U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

DESIGN AND CONSTRUCTION

OF BUILDING EXITS

NATIONAL BUREAU OF STANDARDS MISCELLANEOUS PUBLICATION M151

U. S. DEPARTMENT OF COMMERCE

DANIEL C. ROPER, Secretary NATIONAL BUREAU OF STANDARDS

LYMAN J. BRIGGS, Director

NATIONAL BUREAU OF STANDARDS MISCELLANEOUS PUBLICATION M151

DESIGN AND CONSTRUCTION

OF BUILDING EXITS

Issued October 10, 1935

UNITED STATES

GOVERNMENT PRINTING OFFICE

WASHINGTON : 1935

For sale by the Superintendent of Documents, Washington, D. C. Price 10 cents (paper cover)

DESIGN AND CONSTRUCTION OF BUILDING EXITS

ABSTRACT

The deplorable loss of life that occurs annually in building fires can be reduced

by providing suitable exits. Building-code requirements vary widely as to how

many exits are needed, what sizes they should be, and how the details concerning

them should be worked out. To aid those interested in the problem, surveys of current practice in providing exits and of the rates at which people can effect their escape through different kinds of exits have been made. The methods

employed in the surveys and the results are presented here in detail. To supplement the information thus obtained, opinions have been solicited from numerous

architects, building officials, fire-protection experts, and others. Five methods

of calculating exit width in current use are discussed. As a useful reference when

local requirements are under consideration, suggested requirements are presented,

together with notes on the reasoning employed in connection with them.

CONTENTS

Page

I. Introduction 1 II. Importance of fire losses 2

1. Property loss 2

2. Life loss 2

3. Causes of loss of life by fire 4

III. Building exits survey 11

1. Procedure 11

2. Sources of information 12

3. Field investigations 13

4. Tabulation of data collected 13

5. Population studies 13

6. Location and number of exits 25

7. Stairway widths 26

8. Proportion of treads and risers 26

9. Stairway enclosures 27

10. Exit outlets 27

11. Special forms of exits 28

12. Exit designation 28

13. Exit maintenance 29

IV. Survey of traffic movement in exits 30

1. Procedure 30

2. Sources of information 30

3. Conclusions of previous traffic counts 31

4. Field work 33

5. Methods used in making counts 34

6. Conditions affecting traffic counts made 35

7. Tabulation of counts on stairway discharge 36

8. Characteristics of stairway discharge 36

9. Ramps 37

10. Doorways 38

V. Method of calculating exit width 39

1. Capacity method 39

2. Flow method 40

3. Combined method 40

4. Probability method 41

5. Floor-area method 41

6. Development of a satisfactory method 42

7. Credit for elevators 44

in
IV CONTENTS

APPENDIX

Page

VI. Means of egress 46

1. Recommendations 46

2. Definitions 46

3. Classifications 47

Sec. 3-1. Classification of buildings by occupancy 48

3-2. Classification of buildings by type of construction 48

7—1. Application of chapter 50

7-1-1. New buildings 50

7-1-2. Existing buildings 50

7-1-3. Alterations 50

7-2. Kinds of exits 51

7-3. Minimum number of exits 51

7-3-1. Room doorways 51

7-3-2. Ground-floor exits 52

7-3-3. Floor-area exits 53

7-3-4. Exits for institutional occupancies 53

7-3-5. Exits for places of assembly 54

7-3-5-1. Rooms 54

7-3-5-2. Buildings 54

7-3-5-3. Separation of theater stairways 54

7-3-6. Boiler-room exits 54

7-4. Location of exits 55

7-4^1. Distance to exits 55

7-4r-2. Distribution of exits 55

7-4-3. Outlets from exits 56

7-5. Relation of population to exits 57

7-5-1. Determination of population 57

7-5-2. Population limited 58

7-6. Stairways 59

7-6-1. Width 59

7-6-1-1. Minimum width 59

7-6-1-2. Aggregate width 59

7-6-1-3. Changes in stairway width 60

7-6-1-4. Exit stairways serving floor area below grade 60

7-6-2. Construction 64

7-6-2-1. Materials 64

7-6-2-2. Treads and risers 65

7-6-2-3. Required landings 65

7-6-2-4. Changes in floor level 65

7-6-2-5. Handrails 65

7-6-3. Enclosures 66

7-6-3-1. Construction 66

7-6-3-2. Openings 66

7-6-4. Moving stairs 67

7-7. Ramps 67

7-8. Doorways 67

7-8-1. Width 67

7-8-2. Hanging of doors 69

7-8-3. Revolving doors 69

7-8-4. Door fastenings 70

7-9. Exit passageways 70

7-9-1. Width 70

7-9-2. Enclosures 70

7-9-2-1. Construction 70

7-9-2-2. Openings 71

7-9-3. Inclined exit passageways 71

7-10. Hallways 71 7-11. Horizontal exits 72

7-12. Modifications in required exit widths 73

7-13. Exit designation 73

7-13-1. Exit signs 73

7-13-2. Lighting 74

7-14. Maintenance 74 Index to Recommendations 75
CONTENTS V

TABLES

Page

1. Causes of loss of life from fires • 5

2. Deaths by fire in buildings in New York City, 1920 to 1931, inclusive. 5

3. Deaths per fire 8

4. Causes of loss of life in hotel fires 9

5. Relation of garage and tenement fires to total in New York City 10

6. Summary of exit measurements for office buildings 14

7. Summary of exit measurements for. store buildings 16

8. Summary of exit measurements for factory buildings 17

9. Summary of exit measurements for school buildings 18

10. Summary of exit measurements for apartment buildings 19

11. Summary of exit measurements for hotels 21

12. Summary of exit measurements for hospitals 22

13. Summary of exit measurements for dormitories, churches, and city

halls 2£

14. Summary of exit measurements for theaters 24.

15. Average of exit measurements 25

16. Summary of some previous traffic movement observations 31

17. Survey of exits in school buildings in Rochester, N. Y 32

18. Capacity tests on revolving doors of certain buildings in New York

City 33

19. Summary of observations of traffic movement on stairways 35

20. Summary of observations of traffic movement on ramps 37

21. Summar}^ of observations of traffic movement through gates and door- ways 38

ILLUSTRATIONS

Fig.

1. Doorways placed "as remote as practicable" 51

2. Doorway location for connecting rooms occupied by 100 or more

persons 52

3. Discharge from a theater into a court, thence through a passageway

to the street 52

4. Distribution of stairways in a building where services are in a central

core 55

5. Example for computation of amount of service area alloted to mixed

occupancies 58

6. Relation between exit width and population per floor 61

7. Relation between exit width and floor area 61

8. Results of exits survey compared with curve adopted for office buildings 62

9. Results of exits survey compared with curve adopted for stores 62

10. Results of exits survey compared with curve adopted for factories 62

11. Results of exits survey compared with curve adopted for schools 63

12. Results of exits survey compared with curve adopted for apartments. 63

13. Results of exits survey compared with curve adopted for hotels and

dormitories 63

14. Results of exits survey compared with curve adopted for hospitals and

institutions 64

15. Results of exits survey compared with curve adopted for places of as- sembly 64

16. Example for computation of doorway widths 68

17. Example for computation of exit passageway widths 70

18. Level landings required on inclined passageways 71

19. Various types of horizontal exits 72

Design and Construction of Building Exits 1

I. INTRODUCTION

If buildings are to be safe for human occupancy adequate exits are essential. State governments have a legal right to require that

exits shall be suitable in number, size, and location. This power

is generally exercised through local building codes. Inspection of

representative codes discloses that the degree of safety assured occu- pants of buildings varies widely. There is no apparent reason why

more emphasis should be placed on the subject in one locality than

in another. That such a condition exists seems to be due partly

to the development of regulations independently in different parts of

the country, partly to the existence of varying ideas on what consti- tutes reasonable provision for safety, and partly to a lack of information on fundamentals.

Some five methods of determining the necessary stairways for a given building are in current use. These methods all contain desirable

features, but they tend to become confusing to anyone not a student

of exit design and practice and they have been reported to cause

difficulties for architects, engineers, building officials, and others.

While some maintain that many existing codes are too severe, reducing unreasonably the rentable area of buildings, numerous deaths by

fire testify to the need of extreme care in lowering present requirements.

Fire protection is closely associated with provision for building

exits. This was recognized by the Department of Commerce Building

Code Committee in preparing its report, Recommended Minimum

Requirements for Fire Resistance in Buildings, issued in 1931. The

committee, which has now been discontinued, was responsible for seven reports dealing with various aspects of building regulation that

have been widely used in preparing and revising building codes.

Its membership at the time of its dissolution was as follows:

William K. Hatt, chairman; professor of civil engineering and director, Laboratory for Testing Materials, Purdue University; member, American Society

of Civil Engineers, American Concrete Institute, and American Society for Testing Materials. Albert Kahn, architect, Detroit, Mich.; fellow, American Institute of Architects. Rudolph P. Miller, consulting engineer, New York, N. Y.; past president,

Building Officials' Conference; member, American Society of Civil Engineers,

American Institute of Consulting Engineers, and American Society for Testing

Materials. John A. Newlin, in charge of section of timber mechanics, Forest Products

Laboratory, Forest Service, U. S. Department of Agriculture, Madison, Wis.; member, American Society for Testing Materials, and American Society, of

Civil Engineers.

William Arthur Payne, vice president, Charles T. Wills, Inc., Building Construction, New York, N. Y.; vice president, New York Building Congress. H. L. Whittemore, chief, engineering mechanics section, National Bureau of Standards; manager, American Society of Mechanical Engineers; member,

American Society for Testing Materials, American Association of Engineers,

and American Welding Society.

Joseph P. Worcester, consulting engineer, Boston, Mass.; member, American

Society of Civil Engineers, and American Institute of Consulting Engineers.
2 Miscellaneous Publications, National Bureau of Standards

Upon the completion of its report on fire-resistance requirements,

the committee undertook a study of exit requirements with the

object of developing provisions suitable for building codes. It was

planned that the two sets of requirements should be used together.

In conducting the study, existing requirements were compared and

tentative provisions were drafted to serve as a basis for discussion.

These were sent out to a large number of architects, engineers,

building officials, and other groups, with a request for expression of opinion. The replies indicated wide divergency of views and the

need for a greater amount of data upon which conclusions could be

based.

Early in its work on exits the committee arranged to cooperate

with the Committee on Safety to Life of the National Fire Protection

Association, which is also the Sectional Committee on Building

Exits of the American Standards Association. The latter committee

had considered the problem over a long period. Its representatives

participated in joint conferences and were generous in sharing the

results of their studies.

Appreciating the need for more information the joint conference

instituted surveys of existing exit facilities in buildings, and of the

rate of flow of people through various types of exits. This work was

conducted by John H. Courtney and Harry B. Houghton, associate

engineers at the National Bureau of Standards, and George N.

Thompson, secretary to the committee. The results are embodied

in this report. To these are added proposed requirements which

were in process of development when the Building Code Committee

was discontinued.

To a greater extent than with some other features of building

regulations, exit requirements must rest on composite judgment. The

scarcity of fundamental data, the uncertainty of how both fire and

human beings will act under varying conditions, and the great variety

of occupancies to be dealt with, all tend to create a problem where

divergency of opinion is possible. Experience, good judgment, and

skillful interpretation of such facts as are available become the guides

for arriving at reasonable and acceptable conclusions.

II. IMPORTANCE OF FIRE LOSSES

1. PROPERTY LOSS

The burning of buildings and their contents results in property loss and, much too frequently, in life loss. The property loss was estimated

at approximately $500,000,000 for the year 1930, but dropped to about $270,000,000 for 1933. This discussion is not concerned with

the property loss, important though it may be, but is concerned with

the life loss because of its relation to the subject of exits.

