events.

As indicated earlier, the environmental information processing model generally

holds that physical settings provide more information than possibly can be processed by Individuals at any given time. Hence, the likelihood that a person

will respond adaptively to events requiring shifts in egress strategy may

depend upon whether the most Important, or attention-getting. Information is

easily detectable in an otherwise overloaded or "crowded" information field.

An important implication of this idea is that the architectural design and

layout of the building environment may themselves facilitate—or inhibit

information processing, decisionmaking, and strategy formation.

Clearly, then, successful egress strategy formation demands the ability to

select important information from an environment and to use this Information in

effective decisionmaking. Several models offer useful perspectives on these

issues. These Include Broadbent's "filter" model and Brunswik’s multiple cue probability model.

The selection of information from the environment is addressed by Broadbent's

(1971) "filter model," which compares the initial stages of Information processing (sensation and encoding) to an automatic railway switching system.

According to the filter model, various data are introduced via individual neural

channels which meet just prior to the encoding point in the brain. Here, one channel is permitted to continue emitting signals, while others are placed in a standby mode. In other words, a stop-gate or filter is posited, that protects

the encoding and processing mechanisms against Information overload. Criteria

for filtering information (i.e., opening and closing various input channels)

depend on the attention-getting properties of the information itself. These

properties Include the intensity, biological importance, and novelty of the

information (Miller and Mackle, 1980).

43
Another explanation of the function of this stop-gate involves the use of short

term memory. While Important Information is being encoded and processed, other

incoming data may be temporarily stored in a short term memory buffer (holding

area). The gate thus controls the flow of data from receptors to short term

memory and higher-order information processing centers in the brain. If the

information in the buffer goes unused for a period of time, it may decay (be

forgotten), or alternatively, it may be transferred to long term memory. An

example illustrating both the stop-gate and buffer concepts can be drawn from

the Arundel Park Hall fire. Post-incident interviews revealed that a great

many participants could not recall whether exit signs were illuminated or whether they were even present (Bryan, 1957). These signs were in fact both

present and illuminated, and clearly some occupants did use the signs during

egress. The filter model suggests, however, that sensory information concerning the presence and characteristics of exit signs was overriden by more obvious information (e.g., visual data from the fire itself) requiring rapid processing. Information about the exit signs was either filtered out and never processed at all, or it was encoded into a short-term memory buffer and even- tually decayed. In either case, this information was lost during the relatively short period between the fire event and the post-incident interviews.

Brunswik*s (1956) multiple cue probability model offers a somewhat different

perspective on Information selection. Brunswik held that information transmitted by the environment is always less than consistent and complete, that

there is usually more information available than can be processed, and that at

any time a person must make decisions on the basis of partial and sometimes

conflicting information. As a result, the individual selects information by

perceptually "sampling" the environment. The sampled data are encoded and

compared against previous knowledge, expectations, and needs, and although no single piece of information perfectly satisfies all requirements, some are judged to have a better probability of satisfying requirements. A decision

based on probabilistically weighted environmental Information is called a "best bet" by Brunswik. A simple example concerns the fire victim who finds

all stairways to be blocked by fire products. Several options are available

to this person, including: jumping from a window, riding-out the fire in place,

risking injury in attempting to use a stairway. The environment itself provides

little information about the likelihood of success or failure associated with

any one alternative, but the victim must weigh the subjective probability of

death or injury resulting from jumping against those associated with smoke inhalation and/or burning resulting from using a stair or remaining in the building.

Which strategy appears to the individual as offering the greatest likelihood of

success may well depend upon the person’s prior emergency training (e.g., "close

the door to your apartment and ride-out the fire"), exposure to media headlines

(e.g., "man dies attempting to jump to safety"), and the like.

Strategy formation, then, involves decisionmaking as well as information

selection. The conflict-vigilance model and various heuristics are useful in

explaining cognitive behavior under stressful conditions which may exist during

fire emergencies, and shall be discussed here briefly. The conflict-vigilance

model (Janis and Mann, 1977) offers a step-by-step explanation of decisionmaking

during a stressful event in terms of how people cope with stress. One coping

pattern, vigilance, results in thorough information search and an unprejudiced

44
assimilation of new information. Vigilance alone among the various coping

patterns discussed by Janis and Mann is held to result in effective

decisionmaking

The conflict-vigilance model views behavior as responses to a series of

questions which are posed during a decisionmaking task. Depending on how a person answers these questions, the coping behavior will be either adaptive

or maladaptive.

The first question concerns risk evaluation. When a person determines that

risks will be high if no protective or defensive actions are taken, then

arousal to the danger will occur and the individual will, for example, vigilantly seek escape routes and other options. If failure to initiate protective

actions is not expected to increase personal risk, then the likelihood of

arousal and of altering preceding behavior patterns will be quite low.

The second question concerns the effect of taking the most readily available

protective action in response to exposure to a risk. If the individual

believes that taking the most readily available protective action will result

in a reduction in risk, then the psychological state of arousal is likely to

subside and the individual is expected to Initiate protective actions in a routine fashion. However, the actual risk may well exceed the person's expectations, and the most readily available protective actions may not be the most

effective. Under such conditions, arousal will not diminish, and the individual may become preoccupied with finding a more effective escape route. For

example, a building occupant who is most familiar with travel routes used

daily in nonemergency Ingress and egress is likely, in the event of a fire, to

regard egress on these routes as an effective protective action. On evacuating

the building, the person could find that a portion of this route has been

rendered impassible. The occupant's level of arousal should Increase substantially, and alternative actions will be sought.

The third question in the series concerns whether it is realistic for a person

to expect to find a better alternative action. Information necessary to answer

this question can come from knowledge already acquired by an individual, or from

contact with other persons' experiences, from rumors, etc. Defensive avoidance

and the avoidance of environmental events which Increase anxiety are most likely

to occur when the Individual has little hope of finding a more effective alternative action. The occupant may purposefully "tune-out" life-threatening events,

may attempt to pass on decisionmaking obligations to other individuals in the

Immediate environment ("you decide, I just can't cope"), and may attempt to

perform less stressful actions despite knowledge that such actions are likely

to Increase risk. When an occupant believes it is realistic to expect to find

more effective alternatives, the individual is likely to Initiate a vigilant

search for these options.

The fourth and final question is the most crucial. It concerns the availability

of sufficient time for conducting searches and evaluating new information. If a fire victim believes available time is insufficient, "panic" (e.g., snap judgments; herd behavior) is more likely to occur. That is, levels of stress can become high enough to interfere with the perception, mediation, and processing

of information. As a consequence, effective decisionmaking seldom results.

45
However, when an occupant does perceive that sufficient time exists in which to

carry out the escape task, normal vigilant behavior is likely to continue and

yield effective coping patterns which result in successful escape.

A somewhat different decisionmaking strategy is posited based on optimization

models. These models emphasize the values that individuals place on alternative

course of actions and the subjective probabilities of success or failure of

these alternatives. Such models suggest that during fires occupants will tend

to choose those egress strategies that yield the highest payoff (that are optimal) for the individual. Payoffs are a joint function of the values and

probabilities for each alternative. Thus, a person is likely to choose the

alternative that offers the best balance between success likelihood and risk

of failure.

A special case of the optimization model is a decisionmaking strategy called

"satisficing" (Janis and Mann, 1977). Satisficing implies that people do not

necessarily choose the highest or best payoff. In some situations, because of

the complexity of the alternatives or the stresses on the individual, people

will not consider all the alternatives but only a subset they are able to handle. Under such circumstances, they are most likely to choose alternatives

they regard as workable or satisfying. Thus, if a person in a fire emergency

has as an ultimate objective staying alive, any course of action the person

believes will meet that objective will be adjudged as satisfactory. Time will

not be needed or spent seriously evaluating alternatives to determine the best

option, as is implied by optimization models of decisionmaking.

Another special case Involves elimination by aspects. This strategy treats

selection and decisionmaking as processes of elimination. For example, a building occupant may choose to eliminate one egress route because it has

been blocked by fire products, another because it has become blocked by other

escaping occupants, still another because of unfamiliarity, and so on. The

remaining alternative is chosen.

In summary, using current psychological models of human information processing

to analyze pertinent behavioral assumptions provides a useful, although some- what complex, framework for evaluating Code provisions affecting egress strategy formation. In the next sections of this chapter provisions and their asso- ciated behavioral assumptions are evaluated in relation to specific findings

reported in the technical literature.

4,3,3 Assessment of Behavioral Assumptions Based on the Technical Literature

Literature review. The assumptions presented in section 4.2.1 address the

capacity of occupants to rapidly and effectively process and use information

about the location and function of egressways. The literature review revealed

little substantive technical data directly relevant to this issue. Moreover,

although a number of time-based models of emergency behavior have appeared in

the literature (Bickman et al., 1977; Stahl, 1978a, 1979, 1980), only Stahl's

computer simulation model postulates specific mechanisms by which information

about exits and egress paths is applied to strategy formation and evaluation.

The review of pertinent technical literature which follows here covers the

46
state-of-the-art. Wood (1972), in a post-incident survey of more than 1,000

fires, found a significant positive relationship between familiarity with

particular means of escape and the actual use of these elements. Specifically,

Wood found that about 95 percent of those respondents who left buildings during

fires used the route by which they entered. However, Wood's research design

and findings permit no Inferences about how occupants' sought alternative exits

or formulated egress strategies.

Unlike Wood (1972), Weisman's (1980) study of way-finding in buildings under

nonemergency conditions concluded that occupants' prior familiarity with a building probably accounts for only a small portion of the variance in successful completion of a way-finding task. Rather, the simplicity or complexity of

the building's layout appeared to be the most Important variable in predicting

way-finding success. Weisman's findings suggest two interesting hypotheses:

(1) during fire emergencies, time spent formulating egress strategies is influenced by the complexity of a building's layout, and (2) a person's general

knowledge of a building, which may have accumulated over a long period of

nonemergency building usage, may include little information about emergency

exit location. Similarly, in Huriuchl's (1978) experimental investigation of

exit choice in a Japanese department store, exit visibility was an Important

variable in egress route choice. Huriuchi reported that the most Immediately

visible egressways (in this case stairwells) were the most commonly used by

experimental subjects.

Based on Weisman's and Huriuchl's studies, building layout complexity and

egressway visibility appear to be the most salient environmental cues affecting

escape strategy formulation. However, the available technical literature does

not address occupants' knowledge about emergency exit location and use, except

for institutional and other occupancies in which egress training programs have

been effected. In addition, any assumption that occupants understand the purpose of horizontal emergency exits has not as yet been emprlcially verified.

Assumptions in section 4.2.2 focus on occupants' ability to determine the

safest and most accessible escape routes during potentially stressful fire conditions. Again, fire research directly applicable to this issue is scarce. Wood's (1972) finding that occupants were more likely to Initiate Immediate

egress action even when escape routes were not clearly recognizable, for example, seems to illustrate one manifestation of psychological stress during fires.

Findings from research on environmental stressors other than fire and from

studies of natural disasters provide additional bases for evaluating pertinent

Code provisions and behavioral assumptions. Examples of this research are reviewed below.

Cohen (1978) postulated that in a stress-provoking environment, unique demands

are exerted on individuals' capacities to attend to environmental and social

stimuli. According to Cohen, the nature of the effect of these demands varies

with the intensity, predictability, and controllability of the stress-producing

agent. Recalling that human Information processing is analogous to a limited

channel information network, a person exposed to a stressor may be less able to

process task-relevant information because attention has shifted to the stressor

or its source. Thus, features of the physical and social environments which

47
are largely irrelevant to the task at hand compete with important and necessary

information for the individual’s attention. Since considerable effort may be

expended monitoring task-irrelevant input, the individual will process fewer

relevant stimuli, and this activity could result in overall performance

degradation.

For example, an occupant might attempt to return to a dangerous area in a burning building in order to retrieve a valued personal possession. The

attempt may be motivated by the anguish created by the anticipated loss of the

item or by the sense of embarrassment or guilt associated with having left the

object behind. These feelings may so dominate the individual that there is

insufficient consideration of the risks to be faced or the alternate strategies

which could be employed,

Saegert (1973, 1976) studied cognitive fatigue resulting from Information

overload. Cognitive fatigue often characterizes stress-producing situations.

Under these conditions, the amount of Information that can be effectively processed by the brain can be considerably reduced, and decreased perceptual and

cognitive efficiency have been noted. According to Saegert, overload may

result from an overabundance of stimulation, information, and decision. Stimulus overload implies the excessive stimulation of the human neural system.

Information overload results when the processing of environmental information

produces excessive emotional arousal. An example is the high anxiety of an acrophoblc individual confronting the use of an outside stair. Decision overload results from increases in the number of required decisions and responses

in a given situation, and is particularly applicable to the present investigation, Saegert (1976) suggests that as the response requirements Increase for an individual, the amount of useful feedback from each response tends to

decrease. Under such conditions, responses result from decisions made on the

basis of Incomplete or erroneous evaluations. When this leads to maladaptive

responses, elevated levels of psychological stress for the Individual are likely,

Saegert 's findings are applicable to the situation in which an escaping

occupant must formulate a complex egress strategy in a relatively short time.

The number of decisions or choices which this individual must make is directly

related to the complexity of spatial network to be traversed and to the person’s perception of the fire threat. In a complex spatial setting the number

of decisions likely to be required may be quite high, and the likelihood of

making incorrect decisions may be high as well. As more errors are made,

psychological stress increases, and the sources of this stress compete for the

individual’s attention. Degraded task performance in the form of excessively

time-consuming evacuation or failure to evacuate is a likely outcome of this

scenario

Best (1970) conducted way-finding experiments in public buildings and found

that the uncertainty with which occupants perceived a route correlated positively with the quantity of information individuals must process in order to

successfully negotiate that route to reach a predetermined location within a building. If complex routes require the person to process a greater quantity

of information than do simple routes, complex routes could induce stimulus

48
overload with the result that information processing and way-finding are degraded. With maladaptive responses more likely, stress could increase and

this in turn could result in a further degradation of information processing

and way-finding processes (Janis and Mann, 1977). Would familiarity with a building's layout facilitate successful way-finding? Weisman's (1980) wayfinding research indicates that even when a person intentionally searches for

a route, familiarity with the building layout does not predict successful wayfinding. As discussed in chapter 2.0 of the present report, in an emergency

situation, high arousal favors the performance of well- learned responses, such

as taking a familiar route. But it also interferes with new learning. The

complex layout of a building should not only be difficult to learn under high

arousal conditions, but it should further increase arousal. This analysis

suggests that in buildings with complex layouts, unless occupants are familiar

with fire emergency escape routes, the likelihood of maladaptive behavior or unsuccesful way-finding during a stress-producing fire emergency may be high.

Simon (1967) and Welck (1970) view stress as an interrupter of ongoing behavior

Easterbrook (1959) argues that high levels of emotional arousal are most disrup

tlve of those cognitive tasks requiring attention to large numbers of cues or stimuli. Kelley et al . (1965) presented experimental data describing the

effects of potential entrapment. Holsti (1970) reported experimental data

which suggest that decreasing the time available for decisionmaking results

in Increased error rates. When stress levels were high, relatively few individuals appear to make full use of available information necessary in formulating

an effective course of action.

Field data from natural disasters are reviewed by Janis (1977), who concludes

that perceptions of tlme-to-escape comprise the essential inducer of stress

(possible mechanisms underlying this phenomenon were considered in section

2.3.3 of the current report). Dynes and Quarantelli (1967), who studied

natural disasters, reported that people devote considerable effort and attention to Information gathering. However, a study of combat experience by Glass

(1968) reveals that under life-threatening conditions persons capable of initiating prompt action on their own, are clearly in the minority.

This section has Illustrated ways in which emotional characteristics of fire

situations may Influence important cognitive processes such as decisionmaking.

Consideration also must be given to the role of physiological stressors com- monly found in the fire environment. Chief among these is carbon monoxide (CO)

Chapter 3.0 of the present investigation notes that at certain levels of con- centration within the blood CO has been found to have a detrimental effect upon

sensory threshold and reaction time, especially after initial low-level exposure. Research on CO toxicity in rats by Petajan (1976) found that after 15

minutes of increasing exposure to CO (up to 45.9 percent COHb) , the animals

failed to perform appropriately in a simple shock-avoidance test. Petajan

argued that the failure of the rats to perform adaptively could not be attributed to any physical breakdown in sensory or motor systems, but rather was based upon the animals' inability to process and integrate new information.

Petajan made no attempt to draw Inferences from his findings to the behavior of

human beings. In another animal experiment. Carter, Schultz, Lizotte, Harris,

and Pedersen (1973) also noted that CO affected performance on discrimination

tasks

49
Studies on the effect of CO on human cognitive function report conflicting

findings. Much of this research has addressed performance on time perception

tasks (e.g., Beard and Wertheim, 1967, 1969; Otto, Benigus, and Prak, 1979;

Stewart, Newton, Hasko, and Peterson, 1973), arithmetic problem solving (e.g.,

Schulte, 1963), vigilance (e.g., Groll-Knapp, Wagner, Hauck, and Haider, 1972;

Fodor and Winneke, 1972; Horvath, Dahms and O'Hanlon, 1971), and driving performance (e.g., Forbes, Dill, DeSilva, and Van Deventer, 1973; Ray and Rockwell,

1970; Wright, Randell and Shepard, 1973; McFarland, 1973). Although a number

of investigators report decrements in cognitive behavior at low COHb saturation

levels, others find no such effect. Stewart (1976) concluded that COHb saturations must be above 5 percent to function as a stressor or as an inhibitor of

cognitive processes. He also noted that partial loss of memory may be the

most obvious effect of CO exposure.

Thus there is little technical evidence available which directly supports or refutes behavorial assumptions underlying Code provisions on (1) the ability of

occupants to process, store, and retrieve information about the location and

function of exits during fires, and on (2) the capacity of occupants to choose

the safest and most accessible escape route under stressful conditions. However, studies in the areas of information processing, environment psychology,

natural disasters, and toxicology offer substantial but indirect support for

these assumptions and provisions. The remainder of section 4.3.3 reviews the

strengths and weaknesses of the available technical literature, and comments

upon the extent to which cited studies are useful for evaluating provisions

of the Code .

Strengths and weaknesses of the technical literature . Behavioral assumptions

concerning the capacity of building occupants to select, store, and retrieve

Information about the location and function of exit facilities involve the

notion that occupants consciously familiarize themselves with a building's

egress routes and exits prior to the onset of an actual emergency event. None

of the models of fire event dynamics nor the field studies discussed above

specifically address the validity of this notion. As noted earlier. Wood

(1972) found that most occupants left buildings via the same means by which

they entered. This suggests that people do not generally search for new

routes or egress strategies. However, certain aspects of Wood's research

design make his finding difficult to interpret in the present context. For

example. Wood emphasized single family and other relatively small residential

structures. It is likely that occupants were Inordinately familiar with these

buildings, and with alternate movement routes within them. Wood's research

design does not allow an analyst to determine whether the use of a single

route for entry and emergency egress resulted (1) from the habitual use of

this route during years of occupancy, (2) from conscious decisionmaking by

occupants during actual fire events, or (3) because small buildings (e.g.,

single family residences) offer relatively few entry and exit options.

Horiuchi (1978) suggested on the basis of his experimental data that when

subjects were completely unfamiliar with the experimental setting (ensured

during his study by conducting subjects blindfolded to the starting position in

a building) , the visibility of egress routes was an essential factor in egress

strategy formation. However, Horiuchi 's subjects were firefighters; they are

50
expected to be more sensitive to problems of emergency escape, and to the

location of means of egress. Hence, it seems inappropriate to generalize these

findings to lay populations. The usefulness of Horiuchi's data are further

clouded because his subjects took part in several experimental tasks in the same building. Their possibly increasing familiarity with the building’s layout over time could have affected their performance on later tasks. The effects

of familiarity were not controlled in the research design.

The psychological literature on decisionmaking under stress deals only

indirectly with behavioral assumptions concerning safe and successful egress

route selection during fire emergencies. Moreover, treatments of this problem

by environmental psychologists tend to be theoretical rather than empirical.

To date, there have been no field studies in natural settings as stressful and

as complex as the fire environment. As a result, inferences from environmental

research on way-finding (Bronzaft, Dobrow, and O' Hanlon, 1976; Sadalla and

Magel, 1980; Welsman, 1980) about human behavior under actual fire conditions

should be made with caution. On the basis of Best's (1970) argument, that the

degree of ambiguity and uncertainty of (and therefore the amount of information

obtained from) building circulation routes affects the likelihood of decisionmaking errors, it seems reasonable that the fewer decisions that must be made

about direction and route, the higher the probability that occupants will make

effective way-finding judgments.

The studies by Kelley et al. (1965), Janis (1977), Easterbrook (1959), and

Simon (1967) reinforce the notion that stressors originating in the physical

environment impact can negatively (e.g,, interrupt) decisionmaking and other

pertinent cognitive processes. At present, however, it is not clear how such

stressors prevent or inhibit the selection of effective egress routes during

fire emergencies. It is clear, by comparison, that they cause decisionmaking

to consume more time. The emphasis of Janis (1977), Host! (1970), and Glass

(1968) on decisionmaking under stress created by time constraints reinforces

the importance of time, (more specifically the situational deterioration which

may occur over time), as a stress-producing agent. Although this experimental

work offers important hypotheses about behavior during fires, inferences from

currently available data to further building code development do not now seem warranted

Definitive inferences to humans from toxicological studies involving laboratory

animals are not currently recommended. Petajan (1976) has cautioned against

applying results from these animal experiments to human behavior under naturalistic conditions. Moreover, the overall lack of consistency in currently

available human CO studies weakens inferences and conclusions which might

otherwise be generalized from this line of research.

Neither standard cognitive tasks nor well-controlled experimental procedures

available which reflect the complexities of actual building fire events are currently. Until these have been carefully designed and validated there shall

remain a lack of data illuminating processes by which building occupants

develop egress strategies and select egress routes, especially under conditions

typified by higher than normal levels of physiological and psychological stress.

51
4.4 SUMMARY OF GAPS IN THE TECHNICAL LITERATURE

At present few data clearly and directly support or refute Code provisions

reflecting assumptions about occupants’ information processing capabilities in

connection with emergency escape. The complexity of human cognitive functions,

particularly during stressful and potentially life-threatening events, has

understandably discouraged fire researchers from studlng cognitive behavior.

Moreover, many investigators seem reluctant to consider the cognitive and

motor behavior of individuals during fire emergencies, believing that studies

of non-emergency group behavior, crowd flow, and gross patterns of pedestrian

movement have the greatest payoff as far as building design regulations are concerned (Pauls, 1974; Seeger and John, 1980; Francis and Saunders, 1979).

However, research in cognitive psychology and other areas discussed earlier

in this chapter suggest a role for information selection and decisionmaking

processes within any time-based model of emergency escape. Hence, further

study of cognitive processes in the emergency context is indicated.

For example, it may be possible and relatively easy to measure the speed with

which certain stimuli can be sensed and perceived. Similarly, motor response

time can also be measured. However, the intervening processes by which perceived environmental Information is Incorporated into decisions and action

strategies is currently difficult to quantify and measure. This is especially

true in complex and relatively ambiguous and stressful emergency environments

in which an individual switches between numerous decisions and strategies—both

consciously and subconsciously—at various points during the escape task. Thus,

Caravaty and Haviland’s (1967) equation for estimating life safety during fires,

^ < 1 ( 1 ) ^c

suggests that an individual will reach a safe refuge if and only if the time

required for escape, tg, is equal to or less than the time required for the

toxic environment to reach a critical or untenable state, tg. In many cases

this equation may be difficult to apply accurately. The problem becomes more

obvious when equation (1) is expanded to the form,

<^a +"s

+ + ti + t^

< 1* ( 2 )

where

^s

tt

time required

time required

time required

threat

for sensation of a stimulus from the fire environment,

to become aware of this sensation,

to become aware of the sensation as a potential life

* Based on personal communications with Harold E, Nelson and Bernard M. Levin

of the Center for Fire Research, National Bureau of Standards, between 1977

and 1980.

52
tg = time required to evaluate the quality and extent of the life threat

t£ = time required to initiate effective actions,

t^ = time required to follow-through and complete actions leading to

safety.

Research reported in this chapter suggests that the factors tj- and tg are not

now capable of being estimated with any degree of accuracy. This chapter has

also suggested, moreover, that the processes of egress strategy formation and

resulting escape behaviors may not follow the linear-additive model implied by

equation (2). Rather, some factors may be more heavily weighted than others,

and some elements of the processes may require repetition more frequently than

others during a single fire event. Further research must focus upon the characterization and measurement of these processes before escape time equations

such as (1) and (2) can be routinely applied to building design.

Presently there is also a lack of useful technical information directly

applicable to evaluating Code provisions and related behavioral assumptions

reflecting escape route choice behavior. However, investigations of wayfinding, environmental cue processing, response to natural disasters, and the

effects of stress and elevated levels of environmental toxicants discussed

earlier in this chapter suggest a number of directions for further research.

For example, the capacities of individuals to make decisions under highly

stressful conditions, and in environments characterized by elevated levels of

CO, remain to be examined in detail. The reader will recall that Glass (1968)

could not explain why approximately 50 percent of those disaster victims he

studied were Incapable of making decisions, although they appeared sufficiently

able to perceive and process environmental information.

Future research should employ a sophisticated post-incident interview

technique (see Loftus, 1980) capable of revealing complex route choice behavior,

and of identifying organizational, social, and psychological attributes of the

route selection process. In addition, field and laboratory experiments should

be conducted to determine the influence of architectural design and building

configuration upon route selection and way-finding performance. Finally, future

research should, wherever feasible, strive to study the effects of physiological

and emotional stress on route choice behavior. When practical and ethical con- siderations render the introduction of stressproducing stimuli undesirable, however, researchers may—within the limits of inference—make prudent use of cur- rently available research on CO-lnduced physiological stress (Laties and Merlgan

1979) and on emotionally-induced psychological stress (Koriat, Melkman, Averill

and Lazarus, 1972).

Because the stress-producing qualities of emergency environments may Influence

the amount of time required by individuals to formulate egress strategies and

select egress routes, the significance of stress as an experimental variable

should not be underestimated by future investigators. Janis (1977) has pointed

out that to a certain degree stress arouses a person and increases vigilance to

danger; higher levels of stress tend to interfere with effective decisionmaking.

Properly conducted post-incident interviews with fire victims, possibly in a

53
clinical setting, may provide clues about the onset of stress-induced response

patterns and their relation to decisionmaking and choice behavior during

emergency periods.

4.5 SUMMARY

In summary, a number of assumptions about human information processing and

decisionmaking behavior during fire emergencies underlie several provisions of

the Code . In this chapter, such assumptions were evaluated by reference to

models of cognitive behavior, as well as to data from recent psychological

research on way-finding behavior, environmental cue processing, disaster

response, and stress. Few directly relevant technical data were found within

the field of fire research itself. Taken as a whole, available technical

knowledge is not sufficient to warrant statements specifically supporting or refuting Code provisions which may influence egress strategy formation. However, the literature generally supports the notion that the demands of occupying

a burning building require individuals to efficiently sample information from

the fire environment, and to formulate effective and timely decisions about what

to do. Depending upon the design and layout of a building, and upon the nature

of given fire conditions, these processes will consume some proportion of the

time within which occupants must escape. Errors in judgment and decisionmaking

will frequently consume even more time. However, a crucial gap in current

knowledge about the time-based capabilities of building occupants to effect

rapid emergency escape continues to centers questions of emergency information

processing and strategy formation.

54
5. PROVISIONS AFFECTING DISCIPLINED EGRESS BEHAVIOR AND CROWD MOVEMENT

5.1 APPLICABLE CODE PROVISIONS

5-2, 1.2. 1.3 No lock, padlock, hasp, bar, chain, or other device, or combination

thereof shall be installed or maintained at any time or in connection with any

door on which panic hardware is required by this Code if such device prevents

or is Intended to prevent, the free use of the door for purposes of egress.

5-3 .1.1 The capacity of means of egress for any floor, balcony, tier, or other

occupied space shall be sufficient for the occupant load thereof.

5-3.1 .2 The occupant load shall be the maximum number of persons that may be

in the space at any time, as determined by the authority having jurisdiction,

but shall not be less than the number computed in accordance with the requirements of Chapters 8 through 16 for individual occupancies. (Where both gross

and net area figures are given for the same occupancy class, the gross area figure shall be applied to the building or structure as a whole. A separate

calculation shall then be made for those spaces where occupant load is determined on the basis of net area and if the total occupant load determined on the

net area basis exceeds that on the gross area basis, the means of egress shall

be based on the large occupant load figure.)

5-3. 1 .3 Where exits serve more than one floor, only the occupant load of each

floor considered individually need to be used in computing the capacity of the

exits at that floor, provided that exit capacity shall not be decreased in the

direction of exit travel.

5-3.1 .4 When means of egress from floors above and below converge at an intermediate floor, the capacity of the means of egress from the point of convergence

shall be not less than the sum of the two.

5-6 .2 The travel distance to an exit shall be measured on the floor or other

walking surface along the center line of the natural path of travel, starting

one foot from the most remote point, curving around any corners or obstructions

with a one foot clearance therefrom, and ending at the center of the doorway or other point at which the exit begins. Where measurement includes stairs, it

shall be taken in the plane of the tread nosing.

5-7 .

All exits shall terminate directly at a public way or at an exit

discharge. Yards, courts, open spaces, or other portions of the exit discharge

shall be of required width and size to provide all occupants with a safe access

to a public way.

17-1 .4.3 Responsibility for the planning and conduct of drills shall be

assigned only to competent persons qualified to exercise leadership.

17-1 .4.4 In the conduct of drills emphasis shall be placed upon orderly

evacuation under proper discipline rather than upon speed as such; no running

or horseplay shall be permitted.