2. LIFE LOSS

The loss-of-life statistics, unfortunately, are in no sense as complete

as the property-loss figures. Such information as may be gathered

from various sources, however, indicates that the death toll resulting

from fire is an impressive one. The figures obtained by the United
Design and Construction of Building Exits 3

States Bureau of the Census indicate an average annual loss of life from fire and burns of nearly 7,500 persons. 1 Figures from other

sources often quoted are even higher, ranging between ten and fifteen

thousand lives annually, although the evidence to substantiate these

higher figures is lacking. In both cases, the loss of life results from a

great variety of causes, some only remotely connected with fire. Nevertheless, the losses are of sufficient proportions to justify a dili- gent search into the underlying causes of such an apparently needless

waste of human life. The principal difficulty with the statistics commonly quoted in

connection with loss of life by fire is that they are too inclusive. Thus

all manner of deaths which are in any way, regardless of how remotely,

connected with fire are compiled under the general heading of loss of

life by fire, and the public, which has become accustomed to associate

fires with burning buildings, conjures up a picture of a vast number

of burning buildings in which these ten or fifteen thousand lives are

lost annually. It fails from lack of complete information to take into

account the fact that a great many of these deaths result from burns

and scalds received from industrial processes ; forest fires ; explosions

of vapors, gases, dust, and powder; bonfires; cleaning fluids; matches;

and many other sources which have no connection with burning buildings, and, in many cases, which do not result in fires, in the commonly

accepted usage of the term, at all. The impression thus gained has undoubtedly been of assistance in

the promotion of campaigns for safety to life and protection against

fire and in that connection the misinterpretation of the statistics has

not been important. But where they have resulted in drastic and

unnecessarily restrictive requirements in building codes, it would appear desirable that they be broken down and the causes of loss of life by fire determined as accurately as possible in order to correct the

impression that loss of life by fire means burned to death in a burning

building, or that simply providing a number of stairways or fire escapes on buildings will eliminate this loss of life. This is not to minimize the importance of the statistics but rather, for the purpose

of this report, to so adjust the data that a more proper relation between fives lost by fire, fives lost by fire in burning buildings, and the

influence of exits on the number of lives lost in burning buildings can

be established.

Probably the most nearly complete data on loss of life from fire are

those collected by the United States Bureau of the Census. In the

Census reports deaths resulting from fire are segregated into two

classes: " Conflagration which includes deaths from fires in buildings,

forest fires, deaths under similar conditions, and " Burns", which

includes deaths due to ignition of clothing or bodily burns without

anything else necessarily being set on fire. For the 5-year period,

1916 to 1920, inclusive, the Census report shows an estimated average

of 1,465 deaths annually for the conflagration classification. For the

9-year period, 1921 to 1929, inclusive, the deaths for this classifica- tion averaged 1,620 yearly, an increase which corresponds very

closely to the increase in population for these two periods. In more

recent years there has been a slight decline, the figure for 1933 standing at 1,521. It is difficult to estimate with any degree of exactness

" Safety for the Household, Cir. BS C397, table 5, p. 9 (1932).
4 Miscellaneous Publications, National Bureau of Standards

the number of deaths in this classification occurring in burning

buildings, but it is obviously somewhat less than the average figures

cited. That there is a seasonal trend in the figures is indicated by

the following monthly distribution for the year 1933 of deaths by

conflagration, Continental United States (source, U. S. Bureau of the

Census)

:

January 176 February 178 March 152

April 145 May 81 June 112

July 54 August 78 September 56 October 113 November 182 December 194

This is to be expected in view of the greater use of heating appliances

in the winter months, although it might easily be upset by some

major theater disaster having no relation to heating needs.

For the 5-year period, 1912 to 1916, inclusive, the State of Illinois reported 1,511 deaths from fire and burns, 215 of which are listed

under the causes as burned in burning buildings.2

3. CAUSES OF LOSS OF LIFE BY FIRE

The statistics covering the causes of loss of life by fire in buildings are admittedly meagre, due to the fact that no central agency is charged with the duty of compiling such a record. It is largely

through the efforts of certain State officials and such organizations as the National Fire Protection Association that information of this

character is available at all. It seems to be a well-established

opinion that certain occupancies suffer greater loss of life by fire than

others, but there is little data to support such a contention. The

late Ira H. Woolson, consulting engineer, National Board of Fire

Underwriters, and first chairman of the Department of Commerce

Building Code Committee, stated in a paper presented before the

Building Officials' Conference of America, in 1927, that fires occur at the rate of something like one a minute, day and night, in the United

States.3 Fortunately not all of these fires result in loss of life, but it seems almost impossible with such a frequency of occurrence that

any one occupancy class could avoid life loss at one time or another.

Table 1 has been prepared from data published by the National

Fire Protection Association.4 It does not purport to be a complete

record for the entire country for any given period, but is of considerable interest as a representative list of causes. This table lists the causes of 3,207 deaths from 544 fires involving 104 different occupancies. Dwelling fires are not included because the statistical data

relative to loss of life in dwellings are not readily available.

2 Safety for the Household, Cir. BS C397, table 7, p. 11 (1932).

3 Work of the Nat. Board of Fire Underwriters, Proc. 13th Annual Meeting of Bldg. Officials' Conference Am. p. 52 (1927).

4 Quart. Nat. Fire Protect. Assn. (January 1925).
Design and Construction of Building Exits

Table 1.

Causes of loss of life from fires [Excluding dwelling firesl Occupancy

Cause IVIciDUf&C" turing

build,in^ Public assembly

Residence

building

Miscella- neous

1 otal

Inadequate exits - 152 306 32 4 494 Rapid spread of fire . . 75 30 217 12 334 Jumped from burning buildings 57 6 26 7 96 Trapped in burning buildings 20 2 27 27 76 Overcome by smoke 24 48 9 84

Suffocation while asleep 3 67 2 72, 6 6

Panic unexplained.. . - 5 5

Iroquois Theater fire.. 571 571 Subtotal . . - - --. 336 918 423 61 1, 738 Manufacturing processes (explosions) . 5418

7 24 353 925 Burns and ignition of clothing . . . 2 23 31 64

Fire fighting and salvage . 44 25 18 76

98

163 Miscellaneous (forest fires, building collapse,

etc.) . . - 41 139 No data 18 27 59 74 178 Grand total _ 988 979 547 693 3,207 From the reports of the New York City Fire Department, Rudolph

P. Miller, a member of the U.S. Department of Commerce Building

Code Committee, prepared an analysis of deaths resulting from fires in New York City for the years 1920 to 1931, inclusive. The total number of deaths by fire recorded was 1,453, with a yearly average of

121. Injuries totaled 3,384, with a yearly average of 282. The total

number of deaths by fire in buildings was 1,389, divided among occu- pancy classifications as shown in table 2. Table 2.

Deaths by fire in buildings in New York City, 1920 to 1931, inclusive (From reports of New York City Fire Department)

Class of occupancy Number

of deaths Percentage

of deaths

Residence buildings: Dwellings .. 292

85 800

14

4

21.0

6.1 57.6

1.0 0.3

Furnished-room houses Multiple dwellings (3 or more families) Hotels, including lodging houses Clubs

Total 1, 195 86.0

Institutional buildings: Asylum (1 insane asylum) 25

5 1.8 0.3 Total 30 2.1 Public building. . 1 0.1 Business buildings: Factories, including brewery and auto repair shop 80

10

513

11

5.8 0.7

0.4

0.9 0.8

Moving-picture studio (1 case) Stores Warehouses

Sheds, including piers Total. 119 8.6

Garages, etc.: Garages—public and private. 28

7

1

2.0 0.5

0.1

Stables, including barns Car barn

Total 36 2.6 Buildings in course of construction 3

5 0.2 Unoccupied buildings 0.4 Grand total 1, 389 100.0

5
6 Miscellaneous Publications, National Bureau of Standards

The 64 deaths, making up the difference between the deaths result- ing from fires in buildings and the total deaths from fire, are reported

as having occurred in or in connection with ships, launches, barges, scows, motorboats, automobiles on street, airplanes, railroad car, ferry-house, subway, elevated railway, auto service station, watchmen's shanties, storage yard, yard, street, manhole in street, or a bonfire.

Class 1, public, as established in the report, Recommended Minimum Requirements for Fire Resistance in Buildings,5 including city

halls, churches, schools, theaters, and recreational buildings and

structures, is charged with a large total loss of life. The nature of

the occupancy with its dense population and susceptibility to panics

accounts to a considerable extent for the large total. Theaters have probably the most complete record of loss of any

single occupancy due to the fact that loss of life when it does occur

in theaters is of such size as to receive unusual publicity and conse- quently becomes a matter of easy record. The National Fire Protection Association has published a record 6 of lives lost in theater

fires during the period 1797 to 1930 in the United States, Europe, and

Asia. The records are not complete, particularly in regard to fires in Europe and Asia, but they provide an indication of the extent of the

life loss in theater fires. The total deaths for the 133-year period is approximately 12,000, and of this total the United States is charged

with 1,671.

It was reported some years ago that fires were occurring in theaters

at the rate of 2 per day. It should be borne in mind that the life loss in theaters cannot be measured by the number of fires nor by the

intensity or destructive effects of the fire. There are records of

heavy loss of life in theaters in which there has been little if any fire, the deaths being due entirely to the development of panic conditions

followed by a rush for the exits. An idea of the dense occupancy of

theaters and the possibilities for the development of panic conditions

may be gained from the reported seating capacity of the theaters of

the Borough of Manhattan, New York City. For the year 1930

there were reported to be 301 theaters and moving-picture theaters

in this borough alone with a total seating capacity for 356,623

persons.7 An analysis of the causes of 2,426 deaths in 50 theater fires is given

below: 8 Cause Deaths Inadequate exits and panic 1, 127 Rapid spread of fire cut off exits 79 Jumped to death from windows 1 Burned by inflammable film 10 Burned by open flame 1 Fire fighting 11 No definite data 1, 197

Total 2,426

The record of individual theater fires presents a long list of deaths

due to improperly designed and inadequate exits, poor maintenance,

« BS BH14 (1931).

e Theater Fires, Nat. Fire Protect. Assn. (1930).

7 Bureau of Buildings, Borough of Manhattan, City of New York, Annual Report (1930).

s Theater Fires, Nat. Fire Protect. Assn.
Design and Construction of Building Exits 7 defective construction, violations of ordinance, and panic. The

exits have played an important part among the causes of deaths and

emphasize the necessity for careful design and proper maintenance of

these facilities. Next in importance to theaters in this class in the number of lives

lost are the schools. The National Fire Protection Association lists a total of 423 lives lost in but 30 fires,9 a high average loss per fire compared with other occupancies. This average is much higher than

would be expected in buildings of daytime occupancy and supposedly

having the advantage of frequent fire drills. However, an examination of the records of individual fires discloses heavy loss in a few

fires, 4 fires causing the death of 284 people. The general average

for the recorded school fires is, therefore, considerably less than indicated by the 30 fires mentioned before. As in theaters, the exits in

schools have figured very prominently as a cause of loss of life. The

necessity for a free and unobstructed path of exit has been strikingly

illustrated by several fires, as has also the necessity for proper distri- bution of exits. One school is reported to have been emptied many

times in a minute and a half during fire drills, yet 22 lives were lost when the school burned because the fire drills had never been varied

to provide for the contingency of an exit being blocked. 10 The following tabulation, prepared from data published by the

National Fire Protection Association, gives the causes of loss of life in 30 school fires. 11

Cause Deaths Inadequate exits 252

Exit doors open in, barred windows 36

Exits cut off by fire 37

Subtotal 325

Suffocated while asleep 27 Burns and ignition of clothing 3

Fire fighting and salvage 21 Special hazards 2 Miscellaneous, no data 45

Total 423 The impression is gained from a study of older buildings that those

in which people enter of their own free will, such as office buildings,

stores, etc., have been usually of a better type of construction than

those buildings which they are forced to enter without their consent,

such as schools and certain institutional buildings. This impression seems to be confirmed by the records of many school fires. Incomplete records of church fires do not reveal any loss of life in

this country which might be charged to the fact that the buildings were used as places of assembly, in spite of the frequency of these

fires, which has been reported as 5 per day. Very heavy loss of life, however, has been reported in 2 church fires in foreign countries. Of

154 recorded fires in churches only 11 occurred while the buildings were occupied, and in no case was there any difficulty in getting the

occupants out. 12

8 School Fires, Nat. Fire Protect. Assn.

10 Peabody School fire, School Fires, Nat. Fire Protect. Assn.

11 School Fires, Nat. Fire Protect. Assn. " Church fire?, Quart. Nat. Fire Protect. Assn. (Jan. 1928).
8 Miscellaneous Publications, National Bureau of Standards

Class 2, institutional, as established in the report, Recommended

Minimum Requirements for Fire Resistance in Buildings, consists of

hospitals, sanitariums, homes for the aged, prisons, and buildings of

similar occupancy. It has helped materially to swell the total of

loss of life by fire in buildings. Poor construction, bad housekeeping,

inadequate and poorly maintained exit facilities, isolation, frequently

poor fire-fighting equipment, and the character of the occupancy,

including as it does persons kept under restraint, and a lack of enforcement of existing laws in some cases, all share in the responsibility

for loss of life. Class 3, residential, as established by the report, Recommended

Minimum Requirements for Fire Resistance in Buildings, consists of

apartment houses, hotels, tenement houses, lodging houses, dormitories, and dwellings. It would probably show the heaviest loss of

life of any occupancy if available records were complete. But fatal

fires in residence buildings so frequently cause only one or two deaths

that attention is not focused on them as in the more spectacular

theater or school fire involving heavy loss of life. C. Heller, consulting

engineer, stated in a paper published a few years ago: 13 "By far the

greatest part of the annual life loss occurs in the many small fires in

which one or two die and which attract only passing comment."

This is shown in table 3, reporting 426 fires recorded by Heller.

Table 3.

Deaths per fire

Class of occupancy Number

of fires Liveslost

Number of deaths—

1 2 3 4 5 to 9 10 or more

Dwellings... Nondwellings..

Total.

195 231 398

2,141

122

73

2534152612

13

2152 33 426 2, 539 195 59 41 25 73 33 Mr. Heller comments also: At first glance these figures give the impression that the life losses occurring in dwellings are smaller in number than those in other buildings. This is true only

insofar as the loss per individual fire is concerned, but not the aggregate loss; for the fatal dwelling fires over a fixed time outnumber those of all other occu- pancies combined. In the United States dwelling-house fires, together with fiats and apartments, constitute 65 percent of the total number of fires. The fires from which the table was compiled are those of which the writer has a record and which extend over a period of many years and include such catastrophes as those occurring in the Iroquois Theater, the Collingwood School, and the Asch

Building, which greatly add to the total losses in buildings other than dwellings.

It must be remembered also that prominence is generally given only to the more

noteworthy fires, particularly those in which there is heavy life or property loss, so that thousands of lesser ones escape unnoticed or are not reported in the fire records. Were complete statistics available they would show that the majority

of lives are lost not, as is commonly supposed, in industrial buildings, theaters,

and places of public assembly, but in the home; that the next greatest losses occur in institutional buildings (hospitals, orphanages, reformatories, and similar occupancies) ; and that the victims in both groups are mostly women and children. In the home, they generally lose their lives as the result of carelessness or ignor- ance. In institutional buildings, most of the disasters are due to poor construction and the gross negligence of those in charge, a sad commentary on our system

of social organization.

» Some fundamentals of safeguarding life from fire, Quart. Nat. Fire Protect. Assn. (Oct. 1922).
Design and Construction of Building Exits 9

Table 4 lists the causes of deaths in 96 year-round and 14 seasonal

hotel fires, as compiled by the National Fire Protection Association. 14 Table 4.

Causes of loss of life in hotel fires (NFPA Chart, Jan. 1930)

Cause

Inadequate exits Attempt to descend, using stairway Kapid spread of fire cut off exits

Jumped to death Burned to death—no data Burned to death while asleep Suffocated while asleep Subtotal Burns and ignition of clothing

Fire fighting, salvage Miscellaneous Grand total..

Number of deaths

Year- round

hotels

243

10

1451 318

Seasonal

hotels

57

Total

375 The exits apparently do not share in the responsibility for loss of

fire in the residential classification, when dwellings are included, to the same extent as in the public and institutional occupancies.

While fatal fires in hotels and apartment houses occasionally occur,

it is mainly from the dwellings that the death fist is built up and here

carelessness and ignorance, coupled with poor construction, are the

principal factors. There seems to be small possibility of improvement in the mortality statistics for the home until as a result of

education and improvements in equipment some of these factors are brought more under control. Certainly no improvement in exit

facilities can affect the number of deaths caused .by explosions of various sorts and burns from the many causes reported in dwelling

statistics. In the case of the multiple dwelling, exits are more of a

factor and the necessity for and benefits from their regulation are more easily appreciated.

Class 4, business, as established in the report, Recommended

Minimum Requirements for Fire Resistance in Buildings, includes

factories, warehouses, stores, office buildings, and buildings of like character devoted to business. The loss-of-life record for this classi- fication is even less complete than for the other occupancies, except

for dwellings. While there has been some loss of life in office-building fires it has been relatively small, although the records disclose

several fires resulting in heavy property damage. The slight loss of

life is possibly explained by the fact that the majority of office-building fires apparently start at night when the buildings are unoccupied,

and also, because of the alert population of these buildings, daytime

fires are usually discovered at an early stage and sufficient warning

is given to enable the occupants to escape. Panic conditions have

not often developed during office-building fires. The National Fire

Protection Association has compiled a record of 119 fires in office buildings, 46 of which caused property losses of over $5,000. 15 The

14 Hotel fires, Quart. Nat. Fire Protect. Assn. (Jan. 1930). » Quart. Nat. Fire Protect. Assn. (Oct. 1923).
10 Miscellaneous Publications, National Bureau oj Standards

record of these fires discloses that less than half originated in office rooms. Factory fires reveal rather heavy loss of life in the incomplete

records available. This probably results from the density of population and poor maintenance of exits combined with inferior construction and, in some cases, the fire hazard of the contents. Locked

or obstructed exits are mentioned frequently in the reports as causes

of loss of life, and apparently altogether too much dependence has

been placed on fire escapes in the past. The loss of life in factory

fires demonstrates most clearly that, regardless of how perfect building-code regulations may be, unless such regulations are properly

enforced, particularly the maintenance provisions, they are almost

valueless. A locked exit door may render useless all of the carefully

considered provisions of the building code tending toward safe and

sure egress in a time of emergency.

Records of department-store fires are too incomplete for the compilation of statistics and the fires involving heavy loss of life have

been too few to make this occupancy stand out prominently in the

records. A casual survey of department stores would at once raise

the question why more fatal fires have not occurred. Certainly the

piles of highly flammable materials, open stairways, and crowded

condition of many of our older department stores offer excellent

opportunities for fires, panics, and consequent loss of life. The rela- tively slight loss of life is probably explained by the fact that as in

office buildings the occupants are alert and fire is discovered before

it has gained any great headway; also, because more attention is usually given to fire protection of the property than in some other

occupancies, thereby adding to the protection of the occupants.

Class 5, garages, hangars, barns, as established in the report, Recommended Minimum Requirements for Fire Resistance in Buildings,

consists of garages, hangars, stables, barns, and other buildings of

similar occupancy. The class was at one time considered especially

hazardous because of the nature of the contents, particularly the

garages, but as a result of generally thorough regulation is not now

so regarded. In support of this conclusion evidence submitted by

Rudolph P. Miller to the Commission for the Revision of the Tenement House Act of New York, July 6, 1927, is presented consisting

of figures from the annual reports of the fire department for 8 years

(1918 to 1925, inclusive). The figures for the entire city are given

in table 5. Table 5.

Relation of garage and tenement fires to total in New York City

Year Total In public

garages In privategarages In tene- ments

In tene- ments, orig- inating in

stores

1925.. 14, 483

14, 318

13, 475

13, 281

11, 700

10, 807

10, 158

10, 552

368 364

331 307

311

269 205

157

140

139 122

118

1099380

80

7, 054

6, 650

6, 458

6, 073 5,248

4,883

5, 052

5, 319

953

924

991 1,059 664

583

599

639

1924

1923 1922

1921 1920

1919

1918 Total 98, 774

12, 347

100

2, 312

289

2.4

881 110

0.9

46, 737

5, 842

47.5

6, 412

802

6.5 Average ... Percentage of total
Design and Construction of Building Exits 11

The tables in the reports from which the above figures are taken

classify buildings in which fires have occurred into 31 groups.

# Those

in which the number of fires for 8 years (1918 to 1925, inclusive) has

averaged more than 200, in the order of greatest frequency, are as

follows:

Type of building Fires Tenements 5, 842

Dwellings 2, 211 Tenant factories 1, 152

Factories 564

Store buildings 466

Furnished rooms 321

Public garages 289

Office buildings 203 The only yearly variations from this order are occasional transpositions

of factories and store buildings in fourth and fifth places, and of

furnished rooms and garages in sixth and seventh places.

It is conceded that the number of fires is not the only element entering into the consideration of the fire hazard. The frequency in rela- tion to total number of structures of a given occupancy class is important. The information necessary for a definite conclusion on this

point is not available. However, in 1 925 , fires occurred in 1 1 .4 percent

of public garages and 0.6 percent of private garages; for all garages

the percentage was 2.5. In the same year the percentage for tene- ment houses was 6.5, or more than twice as great as for garages. Fortunately, the density of population of garages is low, and property damage rather than loss of life usually results from fires in such

buildings. The National Fire Protection Association 16 reports 13

fires in garages involving a loss of 32 lives for the period 1921 to 1928.

The exits do not figure prominently among the causes of loss of life, these being principally burns and explosions. It seems unlikely that

the capacity of the exits in this class of occupancy would ever be

severely taxed; the distance to the exits and the proper distribution,

however, are of primary importance in these buildings. With the

increasing use of public garages the necessity for wise regulation of

exit facilities becomes more apparent.

III. BUILDING EXITS SURVEY

1. PROCEDURE

At an early meeting of a joint conference consisting of representatives from the Department of Commerce Building Code Committee

and from the Building Exits Code Committee of the American Standards Association, it was agreed that a study could profitably be

made of exit design practice and performance, especially as it concerned buildings erected within the last 10 years. The staff of the

Department of Commerce committee was therefore asked to conduct

such a survey to the extent that time and funds permitted.

The primary object of this survey was to build up a reservoir of

facts about actual exit conditions that could be tapped at the time

when minimum requirements for building exits were being considered.

The value of such data is readily appreciated.

i» Oarage fires, reprinted from Quart. Nat. Fire Protect. Assn. (April-July 1929). 1158—35 3
12 Miscellaneous Publications, National Bureau of Standards

Nearly all construction design today makes use of mathematical

formulas applicable to the problem involved. Numerous series of

controlled tests can often be made, and, from the data obtained,

formulas can be evolved which will apply generally. Criteria for the

design of means of egress from buildings present a different problem.

It is impractical to conduct tests of exit discharge that would simulate

actual conditions during a fire. However, experience has dictated

certain necessary requirements, and current practice in exit design can be reviewed as to performance, desirability, and economic effect. The number, location, size, and type of exits seemed to be major

items to investigate. The population or area served by the exits

and the maximum distance traveled to reach an exit were also important. Additional features, such as building height, number of fire towers, fire escapes, spiral chutes, and horizontal exits, permanent

obstructions in the stairway enclosures, conditions of final discharge

of stairways, size and type of doors in stairway enclosures, continuity

of stairways, dimensions of treads and risers, and other construction

elements related to exits, had to be noted to complete the picture.