55
17-1.2. 1.1 Every required exit, exit access and exit discharge shall be

continuously maintained free of all obstructions or impediments to full instant use in the case of fire or other emergency.

5.2

UNDERLYING BEHAVIORAL ASSUMPTIONS

5.2.1 Assumptions Concerning the Influence of Designated Leaders Upon Egress

Time During Fire Emergencies

(1) Specially trained occupants (e.g., "floor wardens") assure that building

evacuations are effected within acceptable time limits and minimize the

likelihood of panic during fire emergencies (17-1.4.3; 17-1.4.4).

(2) During actual fire emergencies where specially designated leaders are present, occupants usually take directions from these authority figures; this

minimizes escape time (17-1.4.3; 17-1.4.4).

5.2.2 Assumptions Concerning Pedestrian Movement Under High Density Occupancy

Conditions

(1) In the event of a fire on a floor, balcony, tier or other occupied space

which offers a potential for high density use, the entire population of the

space will in fact be evacuated to the outside or to a place of refuge before

the level of toxicants in the space becomes untenable (5-3. 1.1 through

5-3. 1.4).

(2) Once occupants discharge from a building, they will clear the area and

not congest the discharge area; discharging occupants will proceed directly

to public ways outside the building (5-7.1).

5.2.3 Assumptions Concerning the Effects of Building Configuration and

Architectural Obstructions on Efficient Crowd Movement

(1) Although the natural path of egress travel may be influenced by furnishings

and other fixtures, occupants can generally be expected not to deviate from

straight-line paths (5-6.2).

(2) The improper utilization of security measures or devices increases the

overall time required for emergency escape (5-2. 1 . 2. 1 .3)

(3) The full carrying capacity of means of egress may be expected to be

available at any time a fire occurs (17-1.2.1.1).

5 . 3 COMMENTARY

5.3.1 Problem

A number of Code provisions are intended to increase the likelihood that

emergency egress from public buildings will be orderly and well organized, and

that maladaptive crowd behavior during fires will be minimized. Human behavioral assumptions hypothesized to underlie these provisions address: (1) the

56
degree to which occupants will follow the Instructions of a leader or person in

authority, (2) the ability of occupants to tolerate undesirable conditions (e.g,

crowding) which may be present within egress ways during fire emergencies , and

(3) the Influence of obstructions to effective crowd flow upon efficient

emergency escape.

Many issues pertaining to crowd flow in relation to social and environmental

factors can be understood in terms of social psychological models of group

behavior. Several models are available which elucidate the influence of group

or crowd phenomena upon the behavior of Individuals. The relevance of such

models to Code provisions and underlying behavioral assumptions enumerated in

sections 5.1 and 5.2 is considered below.

5.3.2 Underlying Behavioral Models

Four social psychological models applicable to group behavior offer perspectives

on disciplined egress behavior and crowd movement which can be useful in

understanding large-scale emergency response phenomena in public buildings.

These are (1) the outcome dependence model (Thlbaut and Kelley, ,1959), (2) the

imitation model (Bandura, 1965), (3) the reward-exchange model (Homans, 1961),

and (4) the environmental space model (following Hall, 1966).

The outcome dependence model proposed by Thibaut and Kelley (1959) is based on

the notion that persons experience varying degrees of confidence in the validity of their perceptions at given times. Thus, an individual or group can become dependent for Information upon another individual or group, if the latter can Improve the validity of the former’s perception of some event beyond

the level attainable through other sources. According to Thlbaut and Kelley,

information dependence may be defined in terms of either actual experience or anticipated (future) effects. In the case of anticipated effects, a person or group seeking to validate environmental information tends to increase social

interaction with others upon whom the person or group is dependent for

information.

Before considering an example which Illustrates this phenomenon in the context

of fire emergencies, several social psychological premises of the fire emergency

event will first be identified. So-called panic behavior is more likely when

the time available for safe escape from a life-threatening situation is judged

by an Individual to be insufficient (Janis, 1970; Janls and Mann, 1977; the

reader should also refer to discussions presented in chapter 2.0 and 3.0 of the

current report). The onset of panic behavior also has been related to occupants’

expectations regarding the nature of social and physical interactions in anticipation of and during the use of available egress channels. Such Interactions

can be cooperative or competitive in nature. When occupants view one another

as potential obstacles to safe egress, for example, the likelihood of a so- called panic response Increases. Similarly, to the extent that occupants do

not compete with each other for access to available egress pathways, the entire

group could more rapidly and effectively exit the building. Thus, in situations where occupants view themselves as individuals unaffiliated with any

larger group within the building, which can occur in multifamily apartment

buildings or in mercantile and other public facilities, then the onset of

57
fire might bring individuals together in cooperative or competitive

relationships in regard to the use of available exit facilities. The importance of facilitating the movement of a crowd, particularly in public buildings,

is underscored by the possibility that large numbers of individual occupants can collect and either will compete for, or cooperate in, the use of scarce means

of egress.

Previous research on fire hazards in health care facilities provides an example

of crowd movement which can be explained, in part, by the outcome dependence

model. Investigations of fires in health care facilities have often noted that

during fire emergencies, hospital staff are perceived to be the legitimate

authority figures by patients, visitors, and other transient occupants (Bickman,

et al. 1979; Appleton and Quiggen, 1976; Archea, 1979), Even physicians who are not regular hospital personnel follow the authority of trained nursing staff

during hospital evacuations.

Another approach introduced in chapter 2.0, is the imitation or observational

learning model. As developed by Bandura (1965), this model suggests that individuals copy the behavioral responses of others, particularly if the other

people control resources on which the individuals depend during everyday

(nonemergency) events and activities. The individual might observe that the

other person behaves in a particular manner, and that he or she is positively

reinforced for that behavior. The observed person becomes a model for the

observer, and the environmental cues which set the stage for a particular

behavior from the model become associated in the observer's mind with the

model's behavior. Through a process of vicarious reinforcement (i.e., the

observer experiences the reward or punishment that happens to the model), the

observe imitates the rewarded response patterns of the model whenever a similar

set of environmental cues is introduced. Observation of a model can inhibit an observer's performance of a model's response if the observer perceived that the

model's enactment of the response led to negative consequences. Conversely, an observer's inhibitions about perfonning a response can be reduced if the model

is observed being positively reinforced (rewarded) for the behavior.

During fire emergencies in public buildings, it might not be easy to determine

who to observe. For example, while people dressed in uniforms or hospital

"whites" can clearly emerge as models in certain types of buildings, in public

occupancies such as office buildings or shopping malls identifying those who

control resources can be far more difficult. Here, well-dressed business

executives, desk clerks, or janitors may be identified as appropriate models

depending upon a wide variety of circumstances (e.g., the degree to which each

is known by, and is perceived as credible to, other building occupants).

Although the model is usually conceived of as a person, it also can be a group.

Here, the group is perceived as a source of direction and information about

safe egress during a fire emergency. The case of a transient visitor to an office building is illustrative. The visitor, upon hearing a fire alarm signal

and observing the movement of office workers, joins the group on the assumption

that there will be "safety in numbers." Ifowever, this process could also inhibit the visitor from entering a usable egressway when other occupants are observed ignoring it. Data from post-incident questionnaires administered to

58
victims of the Thurston Hall fire (Bryan, Milke and DiNenno, 1979) indicate

that only a few occupants, having failed to successfully evacuate the building,

refused to await rescue in interior refuge areas. This suggests that a sequence

of responses performed by some occupants (i.e. movement toward interior refuge

zones) may have reassured other individuals about the value of waiting in an interior location until rescued.

The reward-exchange model (Homans, 1961), also introduced in chapter 2.0, uses

the basic concepts of economics and of Instrumental conditioning to explain

face-to-face interactions among individuals. According to Homans, interaction

among individuals will continue and be positively valued so long as the participants receive more rewards (benefits) than punishments from the interaction.

Put differently, interactions that participants find profitable will continue.

Punishments can be direct (e.g., being cheated out of money, being injured) or indirect (i.e., unavoidable). Unavoidable punishments, which Homans calls

costs, refer to the forgone value of an activity. Whenever the psychological

cost-benefit equation shifts toward unprofitable interactions for a participant,

that person is more likely to choose a different course of action, one that is

perceived as more profitable. Thus, competition can arise among individuals if one person's activities results in his or her receiving more than their fair

share of rewards or if their activities result in reductions of rewards to

others to unprofitable or unfair levels.

The relevance of the reward-exchange model to behavioral assumptions underlying

Code provisions affecting disciplined egress behavior and crowd movement is

Illustrated by anecdotes. Accounts of the 1903 Iroquois Theater fire indicated

that some exit doors were either locked or were otherwise inoperable (Foy and

Harlow, 1928), Obstacles resulting from turns in stairways were also reported

to have caused the trampling of many victims. During this fire event, normal

queuing behavior by theater occupants apparently gave way to "survival at all

costs" behavior. In other words, physical Impediments to orderly evacuation

(resulting from locked doors, turns which narrowed the exit channel, or from

fallen persons) may have led to the belief that queuing would not produce the

desired reward (safe escape) and could result in the ultimate cost (death).

Lacking perceptions that would support coordinated action, members of the

audience acted independently, each trying to minimize the risk to his or her

life (i.e., trying to reduce their possible loses), resulting in a desperate

competition for access to egressways under severe time constraints.

The reward-exchange model is also useful in understanding altruistic and

heroic behavior reported in the fire literature. For example, see Bryan,

DiNenno 's (1979), discussion of the Georgia Towers fire. It may be argued

that those who engage in altruistic or heroic acts during fires are invoking

what Homan's calls rare costs, costs which increase a person's worth because

so few people can experience these rare costs. In this sense, having experienced the rare cost of risking one's life for another, one earns the commensurate rewards of being identified as a hero and receiving adulation from others.

However, the reward-exchange model also suggests that a would-be rescuer may

not believe a situation is a serious risk to life, or may find risk-taking

itself rewarding. Otherwise the risk could upset the cost-benefit equation in

favor of not helping an endangered victim.

59
The environmental space model (based on Hall, 1966) developed from studies of

animal and human territorial behavior. This model focuses on the apparent need

of individuals to lay claim to certain areas. This need has been expressed in

two forms: the need for personal space and the territorial need. Personal

space is usually defined as an area with invisible boundaries surrounding a person’s body into which no one may intrude. The size of this surrouding "bubble" varies between cultural groups and for different persons and situations in

the same culture. By contrast, terrioriality refers to the need of individuals

and groups to lay claim to some geographical areas as their own. Territories

are fixed, circumscribed areas access to and the use of which individuals and

groups have the capacity to control. Personal space, which is something the

person "carries around," is sometimes called a portable territory (Gutman, 1972).

When applied to the study of human spatial behavior, the concepts of personal

space and terrioriality aid in our understanding the environmental forms by

which individuals protect their idiosyncracies and resources and project their

identities

Indeed, distancing behavior serves important physical and psychological

purposes. The distance between persons, or between a person and a physical

object, is an important factor in the ability of the individual to properly

perceive objects in the environment. Such environmental data is crucial to

effective negotiation of the environment. But important psychological pro- cesses are believed to govern distancing behavior as well. For example, distancing appears to vary as a function of an individual's role in a given setting. The size of a person's personal space "bubble" is determined in part on

the basis of behavior patterns normally associated with carrying out a role.

For example, the spacing between a lecturer and a large audience differs dramatically from the distance between discussants participating in an Informal

seminar. Similarly, subway passengers typically seek to avoid physical contact with fellow riders until the train becomes quite crowded (Ittelson et al.,

1974). It also has been found that in addition to protecting their own personal spaces. Individuals are frequently reluctant to Invade the personal

domains of others (Horowitz, Duff and Stratton, 1964). Moreover, as already

noted, there are cultural differences in the size and role of personal space

envelopes

The computation of permissible occupant loads in buildings is based, in part,

upon the anticipated capacity of means of egress. Code provisions which specify rates of flow for various egressway elements are typically based on assumptions about the average area occupied by pedestrians, and about the uniformity of pedestrian movement over some time period. Unless a building is

relatively sparsely occupied at the time of a fire outbreak, however, emergency

egress by individuals is likely to Involve some degree of social and physical

interaction with other persons. As the population of a building increases,

moreover, the potential for infrlngments upon each individual's personal space

envelope during emergency egress also Increases. Two questions are relevant

here: (1) What amount of personal space reduction will individuals accept

during fire emergency conditions? (2) What are the effects of personal space

infringment upon rapid and orderly emergency escape? Saegert (1973) reported

that as the number of persons required to occupy a given space increases, the

complexity and uncertainty associated with the event at hand increases, while

the ability of individuals to organize their behavior decreases. Saegert also

60
noted that personal space infringments reduce behavioral alternatives available

to individuals. Furthermore, reduced freedom of choice, combined with unavoidable social and physical interaction among persons, results in decreased cognitive control over the situation by an individual, and in a general increase in

psychological arousal. Thus individuals who cannot accept prolonged infringements of personal space may revert to simpler, more regimented behavior patterns

and may find individually determined and flexible behavior patterns to be

somewhat problematic.

5,3.3 Assessment of Behavioral Assumptions Based on the Technical Literature

Literature review. Assumptions in section 5.2.1 address the degree to which

occupants will follow a perceived "leader" or person in authority during a fire

emergency. Available technical literature provides considerable support for

the notion that individuals and groups will tend to follow the lead of a perceived authority figure, Klein (1976), in a laboratory experiment designed

to simulate egress from a theater from which only one narrow exit was available,

found empirical support for the hypotheses that groups lose coordination under

conditions which personally threaten the members, and that a group under stress

wil perform best in the presence of a strong leader (initially advanced by

Kelley, et al., 1965). Similarly, Glass (1968), in his studies of mass psychology, noted that as many as 50 percent of participants in large-scale

disasters are willing to follow the lead of others and to respond to the

directions of some authority figure. Moreover, McLuckie (1970) reported that

upon being warned of an impending crisis, individuals tended to telephone

"significant" persons to seek recommended action strategies.

Under conditions of stress and impending life threat, individuals who are regarded as "knowing more" may, by consensus of other persons present, be given

decisionmaking authority over the group (Quarantelll and Dynes, 1967), In

support of this finding. Best (1978), in his review of the Beverly Hills Supper

Club fire, concluded that the majority of patrons responded to and followed the

directions of waitresses and bartenders. Yamada (1975) suggested that when

bewilderment among victims becomes extreme, individuals become docile and take

directions more easily. Although Klein (1976) noted the key role played by

leaders in achieving safe egress from a simulated theater fire, Quarantelll

and Dynes (1972), Form and Nostow (1958), Fritz and Williams (1957) and Drabek

(1968) all found that during large-scale natural disasters victims typically

do not wait for an authority figure to provide direction; they tend to react

immediately, attending to their own well being and helping others nearby.

A significant and frequent phenomenon is the emergence of a leader who "gets

people organized" during the early stages of a disaster (Killian, 1954).

Numerous post-incident studies by Bryan (1977) of fire episodes in nursing

homes also provide evidence suggesting that patients and physicians alike are willing to take directions from more knowledgeable staff (e.g., nurses or orderlies). Evidence from post-incident studies of hospital fires reported by

Lathrop (1978) corroborates these findings. But when no leader is perceived

to be present, individuals tend to seek information from other nearby people.

For example, Breaux, Canter, and Sime (1976) reported that during fires people

look to other individuals around them for information which will help define

the situation.

61
The Influence of crowd behavior on individuals is summarized in a report by

Johnson, Stemler and Hunter (1977). Results of research in this area suggest

that groups are more willing to tolerate higher levels of risk than are individual decisionmakers. Studies on altruistic behavior (Latane and barley, 1968;

Pilavin, Radln and Pilavln, 1969) demonstrate rather clearly the potential

influence even small groups can have over an individual's behavior.

Behavioral assumptions in section 5.2.2 underlying Code provisions on occupant

loading can be evaluated using environmental and social psychological research

on density. For example, Saegert (1978) investigated "cognitive overload", an hypothesized result of forcing an individual to process more environmental

information than is psychologically possible. Saegert noted that in crowded

situations with little or no social structure, the likelihood that an individual's goal-directed behavior will be interrupted may be quite high. Saegert

further noted that interruptions to goal-directed behavior frequently leads to

either frustration and aggression, or to withdrawal. Examples of environmental

settings with relatively weak social structures include shopping malls and

theaters

In another study, Saegert (1974) found that Inescapable interaction with large

numbers of people increased arousal within individuals. D'atri (1975) reported

a concommltent elevation in blood pressure under such conditions. Other investigators have suggested that the magnitude of physiological consequences of

inescapable crowd Involvement depends upon the period of exposure and the perception of escape or control alternatives (Averill, 1973; Kahn and French,

1970; Saegert, 1976). Nevertheless, elevated arousal has been shown to interfere with complex information processing required to discern changes in the

environment (Broadbent, 1971; Cohen, 1978).

While the literature suggests that, under certain conditions, effective leaders can facilitate orderly emergency egress, there is almost no technical documentation of emergency experiences during which specially trained leaders (e.g.,

"floor wardens") were available within various public occupancies. Available

research on this topic, moreover, has cast doubts about the effectiveness of

specially trained occupants during crisis situations. For example, although

studies of simulated aircraft evacuations demonstrated the need for specialized

crew training, they also showed the inadequacies of much of the training provided aircraft emergency "leaders" (Mason, 1974; Becker, 1973; Garner and

Blethrow, 1966, 1970). With regard to buildings, Roytman (1969) suggests that

special emergency-related responsibilities be allocated to buildings occupants.

Pauls (1977, 1979), on the other hand, criticizes the usefulness of trained

supervisors in office buildings, noting that assigned floor wardens tended to

be poorly trained and to perform incompetently during fire drill situations.

Hertz, Edelman and Bickman (1978), examining differences between various methods

of training nursing home staff personnel, concluded that in many cases such

staff were unfamiliar with existing fire emergency plans. However, these investigators also found that training did improve the performance of nursing home

staff during evacuation drills, although this effect was not as strong as anticipated, (this may be due to the extremely high staff turnover at such

institutions)

62
Such factors as environmental conditions, type of clothing worn, cultural norms,

the sex of occupants, and the degree of familiarity with other people seem to

Influence the spacing requirements of an individual (Horowitz, Duff and

Stratton, 1970; Evans, 1973). Ciolek (1978) attempted to suggest specific

requirements and dimensions for interpersonal spacing, concluding that personal

space needs increase in settings which are unfamiliar to the individual as well

as in poorly lighted areas. Similarly, Shlffenbauer (1977) noted that

increased illumination appears to decrease feelings of being crowded in a room. Evans (1973) and Pauls (1974) have suggested that individuals might require

more personal space under emergency conditions. Others have argued, however,

that observed increases in the personal space required during evacuations may

be due more to faster walking speeds than to underlying psychological needs

(Canter and Matthews, 1976).

Suggestions also appear in the literature that personal space needs during

emergencies vary as a function of the homogeneity of an occupancy (Canter and

Matthews, 1976) and emergency preparedness (Rivers and Bickman, 1979). Moreover, research on pedestrian movement by Fruln (1971) has shown that as occupant density increases in a given pedestrian way, people are more likely to

reduce their longitudinal ( front-to-back) spacing than their transverse (sideby-side) spacing. Unfortunately, there are no available data describing the

effects of personal space variations on the time required for evacuation.

Other assumptions in section 5.2.2 involve the notion that upon reaching a safe

area, usually outside the building, escaping occupants will clear the area and

thereby not hinder the subsequent evacuation of other occupants. No studies

treat this issue directly. Of some relevance, however, are data describing

re-entry into burning buildings by evacuees. For example. Wood (1972) found

during his post-incident survey that about 44 percent of the fire victims he

Interviewed re-entered the building after having evacuated. Similarly, Bryan

(1977) found that approximately 28 percent of those victims he surveyed also

re-entered. Moreover, Bryan (1977) reported that re-entry was more typical of

male than of female fire victims. There is presently no evidence, however, to

suggest that re-entry into burning buildings by victims Interrupts or otherwise

blocks other individuals who are attempting to escape.

Behavioral assumptions in section 5,2,3 address the potentially inhibitory

effects of building configuration and environmental obstructions on safe and

efficient crowd movement, Mellnek and Booth (1975) found that bends and corners

did not appear to reduce flow rates on stairs. Moreover, the London Transport

Board (1958) found no evidence to suggest that queues of pedestrians formed at

bends or at other changes in pedestrian movement paths. However, the London

Transport Board did find that minor constrictions in passageways tended to

increase overall travel time. This finding was not corroborated by Melinek and

Booth (1975), who argued that slight projections into pedestrian ways, such as those produced by boxes being stored in a hallway, tend to have little effect

upon pedestrian flow rate. In smoke-filled environments, walking speeds were recorded to be lower at corners than they were along linear portions of an experimental pedestrian way (Watanabe, Nayukl and Torlzakl, 1973). Similarly,

Weisman (1980) suggests that even when occupants are familiar with a building,

some architectural configurations may be so complex as to induce confusion and

63
a concommitent reduction in walking speed at such decision points as corridor

junctions. Finally, Sadalla and Magel (1980) demonstrated experimentally that

as the number of turns or bends in a pedestrian path was increased, subjects*

perceptions of the time required to negotiate the paths increased as well. The

importance of this finding could be substantial, particularly when one recalls

that perceptions of time have been found to be linked with the onset of so- called panic behavior (Janls, 1977).

The available technical literature contains no documentation of inhibitions to

crowd flow caused by security procedures or by the improper use of security

hardware in buildings. However, anecdotal accounts of the Iroquois Theater

fire, the Triangle Shirtwaste factory fire, and other more recent tragedies

provide ample evidence of the potential for panic, and for the crushing of

occupants attempting to escape, which may result from locking means of egress.

Thus, although considerable technical evidence can be cited in support of the

assumption that building occupants will follow the directions of a leader or authority figure during a fire emergency, there is very little evidence that

leaders will have been amply trained in emergency escape procedures. Moreover,

while there is a growing body of evidence concerning the role of personal space

in group behavior and pedestrian movement, the relationship between personal

space variation and building evacuation time is presently little understood.

Technical evidence concerning the behavior of occupants upon their evacuation

from burning buildings and regarding the effects of physical obstacles on crowd

flow is not now sufficient to permit an analysis of applicable behavioral

assumptions or their antecedent Code provisions. The weight of anecdotal evidence concerning the Impact of security procedures and the improper use of

security hardware in buildings upon crowd flow and panic behavior, however,

does appear sufficient to support related behavioral assumptions and provisions

of the Code .

Strengths and weaknesses of the technical literature . In general , current

knowledge about whether or not occupants follow the lead of Individuals perceived to be in authority during fire emergencies comes from post-incident fire

investigations. Results of numerous social psychological experiments are con- sistent with this finding, as are several theoretical positions. Examples of

this research were presented above. The literature on natural disasters tends

to stress the emergence of ad-hoc leaders, and this concept may only be useful

in relatively large-scale building fires of long duration.

Currently available evidence on the dependability and usefulness of specially

trained emergency managers (e.g., floor wardens) does not generally support

the assumption, presented in section 5.2, that the presence of such individuals

will facilitate prompt and orderly evacuation. Pauls* (1977, 1979) finding that

many occupants were unable to obtain needed information from floor wardens during evacuation drills is relevant to this argument, particularly in view of his

additional finding that many occupants believed the drill situations to be

actual fire events. Substantial differences between building and aircraft

evacuations, however, tend to make the aircraft studies less useful to the

evaluation of building regulations. The anecdotal nature of reports about

leadership qualities displayed by waiters and bartenders during the Beverly

64
Hills Supper Club Fire (Best, 1978) render generalizations other than informal

ones untenable.

Psychological studies of density and crowding were discussed in connection with

provisions of the Code which bear on occupant loading in public buildings.

Although increased emotional and physiological arousal have been reported to

accompany high density occupancy conditions, it is not known whether such

increases in arousal will inhibit or stimulate vigilance during actual fire

emergencies. In addition, the importance of personal space, and its precise

role in emergency egress performance, remain little understood despite statements by some researchers (Evans, 1973; Pauls, 1974). For example, experience

in a large metropolitan subway system seems to suggest that most individuals

will tolerate an extreme loss of personal space provided this condition is

perceived to be of short temporal duration and provided movement toward some goal is apparent.

Almost no technical data are currently available to evaluate the assumption

that upon evacuating a building occupants leave the discharge area. The most

tangible evidence was presented by Bryan (1977) and Wood (1972), who commented

upon re-entry behavior by evacuees. However, extremely few of the cases investigated by these researchers Involved public occupancy buildings. Morever,

neither investigator documented the Influence of re-entrants upon the egress

perfoirmance of other evacuees.

Crowding, occupant density, and the potential for panic are also relevant to

behavioral assumptions underlying Code provisions intended to limit projections

and other physical obstacles in egress ways. Here too there are not enough

data to permit an evaluation of these assumptions. However, research on individuals' perceptions of traversed distances (Sadalla and St. Magel , 1980) may

assist in evaluating the assumption that during fire emergencies, escaping

occupants tend to traverse linear routes. For example, Sadalla and Magel

found that individuals perceive paths with bends and turns to be longer than

linear paths of equivalent length. If one wishes to assume that, under

emergency conditions, people consciously seek the shortest known paths, then

Sadalla and St. Magel 's finding would appear to support both the assumption

and its antecedent Code provision. It should be kept in mind, however, that

no research on either distance perception or linearity of pedestrian movement

routes has been conducted under conditions designed to simulate building fires.

The assumption that egress ways in buildings will be maintained fully available

for instant use in case of fire emergencies can not be evaluated because there are no technical data on this topic. Although some anecdotal accounts have

suggested that the storage of boxes, etc., within corridors or stairwells might

have little effect on egress flow or escape time, there are currently no empirical data to either support or refute this notion.

The available literature on potential conflicts between emergency escape and

building security objectives consists almost entirely of anecdotes and reports

by fire victims. Indeed, security procedures could have made emergency escape

very time consuming, even Impossible, during numerous fires reported in the

press. It is precisely such events which have given rise, over the years, to

65
public concern about potential conflicts between emergency escape and security

goals. However, no systematic Investigations of the mutual effects of emergency

escape requirements and building security procedures under real or simulated

emergency conditions have been conducted to date. In view of the likelihood

that there are numerous Impediments to speedy egress movement, as well as numerous sources of maladaptive behavior during building fires. It Is Important

to determine what aspects of the problem are actually attributable to the Improper Implementation of security procedures. At present, however, the lack of

technical data on this topic makes such a determination Impossible.

5.4 SUMMARY OF GAPS IN THE TECHNICAL LITERATURE

5.4.1 Research on the Effectiveness of Trained Leaders In Facilitating Rapid

Emergency Escape and In Avoiding "Panic"

The notion that, during simulated emergencies and large-scale natural disasters,

Individuals tend to take directions from a perceived leader was amply Illustrated by laboratory experiments and case studies described In section 5.3.3.

However, the degree to which this phenomenon occurs during building fires can- not be accurately stated on the basis of currently available technical results.

This Is also true of the actual effectiveness of trained leaders during real

fire situations. The principal reason for these gaps Is that, to date, no postincident studies specifically designed to assess the leadership function have

been reported.

Human responses during fire emergencies comprise a highly complex area for

post-hoc research, A substantial proportion of this complexity owes to the

need for Investigators to successfully distinguish truthful and accurate answers

to their Inquiries from answers respondents may fabricate for fear of "looking

bad" or becoming Involved In legal actions. To a certain degree, such difficulties can be overcome by comparing and cross-checking the responses of numerous victims, or witnesses to the same event. In this way. It may be possible to

converge upon a reasonably accurate description of the actual event. Special

techniques for obtaining and using Information from eyewitnesses have recently

been developed for use In police and courtroom Investigations (Loftus, 1980),

and these approaches may be useful In the present context.

It also should be noted that although behavioral assumptions concerning

leadership and direction-taking appear to be generally supported by available

technical literature, situational variables affecting these phenomena have not

been widely Investigated. For example, Keating and Loftus (1974) recommended,

on the basis of their research, that female voices be used for certain portions

of messages delivered by vocal alarm systems, while male voices be used for

other segments. These Investigators noted that the female voice Is less likely

to agitate occupants and cause panic during and Is most appropriate for an Initial alert, while the male voice Is more likely to be associated with an authority figure and therefore should be used to Impart specific Instructions.

However, the extent to which direction-taking Is Influenced by additional factors such as victim's previous emergency experiences, their emotional and physical capabilities, and the degree of social and functional variation

characterizing the affected occupancy, have not been systematically studied.

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Finally, behavioral assumptions regarding the availability and function of

trained leaders presuppose leaders’ knowledge about effective emergency escape

procedures. The few available studies do not support this notion (recall Pauls

finding that even where designated floor wardens were specially trained, they

did not function as expected during fire escape drills). Accordingly, questions about the social dynamics which arise during building emergencies, and

about the nature and quality of training programs, must be considered. Particularly vulnerable are visitors to public (noninstitutional) building because

they will have few, if any, preconceptions about the availability or role of

emergency supervisors.

5.4.2 Research on the Effects of Occupant Loading and Discharge Behavior on Successful Crowd Movement

Presently available data are insufficient to either support or refute human

behavioral assumptions underlying Code provisions affecting building occupant

loading and exit discharge facility design. Although several investigators

have suggested the need to Incorporate personal space requirements and side- to

side body sway into the design of means of egress (e.g. Pauls, 1974; Fruin,

1971), the effects of such factors on escape time, particularly under actual

emergency conditions, remains little understood. For example, the manner by

which occupants physically utilize egress ways (viz, their interpersonal spacing behavior and the biomechanics of walking, stair use, etc.) may well influ- ence the time required to negotiate an entire egress route. But it is not now known at what point and by what mechanisms occupants will relax their own personal s^ace requirements and accept more physically crowded conditions during

egress. The ability to identify this threshold and, more fundamentally, to

determine a logical connection between constriction in egress ways, increased

physiological and emotional arousal, and the onset of maladaptive (panic)

behavior, may eventually lead to modifications in the design of exit components

and systems.