2. SOURCES OF INFORMATION

The desired data were collected in two ways: (1) by an office study; and (2) by an inspection of buildings in several cities. As a first approach in the office study, floor plans from architectural and technical magazines were inspected for exit facilities. Plans

obtained from architectural and engineering offices likewise furnished

excellent material exemplifying current design practice. Suggestions

solicited from architects, engineers, school superintendents, officials of hotel chains, theater executives, and others having specialized

knowledge of exit requirements made a valuable contribution as the

collection of material progressed. The restrictions on design of exits

imposed by some of the laws in effect received their share of attention

in the form of a digest of exit regulations in building codes, labor

laws, and tenement-house acts. These were listed and the fundamental requirements of each compared.

Additional information was obtained by means of a questionnaire

sent out to some of the leading architectural offices in all parts of the

country and containing, among others, this question: Are the present

code requirements for means of egress too severe or too lax?

The answers to this question indicated that this group believed

almost unanimously that many of the present building regulations

as regards exits were too severe. Some of the general arguments

cited to substantiate this opinion were as follows: That many ordi- nances have been rushed through after some catastrophe and are ill- advised and extreme; that heretofore these requirements have been

worked out in an unscientific manner ; that improvements in building

construction such as increased fire resistance and the inciosure of stairways now obviate many of the requirements formerly necessary,

and that more reasonable consideration should be given to the location of buildings and to their occupancy.

But one observer thought that the code requirements were too lax,

referring to exits in summer hotels. These buildings usually fall outside the jurisdiction of municipal building regulation.

This information reflected an important point of view and helped

to make the exit problem clearer.
Design and Construction of Building Exits 13

3. FIELD INVESTIGATIONS

The experience gained in the office study indicated that certain

questions which had arisen could be answered only by observation

of conditions in actual buildings. Accordingly, exit measurements

were taken and general exit conditions tabulated for buildings in

Atlanta, Ga., Greenville, S. C, Greensboro, N. C, Roanoke, Va.,

Washington, D. C„ Frederick and Baltimore, Md., and Pittsburgh,

Pa. These cities were chosen with a view to covering places varying

in size and sufficiently distributed to give a fair general cross section

of building construction.

The smallest city had no building code. The codes of the others

ranged from rather sketchy requirements to those as elaborate as in

any city . Building officials in the cities visited rendered valuable assistance

by furnishing plans of buildings erected since 1920. After a study of the plans, detailed measurements were taken at the buildings selected

for inspection. Special attention was given to buildings where people

slept or were housed for medical or other care. Building managers

supplemented the field notes in some instances by generously donating

floor plans. During the building inspection, notes were also kept on

the marking of the exits and on their maintenance. Wherever possible, figures on the population served by the exits were secured.

Questions were also asked concerning any difficulties experienced

with the exits under normal or emergency conditions. Interviews

with building officials, State labor officials, architects, and school

superintendents further enriched the field notes.

4. TABULATION OF DATA COLLECTED

Much of the information secured is too detailed to warrant publication here. However, conclusions reached are based on a study of these plans and the mass of other data that was collected. Summaries

and tables of the more outstanding findings are included for those

particularly interested in exit design. Tables 6 to 14, beginning on

page 14, list some of the points recorded in the field survey. Table 15

gives some general averages obtained from both the field and the

office surveys.

5. POPULATION STUDIES

The figures under the heading " Population on typical floors"

given in the tables were obtained in a number of ways. In apartment

buildings the resident manager usually had accurate knowledge of the

number of people occupying any floor; in hotels an estimate of the

population on a typical floor was made by counting the number of beds and then assuming all rooms to be occupied; in office buildings,

factories, and schools actual counts were taken where possible; in

theaters the number of seats was noted; and in other occupancies

accurate estimates from those in charge of the building were accepted.
Miscellaneous Publications, National Bureau of Standards

Elevators jjj

;

c

i§

1 1 1 II II III !!!!! 1 1 III

Horizontal exits

Width 9

!o !

1

O O O OO O O OO-H OOOOO O O OHO

Fire

escapes

Width

i i ! j i 1 Mi

i i i 33 iI 6

fc O O O OO O O OOW OOOOO O O iH rH O

Num- ber

of

fire towers O O O OO O O OOO OOOOO rH O OOO

Stairways

.s

6

fc iidistance to

an

exit S 8 S K© £ 8 §§S £8882 § S SK8

Gross

area

person sq

ft S3 §835

j

I g§ j

Popula- tion

on

typical floor

j 3 35S||5

i i

>—„—«—, i

§ g j j

i i

Gross

area

by

floors

1 II

siiiiiisiiiiiiiiiiii iiin liili iini

Floor

no. Jj

11

32ho

to

31 7

toy 5to6 Hi

isS14

to

23ll

to3

[31

to

33 jj

3

to

17 U

to2

Height 1

§ 8 S3 38- 2 55 222 3S2 0500 -* N «««

Building

no.

! j J J J «! *1J« ui 228
Design and Construction of Building Exits 15

o o

c o

o c

go

11

*3S«« of

.2 & "2 8 o I S C 5 " o £ • o <b ^ c a- .s

3 c o-3
16 Miscellaneous Publications, National Bureau of Standards

g «

OJ CD <M 00 <N CNO O O

£0°

3 03 ."S Sox

CO CO O CO CO O O CO CO O CD CD (X CD CP yXyX CD CD £ >H >H ^ >H >H 2^ >H £

o o o o oo o o o

O O O O O OCN o o o

o o o o o oo o o o

NCOOOO^OOOOO 00 00 CO CM CN CD ^CO--D**iiOCD"*-<tf' iO "tfHO CO

lHrt(N(NH r-l(M(M

t- o o o o o < O CO o o O O c lO CO O lO IO TjH < 8 SCO

i-H N (D N CC CT> rji CO O !M I-H rH N (N H

00 N tC CO CO CO CM

H N M CD t-- 00 Oi

CN CN O »—

I

CO o O O £ fc

S S 8 Oi O Oi

a 41 So

§1 oo

5cS

4^53 p

§1o CO CD CN

C3 £?
Design and Construction of Building Exits 17 ooooo o o oo

B ° © ©

S3

fl o x

.B (3 ®

c3 D<o o a

be o W

o»ooo o o oo £££££ 55 8

OOOOO O O ON

»-l O Ot-H © H HO ooooo o o oo

l-Hi-IC<lCOrH,-li-<,-li-l,-lCO

O "O i >o O lO O «3 CO O tr- i O »0 OS O CO < -

OOOOO O O OO

,«!0lOH!0 ©O©0>0 OO CO "<*< co

-<i< co co co co co coco

i eo co -<*i m «o t- oo <
18 Miscellaneous Publications, National Bureau of Standards

<M o o o oo o oo oooo o o oo oooo ooooo ooooo ooo

Z Z Z Z Iz;Iz; ^ ^

££££ Z ZZZ

OOOO OO O Or-l i-HOOO(Ni-l o oo

o oo o oo oooo o o oo

IS*

oooo oo o oo oooo o o oo

iMtO©*iO CO CO CO »Q -J* CO lO CO *0 CO »Q I

NrHINMHili <N <N rH CO <N Tt<<N^<N <M rt< <N <N . as oo >o o »o CM 00 <M 00 »o ooioo »o o oo "O lO lO ^ t- O CO o »oot>-t- «o O »o

ON O CO O CO O Ir- N15 M N ooo

80S0S888 oooo oc 8 00 oooo 8

t TtHlO CS rfi CO CO OOOO Tti 00 CO !>• t~- o»oco<M o

rod co om go" o of 8 88 O 10 "O 'COOOCM-^COlOINlO HHIMlOlO rH CM rH

CO CM r-( I I

<M _ rt 00 CO <N • 00 •* CO CO COCO CO COCO COCOCOCO CO

CM CO iO

: O rH CM CO lO
Design and Construction oj Building Exits

1!

NWWHN <M <M <M i-H rH <M C<1 (M C<) CO H C^l O rH O

ooooo oooo o ooooo ooooo

: i : : : i i : : I : : j

: : : ; :

:

!

'

' ' •

!

' ' ' < ! ! _L_L

%%%%%%% %%%%%% %%%%%%

rH<N <N IN C<J rH HH rH <N <N <M IN Tf< CO N^HNHi

11

BiSSI SIS i 1 8ESS3 sSIl 1

J8381 III! 1 11111 £888 3

J J j J j J JJ j $j d^dd d^d d

1158—35 1
20 Miscellaneous Publications, National Bureau of o o o o o o oo

oo oo oooo ££££ ££££

o ±J .2 S O O O O O O OH oooo oooo

o o o o o o oo oooo oooo

6 ° o & o o o o o o oo o ooo oooo

NHHHHN T-H H H M CO iH rH i-H iH CO iH i-H rH >-l .-I I-H I-H 1

ill

£ ft O a

o o to >o N O) 00

o a

O CN O rfiO

<N CO iH ,-h <N

t>. <N O

lO O CO to o

tO O O to co o to CO N W 00 O

tO t^- N IM lOlQ <N ^ <N tH

CO CO CO CO CO CO CO CM CM CM CM <N

CM CM CM CM

to to t-» 00 Ci O i—I 03 CM CM CM CN CM COCOCO
Design and Construction of Building Exits 21

ceo o o o

o o o

o o o o o o

© o o o o o

o o o o o o

CM CO CO CM (M CN CM

Tt< Tt< Tj< TJH TJH

iO r-icq O O O

<N 00 CO 00 C CO

o o o lO MO N Wrt

CO CON CM CM CN

§33

>>>> £ £ « m awn ^ c« p p'S

<D . <£> <D *J o— O O <D o <b 9 p o

O >>0 O.S

co^cco^

O S CO <s B .2co^£.~

4i co to £2 J§ cmHM5^

© <§ o3 ® cs

>-, c3 go c3 co

> co_g w.2

2 E-i * O

§ s

I 3

* O CO CO

oo co ooo o

o o o o oo o

9„S

OO — O OOO —i

OO ^ O OOO -i

(NINH-irtN ~q ^ _h ,

CO IC O —I 05

£j ^ 2

O O o o

+3 10 o o ss

1C N 00

j-j -2 *-< oo O

-2 £ n
22 Miscellaneous Publications, National Bureau of Standards

V

H2 % P o o

6,

1:3 2 C! ^ m R ©

2 © n

<N <M CO

o ooooooooo

O O O O O <M O OC0

00«-lO<MOO<Ni

O O O O O O O OO

Tt< co us Tti io Tti tj( 9o eo eo

US rH .-H TjH OS OO tO H rfi OO

IO «5 15 ^

N M * U5 (S N 00 0)0

O

3 £

ce o ° 5^5 *

{ 3 o

hP3W
Design and Construction of Building Exits 23

Elevators

>

To

floor

No. CN O

Sprinklered

o o z £

Number

of

horizontal exits © o

Fire

escapes

Width B

No. © o

Number of

fire

towers © o

Stairways

Width

Tj< GO

No.

Maximum

distance

to

an

exit £ 8

Gross

area

per

person

sq

ft

203 143

Population

on

typical

floor

CO

CO -*<

Gross

area t

Floor

area

sq

ft 6,

700 6,300

Floor

no. |

i

Height in

stories 00

Building no.