5.4.3 Research on the Effects of Architectural Impediments and Physical

Obstacles Upon Crowd Behavior and Disciplined Movement

Extremely little technical literature was found applicable to evaluating Code

provisions intended to minimize physical Impediments and obstacles to rapid

escape. The specific effects of physical obstacles (e.g, corridors or stairwells being used as storage facilities) on escape time has not been systematically Investigated. Future "time-motion" experiments under a wide variety of

simulated egress conditions should provide data useful for comparative purposes

Moreover, future post-incident Investigations using sophisticated interviewing

techniques can query victims about problems they may have encountered with

architectural impediments or other physical obstacles.

Similarly, experiments on the effects of locking exit doors or of other

security procedure infractions could be conducted under carefully controlled

simulated emergency conditions. The appropriate dependent variable in such

studies is a measure of elapsed perceived time-to-escape , and this measure

should be compared under various conditions of occupancy, density and occupant

loading, actual as well as perceived alternative escape routes, and emergency

67
training. Although data obtained from such experiments may be useful for

comparative purposes, extrapolations from simulations to behavior during real

emergencies should be made with caution. For example, while maladaptive

behavior may take the form of an incorrect response leading to excessive escape

time in a laboratory simulation, it may take the form of "panic", injury, or even death during a real fire.

Code provisions specifying the measurement of distances to means of egress along

along linear path segments seem to suggest that during fire emergencies occupants

will traverse linear-segmented routes. If individuals traverse nonlinear paths

or if on occasion they meander during an evacuation, then their egress times

will be longer than those produced by purely linear travel. Longer egress times

would imply a reduction in the maximum allowable distance between the furthest

location on a floor and an exit (see provision 5-6.2). Available data do not

make such a recommendation possible now. Future research is required to document actual path lengths and patterns traversed by escaping occupants. This

research may be accomplished during evacuations of large rooms or entire building floors under simulated emergency conditions, using specially placed motion

picture or videotape recording equipment.

5.5 SUMMARY

A number of human behavioral assumptions about crowd movement and disciplined

group behavior underlie selected provisions of the Code . These assumptions

were evaluated by reference to several models of human collective behavior,

data from research in experimental social psychology, field research on natural

disasters, and post-incident fire investigations. In general, the technical

literature suggest support only for those assumptions pertaining to leadership

and direction-taking behavior. Behavioral assumptions pertaining to the effects

of occupant loading and physical obstacles upon orderly and rapid crowd movement appear to be neither supported nor refuted by available technical literature. To the extent that impediments to crowd movement result in maladaptive

collective behavior and panic, future research on the role of building design

in facilitating crowd movement seems an essential precursor to Code development.

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6. PROVISIONS ACCOMMODATING OCCUPANTS’ CAPABILITIES TO SAFELY AND RAPIDLY

NEGOTIATE EGRESS WAYS

6.1 APPLICABLE CODE PROVISIONS

5-2. 1.1. 3. 3 The floor on both sides of a door shall be substantially level

and shall have the same elevation on both sides of the door, for a distance

on each side at least equal to the width of the widest single door. When the

door discharge to the outisde or to an exterior balcony, exterior exit, or exterior exit access, the floor level outside the door may be one step lower

than the Inside but not more than 8 inches lower.

5-2. 1.1. 4. 5 The force required to fully open doors shall not exceed 50 pounds

applied to the latch stile.

5-2. 1.2. 1.2 A latch or other fastening device on a door shall be provided

with a knob, handle, panic bar, or other simple type of releasing device, the

method of operation of which is obvious, even in darkness.

5-2 .1.2 .2 .1 When a door is required to be equipped with panic hardware by some other provision of this Code , then panic hardware shall cause the door latch to

release when a force of not to exceed 15 pounds is applied to the releasing

devices in the direction of exit travel.

5-2. 1.2.

Self-Closing Devices. A door designed to be kept normally closed in

a means of egress, such as a door to a stair enclosure or horizontal exit,

shall be a self-closing door and shall not at any time be secured in the open

position.

5-2. 1.3. 1.1 Where required doors are operated by power, such as doors with

photo-electric actuated mechanism to open the door upon the approach of a person

or doors with power-assisted manual operation, the design shall be such that in

event of power failure the door may be opened manually to permit exit travel or closed where necessary to safeguard means of egress.

5-2 .2 .2 .1 Each new stair and platform, landing, etc., used in conjunction

there with in buildings more than 3 stories in height and in new buildings

required by this Code to be of fire-resistive construction, shall be of

noncombustible material throughout.

Exception: Handrails are exempted from this requirement,

5-2. 2. 2.

There shall be no enclosed usable space under stairs in an exit

enclosure nor shall the open space under such stairs be used for any purpose.

5-2 .2 .2 .4 No arrangement of treads known as winders shall be permitted in new

stairways.

5-2. 2. 2.

Where material of stair treads and landings is such as to involve

danger of slipping, nonslip material shall be provided on tread surface.

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5-2. 2. 2,

The height of every riser and the width of every tread shall be so ; proportioned that the sum of 2 risers and a tread, exclusive of its nosing or

' projection, is not less than 24 nor more than 25 inches.

j 5-2 .2 .2 .8 The minimum number of risers in any one flight of stairs shall be 3. ] 5-2.2.2.10 There shall be no variation exceeding 3/16 inch in the depth of j treads or in the height of risers in any flight. '

i Exception: As permitted by 5-2 *2 ,1 ,4 for monumental stairs, \

I 5-2. 2. 3.1 Means of egress such as stairs, stair landings, balconies, ramps and

aisles, located along the edge of open-sided floors and mezzanines, shall have i guards to prevent falls over the open side. Each new stair and Class B ramp

' shall have handrails on both sides (see also 5-2. 2. 3.4). '

j 5-2 .2 .3 .2 Required guards and handrails shall continue for the full length of I each flight of stairs.

5-2 .2 .3 .4(e) Every stairway required to be more than 88 inches in width shall

have not less than 1 intermediate handrail for each 88 inches in required width

(see also 5-2. 2. 3.1).

Exception: On monumental outside stairs 2 handrails may be permitted

5-2 .3 .7 Access from a building to vestibules or balconies shall be through

doorways not less than 40 inches wide for new and 36 inches wide for existing

towers. These openings and the entrances to the towers shall be provided with

approved, self-closing fire doors swinging with the exit travel. Clear wired

glass not exceeding 720 square inches shall be provided in all doors giving

access to the enclosure.

5-2. 5. 1.3 .3 Visual Enclosure. Outside stairs shall be so arranged as to avoid

any handicap to the use of the stairs by persons having a fear of high places.

For stairs more than 3 stories in height any arrangements intended to meet this

requirement shall be at least 4 feet in height.

5-2. 5. 1.3.

Weather Protection. Outside stairs in climates subject to snow

and ice shall be protected to prevent accumulation of snow or ice.

5-2. 5. 3.

Risers shall be solid.

Exception: The skirt-type, having 1 inch space for drainage , shall be permitted

,

5. 2. 6. 1.4.The slope of a ramp shall not vary between landings. Landings

shall be level and changes in direction of travel, if any, shall be made at landings.

5-2. 6. 2. 2.

Weather Protection. Outside ramps in climates subject to snow and

ice shall be protected to prevent accumulation of snow or ice.

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5-5. 1.1 Exits shall be so located and exit access shall be so arranged that

exits are readily accessible at all times.

5-5. 1.2 When more than one exit is required from a story, at least two of the

exits shall be remote from each other and so arranged and constructed as to

minimize any possibility that both may be blocked by any one fire or other

emergency condition.

5-5. 1.3 Means of egress shall be so arranged that there are no dead end pockets,

hallways, corridors, passageways or courts whose depth exceeds the limits

specified for individual occupancies by chapter 8 through 16.

5-6.5 Where open stairways or ramps are permitted as a path of travel to

required exits, such as between mezzanines or balconies and the floor below,

the distance shall Include the travel on the stairway or ramp, and the travel

from the end of the stairway or ramp to reach an outside door or other exit, in

addition to the distance to reach the stairways or ramp.

5-6.6 Where any part of an exterior way of exit access is within 15 feet

horizontal distance of any unprotected building opening, as permitted by

5-2. 5. 1.3.1 for outside stairs, the distance to the exit shall include the

length of travel to ground level.

6.2 UNDERLYING BEHAVIORAL ASSUMPTIONS

6.2.1 Assumptions Relating to the Effects of Stair and Ramp Design on Occupants* Capabilities to Safely and Rapidly Negotiate Egress Ways

(1) Non-level floors or steps immediately on either side of a doorway may

reduce the discharge rate of the doorway (5-2. 1.1. 3. 3).

(2) Certain materials used on the surface of stair treads may cause slipping,

whereas others may prevent slipping. Slipping by occupants attempting to escape

via an exit stair contributes to reduced egress flow (5-2. 2. 2. 6).

(3) The ratio of rlser-to-tread dimensions influences flow rate along stairs

(5-2. 2. 2. 7).

(4) Stair flights with fewer than 3 risers may cause falls or accidents, or otherwise Impede egress flow (5-2. 2. 2. 8).

(5) Irregular riser or tread dimensions along any stair may contribute to

missteps or falls, and thereby reduce egress flow (5-2.2.2.10).

(6) Handrails prevent falls, slips, or missteps on stairs, and thereby prevent

reductions to egress flow (5-2. 2. 3.1; 5-2. 2. 3. 2).

(7) On stairways greater than 88 inches in widths, an intermediate handrail

will reduce the likelihood of falls, slips, or missteps, and thereby prevent

reductions to egress flow (5-2. 2. 3. 4).

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(8) Egress flow on outside stairs may be impeded by weather conditions which

increase the slipperiness of stairs (5-2. 5. 1.3. 4; 5-2. 5. 3. 3).

(9) Variations in the slope of a ramp between landings may reduce the flow

rate on the ramp ( 5-2. 6.1. 4. 2)

(10) Ramp surfaces not specifically treated to increase slip resistance may

cause slips, trips, missteps, or falls, which reduce egress flow (5-2. 6. 1.4. 4)

(11) Slips, trips, missteps, or falls which reduce egress flow occur more

frequently on outside ramps not adequately protected from the weather, than on ramps which are adequately protected (5-2.6.2.2.4)

6.2.2 Assumptions Relating to the Effects of Physiological and Psychological

Stress Upon Occupants' Capabilities to Safely and Rapidly Negotiate

Egress Ways

(1) Infiltration by fire products into egress ways may impede egress flow

(5-2. 1.2. 3; 5-2. 2. 2.1; 5-2. 2. 2. 2).

(2) Occupants' entry into enclosed stairways may be Influenced by these

individuals' ability to see into the stair enclosure (5-2. 3.7).

(3) Persons having a fear of high places may Impede egress flow on certain

outside stairs (5-2. 5.1. 3.3)

(4) Dead end pockets, hallways, corridors, passageways and courts which exceed

certain limits reduce egress efficiency and increase egress time; these limits

vary according to occupancy (5-5. 1.1; 5-5. 1.2; 5-5. 1.3).

(5) Travel to a means of egress which requires passing through an uprotected

zone or area may result in slower overall evacuation (5-6.5; 5-6.6).

6.2.3 Assumptions Relating to the Biomechanics of Exit Door Operation.

(1) In general, building occupants can apply as much as 50 pounds of force to a door stile, and 15 pounds of force to a panic bar, and in so doing will not

impede flow through a doorway or means of egress (5-2. 1.1. 4. 5; 5-2. 1.2. 2.1)

(2) The design of door hardware Influences flow through the door, under both

conditions of light and darkness (5-2. 1.2.1. 2)

(3) The means of manually operating automatic or power assisted doors (as may

be required during a power failure) are familiar to, or known by, escaping

occupants; hence any need to manually operate such doors will not increase

evacuation time ( 5-2.1. 3. 1.1)

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6.3 COMMENTARY

6.3.1 Problem

The ability of building occupants to safety and rapidly negotiate egressways

may be affected by the sensory-motor capacities of these individuals. Writers

of the Code have recognized, at least in principle, the need to consider human

performance criteria in the design and organization of building egress facilities. This concern is reflected in several provisions of the Code . Human

behavioral assumptions believed to underlie Code provisions Intended to accom- modate occupants’ abilities to safely and rapidly negotiate egressways primarily address three issues: (1) the extent to which accidents such as, slips,

missteps, or falls, which may occur while people negotiate pedestrian ways,

impede flow along corridors, stairs, and ramps, and through doorways; (2) the

degree to which stress and fatigue impair walking behavior and increase the

time required for egress; and (3) the Influence of door and other hardware

design upon occupants’ abilities to rapidly and effectively operate elements

comprising means of egress. Several models which provide useful insights about

human performance capabilities pertinent to emergency escape during building

fire situations are discussed below.

6.3.2 Underlying Behavioral Models

Research in the fields of human factors psychology and biomechanics has given

rise to a number of models explaining human performance capabilities under

various circumstances. Most of the Code provisions and behavioral assumptions

in sections 6.1 and 6.2, respectively, address occupants’ negotiation of stairs

and ramps in buildings. Thus a model of stair and ramp use is presented first.

A general assumption which appears to underlying Code provisions concerning the

design of stairs and ramps is that conditions which increase the likelihood of

trips, slips, missteps, or falls may Increase overall egress time. So-called

"human error" is the most commonly cited cause of accidents involving people’s

negotiation of the environment (Zeller, 1970). By analogy, man-machine and

feedback-loop models have been used to describe behavioral sequences which lead

to accidents (Zeller, 1959). For example, the user of a stair approaches this

portion of an egress way and perceives its configuration. The individual interprets Information perceived about the stair, and compares knowledge of this

egress way with prior experiences with other stairs. This process results in

decisions about required gait, interpersonal spacing, level of vigilance, etc.,

after which actual negotiation of the stair begins.

The stair user continually obtains feedback concerning stair use. As the

occupant ascends or descends the stairway, successful biomechanical behaviors

(l.e., those which result in an unencumbered negotiation of the stair, and

which result in no missteps or falls) are reinforced. The more succesful steps

that are taken on this stair, the more likely is the user to continue exercising

the particular set of biomechanical patterns, and the less vigilant is the user likely to become (Archea, Collins and Stahl, 1979). Negative feedback (unsuccessful steps) most frequently take the form of missteps, which tend to alert

the stair user to exercise greater caution in negotiating the remainder of the

73
stair, and which may also cause the user to be vigilant with regard to potential

stair hazards (Archea et al. 1979).

Thus, stair users continually test their preconceptions about what they expect

to encounter during stair use against the physical properties of the stair

actually negotiated. According to Archea et al. (1979), the user initiates

this test cycle immediately upon approaching a given stairway. Even before

taking the first step, the user compares perceptions of the present stair

environment with an internalized image of stairs in general (i.e., what stairs

ought to be) which have been built up over years of experience using stairs.

If the user finds a close match to exist between the current stair and the

internalized image, then the individual enters the stairway with confidence

that it can be successfully negotiated. Each subsequent movement on the stair

then engages tactile and kinesthetic feedback mechanisms which provide environmental data necessary to test the "fit" between physical properties of the

stair and the user's internalized image. As noted earlier, the individual may

become less vigilant (i.e., less aware of tactile and kinesthetic Information

obtained during stair negotiation) as the internalized image of the stair is

confirmed through actual stair use. According to Archea et al. (1979), experience in negotiating the first few treads may be the most critical in establishing a "working" level of vigilance.

While negotiating a stair, deviations from anticipated physical properties may

require the user to adjust biomechanical behavior patterns. According to Archea

et al. (1979), minor deviations which fall within some acceptable range (e.g.,

occasional irregularities in riser or tread dimensions) are likely to require

only very small biomechanical adjustments. Inconsistencies which fall outside

this range (e.g., a broken tread or handrail), however, if detected, will arouse

the user's vigilance to the stair environment and cause the Individual to

re-evalute the correctness of the originally-chosen behavior pattern, making

any adjustments required. Whether or not the stair user successfully adjusts

to gross deviations in the stair environment may depend, to a large extent,

upon how far the individual has proceeded in negotiating the present stair.

For example, an individual who has only taken a few steps onto the stair, and

who is still in the process of confirming mental hypotheses concerning this

stair, may consciously anticipate errors and therefore be likely to make behavioral adjustments relatively easily. In this instance, stair negotiation is

not likely to suffer. However, a user who has negotiated almost the entire

stair before obtaining negative feedback may have already obtained sufficiently

strong confirmation of mental hypotheses concerning the stair to cause overall

vigilance reduction. In this case, the user may be ill- prepared to respond to

unexpected variations in the physical properties of the stair, and may misstep,

slip, or fall.

Thus, Archea et al. (1979) suggest that stair accidents result when stair users

(1) base their stair use behavior patterns upon erroneous expectations, (2)

select inappropriate biomechanical response patterns, or (3) under- or over- estimate required biomechanical modifications when responding to the physical

properties of a stair.

74
Research on stair use reported by Archea et al. (1979), Carson, Archea,

Margulls, and Carson (1978), and Templer, Mullet, Archea, and Margulis (1978)

also has pointed to the importance of the so-called orientation edge. This

concept may be defined as any abrupt change from the typically visuallyenclosed stair to an open view of another larger space at the top or bottom of

the stair. When descending a moving stair in a department store, for example,

the pedestrian often moves from a visually-confined enclosure to a wide-open

and visually complex space. This sudden change can distract the user from

the fixed stair or moving stair and cause the user to orient toward the activities, people, or milieu within the larger open space. If this results in a substantial reduction in attention to stair negotiation while the individual must

respond to some deviation in the stair Itself, the likelihood of a stair

accident is presumed to Increase.

Presently there are no behavioral models describing ramp use per se . It has

been suggested that general models of pedestrian movement in bounded environments, based primarily upon the negotiation of level planar surfaces, can account for ramp usage (Fruin, 1971). However, models of pedestrian moveraent

in bounded environments typically are based on physical analogs rather than on theories of human behavior. These models are discussed in chapter 7.0 of the

present report. For the purpose of describing occupants’ capabilities to safety

and rapidly negotiate ramps, the stair use model described above appears

plausible

The influences of stress and fatigue on occupant capabilities, particularly

under emergency conditions, involves numerous and diverse perceptual, cognitive

and physiological reactions. These phenomena have not been organized into a single model of emergency behavior under stress. However, concepts from both

environmental psychology and neurophysiology may contribute to a greater

accommodation of occupants’ capabilities to safely and rapidly negotiate egress

ways

For example, stress can be operationally defined as the effect of stimuli

sufficient in Intensity to adversely influence response behavior. Stressors

so defined may be viewed as behavior-interrupting mechanisms of environmental,

emotional, or physiological origin (Simon, 1967). Examples of stressors which

Interrupt ongoing behavior patterns include input (sensory) and motor (neuromuscular) overload, conflicting or contradictory Information from the environment, and sensory-motor system failures (physical disease). Stressors such as these influence behavior either indirectly by affecting the sensory organs, or directly by affecting human central and autonomic nervous systems. Alarm

reactions resulting from stress can generate a local adaptation syndrome (Selye,

1956). The reactions and the syndrome are directed toward the immediate

stressor and have survival as their Immediate objective.

The local adaptation syndrome consists of short-term physio-regulatory processes

which the human body automatically and immediately evokes in response to some physical change. These processes avoid, repel, or utilize stressors which

have interrupted ongoing and adaptive behavior in order to compensate for the

stressors’ presence and restore ongoing activity patterns. When the local

adaptation syndrome is triggered, an Individual can expend considerable energy,

75
attention, and time on stress reduction. Moreover, extremely intense stressors

or those of relatively long temporal duration, may bring about the general acti

vity syndrome characterized by endocrinal activity resulting in physiological

changes throughout the body. Under the most extreme circumstances, adrenal

exhaustion may result, wherein an individual's neuroendocrine system becomes

completely overloaded and is rendered Incapable of responding to any

environmental stimuli at all.

The onset of fire conditions in a building illustrates the processes described

above. On being alerted to a life threat in the building, an occupant's cur- rent pattern of behavior is suddenly interrupted by stimuli (i.e., information

contained in the alert message) which may be perceived by the occupant as both

unanticipated and ambiguous. Such an alert engages the Individual's neurological orienting response mechanism (Sokolov, 1963), which focuses the occupant's

attention on the newly-discovered environmental conditions. This process

Involves activation of the sympathetic nervous system, as well as secretion of

hormones by the adrenal medulla. The result of these physiological processes

is a mobilization of the body's resources in preparation for swift action

(primarily "fight" or "flight"). A marked increase in heartbeat rate and

strength, necessary to satisfy the body's Increased demands for oxygen, also

results

These demands require the spleen to contract (and thereby release stored red

blood cells which are needed to carry the increased oxygen supply), respiration

to deepen, and the bronchi to dilate. These are the principal physiological

steps taken automatically by the human body to meet the perceived challenges of an external threat. Once oriented to the threat, interruptive stressors may

distract the individual from the demands of the impending crisis, may redirect

the focus of concern, or may overload the person's physiological capability to

cope

This cybernetic model of neurophysiological coping bears relevance to human

behavioral assumptions believed to underlie provisions of the Code Intended to

accommodate occupants' capabilities to safely and rapidly negotiate egress ways

For example, the Code addresses itself to the infiltration of fire products

into means of egress. Where such Infiltration occurs, CO often acts to interrupt the body's normal oxygen Intake mecahnisms. As a result, the body's

pulmonary system is adversely stressed in its attempt to reject tlie poisonous

substance (as evidenced by coughing, choking, gagging, etc.). The initial

inhalation of smoke evokes an alarm reaction, which may lead the individual

to seek a less toxic environment. Indeed, the individual is physiologically

prepared to consume larger amounts of oxygen; however, oxygen cannot be biochemically processed in the presence of CO contamination. If the individual

cannot move to a less toxic environment, therefore, the body's vital homeostasl

will be lost.

Stress can also affect cognitive-perceptual processes. Infiltration of fire

products into an egressway can provide escaping occupants their first actual

glimpse of fire products. In this instance, a perceptual-cognitive alarm reac- tion is triggered when the individual realizes that the life threat is consider

ably nearer than previously expected. The orienting response evoked by the

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presence of fire products results in a temporary, although possibly distracting,

adjustment In the focus of the person's attention away from the escape task and

toward nearby fire products. Here, the sudden recognition of the fire's reality

serves to interrupt adaptive behavior (movement through the egress way).

Once an occupant's attention has been redirected away from those components of

egress ways crucial to their successful egress, the likelihood of a potentially

time-consuming misstep or fall is increased. If a stair is being entered, for

example, the redirection of visual attention to fire products above or to one side may result in only kinesthetic testing of just the first few treads. This

redirection of stair users' attention may result in a stair accident which

temporarily impairs the use of the stair by other evacuees (Archea et al. 1978).

Alternatively, environmental stressors may interrupt ongoing adaptive behavior

patterns by causing an individual to avoid a particular action and to reformulate the egress strategy.

Upon opening the door to a stairwell, for example, an occupant may see fire

products, conclude that this means of egress is unsafe, and seek another stair,

means of egress, or refuge.

Impairments to visibility also can limit a person's capacity to rapidly

negotiate means of egress, and can interrupt egress-related behavior patterns.

The light diffusing and obscuring qualities for fire products (smoke), as well

as irritation to the eye's membranes produced by these products, combine to

encourage cautious and hesitant behavior by occupants. Such behavior may

result in reduced walking speed, using a nonlinear walking path, and in some instances, total avoidance of the smoke-filled area. Similarly, occupants tend

to approach and utilize darkened pedestrian ways with extreme caution, and may,

in some cases, prefer to avoid darkened routes entirely.

Finally, acrophobia—abnormal fear of high places—can be triggered by visual

information, which is particularly relevant to the forced use of outside stairs

during fire emergencies. During an evacuation utilizing such a stair, an acrophoblc occupant may hesitate, "freeze", or "panic."

Fatigue may also impair occupants' capabilities to safely and rapidly evacuate

buildings during fires. An illustrative case involves occupants' negotiation

of dead end corridors. Where an occupant has unknowingly been brought to a dead end, a rapid shift in egress strategy may be required. This shift can increase stress for the individual in two important ways: (1) nonproductive

negotiation of an incorrect path uses valuable time, during which effective

egress routes could become blocked; and (2) the sudden realization that a particular strategy was nonproductive may create within the individual perception

that the time remaining for safe escape has dramatically decreased. Under

these circumstances the individual, having made an erroneous response, must

adjust quite rapidly to a new set of environmental conditions. Where the occupant perceives extremely little time available for safe escape, the person's

information processing capacities become highly stressed. Such stress may

result in psycho-motor fatigue. Hence, not only is motor behavior slowed, but

the occupant is less able to process critical environmental information as well

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Behavioral assumptions believed to underlie Code provisions in section 6.2.3

address the operability of exit door hardware during fire emergencies. A biomechanical model of the human body provides some insight into questions posed

by these provisions. In brief, the human body may be conceptualized from a mechanically dynamic viewpoint as a highly complex mechanical structure consisting of numerous mass-spring-damper elements. In addition to their Inertial

characteristics, the skeleton, organs, ligaments, and muscles have elastic

properties as well. Within this model, the torso may be considered a pure mass which is supported by the spinal column resting on the pelvis. Arm-

-shoulder configurations (which are most relevant to the present discussion)

comprise subsystems (see Coermann, 1970). Subsystem components and entire

subsystems are interconnected by a limited set of rigid links. The links articulate at pivot points which may be characterized in terms of their limitations

to free movement. Under the biomechanical model, the body's density is assumed

to be homogenous. The biomechanical manipulation of architectural hardware may

be modeled as the vector motion of spring-like links with intervening pivots.

The relevance of the biomechanical model to emergency escape may now be

considered more specifically. The model suggests that when calculating the

force required to actuate panic hardware, a thorough analysis of static and

dynamic forces applied by the human body through both rigid elements and pivots

is necessary. Such analyses may yield, for example, that different door/ landing configurations provide varying opportunities for Individuals to apply forces

to hardware efficiently and rapidly. They would also illustrate the differences

in panic hardware operation between, say, able-bodied occupants approaching the

door via rapid movement along a level surface, able-bodied persons approaching

the door immediately upon stepping off a stair, and wheelchair-bound Individuals

likely to exert smaller forces through non-normative vector paths.

Another concern of this set of assumptions focuses upon the design of door

hardware. Here too, a biomechanical understanding of arm-shoulder and hand

manipulation is useful. For example, most doors may be quickly and easily

opened by placing one hand on a circular knob, and then by turning this knob

while simultaneously pushing (or pulling) the knob and door. However, the

design and placement of such hardware has typically been intended for persons

of average height, stature, and motor capabilities (Margulis 1981). A child

who must reach upward before pushing upon or pulling a door knob, an arthritic

person who might be unable to rotate the knob sufficiently, or an elderly

individual who may be incapable of applying sufficient force to open a door

into a stairway, may be blomechanically disadvantaged in manipulating exit

doors which are not required to contain panic hardware.

6.3.3 Assessment of the Behavioral Assumptions Based Upon the Technical

Literature

Literature review . Assumptions enumerated in section 6.2.1 concern the use of

stairs and ramps as means of egress. A number of studies reporting data on stair and ramp utilization became available immediately prior to and since the

publicaton of the 1976 edition of the Code . In several instances these data

appear to support applicable Code provisions. For example, the Code prohibits

the placement of non-level floor surfaces or steps Immediately on either side

78
of most doorways (provision 5-2. 1.1. 3. 3) . Designers and building officials

apply this prohibition under the assumption that floor plane irregularities in

the immediate vicinity of doorways may slow egress flow either directly, or Indirectly by causing missteps or falls. This notion is supported by Archea et

al. (1979), who suggest that the sudden shift in people's attention from door

negotiation to the floor surface Irregularity may Indeed decrease the efficiency of the doorway as a means of egress. Additional support is provided by

Peschl (1971), who found that occupants passing through doorways which immediately preceded steps frequently fell or stumbled.

Other behavioral assumptions deal with the matter of traction on walking

surfaces. Archea et al. (1979) suggest that most so-called "slip" accidents

may in fact result from incorrect placement of the foot when negotiating stairs,

and may not result from insufficient traction. Moreover, they point out that

when stair tread surfaces are maintained clear and dry, severe slips in either

ascent or descent, due to reduced traction, may be virtually impossible. Further, these investigators point out that a certain amount of "slip" is required

for safe and efficient stair negotiation, and that excessive friction between

footwear and tread surfaces may also contribute to missteps and other factors

which reduce rapid egress through stairways. This notion is supported by

Carson, et al., (1978) who, finding no statistical relationship between stair

accident rates and stair tread materials, report a positive correlation between

stair accident rates and coefficients of friction. However, Carson et al.

(1978) note that coefficients of friction of materials ordinarily found on stair treads (particularly in residential construction) fall in a range which

cannot be statistically linked with stair accident rates. With reference to

Inclement weather conditions, such as those which may Influence the efficient

use of outside egress stairs, Sigler (1973) found wet stairs to be substantially more slippery than dry stairs. However, Sigler found no statistical

correlation between surface wetness and stair accident rates. Measures taken

to correct slippery conditions on stairs may also lead to anomolous stair use behavior. For example. Miller and Esmay (1961) found that rubber mats and

varnish coatings were each twice as hazardous as paint coatings or bare wood

surfaces of residential stairs. Where tread coverings (e.g., carpets or plastic runners) are applied to stair surfaces in residential structures, it

is estimated that the improper fastening of such coverings may account for as many as 10 percent of all stair accidents (Velz and Hemphill, 1953).

A number of other assumptions concerning effective emergency stair use involve

dimensional relationships between risers and treads, as well as the number of

risers present in stairs. McGuire (1971) suggests that steep and nonuniform

stairs be avoided, citing a study in which 22 percent of all stair-related

accidents were attributable to excessively steep stair design. Based on gait

rhythm data collected during laboratory experiments utilizing a mechanical stair

treadmill apparatus, Terapler (1974) found that individuals are least likely to

experience missteps in ascent when risers were between 6.3 inches (0.16 ra) and

8.9 Inches (0.23 m) , and when treads were between 7.7 inches (0.20 m) and 14.2

Inches (0.36 m). With steeper stairs, Templer found an Increased number of

missteps in descent.

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In contrast, Neutra (1972) and Carson et al. (1978) found no significant

correlation between stairway slope and accident rates. These investigators

note that particular combinations of riser and tread dimensions may contribute

to a greater likelihood of missteps, suggesting that more attention be paid to

these combinations than to gross measures of stair slope.

Concerning the potential effects of stair design upon the speed and efficiency

with which stairs can be negotiated, Fruin (1971) reports a negative correlation between pedestrian movement speed and stair slope. Pauls (1980) concurs with Fruin, suggesting on the basis of his observations of stair use behavior

in public buildings, that within a certain range, larger treads promote more efficient utilization of stairs.

The Code is also concerned with the provision of handrails in egress stairways.

In general, when providing handrails, the designer and building official assume

that the proper location (and subsequent use) of these elements promotes rapid

and efficient use of stairs, particularly during emergencies. Similarly, the

oramisslon of handrails, or their improper design or location, may be assumed to

increase the likelihood of stair accidents and of other impediments to safe

and rapid movement. The literature on stair use behavior and stair accidents

remains equivocal on these points. For example, while McGuire (1971) and

Templer (1974) attribute a substantial proportion of stair accidents studied

to a lack of available handrails, Carson et al. (1978) could establish no significant relationship between the presence or absence of handrails and

accident rates. Interestingly, Carson et al. (1978) note a positive relationship between handrail availability and such less serious stair Incidents as missteps. This relationship, however, is counterintuitive, since missteps

were found by these investigators to be more frequent in cases where handrails

were in fact available.

However, these investigators did find that the severity of stair accidents

tends to increase when handrails are absent, and that in general, accidents on stairs without handrails tend to result in more serious bodily injuries. In

this regard, Pauls (1980) has pointed to the varying needs of individual occupants for handrail support. Archea et al. (1979) also found differenes in the

need for handrail support between elderly persons, children, able-bodied adults,

and other individuals.

Benefits derived from providing center handrails in wide stairs have not been

analyzed in detail by researchers. Galbreath (1969) suggests that while the

provision of center handrails may decrease the likelihood of accidents, it also

reduces the overall width of the egressway. Archea et al. (1979) report that no causal link between the provision of center handrails and accident rates on heavily-traveled stairs has as yet been empirically established. However,

these investigators also recommend the use of intermediate handrails on wide

stairs

Regarding the efficient use of ramps under egress conditions, Fruin (1971)

found that grades up to 6 percent appeared to have little effect on pedestrian

movement speed. This finding is corroborated by Tregenza (1976), who also

notes that a 10 percent ramp gradient could reduce upward walking speed by as

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much as 40 percent. Most recently, the Importance of ramps as means of ingress,

egress and Interior circulation has been heightened by concerns for handicapped

occupants of public buildings. Tregenza (1976) reports that ramps steeper than

8 percent can be dangerous for wheelchair users and other persons with motor

disabilities. Steinfeld (1975) recommends that ramps designed for disabled

occupants vary between 4 and 8 percent, with 5 percent as the preferred design

value. Walter (1971) suggests that a 7 percent gradient was optimal for handicapped users. To date, no evidence was found to support or refute the slipresistance features of ramp provisions of the Code .

Assumptions considered in section 6.2.2 consider the influence of stress and

fatigue on occupants' capabilities to safely and effectively negotiate egressways. A number of these assumptions assert that the infiltration of smoke into

egressways such as stairs, because of its potential effects on human respiratory,

visual, and nervous systems, may exert physiological stresses on escaping occupants, reducing their egress capabilities. Perhaps the most prevalent fire

product is toxic smoke, a critical constituent of which is carbon monoxide (CO).

A number of experiments have been conducted to study the effects of high doses

of CO on both conditioned and unconditioned responses of laboratory animals

(Laties and Merigan, 1979). In most of these studies, the onset of abnormal

behavior occurs at CO concentrations of between 200 and 400 parts per million

for a minimum exposure of one hour. These concentrations are generally

associated with carboxyhemoglobin (COHb) levels of between 13 and 25 percent.

Petajan (1976) has pointed out on the basis of his experiments with laboratory

animals that nonadaptive behavior may result from impairments of animals' abilities to process and utilize new environmental Information, rather than from

purely physiological impairments of sensory and motor systems. Obviously, the

examination of human cognitive, sensory, and motor behavior under exposure to

high concentrations of CO for prolonged periods is life-threatening and is not

advocated here. A number of experiments utilizing human subjects have been

carried out, however, to study potential effects of relatively low CO concentrations over time periods somewhat characteristic of those encountered during

fire emergencies. Under such conditions, most investigators found that COHb

level of up to 30 percent had little effect of human psychomotor response patterns, even when subjects were exposed to low concentration CO for five hours

(Milkulka, O'Donnell, Heinlg and Theodore, 1970; Stewart, Peterson and Buret ta,

1970; O'Donnell, Milkulka, Heinig and Theodore, 1971). Results of these studies

suggest that moderate doses of CO, as might be experienced under certain conditions during building fires, would not adversely affect occupants' escape performance to any significant degree. In support of these empirical findings,

post-incident fire investigations by Wood (1972) and Byran (1977) revealed that

a substantial proportion of individuals interviewed moved through smoke while

evacuating, and that some of these occupants may have traversed up to 400 feet

(122 m) in a smoke-filled environment. Wood called this finding "surprising."

These findings indicate that CO contributes to performance decrement during

fires in only minimal ways. However, anecdotal evidence from actual fires

provides a contradictory viewpoint. The December 4, 1980 Stouffer Inn fire in

Westchester County, New York, (The Herald Statesman, December 14, 1980) provides a case in point. The fire department was on the scene within 12 minutes

81
of the fire's initial detection, and found that a number of victims had already

died from what is believed to have been CO poisoning. County medical examiners

have speculated that in this case the presence of automatic sprinklers might

not have prevented the rapid spread of toxic gases which are believed to have

been the cause of death for numerous victims. In one Instance, the last person

leaving a room inadvertently made a wrong turn and was soon overcome by smoke.

This individual died as a result of toxic gas inhalation. Such events as the

Stouffer Inn fire and the recent hotel fires in Las Vegas, Nevada, point to the

rapid Incapacitation of occupants as a result of smoke products.

One explanation for the apparent disparity between research findings and

anecdotal accounts concerns the nature of building materials which, during fire

conditions, release toxic products. For example, an experiment by Mitchell

(1978) demonstrated that the time required to incapacitate laboratory rats was less in the presence of burning synthetic pol5nneric furnishings than in the pre- sence of burning natural fibrous materials. Extremely few data are currently

available regarding human tolerance to short term exposures (i.e. less than

five minutes) to high concentrations of multiple contaminants. However, the

inhalation of hydrogen chloride simultaneously with carbon monoxide is now known to be corrosive to human respiratory organs (Phillips, 1978). A single

material comprising a room furnishing may release a relatively harmless toxicant when ignited. But when such toxicants combine with other substances in

the fire environment, the result may be debilitating and even lethal (Phillips,

1978).

Another problem associated with the infiltration of fire products into

egressways , is visibility. Phillips (1978) noted that when hydrogen chloride

gas comes in contact with the human eye hydrochloric acid is formed, causing

Intense pain and tearing, and interfering with normal vision. Ammonia and

fluoride gases have similar effects. Such toxicants are capable of impairing

human vision even before smoke density is sufficient to obscure visibility

through diffusion. Experimental data reported by Rasbash (1975), and Jin

(1976), indicate that when visibility is reduced to approximately five meters,

the ability of subjects to negotiate egressways is impaired. Tfowever, these

findings are not corroborated by data from post-incident surveys collected by

Bryan (1977) and Wood (1972).

Research on the effects of CO also has indicated that this toxicant may

influence tje visibility threshold (McFarland, Roughton, Halperin and Niven,

1944; Halperin, McFarland, Niven and Roughton, 1959). Recent studies have

suggested that visual function is relatively Insensitive to CO (Salvatore,

1974). However, Laties and Merigan (1979) note that the brief exposure to

particularly high concentrations of CO may impair vision. An anecdotal account

of one victim's experience during the recent Stouffer Inn fire illustrates this

phenomenon. This individual reported escaping only after having seen a "flash

of light" (as an exit door was momentairly opened). Although the Individual

quickly lost sight of the light source itself, he did remember the general

direction from which the light had come. Thus, it would appear that while occupants are often willing to walk through a smoke-filled egressway, the infiltration of smoke and toxic gases into such channels may create physiological

stresses which inhibit effective egress behavior.

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In addition, the infiltration of fire products into egressways may substantially

increase ambient temperatures in these spaces. Mura (1975) reported that the

highest ambient temperatures which humans can tolerate without undue physiological stress is 42 °C (110°F). Most of the literature on human physiology under

high temperatures has been concerned with relatively long-term endurance, and

stress due to heat has been examined primary in relation to performance decrement and fatigue by humans performing experimental tasks in laboratories

(McCormick, 1976).

The present review of the literature yielded little information concerning

potential effects of dead end corridors upon egress time. The perception that

dead end corridors contribute to fire deaths and injuries continues to be held,

however. For example, Westchester County (New York) Executive Alfred Del Bello

called for a County-wide fire code provision prohibiting dead-end corridors, in

the Immediate aftermath of the Stouffer Inn fire (The Herald Statesman, December 6, 1980). The current investigators* examination of the Stouffer Inn floor

plan, indicating locations where fire victims found (as published in The Herald

Statesman), however, yielded no direct evidence that the presence of dead end

corridors in that building was a direct cause of death. It should also be

recalled that Best (1970) found, on the basis of his field experiments under

nonemergency conditions, no statistically significant relationship between the

presence of dead-ends and subjects' reports of being lost.

One somewhat obvious argument for the limitation or prohibition of dead end

pockets or corridors concerns the notion that a person may suddenly become

intensely stressed psychologically upon realizing that an erroneous — and

potentially very costly—egress decision was made. Although the literature on human behavior during fire situations sheds little light on this notion, the

psychological experiments indicate that when turns or other adjustments are present in pedestrian routes, experimental subjects perceive these routes to be

longer than linear paths of equal length (Sadalla and Magel, 1980). This phenomenon may contribute to occupants' perceptions of increased distance (and

tlme)-to-safety when dead ends are encountered. Indeed, the perception of

increased time-to-safety has been linked "panic" (Janis and Mann, 1977).

The hypothesis that persons with fear of high places (acrophobia) could panic

or otherwise slow movement on unenclosed outside stairs is reasonable but must

be qualified. According to knowledgeable experts who treat acrophobia clinically, the following scenarios are reasonable: Faced with a clear life-ordeath situation posed by a fire emergency, many arophoblcs will successfully

use an unenclosed outside stair if there is no other alternative. If it is

clear to the acrophobic that others who are facing the fire emergency are fearful, many phobics are less likely to have the phobia interfere with using an outside unenclosed stair. If the acrophobic is with someone who can guide

this Individual and offer him or her physical and psychological support during

egress, the acrophobic is increasingly likely to use an outside unenclosed

egress stair. Of course, if the outside stair is sufficiently enclosed to prevent the phobic from seeing over the side or down, this will make the outside

route acceptable to the acrophobic since the cues that would arouse the phobia

are avoided. There is consensus among expert clinicians interviewed by the

current investigators that a properly enclosed outside stair should increase

83
the likelihood that acrophobics will use the stair during a fire emergency as an egress route. These experts do, however, question the adequacy of the

current Code provision for meeting the needs of acrophobics.

Thus, the available literature supports behavioral assumptions on the effects

of fire products on occupant’s capabilities to escape rapidly. Support for

assumptions concerning the effects of dead end corridors, however, remains weak

and equivocal. Clinical evidence appears to support the assumption concerning

occupants with fear of high places.

Behavioral assumptions enumerated in section 6,2.3 address the influence of

doorway and door hardware design upon occupants' capabilities to negotiate means

of egress. Very few data are available describing door operation by building

occupants. Code provisions specifying a maximum door opening force of 50 pounds

applied at the latch style and 15 pounds applied to a panic bar may be applied

under the assumption that these represent normative maximum forces applicable

by most building users. Experimental research by Van Cott and Kinkaid (1972)

suggests that when standing individuals apply right-handed static forces to

vertical handgrips, somewhat less than 50 pounds of force may in fact be available. However, evacuees can often generate additional dynamic forces associated

with potentially rapid movement up to a door. In addition, occupants can be

expected to apply extra forces available from the shoulder and other portions

of the body, if necessary.

Steinfeld, Schroeder and Bishop (1979), studying problems associated with making

buildings more accessible to disabled persons, investigated the ability of

individuals with various disabilities to exert forces on doors and other architectural hardware. These researchers note that more than 23 percent of the

wheelchair users they observed could exert forces greater than 15 pounds in any

required direction. In addition, between 33 and 44 percent of all other disabled subjects tested could exert forces greater than 15 pounds in any required

direction. However, available evidence also suggests that disabled polulatlons, even those with comparatively "nonserious" disabilities, are not able to exert

50 lb (222 N) , which is the maximum force permitted to open a nonfunctional

power-operated door (see Margulis, 1981).

Based on data from a survey designed to study walking and panic behavior during

fires, Yamada (1975) found that the design and configuration of doors influenc'^

the flow rate through doorways. For example, substantial decreases in flow were noted for sliding doors and doors opening against the flow of pedestrian

traffic. The study also noted that people often tended to pull at doors

designed to be pushed. These data suggest that occupants' lack of familiarity

with the opearting characteristics of various types of doors may lead to

increased evacuation time.

Thus, with the exception of data describing panic bar operation (primarily by

disabled occupants), there are presently too few data on door manipulation to

support or refute behavioral assumptions believed to underlie provisons of the

Code enumerated in section 6.2.3.

84
Technical strengths and weaknesses of the literature . Many of the behavioral

assumptions relating to Code provisions Intended to maximize the safe and efficient negotiation of egressway by occupants focus on vertical components of

building circulation systems (l.e., stairs and ramps). Although several studies provided data concerning stair use, the application of much of this data

to the specific Issue of emergency egress remains problematic for a number of

Important reasons. First, all stair use data available In the literature are derived either from field studies conducted In everyday, nonemergency building

environments (e.g., Carson et al., 1978; Fruln, 1971), or from experiments

utilizing relatively unrealistic laboratory apparatus (e.g., Templer, 1974).

Thus, environmental cues and stimuli, sources of psychological and physiological stress, levels of occupant density, and determinants of arousal and vigilance may differ widely between settings from which available data have been

gathered, and those found during actual fires requiring rapid emergency egress.

Second, the nature of the available data on stair use behavior presents certain

difficulties for the building design and regulatory analyst. There have been

no attempts to systematically compare stair use behavior under different

design, structural, and environmental (e.g., smoke) conditions. Hence, there

Is no real basis for determining the relative advantages or disadvantages of

particular conditions. Worse, with the exception of Templer *s (1974) research

on the biomechanics of stair negotiations, all relevant studies Involve non- experlmental research designs. Thus, even given a comparison of design, structural, or environmental conditions, these research designs do not allow

researchers to draw plausible Inferences about the casual relationship between

these antecedents and stair use behavior. Similarly, the failure of Investigators to make systematic comparisons between occupancies, classes of events, and

occupants of varying capability render many of the available conclusions difficult to generalize with any degree of precision. In all, there Is little basis

for supporting or refuting the acceptance of particular design or structural

solutions or of environmental conditions.

The reader also should be cautious when making generalizations about the use of

ramps as means of egress during actual fire situations on the basis of available data. Nevertheless, data reported by Fruln (1971) and Tregenza (1976)

which suggest that ramp slopes greater than 6 percent substantially reduce

upward walking speed do seem useful In establishing performance objectives for

ramp design. By contrast, the lack of data currently available to either support or refute assumptions about the role of weather protection and slip resistance In ramp design make analyses of certain Code provisions at this time

Impossible.

The literature on respiratory and visual stress and fatigue reports data which

are often only Indirectly relevant to anaylses of egress time. Moreover,

findings noted In this literature, when relevant, are sometimes contradictory.

In most cases, studies of CO exposure employed wellcontrolled laboratory

procedures. While laboratory experimentation Is Intended to assure Internal

validity. Its very strengths may severly limit the extent to which Inferences

from experimental data can be generalized to complex settings encountered

during real fires. For example, experimental data describing the effects of

long-term exposure to low level concentrations of CO on behavior should not be

85
assumed to describe behavior under short-term exposure to relatively high level

CO concentrations, or under conditions when CO combines with other toxicants.

Findings reported by Bryan (1977) and Wood (1972) are relevant to the role of

smoke In analyzing emergency escape behavior. However, neither Investigator

actually measured smoke density and levels of CO and other toxicants, nor systematically correlated characteristics of smoke-filled environments (beyond the

mere presence of absence of "smoke") with such observed behavior patterns as re-entry.

Dramatic decreases In occupants’ egress capabilities arising from the exposure

of human eyes to fire products have been well documented (Phillips, 1978).

Such performance decrement Is almost entirely physiological In nature. In addition, reductions In visibility, while they do not physiologically affect the

eyes, may psychologically stress the evacuee. Research by Jin (1976), Rashbash

(1975), and Watanabe et al. (1973) has begun to yield physical measures of

visibility distance under varying levels of smoke density. However, no Investigators have empirically studied the Influence of visibility decrement on egress decisionmaking, strategy formation, and on other cognitive factors which

Influence overall egress time. For example, smoke may be presumed to slow

walking speed under certain conditions, and this Increases egress time. But

perhaps smoke also prompts occupants to seek alternative (potentially smokefree)

paths to safety. How does this behavior Influence egress time? Does the need

to rethink the egress strategy create additional stresses for humans which

exaggerate any time lost negotiating longer paths?

Similarly, It Is not now possible on the basis of available literature to

evaluate either Code provisions Intended to limit dead end corridors and to

regulate the design of outside stairs, or behavioral assumptions concerning

occupants’ use of these design features. Relevant research has suggested a number of useful hypotheses. However, these need to be empirically tested.

Current clinical assumptions regarding the behavior of acrophoblcs do appear

useful In understanding certain problems In the use of unenclosed outside egress

stairs, although the effects of acrophobia on egress behavior In the presence

of Ilf e-threatenlng environmental stimuli are, at present, little understood.

Current data are not useful for describing the effects of door and hardware

design upon evacuation time. Much of what Is available provides a basis for

the design of doors to be operated by handicapped persons. Today, the building

design community generally holds that design solutions Intended for handicapped

persons should pose no obstacles for able-bodied persons. However, there

remains no generally held analytical base which either supports or refutes

behavioral assumptions about door use, and related provisions of the Code .

6.4 SUMMARY OF GAPS IN THE TECHNICAL LITERATURE

6.4.1 Research on the Affect of Stair and Ramp Design on Occupants’

Capabilities to Safely and Rapidly Negotiate Egressways

The stair use model proposed by Archea et al. (1979) has found some support In

the accident and human factors literatures. However, connections between

86
specific perceptual failures and accident modalities, as predicted by this

model, have never been empirically established. Even minor stair mishaps can

be significant during emergency evacuations, insofar as they block egress

pathways and slow pedestrian flow, and increase overall exit time. To the

degree that perceptual failures Indeed increase the likelihood of such events,

their specific role must be more fully understood. This understandably will

make designers better informed as to opportunities for mitigating potential

sources of increased evacuation time. For example, it is Important for

designers to comprehend the role of color, lighting, and surface texture in

occupants' use of stairways, precisely because these factors may either clarify

or obscure visual and tactile stimuli necessary for efficient stair negotiation.

Changes in occupants' attention to stair-specific environmental cues, particularly those which may be brought about in a rapidly changing fire emergency

scenario, have not been investigated and therefore require study.

Available research on riser-tread dimensions is not sufficient to permit

conclusions regarding stair design practice for emergency escape. Future

research on this topic should strive to ascertain the degree to which particular riser-tread ratios influence egress flow rates on stairs. Similarly,

future research on stair tread and ramp surface treatment should be directed

toward developing standard frlction-versus-f low functions useable by designers.

Ramps are frequently provided to facilitate building access and egress by

handicapped persons, particularly those in wheelchairs. In an increasing number of instances, designers are providing ramps exclusively for changes in

level of less than one story. In such cases ramps are clearly useful by both

wheelchair-bound and ambulatory persons. But can this be said for many elderly

individuals, or for people suffering degenerative decreases of the foot, knee,

and hip joints? For such individuals, the presence of a ramp may have an appreciable effect upon the selection of an egress route, and hence, impact

these people's egress times. Differences in ramp effectiveness must be studied across groups of people who differ in mobility characteristics before designers

can provide facilities for vertical movement on a well-informed basis. Similarly, designers require information describing the relative effectiveness of

stairs versus ramps during egress, for nonwheelchalr-bound occupants,

6.4.2 Research on the Affect of Stress and Fatigue on Occupants' Capbilities

to Safely and Rapidly Negotiate Egressways

Behavioral assumptions suggesting that the infiltration of fire products into

egress ways adversely influences egress flow require further empirical verification, Available research and anecdotal accounts discussing the effects of

CO exposure are contradictory and of limited utility. While certain effects of

short duration exposure to low doses of CO have been noted in the literature,

inferences from these findings to behavior during actual building fires are difficult to justify. This report's authors do not advocate the use of human

subjects in experiments which accurately reproduce the toxic and other lifethreatening qualities of fire environments. They do, however, suggest that

animal time-to-safety experiments within toxic environments, as well as simulation excerclses using human subjects, be redesigned to account for greater

percentages of extraneous variation due to likely environmental effects than

has been accommpllshed to date.

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Studies of respiratory, visual, and temperature adaptability of various

occupants under a number of fire scenarios are warranted by available evidence.

For example, contact with toxic fire products may lead to occupants* incapacitation more quickly in a senior citizen's center than in an office building.

Available knowledge on the effects of visibility decrement upon egress speed

also requires expansion and verification.

Clinical experience suggests the need to obtain evidence to specifically

determine the adequacy of the Code provision addressing the needs of acrophobics. This provision requires stairs three or more stories in height to

have partitions at least 48 inch high. However, clinical experience suggests

that partitions are required on outside stairs at least two stories in height,

since the acrophobic response may be likely on an unenclosed stair two stories

high. Clinical experience and anthropometric data also suggest that a 48 inch

minimum may be too low. While it is critical to have a stair properly enclosed

at its entrance, there is debate among clinical experts about whether enclosure

should continue to the bottom of the run, a point that is unclear in the provision, As for the nature of the enclosure, if the walking surface of the landing or treads of an outside stair permits the phobic to see down through the

metal elements, a phobic response is likely. So, too, is phobic response

likely with an enclosure that is only 48 inch high. A significant portion of

the population (assuming that acrophoblcs are representative of the larger

population of their sex in height) will be able to see over a 48 inch partition

and down.

6.4,3 Research on the Effects of Doorway and Door Hardware Design on Occupants'

Capabilities to Safely and Rapidly Negotiate Egressways

Current research on the door-manipulating capabilities of handicapped persons

should be expanded to include all categories of building occupants, as well as the wide variety of door and landing configurations. While the design of

physical elements (doors, hardware and spatial configuration) comprise one class of independent variables, ambient environmental conditions provide another

class. As a point of departure, future investigators should be concerned with

identifying variations in door manipulation performance which may be attributable to changes in lighting and visibility.

Another Important gap in the technical literature concerns knowledge of the

relationship among stress, fatigue, and evacuees* capabilities to manipulate

doors and door hardware, Phillips' (1978) comments illustrate this critical,

although little understood, issue: She notes anecdotes describing evacuees clawing at doorknobs under smoke and fire conditions; apparently these individuals actually thought they were properly turning the knobs.

6 . 5 SUMMARY

In summary, human behavioral assumptions believed to underlie Code provisions

relating to occupants* capabilities to safely and rapidly negotiate means of

egress may be evaluated by reference to biomechanical models of human movement,

toxicological research, stair and ramp use field studies, physiological measurements, and anecdotal evidence from actual fire incidents. At present, much of

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the evidence reported in the experimental and nonexperimental literatures on occupants’ capabilities is contradictory, results in mixed opinions, and does

not permit specific conclusions or inferences to be drawn. As a result, there

appears to be no analytical basis upon which to unequivocally support or refute

applicable Code provisions. It is left for future research to determine the

specific domains (i.e., occupancies of fire scenarios) under which particular

data are valid and useful in this context.

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7. PROVISIONS GOVERNING THE CAPACITY OF MEANS OF EGRESS

7.1 APPLICABLE CODE PROVISIONS

5-2 . 1 . 1 .2 .

Where a doorway Is divided by mullions, the allowable units of

exit width for the entire doorway shall be the sum of the units of exit width

calculated separately for each individual door in the opening,

5-2. 1.1. 3,1 No single door in a doorway shall be less than 28 inches wide,

5-2 , 1 , 1 .3.2 No single door in a doorway shall exeed 48 inches in width,

5-2,1. 1.4.1 Any door in an exit and not exempted by 5-2.1. 1,4,4 or other

provisions of this Code shall be so designed and installed that when a force is

applied to the door on the side from which egress is to be made, it shall swing

in the direction of exit travel from any position to the full instant use of

the opening in which it is installed. During its opening process or when fully

opened, a door shall not obstruct the exit width as determined by 5-2.1. 1.2.1.

5-2 ,1 ,1 ,4 ,2 A door giving access to a stairway shall swing in the direction of

exit travel. A door during its swing shall not block stairs or landings. In

new buildings any door, at any point in its swing, shall neither reduce the

effective width of stair or landing to less than one unit of exit width nor when open interfere with the full use of the stairs,

5-2 .1. 1.4.3 An exit door or exit access door swinging into an aisle or passageway shall not restrict the effective width thereof at any point during

its swing to less than 1/2 the required widths hereafter specified,

5-2.1 .1 ,4 ,4 Any door in a means of egress shall be of the side-hinged, swinging

type and shall swing in the direction of exit travel when serving a high hazard

area or an occupant load of more than 50. Such doors shall conform to the

appropriate requirements of 5-2.1.

5-2.1 ,3.2.1 A revolving door shall not be used in a means of egress.

Exception: Where specifically permitted by some individual occupancy chapter

of this Code for an exit from the level of exit discharge directly to the

outside^ in which case:

(a) Such door(s) shall not be used at the foot or at the top of stairs at

the level of exit discharge,

(b) Such door(s) shall not be given credit for more than 50 percent of

the required units of exit width,

(c) Such revolving door(s) shall be of approved type(s),

5-2 . 1 .3 ,2 ,2 Each allowed revolving door may receive credit as constituting 1/2

unit of exit width.

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5-2. 1.3. 2.

The number of revolving doors used as exit doors shall not exceed

the number of swinging doors used as exit doors within 20 feet thereof.

Exception: Revolving doors may serve as exits without adjacent swinging doors

for the street floor elevator lobbies, if no stairways or doors from other parts

of the building discharge through the lobby, and the lobby has no occupancy

other than as a means of travel between elevators and street,

5-2 .1.3. 2.

Revolving doors shall be equipped with means to prevent their

rotation at too rapid a rate to permit orderly egress.

5-2. 1.3. 3.1 No turnstile or simular device to restrict travel to one direction

or to collect fares or admission charges shall be so placed as to obstruct any

required means of egress.

Exception: Approved turnstiles not over 3 feet high, which turn freely in the

direction of exit travel, shall be permitted in any occupancy where revolving

doors are permitted,

5-2.1 .3.3.2 Turnstiles over 3 feet high shall be subject to the requirements

of revolving doors.

5-2.1 .3.3.3 Turnstiles in or furnishing access to required exits shall be of

such design as to provide 22 inches clear width as the turnstile rotates.

5-2. 1.3. 3.

No turnstile shall be placed in any required means of egress.

5-2.1 .3.3.5 Turnstiles shall be rated the same as revolving doors as regards

units of exit width and rates of travel.

5-2 .2.2.5 Stairways and Intermediate landings shall continue with no decrease

in width along the direction of exit travel.

5-2 .8 .2 .4 A single escalator 32 Inches wide shall be given credit for 1 unit

of exit width. An escalator 48 inches wide shall be given credit for 2 units

of exit width.

5-3.2.

Means of egress shall be measured in units of exit width of 22 inches.

Fractions of a unit less than 12 inches shall not be counted. Fractions of a unit comprising 12 or more inches, added to one or more full units, shall be

counted as 1/2 unit of exit width.

5-3. 2.

Width of means of egress shall be measured in the clear at the

narrowest point of the exit component under consideration.

Exception No, 1: A handrail may project inside the measured width on each side

not more than 3 1/ 2-inches

,

5-3.3 Capacity of Units of Width. The capacity in number of persons per unit

of width for approved components of means of egress shall be as follows:

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(a) Level of egress components, a Class A ramps—100 for travel in either

direction.

(b) Class B ramps—60 for travel in the up direction, 100 for travel in

the down direction,

(c) Stairways—60 for travel in either direction.

5-3. 4.1 The minimum width of any way of exit access shall be as specified for

individual occupancies by Chapters 8 through 16; but in no case shall such

width be less than 28 inches.

17-1 .2.1.1 Every required exit, exit access and exit discharge shall be

continuously maintained free of all obstructions or Impediments to full instant use in the case of fire or other emergency.

7.2 UNDERLYING BEHAVIORAL ASSUMPTIONS

7.2.1 Assumptions Pertaining to the Influence of Architectural Barriers and

Other Obstructions to Egress Flow

( 1 ) Intended maximal use of means of egress can only be achieved when

egress ways are maintained free of obstructions (17-1.2.1.1).