CN

o o

CO rH CN TjT

CDa

"3

jterr -oa

£> o

No o o £ fc

o o o

o DCTION o o

©

CONSTR o o

00 o •* CO

CN Oi CO CN

CO "0 TJH

[STI 1

E-RESJ CN i—1 CN

lO

FIR O O

OF

COJ

al: CO W

[TY O

CNCO

1 ,000 ,

580 CC OS I

CO I o

1-1

! O i

CN

i-l CN

J S3

2 a 'O 3-3 CN -S2 o

a 5 bS 0+= el o «^ p g ,0 fcfl *h «-> £ 2 >>S 3--2

.2 a"S -a +3 ",2 el w 2 a o

<i!HOP?
Miscellaneous Publications, National Bureau of Standards

CD o

0°o

.2 S 03

CO CO CO t— „• h'h 00 8|

'cs'os no

3 a

CM OOOO O

O OOOO o Z to £ fc 5? 5? OOOO o

O O O O CN o 000 o

000

a

*S >»

."S o <1W

a _a

.3 . Ofjofl >>o a go a

,H O.H O ffiS O H.H O

3 ca 3 c3 _o3 S o3 3 03 8

a

•a >»

00 o 00 co 00 CM COO

a3 >» 5 a 3 03 <1pq

<M CO

o o

w

•5? 3 a . o o

8*3 o

cia-s

Q.X3 03 CO 2> if a is 73
Design and Construction of Building Exits 25

Table 15.

-Average of exit measurements

Occupancy Type of construction

Percentage of build- ings having

Average

floor area served by

stairway

Average width of stairway

Average maximum

distance

1 stair- to exit way2 or more

stairways

Office buildings. jrire resistive...

Percent

f 55

10

1 7

Percent

4590

93

10085

6894

7056

sq ft

8, 000

2,700

6, 500

2, 540

4, 200

2, 550

8, 700

8, 900

10, 500

in. 45

4342

4842

40

55

5950

ft 86

7788

53

6338

63

10686

Hospitals.. Hotels.. Dormitories Nonfire resistive Apartments I 1532

f 6

{ 30

{ 44

Apartments

Schools

Stores jFire resistive

Lack of time prevented counts of the population on the floors in

department stores. Only one manager interviewed had ever made

any study of the number of people on any given floor during a rush

period. Many had figures on the total number visiting the store during a business day, but these figures could not be broken down in

order to estimate the population on any given floor. Numerous

checks on the population in office buildings and department stores were available through investigations made by the Committee on

Safety to Life of the National Fire Protection Association. Studies

made by engineers in connection with live-load considerations also

furnished some data on population density.

The check on apartment population was made in the better resi- dential sections. If counts had been made in the tenement districts,

it is believed that the gross area per person would have been materially

lower than that shown in the tables. A number of factories visited had notices required by the State

departments of labor which specified the maximum population permitted on any floor. The actual basis for these allowances could not

be obtained from those interviewed.

6. LOCATION AND NUMBER OF EXITS

With but few exceptions, field measurements revealed that the

maximum distance traveled to reach an exit was less than that permitted in the local building code. These measurements were taken

along the line of travel. In office buildings, for instance, the distance

from the door of the office to the stairway was recorded, rather than

the distance to any remote point within the office itself. As most stairways were found to be placed in dead corners or other

areas least rentable, design considerations played an important part

in fixing the distance to exits. It is also possible that the maximum

distance to exits specified in the code sometimes fixed the design of

buildings.

When compared with the other occupancies, department stores completely equipped with sprinkler systems showed the greatest dis- tance of travel to exits. Comparisons between buildings of fire- resistive construction and other types did not indicate that construction type had been definitely related to maximum distance to exits.
26 Miscellaneous Publications, National Bureau of Standards

JP The majority of the buildings studied were provided with two

stairways. A notable exception to this occurred in office buildings

where one stairway might be said to be the rule rather than the

exception. Table 6, pages 14-15, shows that office buildings of

uniform horizontal cross section and tower sections of set-back

construction frequently were provided with a single stairway.

7. STAIRWAY WIDTHS

All the tables indicate a great variation in stairway width, even for

nearly identical conditions. Repeated questioning failed to establish specific reasons for making stairways 40, 41, 42 or 43 inches, or any dimension approximately 4 inches either way from 44 inches, in

preference to a 44-inch width. Although codes specified certain minimum dimensions for stairway width, variations up to several inches

either side of the minimum were common. Construction details

might account for some of this discrepancy.

Stairways 36 inches wide were found rather frequently while the

great majority were between 40 and 50 inches. Just what increment

of width added to, say a 36-inch stairway, increases the capacity of

the stairway was a question which very few of the architects had

given any detailed study. As might be expected, stairways in schools

and department stores were appreciably wider than those in offices,

apartments, or hotels. A number of those interviewed were of the

opinion that for the same aggregate width it was more beneficial to increase the number of stairways than to increase the width of a few—that is, three 44-inch stairways resulted in better traffic conditions than two 66-inch stairways.

8. PROPORTION OF TREADS AND RISERS

Dimensions of treads and risers measured indicated that the 2 or

3 rules customarily used for proportioning risers and treads are adhered to very closely. Risers of 7 or 7% inches and treads of 10

and 10K inches far outnumbered any other dimensions. These proportions will be seen to check the rules that the sum of riser height

and tread width, in inches, shall not be less than 17%, nor more than

18; that the sum of 2 risers and 1 tread, in inches, shall be not less than 24, nor more than 25; or that the product of the riser and tread,

in inches, shall fall between 70 and 75. The risers in school buildings occupied by small children averaged

around 6 or 6K inches. Opinions of architects and school superintendents on the advisability of this practice fell into 2 groups. One

group claimed that the fatigue was much less where the lower riser was used; the other group maintained that children were not accus- tomed to the lower riser in their homes and other buildings, and,

therefore, that it was more logical and less dangerous to use a 7- or 7^-inch riser in this occupancy.

Because of the different uses of stairways, including those in industrial, private, public, and semipublic occupancies, and because of their position in the plan, the variations of color and materials used,

and the differences in railings and type of nosings, a suggestion was

advanced calling attention to the madvis ability of attempting to design

all stairways under any one rule for proportioning treads and risers.
Design and Construction of Building Exits 27

It was pointed out that certain classes of people would consider a stairway very tiresome while others would take no notice of fatigue.

On the basis of a limited study, it was therefore suggested that the

treads and risers should be proportioned for the different uses to which the stairways were subjected. Further study of this question

may reveal more rational methods of accomplishing this end than

are now in common use.

9. STAIRWAY ENCLOSURES

Enclosed stairways could be said to be current practice, judging

from the large majority found in the buildings visited. An openexit stairway in office buildings, hotels, and apartments was extremely

rare, those not exceeding 2 or 3 stories in height excepted. In school

buildings about equal percentages of open and enclosed stairways

raised a question as to most favorable design. Many superintendents and teachers preferred the open stairway because of its efficiency

in handling the changes of classes. Although the larger department

stores visited had enclosed stairways, many of them were used only

as emergency exits. Stores of 2 or 3 stories and having a small area had enclosed stairways in but few instances. Despite the questions

raised concerning the efficiency of enclosed stairs for certain occupancies and their increased cost for small buildings, an analysis of

those buildings erected only within the past 5 years bore witness to the obsolescence of the unenclosed stairway.

If the definition of an enclosed stairway means that it must be

enclosed from the topmost story to the final discharge to the street, many of the stairways examined would be puzzling to classify.

Stairway enclosures found in hotels and office buildings frequently

terminated at the second floor or a mezzanine from which ornamental

open stairways continued to the street-floor level.

10. EXIT OUTLETS

Where stairway enclosures terminated within the building at the

ground floor, the discharge was either into large corridors, in some

cases having small shops on either side, or directly into a lobby. It was unusual to find a stairway discharging into a corridor so constructed

as to constitute a protected passageway leading to a street, except in

public-occupancy buildings such as theaters and auditoriums. Stairways discharging directly to the outside at ground-floor levels are

greatly in the minority when compared with those discharging into

ground-floor areas, corridors, or lobbies. Value of street frontage

apparently controlled this factor, as the stairways of most factories

discharged directly to the outside at the ground floor. Where stair- ways continued enclosed to the basements in apartments, hotels,

and office buildings, many of them discharged directly to the outside.

Some builders claimed that if many building codes were enforced to the letter buildings would be too severely penalized when erected under

requirements calling for direct discharge to streets or to protected

passageways leading to the street.

1158—35 5
28 Miscellaneous Publications, National Bureau of Standards

11. SPECIAL FORMS OF EXITS

The number of iron fire escapes still in use occasioned some surprise

in this investigation. A further review of buildings having this type

of exit disclosed, however, that many of them had been added as a supplement to the existing means of egress to take care of occupancy

changes. Old wings of buildings now enlarged accounted for a number of others. However, some recently erected buildings still made

use of fire escapes as one of two means of exit. Testimony of building

officials was against the use of fire escapes on new buildings. A few

officials thought that firemen could use outside escapes advantageously

when fighting fires. The tables of the field survey reveal the limited use of fire towers,

spiral slide chutes, and horizontal exits. If tall buildings in New York

and Philadelphia had been included, the total number of fire towers

found would undoubtedly be much increased. Opinions solicited on

the use of fire towers as one means of exit as compared with the use of

enclosed stairways for all means of exit in any given building favored

the enclosed stairway. Opponents of the fire tower pointed to the

increased space necessarily deducted from the rentable area where

these towers are required; defendants of the fire tower claimed additional safety over the enclosed stairway. Further study of the rela- tive value of these two types of exits may be necessary before this question can be conclusively settled. Table 6, pages 14-15, lists a spiral chute in one office building of 11

stories and in another of 19 stories. These chutes were unlighted

within the slide. No check could be made of their performance and

neither had been used under emergency conditions at the date of the

survey. Opinions differed on the advisability of permitting chutes as one of the two required exits. One school of thought would allow them

as an additional safeguard after sufficient stairways or horizontal

exits had been provided.

The number of horizontal exits listed was small. Approximately 8

percent of the buildings checked were thus equipped. Of the 8 percent,

the majority could be accounted for in those cases involving exits

between new wings or additions connected to older construction.

Few were found in new buildings, and those that were might be said

to be for convenience such as bridges connecting office or factory buildings, rather than as a distinct means of egress. Confusion often existed as to the amount of credit that should be

given to a horizontal exit when installed on only 1 floor of a multistoried building—for instance, when a bridge connects 2 buildings on

the fourth story. It has been argued that a horizontal exit on the

fourth floor was of no value to the occupants of the ninth floor should

a serious fire occur on the sixth. In line with this reasoning, a number

of those who had studied the question believed that horizontal exits,

if to receive credit as a means of egress, should be provided on all floors.

12. EXIT DESIGNATION

During the survey special attention to exit marking resulted in a number of interesting disclosures. There was a woeful lack of plainly

indicated street-floor levels within enclosed stairways running to the

basement. Many stairway doors had exit signs placed flat on the

wall—a position rendering the sign invisible at a short distance down a
Design and Construction oj Building Exits 29

hallway. Practically no signs existed telling whether any given stair- way ran to the roof. Numerous office buildings and hotels with

enclosed stairways ending on the second floor possessed no type of directional sign pointing out the line of travel from that point to the

ground floor, and, thence to eventual discharge outside of the building.

Theater exits stood alone as the only example of efficient exit designation. Churches displayed an almost complete omission of any exit

signs. Many of them now have apparatus for lantern slides or motion

pictures, involving need for exit designation within the darkened room.

13. EXIT MAINTENANCE

Exit maintenance, or rather lack of proper exit maintenance, proved

to be a serious handicap to many buildings well provided with exits. In one large department store visited the ground-floor door of an enclosed stairway was found padlocked. Doors opening to the roof were frequently found locked. Building managers claimed it was

essentia] to keep certain doors locked to prevent robberies. The total number of locked exit doors found would give anyone cause for alarm.