(2) Egress is slower through doorways with mullions than through those

without mullions (5-2, 1. 1.2.2)

(3) Doorway width Influences egress time; the optimal width is 28 through

48 inches (5-2. 1. 1.3. 1; 5-2. 1 . 1. 3.2)

(4) Architectural obstructions within egressways (e.g. door hinges,

railings, etc.) may reduce discharge rate (5-2. 1. 1,4, 1; 5-2.1. 1.4.2;

5-2. 1.1. 4. 3).

(5) The degree of reduction of egress time due to obstructions in egress

ways is a function of occupant load (5-2. 1. 1.4.4)

(6) Revolving doors may Increase evacuation time by as much as 100

percent; revolving doors cause congestion and a "bottlenecking" effect which

reduces flow through the egressway; the speed of rotation influences the flow

rate through a revolving door, and within a certain range, an increase in

speed of rotation results in reduced flow through the door (5-2. 1.3.2. 1 through

5-2. 1.3. 2. 4).

(7) Turnstiles have substantially the same effect on the efficiency of

pedestrian ways as do revolving doors (5-2. 1.3. 3.1 through 5-2. 1,3. 3.5)

(8) Variation in stairway width along the direction of egress travel may

result in reduced egress flow (5-2. 2. 2,5),

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(9) To maintain adequate egress flow on an escalator, it must be wider

than a conventional stair (5-2. 8. 2.4).

(10) When an egress channel element varies in width (along its length),

its overall flow capacity is approximately equivalent to the capacity at its

narrowest point (5-3. 2. 2).

7.2.2 Assumptions Pertaining to the Flow Capacity of Egress Channels

(1) Flow rates average 100 persons per 22 inch exit unit per minute (pers/

unit/mln) in level egress ways, and 60 pers/unit/min on stairs (in either

direction) (5-3.3).

(2) In general, the capacity of ramps is substantially more than that of a straight flight of stairs, particularly in the downward direction (5-3.3).

(3) The minimum channel width capable of providing appropriate egress flow

rates is 28 Inches, although this width is expected to yield the same flow

characteristics as an egress element 22 inches wide (according to provision

5-3.2. 1 and its underlying assumption) (5-3. 4.1).

(4) Pedestrians travel in linear files approximately 22 inches in width; an exit between 22 and 34 inches in width provides the same flow capacity as a 22

inch exit; an exit between 34 and 43 inches wide provides 50 percent more flow

capacity than a 22 inch exit; a 44 inch exit provides 100 percent more flow

capacity than a 22-34 inch exit (5-3.2. 1).

7.3 COMMENTARY

7.3.1 Problem

Code provisions governing the capacity of means of egress are intended to assure that exit ways permit escaping occupants to evacuate a burning building as rapidly as possible. This assurance requires not only that exit ways

are of sufficient dimension, but that they minimize opportunities for blockages

or other impediments to egress flow, as well. Human behavioral assumptions

which underlie Code provisions enumerated in Section 7.1 address (1) the influ- ence of architectural barriers and other potential obstructions on egress flow,

and (2) the flow capacity of egress channels.

Conceptual views of pedestrian movement drawn from field investigations of such

behavior are useful in understanding the flow of occupants through exit ways in

buildings. Three models are based on physical analogs (e.g. equating the flow

of gas molecules with pedestrian movement), while one concept is derived from

human behavioral theory. Their relevance to Code provisions and underlying

behavioral assumptions concerned with the capacity of means of egress is

considered below.

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7.3.2 Underlying Behavioral Models

Prevailing models of pedestrian movement have been derived primarily from

physical science concepts. In general, investigators have distinguished high

density from low density flow (Henderson, 1971). A number of researchers have

shown that, under certain conditions, high density human movement may be adequately modeled as an example of particle movement (Peschl, 1971) or fluid

dynamics (Archea, 1979, Henderson, 1971), while others have suggested that low

density pedestrian movement is best modeled as an example of gas flow

(Henderson, 1971). In addition to the physical analogs, the concept of personal

space identified by environmental psychologists (Sommer, 1969) has been usefully

applied in explaining human movement in pedestrian ways (Fruin, 1971).

The particle model, useful in explaining high density pedestrian flow, has been

most succinctly presented by Peschl (1971). According to Peschl, crowd movement

is analogous to the flow of granular particles from bins. The model recognizes

that human beings are not merely granules, that spaces within buildings are not

simply bins, and that pedestrian movement is not governed by the force of

gravity.

However, the particle model posits that under conditions of high density

(crowdlike) occupancy, individuals have virtually no freedom of movement and are little more than elements comprising a flowing granular mass. The model

further suggests that the behavior of this mass may be described mathematically.

The granular analog suggested by Peschl may best describe high density occupancy

conditions within a tightly bounded environment, under a state of panic. Under

such conditions, individuals may attempt to escape as quickly as possible. If

there is a single exit (in the direction of flow), then there is likely to be a "pile up" of people pressing against the exit and its surrounds. Here individuals will occasionally be able to pass through the exit, but most people will

pack against each other attempting to gain access to it. The particle analog

suggests a vessel open at the top and with a small hole in the bottom. Ball

bearings are poured into the vessel, and these, by force of gravity, fall to

the bottom of the vessel. Some ball bearings fall through the hole at the

bottom, which is just large enough to admit one ball bearing at a time. But if

the ball bearings are poured into the vessel at a rate faster than that at which

they leave through the hole, ball bearings soon begin filling the vessel, packing against one another. Soon, very few if any ball bearings are admitted

through the hole. A piston pushing down upon the ball bearings from above will

make it Impossible to empty the vessel.

The particle model is useful in describing the so-called "arch effect", first

observed in the field by Togawa (1955). An arch is a small semicircular web

of people held firmly in place at a doorway by the force applied by people

behind the arch attempting to move toward the doorway. Peschl noted that the

formation of such arches, which can prevent individuals from passing through

the doorway, is difficult to predict. He conducted experiments with both

human subjects and steel balls used to simulate a human mass in order to test

the arch concept. On the basis of these experiments, Peschl concluded that

(1) the wider the exit way, the smaller the probability of arch formation and

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the greater the variability in flow rate; (2) the probability of arch formation

decreases as density decreases; (3) flow rate through doorways decreases as density increases; (4) exit rate is a positive linear function of doorway

width; and (5) pulsating flow through exit ways often results with the natural

formation and dissolution of arches,

A clear illustration of the relevance of the particle model to behavioral

assumptions concerning the capacity of means of egress, particularly under high

density conditions, is found in the eyewitness report of a victim of the Beverly

Hills Supper Club fire (The Cincinnati Post, Thursday, June 2, 1977). The individual recalled having first wondered why the egress line had come to a halt.

This was prior to the intrusion of fire products into the room in question. The

victim next reported pushing against the crowded line ahead. As fire products

entered the room, frustration appeared to build. At the open exit way, the

victim reported, people had "bottlenecked,” forming an arch which enabled very

few people to actually pass through the exit. This individual was saved by

having grasped hold of the mullion dividing the double door of the exit once reaching the arch, and then by finally exerting considerable force and "popping"

out of the arch and through the door (a phenomenon observed previously by both

Togawa, 1955, and Peschl, 1971).

A somewhat different analog useful in describing high density pedestrian

movement is suggested by the hydraulic model (Archea, 1979). The hydraulic

model posits that above some level of occupant density, the movement of people

through a network consisting of corridors, doors, stairs, and similar architectural elements is analogous to the downward flow the water through pipes,

valves, and other elements of a gravity-fed fluid distribution system. Accordingly, the hydraulic model presents building evacuation as a two-phase process.

The initial, or "start up," phase concerns the simultaneous initiation of movement directly toward exits by numerous individuals upon receiving an emergency

alert. This is presumed to be analogous to opening valves and filling basins

at the periphery of a gravity-fed water distribution system (e.g. household

plumbing). The actual egress phase concerns the deliberate and systematic

progression of indiviuals through various architectural elements until they

have finally exited the building. This is viewed as analogous to the path

followed by water as it works its way though a gravity-fed plumbing system,

as the peripheral bains are emptied.

In employing the hydraulic model, one assumes that occupants being modeled are alert and able bodied, and that all occupants of a building or section of a building are not only simultaneously alerted to the fire danger, but that all

occupants simultaneously initiate purposeful egress behavior as well. Moreover,

all occupants are assumed to travel at a uniform rate of flow, and to be sufficiently close to one another so as to severely constrain each other’s freedom

of movement. Finally, the model assumes the undirectional flow of occupants

from occupied spaces along specified paths to predefined exits. In the hydraulic

model, valves and pipes are analogous to egress way elements, while sinks, tubs,

and similar fluid-holding fixtures are analogous to rooms and other occupied

spaces within buildings. Pulling the stopper in a sink is analogous to sounding

a fire alarm and thereby initiating uniform mass evacuation. The focus of the

model is on maximizing the flow capacity of the egress ways. Here, flow rate

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is the key measure of system performance. The processes by which building

occupants respond to alerts and initiate movement toward (as distinct from

through) means of egress are not addressed by the hydraulic model.

In discussing the relevance of the hydraulic model to behavioral assumptions

considered in Section 7.2, comparisons with the particle model described

earlier are useful. Human behavioral assumptions outlined in Section 7.2.1 of

the current report address effects of architectural impediments and other

obstructions to the efficient flow of occupants in egress ways. The hydraulic

model provides analogs to such barriers as decreases in channel width along a given distance, and such physical obstructions or blockages as doors with

insufficient flow capacity. These hydraulic analogs primarily Include

decreases in the diameter of fluid-carrying pipes, and the partial or full

closure of valves, respectively. Such analogs permit the hydraulic model to

describe flow characteristics in egress channels which in fact vary in width,

and which contain turnstiles or other opportunities for bottlenecks to occur.

However, whereas the particle model provides a physical analog for arching at

doorways, blockage or entrapment at tight corners, and the prohibition of

pedestrian movement resulting from individuals being pressed against channel

walls, these phenomena—observed in the field—cannot be properly modeled

using hydraulic analogs. While ball bearings may become jammed and arch

against a very small opening (analogous to human arching at a relatively narrow

exit), liquid will always flow freely (albeit at a reduced rate) through openings, however small. Thus, the hydraulic model best simulates flow reductions

caused by the closure of exits; flow ceases entirely when a channel is com- pletely sealed. In contrast, data indicate that pedestrian flow can become

virtually halted even though exits are open, as in the case of jamming and

arching. This latter phenomenon is better simulated by the particle model.

Whereas the Beverly Hills Supper Club fire provided an example of arching in

support of the particle model, the tragedy which claimed the lives of 11

individuals, and injured approximately 10 others, seeking entrance to the

Riverfront Coliseum in Cincinnati, Ohio, in December of 1979 suggests support

for the hydraulic model. In repeated testimony before an investigatory body

covened during the aftermath of this event, victims reported "waves" of pressure literally lifting them off their feet. Such pressure was reportedly

exerted from the rear of the crowd, which as a mass, was pushing against the

entrance doors (not all of which were unlocked and available for use). The

closer an Individual was to the doors, the greater was the force experienced.

Once the doors were actually opened, several eyewitnesses reported having been

"swept" into the Coliseum. Other victims suggested, when interviewed, that if

more doors had been open, fewer people might have been killed or hurt. No

evidence of arch formation was reported by victims of this incident. Anecdotal

evidence from this incident does suggest, however, that the ease and rate of

crowd flow are directly related to available doorway width.

A rigorous analysis of low density pedestrian movement, based on the 19th

century Maxwell-Bolt zman gas model, was conducted by Henderson (1971).

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Henderson argued that while medium and high density crowd behavior could

effectively be modeled as a problem in fluid dynamics, under low density con- ditions pedestrians behaved in a manner more consistent with the kineticmolecular theory of gases. In particular, pedestrians, irrespective of whether

they move as individuals or as members of small social groups , may be viewed as

(1) being statistically Independent of each other in position and velocity, and

(2) moving with a velocity which is uncorrelated with spatial position.

In Henderson's analogy, occupant density (the number of persons per unit area)

is equivalent to particle density in a gas. Differences between pedestrian

movement modes, l.e, standing still, walking, or running, are compared with

differences between gaseous energy modes. Pedestrian movement is assumed to

take place on a continuous planar surface, and if the low density crowd is

homogeneous, then each individual should exhibit both the same mass and the same probability of attaining expected velocity values in a given mode.

According to Henderson, these assumptions would not be expected to hold for

relatively high density situations. For example, pedestrian movement from a very large open space through a narrow channel may, on occasion, result in

increased population density. Where this density is sufficiently high, the

behavior of pedestrians approaching and moving through the narrow channel might

be better described by a fluid, rather than a gaseous, model. Hence, Henderson's

gas analogy seems relevant; (1) to those situations where low density crowds

move within extremely large, effectively unbounded, spatial settings (e.g. outdoor malls), and (2) to those spatial transitions in which density values,

although increased, still exhibit the kinetic-molecular properties of gases.

The relevance of the gas model to understanding the capacity of means of egress

may now be considered. A frequent barrier to free-flow pedestrian movement

along an egress path way is a wall containing a door ensemble. Under high

density conditions, Peschl's particle model suggests that such a barrier would

entrap pedestrians, jamming individuals against the wall and door opening

(where the door is only slightly wider than any individual seeking to pass

through). Under similar conditions, Archea's hydraulic model suggests that

Individuals would flow slowly through the opening, and that eventually all

individuals would pass through the door. Both models hold that occupant density in and of itself produces forces which move pedestrians in a given direction, and that such movement is influenced by prevailing spatial boundary con- ditions. Under low density conditions, however, such forces are presumed not

to be present. Here, individuals approaching a potential barrier (such as a transition from a relatively open space to a narrow channel) are not likely to

be either pressed against a wall, or else pushed under force toward and through

a narrow door way or channel. Rather, any individual directed toward an opening in a physical barrier will pass through. Moreover, seemingly random search

behavior and meandering, as has been known to occur when smoke severely limits

visibility by transient occupants under low density conditions, may, perhaps,

be effectively modeled by the Brownian motion of gas particles.

Although not itself a descriptive model, the psychological concept of personal

space (Sommer, 1969) is useful in gaining a deeper and more realistic understanding of the actual capacity of means of egress. Discussed earlier in the

current report, personal space refers to the small protective zone, or "bubble,"

97
which individuals create around themselves. Perceptions and behaviors

associated with the establishment, maintenance, and adjustment of personal

space comprise mechanisms by which individuals cope with socio-environmental

stressors of the type usually associated with medium and high density occupancy

and pedestrian movement. For example, Fruin (1971) and Pauls (1974) have shown

that pedestrians appear to purposefully establish minimum distances between

themselves and others. Where occupant density becomes quite high, as in a crowded subway train, or behind a blocked exit way, the psychological need for

personal space apparently remains: individuals’ inability to relieve themselves of crowded conditions for lengthy periods have been known to elevate

stress and anxiety.

Fruin (1971) found that under high density conditions in public transit

facilities pedestrians are more likely to close their ranks by reducing their

longitudinal ( front-to-back) spacing rather than their lateral ( side-to-slde)

spacing. Although longitudinal spacing is governed to a great extent by the

maximum distance required to avoid tripping over another individual's feet,

the need for lateral spacing suggests that whereever possible, pedestrians seek

to avoid brushing against or otherwise contacting other Individuals. Current

provisions concerning the width of stairs and other egress channels, however,

are not based upon analyses which specifically consider the role of pedestrians’

personal space needs. For these reasons, Pauls (1974, 1980) has drawn attention to the problem of effective channel width computation, suggesting that

the traditional 22 inch unit of exit of width, referenced by numerous Code

provisions, may be unrealistic and inadequate.

In summary, human behavioral assumptions which underlie Code provisions

affecting the carrying capacity of means of egress are considered in relation

to three physical models of pedestrian movement and to the psychological concept of personal space. It was shown that while these models and the personal

space concept are each useful in understanding a different aspect of egress

way flow capacity, no single analog or concept is sufficient to completely

describe occupant flow dynamics within buildings. The next Section of the

report treats Code provisions and their underlying behavioral assumptions in

vlev7 of data presented in the technical literature.

7.3.3 Assessment of Behavioral Assumptions Based on the Technical Literature

Literature review. Behavioral assumptions presented in Section 7.2.1 consider

the potential effects of architectural barriers and other impediments to rapid

and safe occupant movement through means of egress. Generally, such barriers

and impediments include doors and doorways, revolving control barriers (i.e.

turnstiles and revolving doors), reductions in egress channel width, and

obstructions caused, for example, by the use of egress ways for storage. Exit

width has long been the key concept used to characterize and measure means of

egress, and for analyzing occupant loading and the adequacy of available means

of egress (Sharry, 1978).

A number of behavioral assumptions are concerned with occupants’ use of doors

during egress. The National Bureau of Standards (NBS) reviewed field investigations of pedestrian movement during periods of normal building occupancy at

98
a number of government office buildings and at a major rail terminal (NBS,

1935). On the basis of data obtained during these investigations, NBS con- cluded that the effective rate of pedestrian flow through doors is approximately 60 persons per minute per 22 inch unit of exit width (p/m/unit), or

1,75 p/sec/m. The same report recommends, for the building types studied,

that up to 100 persons per available unit of exit width be permitted to occupy

Interior spaces. This design capacity would, theoretically, require approximately 1,67 minutes to move all occupants of an Interior space through available

exits (exclusive of the time it might be required to bring occupants to the

exits from various parts of the space). Conclusions reported by NBS in 1935

remain central to Code provisions governing the computation of means of egress

today (Sharry, 1978),

More recently, Togawa (1955) surveyed pedestrian walking speeds and flow rates

through doors in department stores, apartment buildings, places of assembly,

and transportation terminals in Japan, His data, among the most comprehensive

available, indicated that flow rates through doors tend to average approximately

50 pers/mln/unit (1,50 pers/sec/m). A survey conducted by the Institute of

Traffic Engineers (1964) revealed professional opinions suggesting that pedestrian flow through doorways averages 30 pers/min/unit (0.9 pers/sec/m. On the

basis of these data, the Institute of Traffic Engineers recommended a design

value of only 20 pers/mln/unit (0.5 pers/sec/m).

Some of the most recent data were collected by Fruin (1971), who studied

pedestrian movement through doors and other facilities at large transportation

terminals, Fruin found that queues developed when the flow rate through a door was less than that of the feeding passageway, and that for doors swinging

freely in the direction of pedestrian travel, 40 through 60 persons typically

passed through per minute (0,67 through 1.00 p/sec.), Fruin also noticed that

if a door must be operated manually, and if the following pedestrian arrives

before the current individual has completed operating the door, a queue will

develop behind the door. Moreover, Fruin reported that elderly and physically

handicapped pedestrians, or persons encumbered with baggage or packages,

typically require longer periods for door operation. Thus, pedestrian ways

(Involving doors) which are designed at or near capacity pedestrian loads are likely to generate frequent queues and similar impediments to rapid, free human

movement

Peschl (1971) conducted experiments to assess the capacity of door openings

during simulated panic situations. Under a variety of doorway conditions

simulated in the laboratory, groups of people were asked to press against door

ways until all Individuals had moved through, Peschl noted that stable arches

formed openings of 47 inches (1.20 m) , and that the frequency of arch formation

increased as door widths became narrower. Openings of 34 inches (0,86 ra) resulted in extremely stable arches, and made passage through the door almost

impossible. At openings of 24 inches 0,60 m, Peschl found that flow rate was effectively zero. Under one experimental condition, an "exponentially curved"

funnel leading to a door way was used. According to Peschl, this type of

design increased pedestrian movement velocities through door ways by a factor

of three, when compared with movement velocities through doors set flush with

surrounding wall surfaces. Similarly, when an exponentially curved wall was

99
compared with circularly curved walls (also providing a funnel toward a door

way) , Peschel found pedestrian movement through the exponentially curved condition to be 2.5 times as fast. Peschal also noted, in general, that as crowd

density increased, movement speed through door ways decreased, and that the

rate of flow through doors was a linear function of door way width. Finally,

Peschl suggested, on the basis of his experiments, that floor surfaces in the

immediate vicinity of, and leading directly toward, exit doors be sloped downward toward these doors, and that the minimum door width for effective safe

egress is 47 inches (1.20 m)

Melinek and Booth (1975) also observed arch formation at door ways under high

density exiting conditions. These researchers found that arch formation became

conspicuous when the flow rate of an exit reaches 60 pers/min/unit (1.80 pers/

sec/m). They also noted that the frequency of arch formation is inversely

proportional to the square of exit width. The former finding appears substantially higher than Peschl 's (1971) findings that stable arches tended to form

when the flow through doors averaged 40 pers/min/unit (1.20 p/sec/m). The

later finding is, however, consistent with Peschl ’s data.

i'lo data are presently available to illuminate the effects of intermediate

mulllons on egress flow through door ways. Data are available on the effects

of Introducting handrails on wide stairs, an indirectly related problem (London

Transport Board, 1958). Studying the movement of passengers in mass transit

stations, the London Transport Board found that pedestrian movement speed down

a stair 72 inches (1.83 m) v/ide was reduced from 130 to 105 pers/min (2.17 to

1.75 pers/sec),a reduction of some 19 percent, after the addition of a center

handrail. This finding contrasts with the fact that the actual number of

pedestrian lanes on the stair was effectively reduced from three to two, a difference of 33 percent.

Direction of door swing in relation to flow has also been studied. Peschl

(1971) and NBS (1935) each recommend that exit doors be designed to open in the

direction of egress travel, but neither provided supporting technical evidence

to indicate the magnitude of this problem. Yamada (1975) found that egress

time increased by 12 percent when pedestrians were required to pass through

doors which opened against the traffic flow, provided pedestrian density was sufficiently low to permit the doors to be operated at all.

Other comments regarding obstructions to egress flow suggest mixed conclusions.

For example, Stevens (1969) notes that obstructions generally tend to reduce

walking speed along pedestrian ways in buildings. Similarly, Galbreath (1969)

Indicates that side railings along stairways tend to have a negative effect on pedestrian flow. Moreover, Landon-Thomas (1972) has argued that even the

slightest obstruction in an egress way could be fatal. In contrast, Melinek

and Booth (1975) holds that minor restrictions such as wall projections have

little effect on flow rate in corridors. The London Transport Board (1958)

report that obstructions up to 1 foot (0.31 m) had no effect on flow, even under relatively high density conditions. As noted above, however, this organization also reported that the Introduction of center handrails could reduce

flow by as much as 19 percent (while effective walking width is reduced by

some 33 percent). Provisions of the Code specify allowable occupant loads for

100
interior spaces on the basis of available exit width leading from such spaces

(particularly provisions 5-3.3 and applicable appendix notes; see also Sharry,

1978). Accordingly, to the extent that obstructions to means of egress indeed

restrict exit flow and egress time, building designers and managers should

realize that obstructions may ultimately influence permissible occupant loading

on building floors.

Bends or corners along corridors and similar egress path ways frequently result

in variations in the effective width of egress ways. The London Transport

Board (1958) reports no queue formation at bends and corners. Similarly,

Melinek and Booth (1975) found that bends and corners along any given stair way

did not appear to reduce pedestrian flow on stairs. In contrast, Watanabe,

Nayuki, and Torizakl (1973) report that walking speeds decreased when subjects

passed through corners along an experimental walking course.

When linear paths become narrower as one traverses their length, movement speed

may decrease. For example, the London Transport Board (1958) found that while

small reductions in corridor width had virtually no effect on the capacity of

egress ways, such architectural features did tend to increase the overall travel time for individuals. This organization noted that flow (i.e. capacity)

reductions as high as 10 percent requlr channel width reductions on the order

of 33 percent.

A number of additional Code provisions and behavioral assumptions deal with

potential impediments to pedestrian movement which may be caused by revolving

doors and turnstiles. Research reported by NBS (1935) examined the viability

of revolving doors as components of building egress systems. Pedestrian movement through revolving doors in a department store and in a Federal office

building was evaluated. The investigators found that for a revolving door with

leafs 42 inches (1.07 m) wide, an average of 11 to 12 persons discharged per

minute per foot of width (approximately 0.63 pers/sec/m). Evaluating another

doorway in which the revolving leafs were collapsed to form two separate and

adjacent openings each 25 inches (0.63 m) wide, an average of 22 persons discharged per minute per foor of width (1.20 pers/sec/m). These flow rates are considerably lower than those for swinging doors. In addition, the mechanical

operation of revolving doors may not be "sure" (see NBS, 1935, Appendix A,

note 60) and problems associated with their use may be exacerbated under very

high density conditions. On the basis of these findings, NBS (1935) recommends

that revolving doors not be used as means of egress in places of assembly

and certain other occupancies. For most other occupancies, NBS (1935) recom- mends that revolving doors receive 50 percent of computed exit credit. All

editions of the Code published since 1935 have based provisions for revolving

doors on NBS' recommendations.

Pedestrian flow through turnstiles was examined by Fruin (1971). Fruin noted

that free-swinging turnstiles require a headway of between 1.0 and 1.5 seconds,

and accommodate from 40 to 60 persons per minute (0.67 to 1.0 pers/sec). Where

ticket collectors were posted, turnstiles were found to require a headway of

from 1.7 to 2.4 seconds, and to permit between 25 and 35 persons to pass per

minute (0.42 and 0.58 pers/sec). Turnstiles requiring pedestrians to deposit

coins in a single slot device were found to require from 1.2 to 2.4 seconds of

101
headway, and to accommodate from 25 to 50 persons per minute (0.42 to 0.83

pers/sec). Finally, where pedestrians had to deposit coins in a dual slot

device, a headway of from 2.5 to 4.0 seconds was noted, and these turnstiles

were found to permit only between 15 and 25 persons per minute (0.25 and 0.42

pers/sec) to pass through. These statistics appear to be consistent with

(although slightly higher than) those reported by NBS for flow through revolving doors, and to justify the similar treatment of revolving doors and turnstiles by provisions of the Code .

Behavioral assumptions presented in Section 7.2.2 underlie Code provisions

concerning the flow capacity of means of egress. These assumptions address:

(1) pedestrian flow rates per unit width on level surfaces, stairs, and ramps,

(2) the value of fractions of standard width units, and (3) the linearity of

pedestrian movement within means of egress. Several studies report flow rate

statistics, the most pertinent of which are reviewed below. The reader should

note, however, that various investigators often differ in their definition of

critical terms (e.g. "flow" has been defined in terms of "persons per unit

time" as well as "persons per unit time per unit width"). Consequently, it is

not always possible to draw direct comparisons between data reported by different researchers. In addition, comparisons among investigations have been complicated by the fact that extremely few researchers sought to verify a standard

set of descriptive functional relationships. For example, while the London

Transport Board reported a relationship between walking speed and pedestrian

density, Fruin considered the relationship between walking speed and area (defined as the reciprocal of density). Similarly, while these investigators

were concerned with the influence of pedestrian density (however defined) on walking speed , others sought to describe the relationship between density and

flow rate . As a result, analysts should exercise caution when drawing infer- ences from research reviewed here to questions concerning the validity of

either behavioral assumptions about the capacity of means of egress, or their

antecedent Code provisions.

Data describing the movement of pedestrians through linear corridors were reported by NBS researchers (1935), who measured flow rates at arbitrarily

selected locations during periods of normal building occupancy. These investigators noted that under such conditions, flow rate varied across occupancies,

and in general, found a negative relationship between flow rate and channel

width. Togawa (1955) also observed variations in flow rate as a function of

occupancy, corroborating data reported by NBS, and also reported sex differences

Togawa further noted that men traversed level surfaces at an average velocity

of 4.60 ft/sec (1.40 m/sec) while women typically walked at an average velocity

of 3.90 ft/sec (1.19 m/sec), assuming a mean density of approximately

0.90 pers/ft^ (10 pers/m^).

The London Transport Board (1958) found that flow rates in linear corridors

approximated 27.7 pers/min/ft (1.48 pers/sec/ra). This finding is slightly

higher than that reported by Galbreath (1968), who noted linear movement in

corridors to average 21.86 pers/min/ft (1.19 pers/sec/m). The London Transport

Board also reported that flow was often as much as 50 percent higher for short

102
(i.e. less than 10 ft, or 3,05 m) passages when compared with longer segments

of equal width. In order to achieve mean free-flow walking speeds of approximately 3.37 ft/sec (1,03 m/sec) in the forward direction, these investigators

found optimum pedestrian densities to average 7,7 ft^/pers (0,69 m^/pers)^.

When available area dropped to 5,0 ft^/pers (0.45 m^/pers)^ in corridors, forward walking speed was found to approximate 2,20 ft/sec (0.67 m/sec). Forward

movement was noted to stop when occupant density averaged 2,0 ft^/per

(0,18 m^/pers)®.

Free-flow walking speeds reported by London Transport Board averaged some 21

percent lower than those reported by Togawa (1955). Fruin (1971) observed

variation in free-flow walking speed between male and female pedestrians.

Fruin' s data agree extremely closely with those reported by Togawa. In addition to sex differences, variation in pedestrian walking speed may also be due

to such factors as time of day, trip purpose, and the composition of pedestrian

groups. In general, walking speed decreases as pedestrian density increases.

According to Fruin, this is mainly due to reductions in available clear area

for locomotion. However, pedestrian density appears to have relatively little

impact on individual walking speed until average pedestrian area drops to

approximately 40 ft^/pers (3.60 m^/pers)^. Fruin has also found that walking

speed approaches zero when area reaches the vicinity of 3.0 ft^/pers (0,27 m^/

pers)l^, as compared with 2,0 ft^/pers (0,18 m^/pers)^ noted by Galbreath

(1968), In addition, Fruin noted that peak flow volumes in corridors averaged

approximately 25 pers/min/ft (1.37 pers/sec/ra), and that maximum flow capacities were attained when pedestrian volume was about 5.0 ft^/pers

(0.45 m^/pers)^,

Melinek and Booth (1975) reported that the flow capacity of corridors between

3.2 and 9.6 feet (1.0 and 3.0 m) wide averaged 28 pers/min/ft (1,5 pers/sec/m).

These investigators suggested that a free-flow walking speed of 4.16 ft/sec

(1.3 m/sec) be assumed, and that free-flow walking speed could be attained at

densities up to 11.1 ft^/pers (1 m^/pers).!! At higher densities, flow rates

were found to decrease.

Stairs are vital elements of emergency egress systems. Accordingly, a number

of investigations of pedestrian movement on stairs have been conducted. For

example, NBS (1935) reported flow rates from 165 separate observations of

stairs. The discharge rate of stairways was found to vary somewhat across

^ Equivalent to 0.13 pers/ft^

^ Equivalent to 0.20 pers/ft^

^ Equivalent to 0.50 pers ft^

^ Equivalent to 0.03 pers/ft^

Equivalent to 0.33 pers/ft^

Equivalent to 0.09 pers/ft^

(1.45 pers/m^)

,

(2.22 pers/m2).

(5,55 pers/m2).

(0.28 pers/m^)

(3,70 pers/m2)

(1 pers/m2).

103
occupancies, as well as on the basis of story height and riser-tread ratio.

Under conditions of normal occupancy, NBS reported that flow down stairs averaged approximately 57 pers/mln/22 inch width unit (1,70 pers/sec/m). An

inverse relationship between stair width and discharge rate was also found.

Moreover, NBS investigators noted that people moved more slowly, and at higher

densities, on the first half of stair flights. After intermediate landings

were passed, however, a decrease in density and a concommltant increase in

walking speed were observed. Finally, data recorded by NBS suggest that occu- pant density on stairs varies with the speed of movement. For example, under

rapid discharge conditions, density averaged 0.25 pers/ft^ (2.78 pers/m^); at

more liesurely discharge rates half this density was observed. On the basis of

these findings, NBS recommended that analysts assume a discharge rate of 45

persons per minute per 22 inch exit unit (1.35 pers/sec/m) down stairs, under

conditions where occupants are not likely to interfere with one another on stair ways. This is substantially lower than 57 pers/min/unit (1.70 pers/sec/ra)

NBS found empirically, although is consistent with stale discharge recommendations promulgated earlier by the National Fire Protection Association (1917).

Togawa (1955) concluded on the basis of his field observations that stair

width alone was not an effective predictor of flow rate on stairs. Instead,

Togawa believes that the most useful predictor of flow rate is individual

walking pace, and that for stairs, the critical dimension is tread depth.

Moreover, Togawa observed that travel time on stairs is inversely proportional

to staircase angle and story height, and that downward walking speed averages

1,64 ft/sec (0.5 m/sec). Finally, Togawa suggested that travel time, either

up or down stairs, could be estimated by applying the formula

t = 4H (3)

where t = travel time in seconds

H = story height in meters.

Flow rates on stairs reported by Togawa are substantially equivalent to those

described by NBS (1935).

Findings presented by the London Transport Board (1958) concerning the capacity

of stairs differ from those reported by both NBS and Togawa. London Transport

Board researchers found flow rates on stairs to average 35,2 pers/min/unit width

(1.04 pers/sec/m) in ascent, and 37,4 pers/min/unit width (1.15 pers/sec/m) in

descent. These are substantially lower than flow rates reported by either NBS

or Togawa, as well as those assumed within the Code .

Fruln (1971) also found movement speed on stairs to be higher in descent than

in ascent. He noted that males traverse stair flights more rapidly than do

females, and that in general movement speed decreases as the angle of staircase incline increases for both upward and downward travel (contradicting

Togawa 's finding that movement speed increases , or travel time, in Togawa *s own

terms, decreases, as the angle of incline increases). Moreover, Fruin found,

that within low and moderate ranges pedestrian density appears to have relatively little effect on stair traffic flow. According to Fruin, flow rates in

104
the vicinity of 18.9 pers/mln/ft (1.03 pers/sec/m) are representat J.ve of

crowded conditions under which queuing occurs at stair entrances.

Similarly, Mellnek and Booth (1975) suggest that flow rates averaging 37.4

pers/min/width unit (1.1 pers/sec/m) represent the normal capacity of stairs.

In addition, these investigators note that as crowd density increases, flow

rate on stairs also Increases until it reaches a certain level. At that point,

flow decreases again. Melinek and Booth also found that bends and corners along stair ways did not measurably reduce flow rate.

According to Yamada (1975), people travel up stairs more rapidly than they

travel down, where stairs are not more than three stories high. Yamada also

notes that people aged 50 and over often require as much as 40 percent more

time than do younger pedestrians to descend 14 flights.

Pauls (1974, 1977, 1979, 1980) challenges the assumption promulgated by NBS

(1935) and the Code regarding the design flow rate of 45 pers/min/unit width

(1.34 pers/sec/m). On the basis of his observations of forty evacuation drills

in high rise office buildings, Pauls argues that this assumption may overestimate actual flow rates by more than 50 percent, particularly during winter

months in cold climates where escaping occupants are likely to wear bulky

clothing. Under many conditions, Pauls found that speed of descent on stairs

tends to be considerably more variable than is assumed (indirectly) by users of

traditionally-promulgated design flow values. Pauls suggests that a "comfortable" range for evacuation movement of between four and six stories per minute

requires densities within the range of 0.1 and 0.2 pers/ft^ (1.11 and 2.22

pers/m^). He also found that such movement becomes virtually impossible when

density reaches 0.45 pers/ft^ (5.00 pers/m^). Pauls has stated that flow rates

greater than 30 pers/min/width unit (0.9 pers/sec/m) are usually only achieved

under ideal conditions, where building occupants have been specifically

Instructed about evacuation procedures, where they are motivated to act effectively, and where they are familiar with regimented movement.

Pauls found evacuation time in "total evacuation drills" (those in which all

occupants are alerted at once are presumed in initiate evacuation simultaneously) to depend upon total building population and available stair width.

For example, a ten story building with 100 occupants per width unit could

typically be evacuated in less than five minutes (plus or minus 20 percent).

In contrast, a 30 story building with 1,000 occupants per width unit has been

shown to require more than 30 minutes to evacuate. Pauls notes that although

most evacuees participating in the observed drills had obtained prior drill

training, they were typically unaware that the evacuation was in fact only a drill

On the basis of his most recent analyses of crowd movement on stairs, Pauls

(1980) has presented the concept of "effective stair width," suggesting that

pedestrians typically maintain themselves at a distance of approximately six

inches (150 mm) from the sides of stair wells. Apparently, this spacing

results from Individuals* body sway, fear of bumping into side walls, and

utilization of handrails. Consequently, Pauls suggests, a typical two-unit

stair 44 inches (1.10 m) wide may only have an effective width of 32 inches

105
(0.81 m) . According to the Code , such a stair would permit a load of 120 (60

X 2) pers/min; according to Pauls' calculation, however, the same stair might,

under certain conditions carry only 38 pers/min.

Regarding flow rates on ramps, NBS (1935) summarized findings reported earlier

by the Illinois Central Railway System demonstrating that flow on ranps is

essentially equivalent to that on level surfaces. NBS researchers also noted

that, according to their own observations of ramps in New York City's Grand

Central Station, pedestrian density on ramps averaged approximately 8 ft^/pers

(0.72 m2/pers)12^ and peaked at approximately 6.2 ft^/pers (0.56 m2/pers)13.

Under similar conditions, NBS concluded that the discharge rate of ramps is

faster than that of stair ways.

Evans (1950) estimated flow down ramps to be 37 pers/min/unit (1.10 pers/sec/m)

width when slopes were within the range of 6 to 12 percent. Also within this

range, walking speed was not found to vary significantly with slope. Moreover,

walking speeds on ramps were found to be slightly higher than those on level

passages: 4.2 ft/sec (1.28 m/sec) for ascent on a 12 percent ramp, to

4.8 ft/ sec (1.46 m/sec) for descent on a 2 percent ramp, as compared with 3.5

through 4.5 ft/sec (1.07 through 1.37 m/sec) on level surfaces.

Fruin (1971) also found that for grades up to 6 percent, ramp grade has little

effect on walking speed. Other researchers have suggested that grades as small

as 5 percent effect walking speed. A controlled experiment in which military

personnel walked on a variable-grade treadmill, reviewed by Turner and Collins

(1979), indicated that an increase of grade from 5 to 10 perc-^nt decreased

average walking speeds by approximately 11.5 percent. Increasing ramp grade to

20 percent decreased walking speed by a total of 25 percent. Melinek and Booth

(1975) reported that for upward-sloping ramps, walking speed decreases by 2 percent per degree of grade. They also noted that for downward-sloping ramps,

walking speed increases for small grades, but decreases for larger slopes. In

general, maximum downward walking speed is associated with gradients of

approximately 7 percent.

Tregenza (1976) agrees with other researchers noting that at slopes of 5 percent or less, gradient has virtually no effect on walking speed. Citing

data collected by the Road Research Laboratory in the United Kingdom, however,

Tregenza Indicated that a 10 percent ramp gradient could reduce upward walking

speed by as much as 40 percent. Under certain conditions, especially where

elderly or partially mobile persons are concerned, a similar effect can occur with downward travel.

In summary, considerable data describing pedestrian flow on level surfaces,

stairs, and ramps has been reported in the technical literature. Although it

often is not reasonable to compare data collected under different conditions

(e.g. evacuation drills in office buildings versus normal movement in transit

12 Equivalent to 0.13 pers/ft^ (1.39 pers/m^).

1^ Equivalent to 0.16 pers/ft^ (1.78 pers/ra^).

106
facilities), observations under a wide variety of circumstances do permit

certain conclusions. In particular, data currently available in the technical

literature support the assumption that ramps, within certain limits, permit

flow rates substantially similar to those found on level surfaces. In addition,

available data support the assumption that walking speed on ramps is faster than

that on stairs. However, available data do not support the assumption that

downward walking speed on ramps is always faster than upward walking speed.

Elaborating on the general issue of egress way capacity, the Code specifies

that although the fundamental unit of exit width is 22 inches (0.56 m) for the

purpose of establishing occupant load limits, the minimum width required for

any egress way element is 28 inches (0.71 m) , Several references to the available technical literature support this feature of the Code . For example,

Langdon-Thomas (1972) has expressed considerable concern over the possibility

that even the slightest obstruction to movement in means of egress may have the

most serious consequences. As a results, he has recommended a minimum width of

30 inches (0,76 m) for individual egress channels and elements. Similarly, the

Fire Protection Handbook (NFPA, 1976) cites Fruin’s (1971) findings that while

adult men typically measure less than 20.7 Inches (0.53 m) across the shoulders,

additional allowances must be made for clothing (especially heavy winter

clothing) and for body sway. Fruin has suggested that the average adult "body

ellipse" be taken as 24 inches, or 0.61 m. The Fire Protection Handbook further

considers the question of side-to-side body sway, estimating sway on each side

to be approximately 1,5 inches (0.04 m) under free flow conditions, and as much

as 4 inches (0.10 m) on each side under more crowded conditions, particularly

on stairs. On the basis of such estimates, the Handbook recommends that egress

channel width be no less than 30 inches (0,76 m).

Finally, Code provisions governing the capacity of means of egress appear to be

founded on certain assumptions concerning the linearity of pedestrian movement.

In general, a majority of investigations of pedestrian movement reviewed by NBS

(1935) led the organization to concludu that, on the average, people moving

through corridors or stair ways can be assumed to travel in linear files 22

inches (0.56 m) wide. According to NBS, the origin of this assumption lies in

military experience. By extentlon, this line of reasoning leads to the notion

that a 44 inch (1.12 m) wide channel adequately supports movement by two linear

files of pedestrians. The Fire Protection Handbook (NFPA, 1976), citing more

recent research by Fruin (1971), accepts the assumption that people tend to

travel through egress ways in linear files. This notion is further supported

by Soviet research on emergency egress summarized by Roytmann (1969).

London Transport Board (1958) researchers report that they could not detect

this "lane" effect for footways more than 48 inches (1.22 m) wide. However,

these investigators noted that for narrower stair ways and corridors flow rate was dependent on the number of available lanes of unit width. The London

Transport Board also suggests that widths falling between unit multiples have

capacities that are not simply predicted by computing fractions under the

"lane" model. For example, when a center handrail was introduced in a stairway

previously capable of permitting three files abreast, the lane model suggests

a reduction in the stair's capacity by one third (since, presumably, the rail

eliminates one aisle). However, actual flow on the stair was reduced by a

107
small amount, suggesting pedestrians walked in staggered, rather than purely

linear, files. In discussing the rationale for permitting credit only for

additional exit width increments of 12 inches (0.31 m) , Appendix notes to the

Code also support the notion that flow may be meaningfully increased by providing sufficient space for staggered files, Galbreath (1968) interpreted the

London Transport Board's data, discussed above, to suggest that staggered

(rather than purely file-like) movement is most common, particularly when tall

buildings are being evacuated. The Institute of Traffic Engineers (1964)

report finding no studies which actually verify the 22 inch (0,56 m) lane

effect, noting further that lanes of this dimension may be too narrow to permit

free flow pedestrian movement on stairs.

By far the most noteable challenge to the unit width concept, particularly as this concerns the granting of credit for fractions of units, derives from the

work of Pauls (1974, 1977, 1980), In his study of some 40 evacuation drills in

high-rise office buildings, Pauls notes that occupants did not move down stairs

in a highly regimented fashion, either shoulder-to-shoulder or even in staggered files. Rather, pedestrians observed by Pauls appeared to make every

effort to maintain a body buffer zone (similar to the body ellipse concept

discussed by Fruin) , even in cases where density was fairly high. Pauls suggests that this spacing behavior is influenced by such factors as type and

weight of clothing worn, occupants' cultural backgrounds, pedestrians' sex, and

their social relationship with nearby persons. Further, Pauls argues that

shoulder-to-shoulder movement is rare on stairways narrower than 4,0 feet

(1.22 ra) . Where it does occur, according to Pauls, it primarily involves

pedestrians trying to talk to one another,

Pauls also found that side-to-side body sway, and pedestrians' varying need for

handrail support, influences movement behavior on stairs. On the basis of his

research, Pauls (1980) recommends a minimum width of 55 inches (1.40 m) for

stairs normally subject to heavy use. This dimension takes body sway into

account, permits movement two-abreast, and allows convenient passing on the

stair.

As indicated above, Pauls (1980) has paid particular attention to the problem

of granting credit for fractions of egress width units. He has argued that

flows down exit stairs tend to be proportional to stair width, and that the

relation between width and flow is essentially linear. Thus, since each additional inch of exit width has the potential of increasing flow rate, each such

inch should be considered for credit under provisions of the Code . At present

the reader will recall, one-half credit is given for extra width from 12 to 21

inches (0,31 to 0.53 m) ; no credit is given for extra width from 1 to 11 Inches

(0,03 to 0.28 m) . According to Pauls (1980), this step-like function has no basis in available empirical data, while the linear "effective width" model, on

the other hand, can be justified both by Pauls' own data and by those reported

much earlier by NBS (1935).

Strengths and weaknesses of the technical literature . A number of behavioral

assumptions underlying Code provisions which concern the potential effect of

architectural barriers consider the influence of doorways and Intermediate

mullions on egress flow rate. Most of the available data on flow through door

108
ways (NBS, 1935; Togawa, 1955; Fruin, 1971; Melinek and Booth, 1975) are based

on field observations made under conditions of normal building occupancy. A

number of difficulties arise, however, when these data are applied in analyses

of emergency egress situations. First the process by which occupants form

queues at doorways may itself be substantially influenced by circumstances

brought about by actual fire conditions. While queuing regularly takes place

under normal occupancy conditions, it has been found to become somewhat disorderly during some fires (as reported after the Berverly Hills Supper Club

fire), yet remain orderly during others (as reported after the Stouffer Inn

fire). Clearly, however, the assumption that door width and design alone

influence door flow characteristics seems misguided, and while door ways may

be examined under nonemergency conditions, results of such tests may not be

predictive of emergency performance.

Second, while the code-writer may be tempted to draw causal inferences about

the role of exit design in achieving desired flow rates, available data derive

from studies lacking experimental controls which permit such inferences; at

best, these data report trends and correlations. Moreover, the available data

do not now permit the code-writer or analyst to estimate the probability with

which a given exit width or door design will be adequate under hypothetical

emergency conditions. Thus, although a considerable amount of data are available describing the flow capacity of door ways, the technical basis for designing door ways to accommodate overall emergency requirements remains weak. On

the other hand, a good deal of research is now available describing such specific phenomena as arching at doorways (Togawa, 1955; Peschl , 1971; and others).

Although the effects of arching on egress time remain to be quantified, investigators' beliefs that door ways within a certain width range often result in

time-consuming queues and arches do appear to be supported.

Available literature concerning the potential effects of Intermediate mullions,

door hinges, and other similar projections into door ways on door flow rates is

insufficient to support or refute Code provisions and their underlying behavioral assumptions. This is also true for doors which open against traffic, and

for mid-stream exit channel width reductions. Research by Melinek and Booth

(1975) and the London Transport Board (1958) provide the strongest indications

that minor architectural obstructions have little or no effect on egress flow.

However, data reported by these investigators were not collected under either

real or simulated emergency conditions. Here again, it is not possible to assess whether emergency conditions exert additional forces on escaping occupants, sufficient to alter the effects of otherwise minor obstructions to flow.

Code provisions pertaining to revolving doors and turnstiles are based largely

on recommendations by NBS (1935). Fruin is the only other investigator to have

empirically addressed these elements. There presently exist no empirical

grounds upon which to challenge the pertinent Code provisions.

Available literature describing the capacities of stairs, ramps and level

surfaces, while somewhat voluminous, has not developed in a cumulative manner.

To data, investigators have rarely attempted analytical comparisons among their

findings, data collection strategies and objectives frequently differ in subtle

109
ways, and variables frequently have been defined Inconsistently across investigations. For example, Togawa and other investigators studied pedestrian

walking speed in relation to density , defined as the number of persons per unit

area, Fruin, on the other hand, studied speed and flow in relation to area,

which he defines as available area per person, the reciprocal of density.

Another shortcoming of this literature concerns ambiguities Imposed by data

collection techniques. For example, studies of pedestrian walking speed usually

involve timing pedestrians as they pass between two fixed points along a measured linear path (e.g, a corridor). Although the length of the measured path

remains constant for all pedestrians, the actual lengths of pedestrians’ movement paths do not, since some pedestrians are more prone than others to deviate

from "purely" linear walking patterns. Thus, if two pedestrians walk the measured path in the identical period of time, the recorded speed of one will be

equal to that of the other, even though their actual walking paths—and thereby

their actual walking speeds—differ. Such ambiguities make it difficult for

the code-writer or analyst to infer trends or draw definitive conclusions from

published studies.

The work of Pauls (1974, 1977) departs somewhat from that of other researchers,

particularly in that he specifically Investigated fire exit drills in public

occupancy buildings. According to Pauls, moreover, many occupants participating

in these drills actually believed real emergencies to be in progress. In addition to data concerning the time required to evacuate buildings differing in

height and under a variety of egress scenarios (e.g. evacuation en-masse, versus "staged" evacuation), Pauls also collected numerous data on film, video

tape, and sound tape which describe a large number of behavior patterns occurIng along egress routes. Flows reported by Pauls are in most cases lower than

those published by other investigators. According to Pauls, flow rates

reported elsewhere are artificially high, perhaps due to the artificiality of

the situations studied. These differences between Pauls’ data and those reported

by other researchers remain to be verified and explained empirically.

Pauls’ findings are often difficult to compare directly with those reported by

other Investigators, primarily because Pauls usually reports walking speeds

and flows down stair ways in terms of stories per unit time. This difference

poses serious problems to the analyst wishing to employ Pauls’ data, particularly since story height may vary considerably between building types. Pauls’

data, accordingly, appear most directly useable when applied to high-rise

office buildings. More generally, however, the fact that Pauls’ flow data

under drill conditions (which in some ways simulate emergency events) appear

substantially lower than those collected in transportation facilities and

elsewhere (under decidedly nonemergency conditions) gives cause to reevaluate

the present basis for computing building occupant loading for the sizing means

of egress. Given the significance of Pauls’ findings to goals of the Code , a number of his studies warrant replication, particularly true where the codewriter is Interested in making generalizations from Pauls’ data describing

office buildings to other occupancy categories.

Research on pedestrian movement down ramps involves methods and techniques

substantially similar to those employed in stair use research. Although

conclusions regarding pedestrian flow on ramps are analogous to those reported

no
In connection with stairs, numerous studies, including those reported by NBS

(1935) suggest that pedestrian behavior patterns have more in common with movement on level surfaces than with movement on stairs. At present, most investigators of ramp use report similar findings concerning differences between pedestrian performance in ascent versus descent, although the precise relationship

between ramp slope and walking speed remains clouded by equivocal findings.

Available data pertaining to assumptions about the linearity of pedestrian

movement and the long-accepted "standard" 22 inch (0.56 m) exit width unit are problematic. As pointed out by NBS (1935), the idea of studying pedestrian

movement in terms of linear files of standard width stems from military experience. But to what extent is regimented military walking behavior generalizeable to the movement of building occupants, either under normal or emergency

conditions? Despite methodological shortcomings which at times render Pauls'

and Fruin's data difficult to Interpret and apply, their identification of

such clearly observable pedestrian behavior patterns as slde-to-slde body sway

and personal space maintenance raise important questions about the validity of

the current standard. On the other hand, available data also suggest that

under relatively high density conditions, escaping occupants may be willing to

forfeit comforts associated with personal space maintenance, and given little

freedom of choice within an egress channel, may effectively follow linear

paths and move in files of unit width. Thus, with no replacement for the 22"

unit clearly in view, the current standard should not be abandoned.

Pauls has attributed the validity of his findings concerning egress behavior

down stairs, to a great extent, to the fact that many occupants of the buildings

he studied believed that the drills were actual emergencies. However, Pauls

has made this supposition on the basis of a relatively small sample of drill

participants, perhaps on the order of 10 percent. Moreover, these individuals were not forced to escape in the presence of fire products, nor did they receive

such ambiguous signals as distant shouts, etc., which might have affected escape

behavior (refer to Chapter 3 of the present report). Indeed, the problem of

predicting behavior during drills remains unresolved, as noted in Chapter 2.

From a scientific perspective, consequently, Pauls' recommendations concerning

the design of exits to facilitate emergency escape should, perhaps, be viewed

more as hypotheses than as statements of fact. Replications of Pauls' work,

both under more controlled conditions and under a wider range of occupancies

and emergency scenarios, are indicated,

7.4 SUMMARY OF GAPS IN THE TECHNICAL LITERATURE

7.4,1 Research on the Influence of Architectural Barriers and Other Potential

Obstructions to Egress Flow

The majority of studies available describe the influence of architectural

barriers and other obstructions to egress flow focus on pedestrian movement

through door ways. Provisions of the Code specify the design of door ways on

the basis of occupant loading criteria and available door width. One point on which there is little equivocation in the literature is the finding that, under

conditions of relatively high occupant density, queues form as individuals wait

to pass through door ways. However, researchers have yet to study the questions

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of how queue formation and processing influence egress time, and how door

width specifications may be adjusted to compensate for time potentially lost

in queues

A closely related gap in the technical literature concerns the predilection of

most researchers to study pedestrian behavior in relation to some one egress

way element (e.g. doors) in isolation. Indeed, the task of exiting a building

usually Involves passing through numerous door ways, as well as corridors,

stairs, and lobbies, all of which are more or less interrelated. When a queue

forms at a door way, for example, it is not merely flow through this door that

is affected: the capacity of the preceding stair or corridor is being taxed

as well. Future research must address the interdependencies between adjacent

egress way elements, and provide guidelines for the design of effective

transitions between elements,

7.4.2 Research on the Flow Capacity of Egress Channels

Flow rate has been the most universally accepted measure of the performance of

means of egress. Considerable work remains, however, to develop a standard

measurement method. In the absence of such a standard, it will continue to be

difficult to determine precisely why data from various investigations often

disagree. For example, Pauls and Fruin each found different variables to

interact with flow rate and walking speed; Togawa found no such interaction

effects. Similarly, although Pauls and Fruin have both advocated an incorporation of body sway and personal space maintenance behavior into computations of

flow capacity, there remain neither standard measures nor verified models of

these phenomena,

7.5 SUMMARY

A number of human behavioral assumptions underlying Code provisions which

govern the capacity of means of egress were presented. These assumptions were evaluated by reference to several models of pedestrian movement, data from laboratory and field studies of walking behavior during normal occupancy conditions, and observations of stair use during fire exit drills in high-rise

office buildings. With regard to Code provisions affecting the design of

doors, available technical literature support only those assumptions concerning

the deleterious effects of particularly severe constrictions or obstructions.

However, behavioral assumptions underlying provisions governing the design of

corridors and stairs find challenge within the technical literature. This is

especially true of provisions depending on the validity of assumptions about

the linearity of pedestrian movement and the 22 inch (0.56 m) unit width standard. Because there remain differences in reported data describing pedestrian

behavior on stairs and level surfaces, inconsistent definitions of Important

variables, and nonstandardized techniques for measuring the performance of means of egress, it is not now possible to either support or refute existing

provisions and their underlying behavioral assumptions on the basis of the

available technical literature. The most Important objectives for future

research on the subject of the capacity of means of egress are: (1) the development and validation of standardized measures and measurement methods, and (2)

the systematic analysis of complete egress systems emphasizing transitions

between means of egress elements.

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8. SUMMARY AND CONCLUSIONS

The primary objective of the investigation has been to assess available research

pertaining to the exit facility design and emergency escape provisions of the

NFPA Life Safety Code (1976 Edition), in order to determine the technical support for such provisions. The central foci of the investigation are the timebased capabilities of building occupants to effect rapid evacuations, in relation to evacuation time available during fires. A number of functional criteria

(e.g. maximum travel distance, building configuration, remoteness of exits, and

barriers to egress flow) are examined in relation to Code provisions influencing

the design of means of egress, and fire protection and protective signaling systems for places of assembly, residential occupancies, mercantile occupancies,

and business occupancies. Provisions affecting fire exit drill and building

management practices are also considered.

To effectively treat this broad problem, the current report organizes Code

provisions and related technical discussions in relation to areas of potential

impact; provisions affecting pre-emergency training and preparation (Chapter

2), occupants’ perception of the emergency environment and recognition of

egress facilities (Chapter 3), egress strategy formation (Chapter 4), disciplined egress behavior and crowd movement (Chapter 5), occupants' capabilities

to safely and rapidly negotiate egress ways (Chapter 6), and the capacity of

means of egress (Chapter 7).

Within each chapter, provisions of the Code which have a common area of

potential impact, and human behavioral assumptions underlying these provisions,

are presented. The technical literature bearing on these provisions and

assumptions is reviewed, including references to applicable theories and models,

pertinent empirical data from published experiments and field studies, and

where appropriate, journalistic or anecdotal accounts of actual fire events.

The validity and generalizability of findings presented in the literature are discussed, and the degree of technical support currently available for egress

provisions of the Code is evaluated. Finally, each chapter provides a summary

of gaps in the technical literature, recommending specific areas requiring

additional reseach. The remainder of Chapter 8 summarizes Code provisions,

behavioral assumptions, technical literature, and recommendations presented in

each of the substantive chapters of the report.

8.1 SELECTION OF CODE PROVISIONS

Code provisions addressing occupants' "readiness" for fire emergency situations

were selected for analysis, emphasizing provisions for the conduct of fire exit

drills which appear in Chapter 17 (Operating Features) of the Life Safety Code . Provisions selected for study are presented in Section 2.1 of the report. A

number of provisions are noted which potentially influence occupants' perceptions of the emergency environment and their recognition of egress facilities.

The principal sources of these provisions were Chapters 5 (Means of Egress) and

6 (Features and Fire Protection) of the Code . Provisions selected for analysis

are enumerated in Section 3.1 of the present study. Once occupants have determined that a fire emergency is in progress, they must decide on a specific course of action. When a decision in made to evacuate, an egress strategy must

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be formulated and acted upon. A number of Code provisions were found which

potentially affect occupants’ cognitive behavior and their ability to make

effective decisions leading to successful emergency escape. These provisions

are drawn primarily from Chapter 5 (Means of Egress) of the Code , and are presented in Section 4.1 of the current report. Problems associated with emer- gency escape during fires in public occupancy buildings are often complicated

by the fact that occupants are members of social groupings which may vary quite

widely with regard to a number of characteristics. Hence, the control of

social interactions during fires may be a desired outcome of building management, and to some extent planning and design as well. A number of provisions,

drawn primarily from Chapters 5 (Means of Egress) and 17 (Operating Features) are noted which potentially influence social behavior in the emergency environment, and are shown in Section 5.1 of the report. Provisions intended to

minimize human physiological impediments to the safe and rapid use of egress

ways were selected principally from Chapter 5 (Means of Egress) of the Code . These are presented in Section 6.1 of the report. Finally, those provisions of

Chapter 5 of the Code which focus on the carrying capacity of egress way elements, and which may substantially influence the efficiency with which buildings

are evacuated, are presented for analysis in Section 7.1 of the present study.

8.2 UNDERLYING BEHAVIORAL ASSUMPTIONS

Provisions of the Code were selected for analysis because of certain assumptions

concerning the potential affect of code compliance on escape performance

during fire emergencies. That is, when designers or building officials make

design or compliance decisions with respect to many Code provisions, they do

so in the underlying belief that, on the average, occupants will respond properly, and that compliance with such provisions thereby increases the likelihood that occupants will survive fires. Initially, the project staff hypothesized a set of human behavioral assumptions pertaining to Code provisions

within each Impact area. Then, a procedure was established for submitting this

set for expert peer review (note Appendices A and B of the current report. The

project staff accepted behavioral assumptions as modified during the peer

review process as the best currently available .description of human behavioral

patterns assumed to underlie selected provisions of the Code .