A very common practice in many buildings, and apartments

topped the list, was to prop open the fire doors of enclosed stairways

in an attempt to increase the ventilation. For the sake of easier

communication during congested periods, fire doors in schools and

stores were also found propped open. In one or two instances fire doors originally installed had been removed to make communication

easier between floors. Packing boxes, receptacles, advertising, and articles of all kinds were found in stairway enclosures, on landings, in hallways and

corridors, and in front of exit doors, or horizontal exits. Exposed

radiators, piping, incinerator chutes, chimneys, columns, and beams

frequently cut down the normal width of stairway enclosures. While

building officials recognized the hazard of blocking exits, or interfering

with the intended purpose of fire doors, they were unanimous in declaring that successful enforcement of provisions dealing with exit maintenance was one of their most difficult problems.

Building officials also made frequent observations on the exit problem involved in the remodeling of old buildings. One pointed out that

in his own city many old private residences had been converted into

rooming houses, often without his knowledge and resulting in totally

inadequate exit facilities for the new use. Increase in the population

of a building over that contemplated in the original design of the

exits caused many inspectors unpleasant moments. From the number of plans examined where additional exits were ordered to comply

with the code, some latitude evidently exists on the part of those

designing exits. One inspector was said to have lost his job because

he insisted on the number of exits specified by the code. On the other

hand both architects and engineers claimed that the exit provisions

of some codes were almost impossible to interpret without frequent

explanation from the building official, that they hamper design, and

that they were all too often unreasonable and economically unsound.

This summary has touched but briefly on the exit conditions found.

However, taken in connection with other conditions peculiar to individual buildings, it furnishes a background of current practice that is useful in developing rational provisions for exits.
30 Miscellaneous Publications, National Bureau of Standards

IV. SURVEY OF TRAFFIC MOVEMENT IN EXITS

1. PROCEDURE

The rate at which people normally ascend or descend stairways, or pass through hallways and doorways, is of primary interest to those

responsible for exit design. Knowledge of this rate enables the designer to adjust his exit widths more rationally to the building population, and as they should relate to each other if efficiency and economy

are to be secured.

The joint conference already mentioned believed that as a complement to the survey of current design practice found in buildings erected

within the past 10 years, a survey of traffic movement in exits would

help in pointing the way to more logical conclusions for exit requirements.

The staff of the Department of Commerce Committee, after completing the inspection of exits in existing buildings, then proceeded

to secure data on the movement of people through exits. The

second survey was carried out in much the same manner as the first

by office and field studies—for it was found that preliminary office investigation not only contributed largely to the total information but

also revealed those points on which a field investigation might well

be concentrated.

The inquiry was to include: (1) The relation of discharge rate to

exit width; (2) the difference between rate of flow up and down stair- ways and the relation of rates of flow on stairways to rates on ramps, on the level, and through doors; and (3) the number of square feet occupied per person in exits when discharging crowds of people.

It was hoped that sufficient evidence could be secured to answer controversial questions, to check existing data on the subject, and to determine what basic facts, if any, had not been developed.

2. SOURCES OF INFORMATION

Many observations have undoubtedly been made on the rate at which crowds of people normally move through different types of

exits. The complete data readily available on observed conditions of this movement are, however, rather meager.

A number of traffic observations have been made in the past by

engineers of railroad companies as an aid in the design of terminal

stations. The Illinois Central Railroad courteously supplied the

detailed traffic studies made in connection with the Chicago Terminal

Improvement, summaries of which appear in volumes 25 and 26 of the Proceedings of the American Railway Engineering Association. 17 The firm of Jacobs and Davies, Inc., furnished a reprint of a paper by

J. Vipond Davies and J. Hollis Wells, presented before the American

Institute of Architects at Washington, D. C, December 16, 1909.

This paper contained summaries on traffic counts made at congested

points in New York City as a preliminary step in the Hudson Terminal

design.

The conference also had the benefit of studies conducted by the

Committee on Safety to Life of the National Fire Protection Association. The findings of this committee are discussed in the Proceedings

" Vol. 25, pages 512 to 524 (1924); vol. 26, pages 728 to 734 (1925).
Design and Construction of Building Exits 31

of the National Fire Protection Association, particularly those for the

years 1917 and 1918, and in the Quarterly of this association.

Other studies on the capacity of revolving doors, efficiency of exits in

schools, and a test on discharge rate in a large theater completed the

information which was collected and studied before attempting a field survey.

3. CONCLUSIONS OF PREVIOUS TRAFFIC COUNTS

Summaries of some of the conclusions reached as a result of the

studies made by the Illinois Central Railroad and those for the

Hudson Terminal are given in table 16, as follows:

Table 16.Summary of some previous traffic movement observations

Subject of study Width

Slope

Vertical height

Number of persons dis- charged

per foot of width per minute

Direction

of travel Rise Tread

Stairways of I. C. R. R

Ramp of I. C. R. R

ft

{ 8

J 5

1 4

I 4

8

8 fin.6

3

in.76

7

in.12

1113UH

ft17

1114

11

in.5

88

18

1918

29

272820

183020

20

Up. Down.

Up. Down.

Up. Down.

Up. Down.

Level passageway of I. C. R. R_

Stairways of Hudson Terminal

Level passageways of Hudson Terminal

Stairways of Rapid Transit R. R. at Sydney, Australia.. )-

The rate at which passengers can pass through doors was also checked in the Illinois Central study. A double swinging door, each

leaf 3 feet wide and both leaves open, accommodated 117 persons in

1 minute, the movement being in 1 direction only. The same door,

1 leaf locked, accommodated 77 persons in 1 minute. These figures,

when reduced to discharge rate, show that the 6-foot opening had a discharge rate of 19 persons per foot of width per minute, while the

3-foot opening had a discharge rate of 26 persons per foot of width

per minute.

Computations made on the number of square feet occupied per

person on stairways, on ramps, and on passageways checked in the

Illinois Central studies gave a figure of 5.7 square feet per person on

the stairways, 10.5 square feet on the ramps, and 11.1 square feet on

level passageways. The Hudson Terminal study noted 10.0 square

feet per person on a level passageway under crowded conditions, the

passageway discharging approximately 30 persons per foot of width

per minute at that time.

A check of the discharge rate from a theater, made under the

direction of the late Philip A. Mason, when building commissioner

of Hartford, Conn., showed a stairway discharge of 13 persons per

foot of width per minute and a doorway discharge of 32 persons per

foot of width per minute. These figures are the average of a number

of observations and represent a normal rate of discharge at the end

of the performance. The theater in question had a capacity of 3,200,

and was filled the night the count was taken.
32 Miscellaneous Publications, National Bureau oj Standards

A very interesting and extensive study of exits in schools was con- ducted by J. M. Tracy, superintendent of schools, Rochester, N. Y.,

as part of the program prompted by the Committee on Safety to Life

of the National Fire Protection Association to determine the efficiency

of exits in such buildings. The individual discharge rate for separate

exits was not recorded and it is not known how these exits were

distributed on the floor areas. However, the actual time necessary

to empty a building of its occupants during a fire drill was checked

for over 50 schools. An average rate of discharge, assuming all the

exits in the building to be used, was computed for a 22-inch unit

of exit width—that is, a building having a total of eight 22-inch

units of exit width, and discharging 600 pupils in 2 minutes, was computed to have an average discharge rate of 37.5 pupils per 22-inch

unit per minute. The results of these studies are given in table 17

below.

The results of capacity tests on revolving doors furnished by one

of the large companies that manufacture such doors, are reproduced

in table 18, page 33. Tasle 17.

Survey of exits in school buildings, Rochester, N. Y.