Chapter 2 of the report addresses pre-emergency training and preparation.

Human behavioral assumptions found to underlie pertinent Code provisions

clustered into four subsets, including: (1) the ability to predict occupant

responses during actual fires, (2) the transfer of responses learned during

fire exit drills to actual fire situations, (3) occupants' attitudes toward

fire exit drills, and (4) the accomodation of training procedures to diverse

fire scenarios. Specific assumptions are given in Section 2.2.

Chapter 3 of the report treats provisions affecting occupants' perception of

the emergency environment and their recognition of egress facilities. Human

behavioral assumptions underlying related Code provisions clustered into the

following subsets: (1) the effect of door and window design on egress route

identification, (2) the effect of illumination level on egress route identification, (3) the role of signage and directional information in egress route

recognition, and (4) the ability of audible and visual alarm signals to effectively alert building occupants to a fire threat. Refer to Section 3.2.

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Chapter 4 considers Code provisions which may influence the ways building

occupants formulate emergency escape strategies during fires. Underlying

behavioral assumptions concern: (1) occupants’ capacities to process information about the location and function of means of egress, and (2) occupant's

abilities to determine the safest and most accessible escape route under

stressful and life-threatening conditions. See Section 4.2.

Code provisions considered in Chapter 5 of the current report potentially

affect disciplined emergency escape and crowd movement. Three categories of

human behavioral assumptions were found to underlie such provisions: (1) the

influence of designated leaders on escape time during fire emergencies,

(2) pedestrian movement under high density occupancy conditions, and (3) the

effects of building configuration and architectural barriers on efficient

crowd movement. These assumptions are presented in Section 5.2.

Chapter 6 deals with the physical capabilities of occupants to safely and

rapidly negotiate egress ways. Human behavioral assumptions underlying Code

provisions which potentially influence such capabilities cluster in three categories: (1) the extent to which accidents such as slips, missteps, or falls,

which may occur while people negotiate pedestrian ways, impede flow along

corridors, stairs, and ramps and through door ways, (2) the degree to which

stress and fatigue Impair walking behavior and increase the time required for

safe escape, and (3) the influence of door and other hardware design upon occupants' abilities to rapidly operate elements comprising means of egress. Note

assumptions in Section 6.2.

Finally, Code provisions treated within Chapter 7 concern the capacity of means

of egress. Two categories of behavioral assumptions appear to underlie these

provisions. These are: (1) the influence of architechtural barriers and other

potential obstructions on egress flow, and (2) the flow capacity of egress ways.

Refer to Section 7.2.

8.3 TECHNICAL COMMENTARIES

Thorough reviews of the theoretical, empirical, and journalistic literature

applicable to Code provisions and their underlying human behavioral assumptions

were conducted. These reviews made it possible to state, in technical terms,

the fundamental nature of various facets of the emergency escape problem, to

explain behavioral phenomena known to occur during fire emergencies, and to assess the state-of-the-art of technical data which either support or refute

the Code provisions under study.

8.3.1 Problem Statements

Code provisions affecting pre-emergency training and preparation are intended

to maintain occupancies at a sufficient state of emergency readiness, to reduce

the likelihood of maladaptive responses during actual fires, and to minimize the

time required by occupants to either escape buildings or move to refuge areas.

In general, these provisions are based on the assumption that behavior patterns

learned during training situations transfer to actual emergencies, and thereby

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result in effective behavior during real fire events. Problems addressed within

Section 2.3.1 of the current report concern the validity of this supposition, as well as other questions about the value of pre-emergency preparation and

training.

Under certain conditions, the design and provision of emergency exiting

facilities may directly affect occupants’ perceptions of the emergency environment, as well as their recognition and subsequent use of these facilities.

Chapter 3 treats Code provisions intended to achieve easily identifiable egress

ways, facilitate rapid and accurate escape route determination, and to confirm

occupants’ awareness of immediate fire conditions. These provisions presuppose

causal relationships between the design of architectural features, and such

attributes of emergency escape performance as stimulus detection, situation

definition, and egress strategy formulation. The verifiability of this supposition, the validity of causal relationships between physical design and escape

performance, and the availability of empirical support for applicable Code

provisions are the chief problems outlined with Section 3.3.1.

Additional Code provisions are intended to assure that occupants are not

entrapped in the event that any single exit route becomes blocked by fire products, that occupants will not become unnecessarily confused if exits are not

immediate accessible, and that escapees do not overshoot discharge points along

any escape route. Decisions which occupants must make concerning the formulation and revision of escape strategies are often required on a number of occasions during the emergency event. Design provisions which potentially affect

the quality of occupants’ egress strategies presuppose that escaping occupants

obtain information vital to decisionmaking from the social and physical environments during the course of the fire event. Technical problems associated

with these issues are presented in Section 4.3.1 of the report.

A number of Code provisions are intended to assure that emergency egress from

public buildings will be orderly and well organized, and that maladaptive crowd

behavior which could lead to panic or abnormally lengthy escape time will be

unlikely. The special problems associated with crowd behavior and the implications of building design for crowd management are introduced in Section 5.3.1.

Whether or not building occupants can safely and rapidly negotiate egress ways

may be substantially affected by the sensorimotor capabilities of these individuals. This effect is potentially influenced by a number of building design

provisions treated in Chapter 6 of the current report. Section 6.3.1 introduces the problem of accomodating human performance capabilities in egress

design provisions of the Code .

Code provisions governing the capacity of means of egress are intended to assure

that exit ways can adequately carry anticipated occupant loads during fire emer- gencies. To accomplish this purpose requires not only that exit ways are of

sufficient dimension, but that their design and arrangement minimizes opportunities for blockages and other impediments to rapid egress flow. Section 7.3.1

of the report presents the problem of evaluating exit way capacity, in view of

occupants’ sensorimotor capabilities and the dynamics of fire situations.

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8.3.2 Behavioral Models

Theories, models, and concepts from the behavioral sciences and other pertinent

disciplines provide an important framework for understanding fire emergency

events and for guiding the development of more effective design solutions.

Consequently, they provide a useful basis for evaluating Code provisions which

potentially impact occupant performance during fires.

In evaluating the effectiveness of pre-emergency training and preparation,

three models drawn from the psychology of learning appear to offer Insights useful in understanding relationships between training and behavior during actual

emergencies. These models are the instrumental conditioning, social learning,

and cognitive models. Instrumental conditioning is based on the assumption

that an individual, through reinforcement in the form of reward or punishment,

acquires connections between specific environmental events or stimuli and particular behavioral responses. Stemming from Instrumental concepts, social

learning emphasizes the Importance of social environmental stimuli to the

behavior of any individual. According to the social learning model, the behavior of others may have considerable influence over the behavior of an observing

Individual, who may find imitative and vicarious behavior to be positively

reinforcing. Social learning also suggests that individuals often depend upon

others in the immediate environment for help in achieving goals. In contrast,

the cognitive model treats learning as a developmental process by which information from the environment is assimilated. Interpreted, and applied by individuals as they continuously make decisions essential to effective environmental

accomodation. According to one popular approach to cognitive learning, individuals are thought to test their own mental image, or "cognitive map" of an event (which may or may not be accurate or correct) against the reality of the

event being confronted. Here an individual’s success in negotiating the event

may well depend upon the "fit" between the cognitive map (the mental guide for

behavior) and the actual event, as well as on the individual’s ability to make

rapid mid-stream corrections in the cognitive map. These models are considered

in detail in Section 2.3.2.

Three theoretical explanations of human perception provide insights to occupants

perceptions of emergency environments and their recognition of egress facilities

These are psychological field theory, environmental information processing

theory, and signal detection theory. Psychological field theory (or "Gestalt"

psychology) posits that physical objects are always viewed against a background

which provides varying degrees of contour, contrast, and boundary to the object.

Characteristics of the background field may substantially Influence the clarity

with which an object is perceived. With its origins in Gestalt psychology,

environmental Information processing theory suggests a mechanism by which individuals Interact with their physical surroundings, simultaneously extracting

information from them and contributing to their change. Based on psychophysical

research, signal detection theory posits that environmental stimuli must continually compete with other, less relevant, stimuli. Further discussion of these

approaches is provided in Section 3.2.2.

Environmental Information processing appears to provide the most useful

conceptual framework for understanding emergency egress strategy formation.

This model holds that soclophyslcal settings supply individuals with at least

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as much information as any person can effectively process and use, irrespective

of whether the available information is of sufficient quality or quantity to

permit successful event negotiation. Accordingly, fire situations can be con- ceptualized as situations in which escaping occupants continuously seek out

information they need to make effective behavioral decisions. In addition to

the general framework posited by the environmental information processing model,

a number of other models which describe processes by which information is

stored, retrieved and utilized, and which illuminate potential impediments to

information processing, were also considered within Section 4.3.2.

Models of group behavior, drawn from the field of social psychology, provide a framework for understanding problems which may arise when large groups of

people attempt to escape public buildings during fires. The outcome-dependence

model, for example, suggests that individuals and groups for which some information dependency exists rely upon other people perceived to be better informed

(e.g. visitors to office buildings may, during a fire, depend upon workers in

the building whom they expect to be much more familiar with exit locations).

The imitation model suggests that under certain circumstances individuals will

copy behaviors exhibited by other persons they perceive to be role models. The

reward-exchange model posits that an Individual will interact with others only

to the extent that the products of such interaction are perceived to be congruent with the individual's own objectives. The environmental space model is

based on anthropological research and focuses on individuals' apparent need to

circumscribe territories for themselves. These territories may be useful as protective boundaries between an individual and other persons in the immediate

environment. Consequently, according to the model, individuals strive to

maintain personal space buffer zones. Relationships between such models and

problems associated with disciplined egress behavior and crowd movement during

fire emergencies are treated more fully in Section 5.3.2.

Models stemming from research in human factors psychology and biomechanics are useful in explaining occupants' performance capabilities under various circumstances which may arise during buildings fires. The man-machine and feedbackloop models suggest, for example, that in the process of negotiating an egress

way, an individual conducts perceptual, tactile, and kinesthetic tests of

environmental conditions, while receiving feedback from the environment concerning its state. The cybernetic model of neurophysiological coding suggests that

stressors from the environment interact with human neurological processes, and

may interrupt or overload individuals' abilities to cope with environmental

stress. The biomechanical model describes the human body as a highly complex

structure consisting of numerous mass-spring-damper elements. Such a conceptualization of the body appears useful in describing the way a person negotiates

elements of egress ways (e.g. stairs) or operates pertinent architectural

hardware (e.g. doors). These models are the subject of Section 6.3.2.

Models adopted from both the physical and behavioral sciences are useful in

conceptualizing the performance of means of egress and for predicting their

capacities. The particle model treats emergency egress as being directly analogous to evacuating ball bearings from a funnel-shaped bin. In the hydraulic

model, the movement of masses of people through complex building configurations

is viewed as analogous to the gravity-induced movement of a fluid through a

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system of pipes, valves, and catch basins. The gaseous model has been suggested

to describe low density pedestrian movement, under conditions where individuals

exercise considerable freedom of choice. Although not itself a descriptive

model, the psychological concept of personal space, which posits individuals’

needs to maintain protective buffer zones around themselves, is useful in understanding limitations to the capacity of egress ways. These models and concepts

are discussed in relation to Code provisions affecting the capacity of means of

egress in more detail in Section 7.3.2.

8.3.3 Assessment of Behavioral Assumptions Based on the Technical Literature

Pre-emergency training and preparation . A review of the literature pertaining

to provisions and assumptions concerning pre-emergency training and preparation

yielded mixed conclusions. In many instances, assumptions in this area imply

that panic is a likely outcome of fire emergencies. However, the term "panic"

lacks a widely accepted technical definition. Controlled social psychological

laboratory experiments have shown panic-like responses to result when time-toescape is perceived to be insufficient, and when leadership is unavailable.

Journalistic accounts of actual fires have also recorded panic-like behavior

under similar conditions. On the other hand, post-incident technical studies

of fires have shown that such panic is a rather infrequent occurrence. Behavioral assumptions underlying pre-emergency training and preparation provisions

of the Code also imply that the threat of panic may be reduced through fire

exit drill training. A number of post-incident studies support this notion,

although no direct evidence of a relationship between drill training and panic

reduction is currently available in the technical literature.

The question of whether behavior patterns learned during exit drills and other

forms of pre-emergency preparation transfer to actual emergency conditions has

been considered by a number of investigators. Ifowever, there remains no empirical evidence of a transfer of training from exit drill performance to emer- gency egress behavior. Some fire researchers have also noted the importance of

exit drill frequency, although no empirical evidence currently exists

demonstrating the effect of drill frequency on performance during actual emergencies. Two Incidents recorded in the literature actually question the

benefit of frequently-conducted exit drills.

Virtually no technical data are presently available describing occupants*

attitudes to drills and drill participation, or illuminating the relationship

between occupants' attitudes and their performance either in drills or actual

emergencies. The problem of accommodating training procedures to the peculiarities of Individual occupancies also has been noted in both the Code and the

literature. To date, most research on drill effectiveness has been conducted

in occupancies with distinct leadership hierarchies (e.g. nursing homes), and

results of studies in these occupancies may not generalize to other building

types (e.g. shopping malls). In summary, the technical literature neither universally supports the behavioral assumptions underlying Code provisions affecting pre-emergency training and preparation, nor supports specific alternatives.

Perceptions of the emergency environment . Available technical data are insufficient to either support or refute most assumptionns underlying Code

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provisions pertaining to occupants' perceptions of emergency environment and

their recognition of egress facilities. Various studies appear to refute

assumptions concerning emergency alerting signals. Extremely few technical

data pertaining to the effect of door and window design on route perception

were found. Virtually none of these data specifically addressed problems asso- ciated with emergency egress. Similarly, very little research concerning the

effect of illumination level on egress route perception has been conducted,

and it is not now possible to either confirm or refute the minimum illumination

level currently specified in the Code .

A number of experiments have been conducted to examine visibility under smoke

conditions. However various methodological difficulties make it difficult to

interpret findings from these studies. Moreover, conclusions about optimal

visibility distance, particularly under smoke conditions, remain somewhat

equivocal. The Code provision specifying a maximum switchover delay between

standard and emergency lighting, and its antecedent human behavioral assumption, are supported by available psychophysical literature on light-dark adaptation. It should be noted, however, that the literature reports data from

laboratory experiments lacking many of the ambiguities and stimuli which may

be present during actual fire emergencies.

Current knowledge about the effectiveness of signs and visual information is

based upon laboratory experiments designed to test the visibility and understandability of such signage. However, little is known about how, and whether,

directional signage is actually used by escaping occupants during fire situations. The question of whether the visibility of directional signs is impaired

by smoke has been specifically considered in the literature. Although the

available data are not extensive, they do suggest that such signs, while commonly

positioned overhead, would be more easily seen under smoke conditions if

positioned within two to three feet (0.61 to 0.92 m) from the floor.

A number of toxicological investigations have considered potential effects of

carbon monoxide (CO) on information perception and reaction time. However,

research with human subjects is not sufficient to warrant useful conclusions at

this time.

A small number of studies are available describing the effectiveness of arrows

in way-finding, although no data have been found which show the effects of fixed

directional arrows on emergency egress behavior and time. Data from highway

research suggests that human subjects respond more quickly to graphic symbols

than to information presented on verbal signs. No data were found indicating

whether or not this is also true for pedestrians. Similarly, no data are cur- rently available to suggest that verbal "NO EXIT" signs deter occupants from

making incorrect egress route decisions, or that the presence of such signs

reduces overall building evacuation time.

Much of the literature reporting data on the effectiveness of audible and

visual fire alarm signals stems from nonexperimental post-incident investigations of actual fire events. These studies indicate that alarm signals are frequently not perceived by occupants as signaling an actual emergency. A

number of sociological investigations of large-scale natural disasters, as

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well as journalistic accounts of fires, support this notion. These findings

tend to refute the behavioral assumption that alarm signals will effectively

initiate prompt and purposeful emergency egress action, which tends to underlie

a number of Code provisions. The effectiveness of visual alarm devices,

important to hearing-impaired building occupants , has not been examined in the

literature.

Regarding the quality of alarm signals, a number of investigators have suggested

that responses elicited by manual alarm bells tend to be ambiguous and confused.

These researchers note that upon receipt of such alarms, occupants are often

observed attempting to seek additional information, rather than taking prompt

action to evacuate. On the other hand, a small number of anecdotal accounts of

actual fires point to victims who, having seen or heard an alarm signal, formulated an effective egress strategy, and subsequently escaped unharmed. Generally, however, available technical evidence suggests little support for the

assumptions that alarm devices, once activated, will provide unambigous emer- gency Information, or that they will reduce overall escape time.

Egress strategy formation . Taken as a whole, available technical data are not

sufficient to either support or refute behavioral assumptions underlying Code

provisions which may influence the ways occupants formulate emergency escape

strategies. However, the psychological literature does clearly indicate that

occupying a burning building can be a highly stressful, if not life-threatening

event, requiring individuals to make complex and potentially very costly decisions under severe temporal and environmental constraints, and under pressing

physiological demands.

As of the current Investigation, there are few technical data available

directly relevant to assumptions about occupants* capacities to rapidly and

effectively process and utilize information concerning the location and function of means of egress. In general, questions about how escaping occupants

make specific route choices, or about the kinds of information they sought from

the environment have not been raised by fire experts. Findings from empirical

Investigations of way-finding in buildings indicate that floor plan complexity

and the visibility of route elements, are key predictors of wayfinding success. These findings, however, contrast with data from post-incident fire studies

which suggest occupants' familiarity with building layout and exit locations

to be the chief predictor of effective emergency escape.

Few data are available from the field of fire research that are useful in

evaluating the assumption that occupants are capable of effectively determining

the safest and most accessible escape routes while exposed to the psychological

stresses produced during fire emergencies. Findings from seemingly pertinent

psychological and toxicological experiments conducted under narrowly defined

laboratory simulations, moreover, may be difficult to generalize to actual fire

situations, partly because of the impracticallty and immorality of conducting

research in which human subjects are exposed to actual or potential life

threats. Furthermore, psychological Investigators have not systematically

studied building fires as a special class of events, and hence, generalizations

from psychological investigations of decisionmaking and behavior under stress

or life threats are little more than untested hypotheses about responses during

fires. Research on natural disasters has also addressed the effects of stress

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on decisionmaking and escape route choice. Although this work has not

specifically attempted to clarify mechanisms by which environmental stressors

prevent or inhibit effective decisionmaking during emergency situations, it

has generally found that under such conditions decisionmaking is more time

consuming

Disciplined egress and crowd movement . Behavioral assumptions regarding

leadership and direction-taking behavior, two important aspects of disciplined

egress and crowd movement during emergencies, appear to be at least partially

supported by available technical literature. In particular, most researchers concur in the belief that under many circumstances, individuals and groups tend

to follow directions from strong and clearly perceived leaders or authority

figures. However, some criticism of the preparedness of assigned leaders, or "fire wardens," has appeared in the fire literature. Moreover, there exist

virtually no data either supporting or refuting the assumption that the pre- sence and actions of specially trained emergency managers facilitates orderly

building evacuation and shortens overall egress time. What little is currently

known about the use of such personnel stems from aviation research on the eva- cuation of commercial aircraft cabins. Grounds for generalizing from such

experiments to much larger scale building evacuations have not been established.

The literatures of social and environmental psychology provide important

sources of data for evaluating assumptions about pedestrian movement under high

density occupancy conditions. Investigators from these disciplines have

suggested that cognitive overload, frustration, and increased arousal tend to

characterize the high density occupancy experience for many Individuals. However, it is not now known how these factors influence emergency egress behavior

patterns. Some investigators have suggested that increased psychological

arousal, and related maladaptive behavior, may result from encroachments upon

an individual's personal space envelope. Yet, at least one researcher notes

that during life threating emergencies, people may be quite willing to forego

all but the most essential personal space.

The orderly evacuation of large numbers of occupants from public buildings

implies that once individuals have actually exited to the outdoors, they will

remove themselves a sufficient distance from the structure to permit persons

behind them to exit as well. Indeed, the Code provides that public occupancy

buildings be designed so that exits discharge either to a street or to an area with sufficient holding capacity. In conforming to such provisions, building

designers may have to assume that once occupants exit a structure, they will in

fact remove themselves from the immediate vicinity of the point of discharge.

Specific Investigations of exit discharge under naturalistic conditions do not

appear in the literature. However, a number of post-incident fire investigations (very few of which dealt with public occupancy buildings) had indicated

that re-entry by some evacuees is not uncommon. No research has been conducted

to assess the influence of re-entrants upon the egress performance of other

occupants. Re-entry is a key issue because it introduces the potential problem

of two-way traffic in egress ways, a subject largely Ignored by the Code .

Behavioral assumptions concerning potential effects of architectural barriers

on crowd movement were evaluated with reference to findings from studies of

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pedestrian movement and crowd flow phenomena. In general, available data

indicate that such minor egress way constrictions as might result from stair

railings, door hardware, etc., do not measurably impair the performance of

occupants using means of egress. The perceived complexity of a building’s

floor plan may, however. Influence escape time. This conclusion is evidenced,

in part, by research suggesting that paths which contain bends and turns are frequently perceived by experimental subjects to be longer than linear paths

of equal length. On the other hand, available data do appear to support

behavioral assumptions underlying Code provisions specifying maximum forces

required to open doors and to manipulate panic hardware. To date, however,

researchers conducting post-incident investigations of fire events have not

addressed the question of whether either escape route complexity or architectural obstructions influence actual emergency egress performance.

The assumption that means of egress will in fact be maintained clear and fully

available for immediate emergency use cannot now be evaluated by reference to

technical data. Similarly, while anecdotal accounts have occasionally cited

potential conflicts between building security and emergency egress objectives

(e.g. journalistic reports of escaping occupants who have encountered locked

exit doors), such conflicts have not as yet been systematically investigated by

researchers.

Occupants* capabilities to safely and rapidly negotiate egress ways . The

current investigators found considerable contradiction in available data

describing occupants' capabilities to negotiate egress ways. Consequently,

specific conclusions about either the validity of behavioral assumptions or the

efficacy of Code provisions which affect such capabilities cannot be drawn. For

example, a number of behavioral assumptions concern the notion that accidents

(e.g. slips, falls) along means of egress may Impede flow along such elements

as corridors, stairs, ramps, and through door ways. Investigators have studied

stair riser-to-tread ratios, surface friction, and other physical characteristics of egress ways to determine potential causes of accidents. However, the

accident literature has failed to reach consensus on the causes of slips, missteps, and falls, has presented no statistically significant correlation between

accident rates and surface friction, and presents contractory conclusions

regarding the role of stair riser-to-tread ratios in stair accidents. Moreover,

specific effects of occupant accidents during emergency evacuations has never been systematically Investigated. As a result, it is not possible to determine

whether mishaps—which may Impede overall egress flow in means of egress —occur with greater frequency during stressful emergency situations, or to what degree

they adversely affect overall escape time.

The Code requires that handrails be provided on stairs under the assumption that

handrails will facilitate the safe and rapid negotiation of egress ways by, at

least in part, reducing the likelihood of missteps, slips, and falls. However,

the available literature does not permit specific conclusions concerning the

provision of handrails, particularly Intermediate handrails which may be

required for stairs wider than 88 inches (2.24 m)

,

Research on ramp negotiation indicates that ramp slope may affect the ease,

speed, and safety with which pedestrians use such facilities. The literature

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on ramp use has not, however, specifically considered surface friction in

sufficient technical detail to permit useful conclusions to be drawn at this

time

Physiological stress and fatigue may also affect occupants’ capabilities to

safely and rapidly negotiate egress ways, and assumptions concerning these

phenomena often underlie design provisions of the Code . Technical data relevant to fire egress situations stem primarily from animal and human toxicological research, and from laboratory experiments in human perception. Anecdotal

accounts reported by fire victims provide additional insight. Several wellcontrolled studies have demonstrated the deleterious effects of prolonged CO

exposure on both visual and psychomotor performance. However, the low level

dosages required in the conduct of experiments using human subjects, and the

unrealistic design of many toxicological experiments, has led to findings which

are often contradicted by the reported experiences of fire victims. Moreover,

limited data from laboratory experiments and field studies on human behavior

in smoke-filled environments are contradicted by a number of journalistic

accounts of fire victims’ experiences.

Potential effects of multiple toxicants (which may combine chemically to

produce additional physiological stressors) on emergency egress performance

have not been systematically studied by researchers. Heat stress, another

important consideration, also has been the subject of physiological investigation. However, the focus of this work has been on long-term endurance under

noneraergency conditions, and hence it is difficult to draw specific conclusions

from these studies which would be pertinent to the problems of building fires.

Smoke conditions potentially influence visibility. While a number of studies

have described the effect of variation in smoke density upon visibility distance, no data are available establishing a direct relationship between smoke

density and various factors contributing to escape performance. Several

researchers have suggested, however, that impaired visibility can trigger other

forms of physiological and psychological stress, which may in turn adversely

affect egress performance.

The present review of the technical literature yielded limited useful

Information concerning potential effects of dead-end corridors on egress time.

The assumptions that acrophoblcs may impede flow on outside egress stairs is

based on current clinical judgment, although the effects of acrophobia under

life threatening conditions remain little understood and are presently the

subject of controversy among clinicians.

In conclusion, the literature on respiratory, visual, and thermal stress and

fatigue report data which are often only indirectly relevant to analyses of

emergency egress performance. In virtually no cases do research findings

point unequivocally to any single explanation or solution. However, findings

reported in the literature appear to contradict behavioral assumptions underlying relevant Code provisions.

The capacity of means of egress . Data reported in the technical literature

permit few clear conclusions regarding the effects of architectural impediments

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and other obstructions on egress flow. For example, doors are potential

impediments to pedestrian movement along corridors and between elements of

egress routes. Estimates of mean pedestrian flow through doors ranging from

30.2 pers/mln/22 inch unit (0.90 pers/sec/m) to 58.8 pers/min/unit (1.75 pers/

sec/m) have appeared in the literature, (the Code suggests that 60 pers/min/

unit, or 1.78 pers/sec/m, can pass through exits along horizontal surfaces).

Similarly wide variations in estimates of the effects of egress way width

reduction (which often occurs at door installations) upon flow efficiency have

also been reported. The question of whether, and how, door swing direction

Influences flow through door ways, perhaps one of the most critical issues in

the provision of doors, has received only minimal attention. Japanese research

has shown that egress time may decrease by as much as 12 percent when exit

doors swing against traffic flow, provided that pedestrian densities are not so high as to prevent the doors from being opened.

In addition to flow reductions which may accrue from door design and

installation, various Investigations have Indicated that such other architectural obstructions as railings may also impede pedestrian movement. For example, the addition of center handrails on wide stairs has been shown to reduce

downward flow by as much as 20 percent. Insofar as other forms of obstructions

are concerned, available data suggest that obstructions up to one foot (0.31 ra) in width tend to have little or no impact on pedestrian flow, even in relatively

high density situations.

Other potential sources of reduced pedestrian flow implied by Code provisions

include bends and corners, often found along corridors and stair ways. Data

reported in the literature generally indicate that flow rates are maintained at

bends on stairs, and that queue formation at corners in corridors are atypical.

One experimental Investigation of corridor use, in which corridor layouts were artificially configured in a laboratory, reported reductions in walking speed

at comers.

In actual buildings, it is not uncommon to find width reductions over the

length of a linear corridor segment. Available research suggests that relatively small width reductions have no measureble effect on pedestrian flow. In

fact, corridor width reductions of 33 percent have been shown to produce flow

reductions of 10 percent.

The Code severely restricts the use of revolving doors as means of egress, as well as the placement of turnstiles in pedestrian ways expected to be used as means of egress. In those cases where such devices are permitted, the exits

may not account for more than 50 percent of required exit units. These restrictions are predicated on the notion that revolving doors and turnstiles substantially reduce pedestrian flow, thereby increasing required egress time. Available data on revolving door performance indicates flow through these devices

to be between one third and one half that of ordinary doors. Other research

has examined pedestrian flow through turnstiles under a variety of conditions

(e.g. involving the depositing of coins or taking of tickets). Depending on the specific circumstances, flow through these devices appears to vary from

8.4 to 33.6 pers/min/unit (0.25 to 1.00 pers/sec/m), substantially below the

average flow rate of 50.4 pers/min/unit (1.50 pers/sec/m) reported for ordinary

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doors. Thus, although available data do not permit an evaluation of the degree

of restriction in the use of revolving doors and turnstiles permitted by the

Code , they do support the need for such restrictions.

As with analyses of egress way obstructions, available data point to relatively

few specific conclusions regarding the capacities of individual means of egress.

For example, researchers have generally found pedestrian flow in level corridors to vary from 43,7 to 53.8 pers/min/unit (1,30 to 1,60 pers/sec/m), substantially lower than the flow rate of 100 pers/min/unit (2.98 pers/sec/m)

recommended by the Code , Thus, flows assumed by the Code appear, in comparison

with empirical findings, unrealistically high. The literature has also suggested that the variance in reported flow rates may be attributed to peculiarities associated with various occupancies, and to variation in the widths and

lengths of corridors studied (the Code reflects virtually none of these

occupancy-related differences in corridor performance). Thus, the age, sex,

and other physical characteristics of occupants, architectural and organizational features of buildings, and the physical characteristics of corridors,

appear to influence pedestrian performance in corridors in some way. Unfortunately, however, neither specific contributions of each factor nor interactions

among factors have been empirically investigated.

It is even more difficult to draw specific conclusions about the capacity of

stairs. Although the Code recommends a design rate of 45 pers/min/unit (1.34

pers/sec/m) in descent, empirical studies have shown that measured flow rates

may vary between 30.2 and 57,1 pers/min/unit (0.90 and 1.70 pers/sec/m) in

descent. The National Bureau of Standards (NBS, 1935) reports the highest rate

shown above, indicating that this was measured under somewhat ideal conditions.