Existing

exits

Number

of

occupants

Emptying

time 1

Average

number

discharged

per

22-inch

unit

per

minute School number

Existing

exits

Number

of

occupants

Emptying

time 1

Total

number

of

exits

Total

number

of 1

22-inch

units

Total

number

of

exits

Total

number

of

22-inch

units

min sec min sec

5 10 400 1 20 30 26 8 18 1,550 2 00

5 8 600 2 00 37.5 27 20 40 920 40 9 14 485 48 43.1 28 5 11 580 .... 48

9 18 662 ~2 00 18.3 29 4 38 609 45

3 8 691 1 58 43.6 30 3 6 525 1 40

3 8 416 1 15 41.5 31 2 4 275 1 00

6 13 930 2 00 35.7 32 5 12 779 1 10

7 12 1,400 1 30 77.7 33 7 14 500 1 10 6 12 780 1 30 43.3 34 5 11 1,230 1 30

5 12 834 1 40 41.7 35 25 50 865 30

6 12 450 1 30 25.0 36 8 19 404 1 30

3 8 522 1 25 46.0 37 8 19 875 2 15

7 16 1, 145 2 00 35.8 38 8 19 291 1 09

2 4 260 1 05 60.0 39 4 8 903 1 40

8 13 800 1 30 41.0 40 6 13 1,000 1 15

g 15 1,536 2 00 51.2 41 6 12 530 1 30

8 15 1,700 1 35 71.5 42 2 5 240 .... 50

5 10 531 1 05 49.43 10 11 67 05

5 9 1,060 2 35 45.6 44 4 10 372 2 45

6 10 580 1 40 34.8 45 - 6 24 1,639 2 54

g 23 1,221 1 35 33.5 46 6 24 1,528 2 15

3 8 600 1 45 42.7 47 10 18 516 1 10 24 48 600 45 16.6 48 5 9 548 47

28 56 1, 115 30 39.8 49 7 28 1,668 "I" 45

10 22 1, 298

~~~2 00 29. 5 50 5 20 1,532 2 10

School number

1.2.

3.4.6.

6.7.

8.9.

10

11

12. 13

14

15. 16

17. 18.

19. 20.

21. 22.

23.

24. 25.

.as

3 P.'

> o 3

43.0

34.5

65.9

43.5

52.5

68.7

55.5

30.6

74.5

34.6

14.1 20.4

13.3 67.7 61.6 29.4

57.6

5.6 13.5 23.5

28.3

77.6

34.0

35.3

drill.Actual time required under normal conditions in September 1927 to empty the buildings during fire
Design and Construction oj Building Exits 33

Table 18.

Capacity tests on revolving doors of certain buildings in New York City 1

Name

John Wanamaker's...

Total.. Y.M.C.A...

Total Hotel Commodore..-

Total Hotel Astor _ Total..

Childs' Restaurant

Total Bank of the United States Total World Building. Total Manhattan Life Building..

Total... American Tract Society Building. Total Commercial Cable Building

Total Bank of Commerce Building

Total...

Boreel Building. Total..

Direction

of traffic

fin... lOut.

fin... \Out.

fln—

\Outfln... lOut.

/In... LOut.

(InlOut.

/In... (Out.

fln... \Out_

fln... lOut.

fln... \Out.

fin... lOut.

fin... lOut.

At end

first 15 min

At end

30 min At end

45 min

At end

60 min

Max. rate converted

into hourly

basis

38

31

81

71 129

105 176

163 188 232

69 152 234 339 420 99

55

201 152 278 245

398

355 480 440

154 353 523 753 920

94

54

169

123 206

190 240

295

376

216

148 292 396 535 592 240

209 449

478

427 952 872

905 1,824

337

86 644162

931 317

1, 134 487

1,148 620

423 806 1,248 1,621 1, 768

109 110 436 440

219 —

876

130

199 227 308

355 444

496 629

520 796

329 535 799 1, 125 1,316

164

128

311 238453

251 559 432

656 512

292 549 704 991 1, 168

160 172311 310

416

421

533 516 640 688

332 621 837 1,049 1,328

276

291

567

551 545 787

777

1,018

1, 034

1, 104

1, 164

1,096 1, 564 2. 052 2. 268

298 200

502 345748

533

961 679

1 192 '800

498 847 1,281 1,640 1,992 82

100

163 197231 274

337

363 424

356

182 360 505 700 780

i Count made through 1 door only. Courtesy Van Kannel Revolving Door Co.

4. FIELD WORK

A review of the tests on traffic movement, summaries of which have

been enumerated in preceding paragraphs, indicated that certain gaps

in these data could well be closed up by making further counts. It

also appeared desirable to check some of the previous findings, especially those where but few observations were available. A field survey was then instituted in Washington, D. C. Traffic counts were taken

at some of the larger Government office buildings, at department

stores, and at theaters. Congested conditions which would produce
34 Miscellaneous Publications, National Bureau of Standards

maximum use of exits were extremely difficult to obtain, so to broaden

the field work additional observations were made in New York City

at the Grand Central Terminal, at certain of the subway and elevated

exits, at theaters, and at a number of other points where there was a

likelihood that the exits would be used to capacity. All these observations were on random conditions of flow.

5. METHODS USED IN MAKING COUNTS

The mechanical details involved in timing the movement and in

counting the number of people walking through exits were simple.

The time was recorded by a stop watch. The counts were taken by means of a mechanical hand counter. The probable error involved in making a count was determined by having 2 observers make concurrent checks of the discharge of people through a few typical exits at a congested period. Several trials showed that the counts differed by

approximately 2 or 3 people for every 300, a difference so small as to warrant the use of but 1 counter.

It was found preferable also for the observer recording the time

with the stop watch to read the counter, rather than to ask the observer

making the count for the reading thereby momentarily interrupting a continuous check and probably introducing a slight error in the

count as a few people would pass by while the reading was made.

When the exits were filled for periods of several minutes the count was taken at intervals of 30 seconds; at other times any interval that

gave an apparent maximum flow whether it was 10 or 60 seconds, was recorded.

Stairway or ramp discharge was studied in different ways. Where

rates were only checked, both observers stationed themselves at a con- venient point and counted the number of people passing as they

reached the top or bottom of the exit. The readings were not started

until the stairways or ramps were filled from top to bottom between

handrails.

Observations to determine the number of square feet occupied per

person at the time when people are moving normally up or down

stairways as well as the rate were taken in 2 ways. Where it was

possible to see the people as they entered a flight of stairs, an individual was picked out as he entered the stairway, the count was immediately started at the other end and continued until the person selected

completed the passage. The count was then stopped and the time

recorded, thus giving the total number of people in the stairway during

the interval required for any 1 person to traverse it. Where it was

not possible to see the beginning of the discharge, the observer with

the stop watch stationed himself at the other end of the stairway,

whistled as he entered with the crowd as a signal to start the count,

and then walked through the stairway recording the time required to reach the observer making the count. Naturally, fewer counts are possible by this second method during any peak period. These

counts were made only when the stairways discharged at what appeared to be capacity.

A large number of counts were taken of the traffic movement on

stairways ranging in width from 3 to 8 feet. Unfortunately, it was

not found possible in this survey to obtain discharge rates on stairways

whose widths varied by increments of about 6 inches. The relative
Design and Construction oj Building Exits 35

efficiency of stairways, say one 44 and the other 50 inches in width, is open to question.

All essential measurements of stairways, ramps, passageways, and

doorways were taken in order to make the necessary computations

for discharge rates. The width of stairways was that measured from

wall to wall rather than the clear width between handrails, the width

for treads included any nosings, and for doorways the actual door

width was recorded. Any peculiarities of movement or conditions

that might make interpretation of test results easier were also noted.

6. CONDITIONS AFFECTING TRAFFIC COUNTS MADE

The counts of traffic movement at the Grand Central Terminal,

where more than 165 separate observations were taken on stairways,

40 on ramps, and more than 50 on gateways, were made during the

morning and evening rush hours. The points selected for traffic checks were chosen after a brief study to determine where traffic appeared to be the greatest. The exits commonly used by commuters—those people who are always in a hurry to get in and out of a

station—proved to have a faster discharge rate than those used by

through passengers, who were, of course, encumbered with baggage and

unfamiliar with the exits. No counts were recorded when any contrary movement took place in an exit because of the apparent retarding effect on discharge.

A number of theaters were studied, but many of the counts made in

them were rejected. Theater patrons, when leaving at the close of a performance, usually walked slowly. This leisurely exit is reflected

in the rates of discharge for theater stairways, approximately 13 per- sons per foot of width per minute as listed in table 19, below, which

coincides with the rate obtained in the study previously mentioned for a theater in Hartford, Conn.

Table 19.

Summary of observations of traffic movement on stairways

Location Width

of stairs

Slope

Vertical height

Number of persons dis- charged per

foot of width

per minute

Number of square feet occupied

per person

Direction of travel Remarks

Rise Tread Average Max- imum

Average Min- imum

ft in. in. in. ft in. Grand Central Ter- 8 1 734 11 18 9 12 16 5.9 4.2 Up....

minal, tracks 109 and

110. U. S. Census 7 3H 7 12 10 3J4 23 24 Down. Exit iduring

fire drill.' 44th Street Theater,

7 12 10 14 18 ...do... Do.

6 3 m 11J4 15 11 13 "~8.T ~~5.T ...do... N. Y. Subway, 34th Street 6 7 11H 17 18 and 7th Avenue, N. Y.

U. S.Veterans' Bureau. 6 7 11 12 3 14 17 ...do... U. S. Census 5 6 7 14 17 ...do... Do. Grand Central Ter- 5 m 12 14 4 19 28 "1.T "§."9" ...do... minal, track 115. 5 m 12 14 4 18 24 4.9 3.8 Up.... Grand Central Ter- 5 7H 12 14 4 18 20 minal, tracks 116 and 117. U. S. Civil Service 4 1J4 11*4 13 17 18 Down. Do.

Commission.

TJ. S. Census 4 m 11J4 20 7 13 14 ...do... Do.

National Bureau of 3 7 11J4 13 5 31 34 ~~4.T "~4.T ...do- Controlled

Standards. test. 3 7 11H 13 5 29 29 4.1 4.1 Up.... Do. 1158—35 6
36 Miscellaneous Publications, National Bureau of Standards

Government office buildings in Washington, D. C, were studied at the closing hour. Some interesting counts were also made of the

traffic movement during fire drills at the so-called " temporary office buildings." These drills were compulsory, and were conducted by the

fire marshal in charge of the buildings. The occupants were not

warned when a drill was to take place. At the sound of the fire gong

everyone left the building at a normal rate by exits which had been

assigned to specified floor areas. No attempt was made to form ranks.

A high rate of discharge for a stairway checked during one of these drills will be noted in table 19, page 35. A maximum flow condition was

created by closing a stairway ordinarily used, thus adding its entire

load to the particular stairway under observation. This stairway was unusual in that two 5-foot stairways were connected at an intermediate landing with a single stairway 7 feet 3% inches wide, producing

a bottle neck in the direction of flow.

A controlled test of traffic movement on a 36-inch stairway was made at the National Bureau of Standards. This stairway was

unenclosed, had a railing on one side, treads of UK inches and risers of 7 inches, a story height of 13 feet 5 inches, and was constructed

with two landings, each 3 feet square and each one making a 90-

degree turn. A crowd of people was assembled in the hallway at the

top of the stairway and asked to descend as they naturally would

without attempting to run. As will be noted in table 19, page 35, a maximum rate of discharge of 34 persons per foot of width per minute was obtained. During this test the number of square feet occupied

per person averaged 4.1. However, by placing all the people in the

stairway that could be accommodated when there was no motion, but

1.4 square feet was occupied per person.

7. TABULATION OF COUNTS ON STAIRWAY DISCHARGE

The results of the observations on stairways are given in table 19,

page 35. The average figures in the tables represent a large number of

observations taken not only at different hours of the day, but also on

different days. The column giving the number of persons discharged

per foot of width per minute was calculated by determining the number of persons passing in 1 minute and dividing this number by the

stairway width in feet. Thus, on a 3-foot stairway, where 93 people were discharged in 1 minute, the rate per foot per minute was computed to be 31. If a 22-inch unit were used to compute discharge

as is sometimes done, a rate of 93 per 22-inch unit per minute would

be obtained where credit for only a single unit was allowed the 36-inch

stairway; if the same 22-inch unit were used and the computation

based on the proportion of 36 inches to 22 inches, the rate would be

57 persons per 22-inch unit per minute. The results obtained in the

Illinois Central and Hudson Terminal studies, table 16, page 31, were

also referred to the rate per foot of width per minute.

8. CHARACTERISTICS OF STAIRWAY DISCHARGE

The varying rates of stairway discharge found, while they bear a

certain relation to stairway width, also indicated that normal discharge rates may vary widely with different occupancies. For any

one stairway with the same class of occupancy using it, the total
Design and Construction of Building Exits 37

number of persons discharged per unit of time remained nearly constant—-that is, with rapid movement necessitating considerable space

between the individuals, the number of people discharged per unit

of time remained the same as when the movement was slower but

therefore denser. This condition has been noted in other tests. Discharge rates as related to stairway width indicated a number of

possibilities. For average conditions of stairways varying in width

from 3 or 4 feet up to 6 or 7 feet, the number of persons discharged

might be taken as roughly proportional to the width of the stairway.

On the other hand, stairways 3 or 4 feet wide appeared to give much

higher rates of discharge per foot of width than those 7 or 8 feet wide,

especially where the wider stairs had no intermediate handrails.

Even where an overflow was waiting to enter a stairway, a condition

existing on the stairway (8 feet 1 inch wide) in the Grand Central

Terminal, as soon as the crowd entered the stair it became scattered

and the discharge rate was therefore reduced.

Observations of the characteristics of the movement on stairways

showed that the movement was slower and denser on the first half of

any flight than it was on the second half. Increased space between

individuals resulting in faster movement took place after the intermediate landing was passed. In both flights, the appearance of the

movement under random flow appeared similar. Whenever a rank

of people formed to take up the complete width of the stairway, it was invariably followed by a lesser number, so the final effect might

be said to resemble a series of successive wedge-shaped units dis- tributed rather evenly over the length of the flight. Conditions of

maximum flow did not occur unless a number of people were waiting

to enter an exit. The space occupied per person while moving up or down a stair- way necessarily varies widely with the speed of the movement.

Table 19, page 35, shows the fluctuation in these figures. Although

under fast discharge a little over 4 square feet is occupied per person,

when the discharge is leisurely nearly double this space will be

occupied.

9. RAMPS

Studies on ramps were difficult to make as very few could be

located that were used to anything near capacity. Table 20, below,

lists the results of some 30 observations made on 2 ramps in the

Table 20.

Summary of observations of traffic movement on ramps

Grand Central Terminal track

nos. Width of ramp

Length Slope Area

Number of per- sons discharged

per foot of width

per minute

Number of square feet occupied per person

Direction of travel Average Maxi- mum

Average Mini- mum

Ill and 112

109 and 110

ft 66in.4Hft 137

137

in.2

2

1 in 9.7..

1 in 9.7..

sq ft 875

875

f 15

1 21

19

2123

22 Down.

Up.

Do.

8.

1

7.9 6.26.3 Grand Central Terminal used by commuters. Wider ramps were

also observed in the terminal, but, inasmuch as they never seemed to
38 Miscellaneous Publications, National Bureau of Standards