NBS (1935) recommends that a design rate of 45 pers/min/unit (1.34 pers/sec/ra)

would more adequately accommodate normal variations in density. Code recommendations concerning the capacity of stairs are based on this recommendation.

However, Pauls, who has conducted the most extensive investigations of crowd

movement and building evacuation, has pointed to both his own data and those

of other researchers, which consistently Indicate that design rates recommended

by the Code are too high. Pauls recommends that flow down stairs is ordinarily

on the order of 30 pers/min/unit (0,90 pers/sec/m) under conditions of normal

building occupancy. Pauls has also found that, irrespective of stair design,

overall evacuation time for high-rise buildings may vary quite widely depending

on the method of evacuation employed (i.e. total versus staged), as well as building height.

Walking speed on stairs also has been investigated in relation to stair slope

and direction of travel. Here too, it is difficult to draw specific conclusions on the basis of data reported in the technical literature. For example,

stair slope has been found to be both positively and negatively correlated

with walking speed. Moreover, while two investigators found that pedestrians

move faster down than up stairs, another researcher reported the opposite

finding.

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The Code treats all ramps^^ as substantially equivalent to level corridors for

purposes of computing downward capacity. That is, ramps are expected to carry

100 pers/min/unit (2.98 pers/sec/m). In the upward direction, the Code suggests

that while Class A ramps will carry pedestrians at the downward flow rate.

Class B ramps will only carry 60 pers/min/unit (1.78 pers/sec/m). In general,

data reported in the technical literature indicate that for most ramps with

slopes between 1 in 50 and 1 in 8 (i.e. 2 and 12 percent), flow characteristics

are substantially similar to those associated with level corridors. However,

some investigators have noted lower flows on ramps with slopes greater than 5 to 7 percent, for both upward and downward travel. Hence, available data

appear to support some of the assumptions underlying Code provisons concerning

the capacity of ramps. In particular, flow on most ramps is similar to that

in level corridors, and pedestrian movement speed is higher on ramps than on stairs. Available data do not permit the general conclusion that downward

travel on ramps is typically equal to, or greater than, upward travel.

Code provisions governing the capacity of means of egress are partially based

on certain expectations about the linearity of pedestrian movement. Data on the capacity of egress ways reported by NBS (1935) led investigators at this

organization to recommend that people may safely be assumed to travel in linear

files 22 inches (0.56 m) wide. This assumption (which serves as the basis for

present Code recommendations) has more recently been supported by Soviet data

on occupant circulation within buildings, and to a lesser extent has also been

supported by data collected by Fruin in the United States. Other investigators

have shown, however, that although such linear movement might occur within particularly narrow egress channels, the "lane" effect is generally not apparent

when channels surpass approximately 4.0 feet (1.22 m) in width. For such wide

channels, a number of researchers noted "staggered" files to be most common.

Pauls, however, found even staggered files to be atypical, since occupants

(particularly stair users) seek to maintain body buffer zones, and since there

may be some variation in the size of buffers required by each Individual in an egress way. Pauls also reported wide variations in side-to-side body sway and

need for handrail support during stair use to be quite common. On the basis of

these findings, Pauls recommends that the minimum width for heavily used stairs

in public occupancies be 55 inches (1.40 m) . According to Pauls, this design

value would permit shoulder-to-shoulder walking, as well as easy passing on stairs , in view of the relatively nonlinear movement paths typically found on these elements. This recommendation contrasts sharply with design values provided by the Code ; (1) minimum width of 44 Inches (1.12 m) for Class A stairs;

(2) minimum width of 36 inches (0.92 m) for Class B stairs^^; (3) absolute

minimum of 28 inches (0.71 m)

Class A ramps are defined to have a minimum width of 44 inches (1.12 m) , a maximum slope of 1 in 10 , and no limit to the maximum height between landings. Class B ramps are defined to have a minimum width of 30 inches

(0.76 m) , a maximum slope of 1 in 8, and a maximum height of 12 feet (3.66 m)

between landings.

Class B stairs are usually the minimum required by the Code for public

occupancies

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Pauls has further argued that the relationship between stair width and downward

flow is both linear and continuous, and that each extra inch of stair width can potentially Increase flow rate. The Code permits half credit for all extra

inches between 12 and 21 (0.31 and 0.53 m) , and gives no credit whatever for

extra width between 1 and 11 inches (0.03 and 0.28 m) . This recommendation

conforms to a step-like relationship between stair width and downward flow.

Referring to both his own data and those of other researchers, Pauls argues

that there is no empirical basis for Code '

step-like approach to allowing

credit for extra stair width, and that available evidence suggests instead the

efficacy of his continuous "effective width" concept.

The reader should note that although numerous studies of egress way capacities

have been conducted since the first comprehensive report on this topic was published by NBS in 1935, the majority of this research has been neither cumu- lative nor replicative. That is, there is no evidence that investigators

specifically sought to build upon earlier findings or test hypotheses advanced

by other investigators, or that they repeated studies to assess the consistency

and validity of previously measured behavior. Moreover, while it is tempting

to compare findings reported by various investigators (as was indeed done

above), the reader should bear in mind that researchers have tended to work on the basis of widely varying research questions, study designs, operational

definitions, and behavioral measurement methods. Finally, it is important to

remember that all empirical investigations of egress carrying capacities

reported in the literature were conducted either under contrived laboratory

conditions, or under nonemergency conditions associated with every-day use of

pedestrian ways in buildings. The only exception is, of course, Pauls'

Investigation of building evaluation during fire exit drills.

8.4 SUMMARY OF GAPS IN THE TECHNICAL LITERATURE

8.4.1 Overview

Clearly, provisions regarding crowd movement and the capacities of means of

egress are, at present, the most easily discussed topics with reference available to empirical research. Yet even here current knowledge in these areas remains equivocal on numerous critical issues. Analyses of other attributes

of safe and rapid building evacuation require considerable reliance on technical literature outside the field of fire research. On the basis of such literature, it has been possible only to suggest hitherto untested relationships

between human behavior in psychological laboratories, large-scale natural disasters, or nonemergency socio-environmental settings, and that believed to occur during building fires. In response to these realities, an important objective

of the current report is to identify specific gaps in the technical literature,

pointing to areas for future study.

8.4.2 Pre-emergency Training and Preparation

The questions of whether panic is a clear and constant threat and whether

potential dangers inherent in panic are reduced through pre-emergency preparation and training, and implied by provisions of the Code which are covered in

Chapter 2 of this report , are not now answerable on the basis of current

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knowledge. This is true, at least in part, because researchers have yet to:

(1) adopt a standard operational definition of panic and a standard method for

measuring panic behavior, (2) identify and measure environmental and situational stimuli which trigger panic or increase its likelihood, (3) describe

perceptual and cognitive processes which lead to panic, (4) understand the

processes by which leadership and the subsequent division of tasks and responsibilities reduce the likelihood of panic, (5) specify the relationship between

preemergency training and the occurrence of panic, and (6) specify the relationship between occupancy characteristics and the likelihood of panic.

The general assumption that behavior learned during fire exit drills transfers

to actual fire situations remains to be empirically demonstrated. In the

future, such demonstrations will require researchers to design and conduct

longitudinal field experiments which permit assessments of various training

protocols in a number of occupancies, and which would allow investigators to

evaluate the effects of time on learning. Stahl (1978b) provides a basis for

such research designs. Where future research in this area attempts to introduce simulated life threats as Independent variables, safeguarding human

participants will be of paramount importance.

Additional research should address the role of occupants* attitudes toward

drills and drill participation. Required data include; (1) correlations

between occupants’ attitudes toward drill participation, their performance

during drills, and where possible, individuals' performance during actual (or

perceived) emergencies, and (2) correlations between attitude change and

behavior change.

8.4.3 Perception of the Emergency Environment, and Recognition of Egress

Facilities

Few data presently exist to permit an evaluation of assumptions about potential

effects of door and window design on egress route perception. However, anecdotal accounts of fire victims' experiences Indicate the importance of interior

design to evacuation, particular for transient occupants of public buildings.

The degree to which various door and window placements can be discerned from

surrounding decor can be studied using laboratory experimental designs.

Similarly, the influence of Interior design on exiting time can be evaluated by

means of field experiments conducted in real buildings. This research can become considerably more complicated, however, if it is desired that lifethreatening stimuli be introduced or at least simulated. Here, the safety and

well-being of human subjects must be of primary concern.

Available data describing the adequacy of Illumination for egress are ambiguous

and difficult to apply to evaluations of Code provisions and their underlying

behavioral assumptions, especially where conclusions about illumination and

visibility in smoke are sought. Here, it will be necessary to study the effects

of smoke on visibility under various lighting and environmental conditions within the safe confines of the laboratory. Experimental data may later be evaluated in relation to victims' reports documented during post-incident analyses

of actual fires.

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Previous research on directional signage has emphasized the visibility of signs

under varying conditions of illumination, by individuals varying in their

familiarity with a building's circulation system. The questions of whether,

and how, directional signs are used during emergency situations have not as yet

been addressed. Factors which should be considered in future investigations

of directional signage should include sign location, mode of display, lettering

and/or graphic design, as well as variations in occupants' visual acuity and

familiarity with the research setting (where this is an actual building), smoke

density (where feasible), and illumination.

Assumptions about the ability of alarm devices to alert building occupants to

take effective action during fire emergencies require further verification.

Among the factors which have not been adequately investigated to date include

(1) mode of signal delivery, (2) clarity of alert messages and their consistency with occupants' perceptions, (3) relationship between alarm signals and

pre-emergency training, (4) occupants' familiarity with available egress routes,

and (5) physiological and psychological Impediments to effective alarm signals

perception.

8.4.4 Egress Strategy Formation

Although a considerable knowledge base now exists describing human Information

processing and decisionmaking behavior, relatively little is known about the

ways building occupants select information from emergency environments, plan

escape strategies, modify or switch strategies to accomodate sudden environmental changes, and make decisions which lead to safe escape or failure during

building fires.

To expand knowledge about these facets of effective emergency escape, it is

necessary to more rigorously debrief victims after fire events, using rather

sophisticated clinical techniques for externalizing individuals' behavior. In

conjuction with such debriefing, it will also be necessary to more thoroughly

cross-valldate individuals' self-reports against those contributed by other

victims. In this way, it may not only be possible to obtain a clearer understanding of an occupants' decisionsmaking behavior and of the specific environmental factors leading to decisions, but to determine the confidence with which

inferences may be drawn from individuals' reports, as well. Future debriefing

protocals should be designed to permit the analyst to determine how interior

design, building configuration and layout, and physiological and emotional

stress influence egress strategy formation and route choice,

8.4.5 Disciplined Egress Behavior and Crowd Movement

The technical literature on group psychology and crowd behavior appear to

support behavioral assumptions about leadership and direction taking only

indirectly. Laboratory experiments and post-incident studies of large-scale

natural disasters illustrate the tendency of many individuals and groups to

take directions from perceived leaders or authority figures. Unfortunately,

however, too few data describing direction taking during building fires are presently available to permit definitive conclusions. Similarly, the effectiveness of trained leaders (e.g. "fire wardens") during real fire emergencies

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has not been examined empirically. These gaps in the literature exist

primarily because to date, post-incident data collection protocols have not

been designed to specifically assess the leadership function. In the future,

specially designed debriefing protocols, of the type described above, should

assist analysts to evaluate the effectiveness of various leadership scenarios.

Presently available data are not sufficient to either support or refute

behavioral assumptions which underlie Code provisions affecting building occu- pant loading and exit discharge facility design. In addition, extremely little

material applicable to evaluating Code provisions Intended to minimize physical

impediments and obstacles to rapid escape was found in the literature. In the

future, knowledge of crowd movement may be advanced through the conduct of

time-motion studies under a variety of simulated emergency and exit configuration conditions.

8.4.6 Occupants' Capabilities to Safely and Rapidly Negotiate Egress Ways

In large part, assumptions underlying Code provisions accommodating occupants'

capabilities to safely and rapidly negotiate egress ways concern the need to

prevent slips and falls along elements of egress ways, and to accommodate

occupants' varying physiological abilities. The literature on walking accidents, particularly with respect to stairs, offers tentative support for the

assumptions that under certain conditions slips and falls are more likely, and

that falls on stairs can impede pedestrian flow and thereby reduce the efficiency of egress ways. However, the literature is rather equivocal on the

subject of stair accident causation. Consequently, it is not now possible to

offer specific design recommendations for reducing the likelihood of these

potential impediments to flow. Clearly, future research should focus on this

gap.

The assumption that fire products which have infiltrated means of egress will

adversely affect egress flow also requires additional empirical verification.

Available experimental evidence does not point to any one conclusion regarding

potential effects of CO exposure, and such evidence has been contradicted by

anecdotal and journalistic accounts of experiences reported by fire victims.

Additional data describing human respiratory, visual and thermal adaptability under a wide range of fire scenarios are required before the effects of

fire product infltration on the efficient use of egress ways are fully understood. Other areas requiring further investigation include the role of smokeinduced visibility decrement in egress way negotiatation , the ability of

handicapped and other public building occupants to manipulate doors and door

hardware, and the role of stress and fatigue in emergency escape.

8.4.7 The Capacity of Means of Egress

Provisions of the Code specify the design of door ways on the basis of occupant

loading criteria and available door width. One point on which there is little

equivocation in the literature is the finding that, under conditions of relatively high occupant density, queues form as individuals wait to pass through

door ways. However, researchers have yet to study the questions of how queue

formation and processing Influence egress time, and how door width specifications may be adjusted to compensate for time potentially lost in queues.

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A closely related gap in the technical literature concerns the predilection of

most researchers to study pedestrian behavior in relation to some one isolated

egress route element (e.g. doors). Indeed, the task of exiting a building may

involve passing through numerous door ways, as well as corridors, stairs, and

lobbies, all of which are interrelated. When a queue forms at a door way, for

example, it is not merely flow through this door that is affected: capacity

of the preceding stair or corridor is being taxed as well. Future research

must address the Interdependencies between adjacent egress way elements, and

provide guidelines for the design of effective transitions between elements.

Flow rate has been the most universally accepted measure of the performance of

means of egress. Considerable work remains, however, to develop a standard

measurement method. In the absence of such a standard, it will continue to be

difficult to determine precisely why data from seemingly similar investigations

often disagree. For example, Pauls and Fruln each found different variables

to interact with flow rate and walking speed; Togawa found no such interaction

effects. Similarly, although Pauls and Fruln have both advocated an incorporation of body sway and personal space maintenance behavior into computations

of flow capacity, there remain neither standard measures nor replicable models

of these phenomena,

8.5 CONCLUSIONS

8.5.1 Overview

The primary objective of the investigation has been to assess available

research pertaining to exit facility design and emergency escape provisions of

the NFPA Life Safety Code (1976 Edition), in order to determine the technical

support for such provisions. The intention of the authors is not to pass

judgment on the validity or usefulness of Code provisions. Indeed, where

technical support for Individual provisions is either weak or unavailable, the

authors do not recommend eliminating or otherwise modifying these provisions.

In such instances, rather the authors suggest that code-writers approach their

task with caution, and that further technical Investigations be conducted.

Substantive conclusions about available technical support for Code provisions,

as drawn by the current investigators, are summarized below.

8.5.2 Provisions Affecting Pre-emergency Training and Preparation

Behavioral assumptions underlying code provisions affecting pre-emergency

training and preparation may be evaluated by reference to psychological models

of learning, experimental data reported in the psychological literature, and

the growing body of evidence from post-incident fire investigations. To date,

experimental and post-incident investigations provide mixed conclusions concerning the supportability of these assumptions. Moreover, available evidence does

not often permit direct inferences to be drawn between research findings and

the specific questions raised by code provisions. Future modifications to provisions affecting pre-emergency training appear to require additional research

on the role of training and its relation to emergency behavior.

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8.5.3 Provisions Affecting Perception of the Emergency Environment, and

Recognition of Egress Facilities

A number of human behavioral assumptions about the perception of emergency

environments and recognition of egress facilities underlie various provisions

of the Code . These assumptions were evaluated by reference to several models

of perception, to limited data from experiments on visibility, and to a small

body of evidence from post-incident fire investigations. Taken as a whole,

available data neither support nor refute behavioral assumptions about occupants' emergency perceptions at a level technically sufficient to permit a thorough evaluation of pertinent Code provisions. Where data are available in

sufficient quantity, however, it has been suggested that behavioral assumptions

underlying alarm provisions of the Code tend not to be supported. The Code

provision specifying a maximum (10 second) switchover delay between standard

and emergency lighting, on the other hand, tends to be supported by available

technical data. Initial emergency perceptions are important, and their relationship to rapid escape has been shown. Consequently, future research which

leads to more effective perceptions of the fire environment by victims is

recommended

8.5.4 Provisions Affecting Egress Strategy Formation

A number of assumptions about human information processing and decisionmaking

behavior during fire emergencies underlie several provisions of the Life

Safety Code . Such assumptions were evaluated by reference to models of cognitive behavior, as well as to data from recent psychological research on wayfinding behavior, environmental cue processing, disaster response, and stress.

Few directly relevant technical data were found within the field of fire

research itself. Taken as a whole, available technical knowledge is not sufficient to warrant statements specifically supporting or refuting Code provisions which may Influence egress strategy formation. However, the literature

generally supports the notion that the demands of occupying a burning building

require individuals to efficiently sample information from fire environment,

and to formulate effective and timely decisions about what to do. Depending

upon the design and layout of a building, and upon the nature of given fire

conditions, these processes will consume some sizable proportion of the time

within which occupants must escape. Errors in judgment and decisionmaking

will frequently consume even more time. A crucial gap in current knowledge

about the time-based capabilities of building occupants to effect rapid

emergency centers on questions of emergency information processing and strategy

formation.

8.5.5 Provlsons Affecting Disciplined Egress Behavior and Crowd Movement

A number of human behavioral assumptions about crowd movement and disciplined

group behavior are believed to underlie selected provisions of the Code . These

assumptions were evaluated by reference to several models of human collective

behavior, data from research in experimental social psychology, field research

on natural disasters, and post-incident fire investigations. In general, the

technical literature suggest support for only those assumptions pertaining to

leadership and direction-taking behavior. Behavioral assumptions pertaining to

133
the effects of occupant loading and physical obstacles upon orderly and rapid

crowd movement appear to be neither supported nor refuted by available technical literature. To the extent that impediments to crowd movement result in

maladaptive collective behavior and panic, future research on the role of

building design in facilitating crowd movement seems an essential precursor to

Code development.

8.5.6 Provisions Accommodating Occupants’ Capabilities to Safely and Rapidly

Negotiate Egress Ways

Human behavioral assumptions believed to underlie Code provisions relating to

occupant's capabilities to safely and rapidly negotiate means of egress may be

evaluated by reference to biomechanical models of human movement, toxicological

research, stair and ramp use field studies, physiological measurements and

anecdotal evidence from actual fire incidents. At present, much of the evidence

reported in the experimental and nonexperlmental literature on occupants'

capabilities presents contradictions and mixed opinions, and does not permit

specific conclusions or inferences to be drawn. As a result, there appears to

be no analytical basis upon which to unequivocally support or refute applicable

Code provisions. It is left for future research to determine the specific

domains (l.e. occupancies of fire senarlos) under which particular data are valid and useful in this context.

8.5.7 Provisions Governing the Capacity of Means of Egress

Finally, a number of human behavioral assumptions underlying Code provisions

which govern the capacity of means of egress were presented. These assumptions

were evaluated by reference to several models of pedestrian movement, data

from laboratory and field studies of walking behavior during normal occupancy

conditions, and observations of stair use during fire exit drills in high-rise

office buildings. With regard to Code provisions affecting the design of

doors, available technical literature support only those assumptions concerning

the deleterious effects of particularly severe constrictions or obstructions.

However, behavioral assumptions underlying provisions governing the design of

corridors and stairs are challenged by the technical literature. This is

especially true of provisions depending on the validity of assumptions and the

linearity of pedestrian movement and the 22 inch (0.56 m) unit width standard.

Because there remain differences in reported data describing pedestrian behavior on stairs and level surfaces, inconsistent definitions of important variables, and nonstandardized techniques for measuring the performance of means

of egress, it is not now possible to either support or refute existing provisions and their underlying behavioral assumptions on the basis of the available

technical literature. The most important objectives for future research on the subject of means of egress capacity are: (1) the development and validation

of standardized measures and measurement methods, and (2) the systematic analysis of complete egress systems emphasizing transitions between means of egress

elements

134
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149. Sadalla, E. and Magel, S., "The Perception of Traversed Distance,"

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151. Saegert, S., "The Effects of Spatial and Social Density on Arousal,

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of Psychology, unpubli. Ph.D. dissertation, 1974.

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In, Proshansky, H. , Ittelson, W. , Rivlin, L. , (eds.). Environmental

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Crowding , Hillsdale, NJ: Lawrence Erlbaum Associates, 1978.

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155. Schiffenbauer , A., "The Relationship Between Density and Crowding: Some

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159. Selye, H. The Stress of Life . New York: McGraw-Hill, 1956.

160. Shaw, M. and Costanzo, P., Theories of Social Psychology , New York:

McGraw-Hill, 1970.

161. Sharry, J. (ed.) Life Safety Code Handbook , Boston: National Fire

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162. Sigler, P. A., "Relative Slipperiness of Floor and Deck Surfaces."

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163. Simon, H. A. "Motivational and Emotional Controls of Cognition."

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166. Solokov, E. N., "Higher Nervous Functions; The Orienting Response." In

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Skills." In Archives of Environmental Health , 1973, 349-354.

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149
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APPENDIX A: MEMBERS OF PEER REVIEW PANEL

Irwin A. Benjamin

National Bureau of Standards

Center for Fire Research

Bldg. 224, Rm. B250

Washington, D.C. 20234

J. Armand Burgun

Rogers, Butler, Burgun & Shahine

521 Fifth Avenue

New York, NY 10017

Bertram M. Vogel

National Bureau of Standards

Center for Fire Research

Bldg. 224, Rm. B250

Washington, D.C. 20234

Donald Belles

Fire Protection Consultant

Suite 200

101 Cumberland Avenue

Madison, TN 37115

Harold E. Nelson

National Bureau of Standards

Center for Fire Research

Bldg. 224, Rm. A363

Washington, D.C. 20234

Thomas Jaeger

Gage Babcock and Associates

301 Maple Tower West, Suite 2C

Vienna, VA 22180

Richard G. Bright

National Bureau of Standards

Center for Fire Research

Bldg. 224, Rm. A263

Washington, D.C. 20234

John L. Bryan

University of Maryland

Dept, of Fire Protection Engineering

College Park, MD 20742

John G. O'Neill

National Bureau of Standards

Center for Fire Research

Bldg. 224, Rm. A263

Washington, D.C. 20234

Thomas Seymour

U.S. Dept, of Labor

OS HA

Rm. N 3463

200 Constitution Avenue, N.W.

Washington, D.C.

Alan I. Gomberg John Fannin

National Bureau of Standards U.S. Fire Administration

Center for Fire Research

Bldg. 224, Rm. A263

Washington, D.C. 20234

FEMA

2400 M. Street, N.W.

Washington, D.C. 20472

Jonas Morehart

Room 4709, HEW North

Dept, of HEW

330 Independence Avenue S.W.

Washington, D.C. 20201

William Hanbury

U.S. Fire Administration

FEMA

2400 M. Street, N.W.

Washington, D.C. 20472

A-1
Donald Moore

Dept . of HUD

Architectural Engineering Division

451 7th Street, S.W,

Washington, D.C. 20411

John G, Degenkolb

1720 Chevy Knoll Drive

Glendale, CA 97206

Michael Slifka

National Conference of States on Building Codes and Standards

1970 Chain Bridge Road

McLean, VA 22102

Richard Stevens

National Fire Protection Association

470 Atlantic Avenue

Boston, MA 02210

James K. Lathrop

National Fire Protection Association

470 Atlantic Avenue

Boston, MA

John B, Ferguson

Rolf Jensen and Associates, Inc.

5803 Rolling Road

Suite 207

Springfield, VA 22152

Leonard Bickman

Loyola University of Chicago

Applied Social Phychology Program

6525 N. Sheridan Road

Chicago , IL 60626

John Archea

College of Architecture

George Institute of Technology

Atlanta, GA 30032

A-2
APPENDIX B: INSTRUCTIONS TO REVIEWERS

MEANS OF EGRESS BEHAVIORAL ASSUMPTIONS REVIEW PACKAGE:

INTRODUCTION

Aim of the Study

To assess means of egress provisions of the LIFE SAFETY CODE (1976 edition), by

evaluating the validity and plausibility of human behavioral assumptions

believed to underlie these provisions.

Scope

The study addresses primarily means of egress provisions of the CODE, as well

as related provisions concerning fire exit drills, lighting and signage, and

emergency alarm. Under examination are provisions from: Chapter 5 of the CODE

(Means of Egress), Chapter 8 (Places of Assembly), Chapter 11 (Residential

Occupancies), Chapter 12 (Mercantile Occupancies), Chapter 15 (Business

Occupancies), and Chapter 17 (Operating Features).

Approach

Current means of egress provisions are intended to achieve certain minimum

levels of building and human performance during fire emergencies. Accordingly,

many of these design provisions rest upon a series of expectations, or assumptions, about the emergency egress behavior of building occupants. In numerous

cases, these assumptions are based on professional experience, analyses of

egress problems, and research data. In many other instances, however, assumptions about human capabilities and performance are not always obvious, and may

not be consciously considered by code writers and building designers. As a result, the application of some provisions may have the effect of achieving one level of performance in reality, while eroneously intending to achieve another

level

This study seeks to evaluate human behavioral assumptions believed to underlie

particular provisions of the LIFE SAFETY CODE. To accomplish this goal:

(1) behavioral assumptions must be identified and stated, and

(2) these assumptions must be evaluated against state-of-the-art knowledge

from a variety of technical fields.

This "review package" is intended to assist the project staff in completing

step (1): the identification and statement of assumptions about emergency

egress behavior.

B-1
Built-in Biases

The author’s* several years experience in the study of human behavior during

fires may have resulted in biases which are unavoidably reflected in behavioral

assumptions listed in this package.

HOW TO USE THIS PACKAGE

Purpose

The purpose of the review package is to elicit your opinions about the

correctness and completeness of a set of behavioral assumptions prepared by

the author. These assumptions necessarily reflect only one interpretation of

CODE provlsons. Hence, the value of this exercise depends a great deal upon

the quality of feedback it evokes from life safety professionals like yourself.

Therefore, we invite and encccourage you to comment on human behavioral

assumptions WE believe underlie provisions of the LIFE SAFETY CODE, and to

comment on our interpretation of that document. Moreover, any additional ideas

and insights which you contribute regarding expectations about human behavior

during fires would be highly useful and most welcome.

Please bear in mind that the function of this exercise is NOT to pass judgment

upon the LIFE SAFETY CODE itself.

Organization and Format

The set of assumptions listed on the following pages is subdivided into 5 general categories. These were chosen to represent principal areas of human

behavior believed to be relevant to emergency egress performance. The

categories are:

(1) Pre-emergency preparation and/or training.

(2) Perception of the emergency environment, and recognition of

egress facilities.

(3) Egress strategy formation.

(4) Initiation of egress behavior.

(5) Follow-through and completion of egress behavior.

Within each category, means of egress provisions and their related behavioral

assumptions (as developed by the author) are listed as shown in the examples on the following page.

* F, I. Stahl, project principal investigator.

B-2
Instructions

Consider the examples on the following page. Then, please comment upon

assumptions shown next to each of the CODE provisions listed on the remaining

pages. Show any changes In word usage, structure or grammar you feel would

make particular assumptions more complete or correct. Where you feel necessary,

don't hesitate to change entire assumptions or to add new ones. Please use the

backs of pages for any additional comments.

B-3
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NBS«n4A (REV, 2-80

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 82-2480

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

April, 1982

4. TITLE AND SUBTITLE

TIME-BASED CAPABILITIES OF OCCUPANTS TO ESCAPE FIRES IN PUBLIC BUILDINGS:

A REVIEW OF CODE PROVISIONS AND TECHNICAL LITERATURE

5. AUTHOR(S) Stahl, James J. Crosson, Stephen T. Margulis

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7. Contract/Grant No. national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

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

Home and Public Building Safety Division

U.S. Fire Administration

111 Federal Emergency Management Agency

Washington, D.C. 20472

10. SUPPLEMENTARY NOTES

8 . Type of Report & Period Covered

FINAL

I I 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)

This document reviews available technical literature pertaining to exit facility

design and emergency escape provisions of the National Fire Protection Assocatlon's

Life Safety Code (1976 Edition) in order to determine the technical support for such

provisions. The report focuses on the time-based capabilities of building occupants

to effect rapid evacuations, in relation to evacuation time available during fires.

A number of functional criteria are examined in relation to Code provisions

influencing the design of means of egress and fire protection and protective

signalling systems for places of assembly, residential occupancies, mercantile

occupancies, and business occupancies. Provisions affecting fire exit drill and

building management practices are also considered. The technical literature bearing

on applicable Code provisions is reviewed, the validity and generalizeabillty of

findings presented in the literature are discussed, and the degree of technical

support currently available for egress provisions of the Code are evaluated.

In addition, gaps in the technical literature are identified, and recommendations

regarding future research are offered. Finally, preliminary conclusions about the

supportability of Code provisions are presented.

12.

KEY WORDS (S/x to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

Emergency egress; fire protection; fire safety; human behavior in fires; human

factors; Life Safety Code , means of egress.

13.

AVAILABILITY

Unlimited

I I For Official Distribution. Do Not Release to NTIS

r I Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

168

15. Price15.00

USCOMM-DC 6043-P80


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