be used to capacity, no counts were taken. An attempt to make a count on a ramp at the Griffith Stadium in Washington, D. C, which was 17 feet 6 inches wide, proved unsuccessful because the observers were unable to get anything approaching accurate readings on a ramp of this width.

Given similar conditions, the discharge rate on ramps was faster

than on stairways. Naturally, the width of stairway treads reduces

the normal 30-inch stride more than a ramp with a slope of 1 in 10

or less, and would therefore result in effecting a slower discharge

rate for the stairway.

10. DOORWAYS

Table 21, below, lists the average discharge rates for counts made

at gateways, swinging doors, and revolving doors. It should be

borne in mind that these studies were not made to determine the

efficiency of the various types of doors. Most of the counts of traffic through doorways were taken when the doors were fastened open.

Just how much slower the discharge rate is when doors are swinging,

would require further special study.

At the Grand Central Terminal, the readings were taken at the

gateways as they were opened to let the crowds through that had

been waiting in the concourse; they therefore show a higher rate of

discharge than the doorways in the office buildings or department

stores. Table 21.

Summary of observations of traffic movement through gates and doorways

Location Type of exit Total width

Number of per- sons discharged per foot of width per minute

Average Maxi- mum

Remarks

Circus grounds Grand Central Terminal,

tracks 41 and 42. U. S. Veterans' Bureau. _ Department store U. S. Bureau of Printing and

Engraving.

National Geographic Society... U. S. Department of Commerce- Grand Central Terminal,

tracks

113 and 114

Ill and 112

109 and 110... 107 and 108.. 103 and 104.. U. S. Census, "C" building—

TJ. S. Census, "D" building- Department store, Washington, bo.

TJ. S. Treasury.

TJ. S. Government Printing

Office.

Gateway

do

Pair swinging

doors. do

do

do.... ....do—

.

Gateway. do—

do.... do.— doPair swinging

doors. do Revolving door. do—

1 swinging door. Revolving door.

Both doors fastened open. Do.

Do. Both doors operating. One door closed. Both doors fastened open

Both doors fastened open

for fire drill. Do. Width of single leaf used to compute discharge rate. Do.

Fastened open. Leaves of door collapsed leaving opening of 2 feet

1 inch each side.
Design and Construction oj Building Exits 39

The figures for revolving doors do not necessarily represent absolute

capacity. The readings were clocked for those moments when the

doors appeared to be accommodating people as fast as convenient.

Egress only was checked. Observations of the action of people in revolving doors led to the belief that the width of the leaf has very

little relation to the number of persons discharged. As might be

expected, it was exceptional for 2 people to pass through a single

pocket of these doors at the same time.

Movement through doorways displayed one characteristic in com- mon with stairways—the tendency for those having a width of about

5 feet or less to have a higher rate of discharge than those over about

8 feet in width. A comparison of the rates of discharge through doorways with those up or down stairways shows a faster rate for doorways under similar traffic conditions.

The figures in tables 19, 20, and 21, giving the summary of observations of traffic movement in various types of exits, were carefully

considered by the joint conference. Although there were marked

variations in results, probably attributable to the fact that in some

cases the exits were not used to their maximum capacity, the judgment of the conference was that rates of 45 persons per 22-inch unit

per minute for travel down stairways, and 60 persons per 22-inch

unit per minute through doorways, which had been in use on the

basis of earlier observations, were sufficiently confirmed to warrant

their retention in connection with the requirements under development. This is equivalent to a ratio of 4 to 3 as between the flow to be

expected through doorways and down stairways.

Varying width, story height, and proportions of treads and risers,

coupled with the mental and physical traits of people, render it nearly

impossible to obtain other than general averages of discharge rates from exits. V. METHODS OF CALCULATING EXIT WIDTH

Several broad controlling principles are utilized to compute the

necessary exit width. These are discussed below:

1. CAPACITY METHOD

This method is based on the theory that sufficient stairways should

be provided at each floor to accommodate all the occupants on that

floor without the necessity of any movement within the stairway.

There are two principal ways of arriving at the necessary stairway

size. In one the total area of landings and stair treads [is obtained

and is divided by a figure representing an assumed area per person.

In the other, 1 person is assumed to stand on every other tread in a 22-inch width, and the area of landings is divided as in the previous

case to give the additional persons that may be included.

Theoretically this provides a safe area of refuge for everyone within

the protective barrier formed by the stairway enclosure. It allows

for the subsequent safe and orderly evacuation of the building without the necessity of forcing aged or infirm people to travel at a rate beyond their physical capacity. It recognizes that travel down a long

series of stairs in high buildings is exhausting even to normal persons. The knowledge that there is a safe place for everyone is held to minimize the possibility of panic.
40 Miscellaneous Publications, National Bureau oj Standards

Such a method takes a large amount of space away from the

rentable area of the building and reductions are resorted to to over- come this objection by making allowances when the building is sprinkled or when horizontal exits are provided. These devices are not

always conveniently installed and the arbitrary allowances made for them may or may not accurately represent their value in replacement of stairway facilities. While it is true that safety should be the

first consideration, there is a very real question whether the degree of

safety offered by this method is necessary, particularly in low buildings where a certain amount of flow out of the building appears to be

inevitable. Authorities also maintain that people will not stand still in stairways even in high structures.

2. FLOW METHOD

This method is based on an assumed rate of flow of people, com- monly at the rate of 45 persons per 22-inch width per minute down

stairways and of 60 persons through doorways. It is usually coupled

with an assumed length of time within which it is expedient to evacuate the building. The object is to get the people out and away from

the threatened area in as short a time as possible.

With certain occupancies such as theaters where simultaneous exit

by all is needed and in certain cases where drills are a regular feature

as in schools, the method has many desirable features. It provides a

definite objective to be accomplished. The result calls for considerably less stairway width than the preceding method. For comparatively low structures the method has an obvious application since it recognizes that flow out of such structures is a natural procedure.

However, its use is confined to a few occupancies and to buildings of

moderate height. Continuous movement down stairways, especially

in high buildings, cannot be expected without serious effects upon some of the occupants. Any calculations assuming continuous

orderly movement in such structures runs contrary to observation

and experience.

3. COMBINED METHOD

This method attempts to correct the defects of the capacity and

flow methods through a formula intended to apply the flow method to low buildings and an increasing emphasis upon capacity until this

controls in high buildings. The formula contains various factors

involving such features as type of construction, enclosure of openings,

hazard of occupancy, presence of horizontal exits, etc., all of which

affect the final result. The method offers a means by which definite relationships may be

preserved between height, character of construction, and other

features. It recognizes that people can file out rapidly in low buildings and cannot be expected to do so in high ones. And it effects a

transition from one method to the other in a gradual and systematic manner. The results reached through application of this formula have never been entirely satisfactory even to its advocates. The relative

weights assumed for the various factors are empirical. There is a constant increase in the aggregate stairway width throughout the

building, as the building becomes higher which is a principle whose
Design and Construction of Building Exits 41

necessity is doubted by many authorities. The results obtained in

terms of stairway width, especially where fire towers, horizontal exits,

and other features are not present, are very large in tall structures,

causing disproportionate amount of space to be devoted to stairways

as compared with usable floor area.

4. PROBABILITY METHOD

This method secures an answer directly in terms of number of

standard 2-unit-width stairways by dividing an arbitrary figure

varying with the occupancy, such as 1,000, into the total population

of all floors above the first, with a proviso that a maximum of only the

6 most densely populated of such floors need be considered. Provision is made for taking care of fractions in the result. The method is direct and simple. It introduces an element that

is absent in the preceding ones, namely, a limit as to the probable need

for simultaneous use of the stairways. Other methods have assumed

that all persons on each floor will need egress facilities at once, while

this method infers that such an arrangement is neither practical nor

necessary.

In the case of set-back buildings the method is further complicated

by supplementary provisions in order to make it work. In the

case of high buildings there is a doubt as to whether 6 stories out of

40 are all that need to be considered. The method also makes use of

assumptions as to the influence of type of construction that are not

agreed to by all authorities. In the case of low buildings of large

floor area the results are so small as to be of questionable value.

5. FLOOR-AREA METHOD

This method presents in tabular form a series of floor areas with

the number of standard 2-unit-width stairways required for each.

The areas vary with the type of construction and class of occupancy.

They are further modified by the position of a given floor in the

building. The table represents some typical floor such as the third,

with an increase in allowable area per stairway for floors below and a

scale of percentage reductions for higher floors. Like the probability

method this concedes that it is impracticable to provide a place for

everyone in the stairway enclosure. However, it retains a slight

variation according to height instead of fixing a maximum number of

floors to be considered.

Computations are fairly easy to make. Eesults do not reach

such large numbers of stairways as to cut down useful area excessively.

However, there appears to be no consistent relationship between

stairways and number of persons accommodated by them. The

allowance for increase in height is so slight that there is a question

whether it is significant enough to warrant the additional calculations

required. The method, being based on area rather than occupants,

takes no account of varying population within a given occupancy.

Abrupt jumps also occur in the tables at points where floor areas change.
42 Miscellaneous Publications, National Bureau of Standards

6. DEVELOPMENT OF A SATISFACTORY METHOD

Each of the methods already described selects certain conditions

which must be fulfilled in order to insure a reasonable degree of safety.

Refuge for all, escape at a predetermined rate, a combination of the

two, and probable need for simultaneous use, all start with certain

assumptions and then endeavor .to apply mathematics that will accomplish the desired result. No method attempts to apply any factor for

panic. Only one makes assumptions that some exits will be blocked

because of smoke or fire. This, as worked out by means of a formula,

applies not to the number of stairways but to increase in the aggregate width and there is thus no assurance that the extra allowance

will be transformed into additional stairways.

In view of all the uncertainties involved in the problem, complicated methods and refinements of detail seem scarcely justified. At

the outset it may be pointed out that the needs of probably over 95

percent of all buildings will be covered by the minimum requirement

for 2 stairways. Perhaps on a basis of population contained the per- centage would run somewhat higher, but the necessity for going beyond 2 standard 2-unit-width stairways does not arise in the average

building. It may well be kept in mind that most of what follows applies to the relatively infrequent building of large size, usually of fire- resistive construction and designed by experienced talent. In weighing the advantages and disadvantages of each method the

primary consideration, of course, is safety ; but it is apparent that what

constitutes safety cannot be definitely established. It therefore is fruitless to reject considerations of loss of usable space on the ground

that such considerations have no standing. No one would dispute

that profit should yield to safety where it can be shown that certain

requirements will provide safety. But where it cannot be so shown it

is legitimate to balance economic considerations against theoretical

assumptions.

Experience is obviously one method of approach. If it could be

shown that certain cities had utilized a particular method of dealing

with egress requirements over a period of years, that buildings had

been erected in strict conformity to it, and that maintenance had been

perfect, and if the loss of life in fires where exits were a factor were known over the same period, some evidence would exist for or against a given method. Unfortunately, such evidence is not available in

sufficient detail and over a long enough period to be of much use. Another means of approach is to compare exits found in representative buildings in a number of cities with those demanded by the vari- ous methods already cited. It ma}^ be argued that simply because

certain provisions for exits exist this is not necessarily proof that they

are adequate, yet there is a certain weight in an accumulation of instances where certain measures have been followed coupled with no

conspicuous trouble. Traditional principles developed by responsible

architects and engineers in the design of buildings are not to be ignored. Such principles may not be susceptible of definite analysis as to the extent of provisions for safety, but competent designers come

to have a certain "feel" for the right thing arising out of long study of needs and observations of buildings in actual use. There is a further

consideration in that such buildings have been designed with thought

to their economic use and that practical considerations have not been

entirely subordinated to theoretical provisions for safety.
Design and Construction oj Building Exits 43

There is one distinction which helps in building up a method in

dealing with the subject. People who are awake, alert, and in good

physical condition are better able to take care of themselves in such an emergency as fire than those who have been just aroused from sleep or are sick or infirm. The distinction is so obvious that it has been

applied in the case of several of the methods described. There is a

further classification, that of people assembled in such locations as

theaters, assembly halls, and the like. Experience teaches that,

although such people are alert, panic communicates itself much more

readily under such circumstances. There is no interval before the

exits come into full use. The demand is immediate and simultaneous on the part of all. Such a condition justifies separate treatment.

It now becomes necessary to search for those features of existing

methods that will best fit the needs of each group of persons or to develop new methods. Manifestly, in the case of those asleep, the

sick, aged, and the infirm, the most liberal provisions should be made.

They cannot be expected to use the same degree of discretion nor to move with as great celerity as the others. Accordingly, it seems wise

to apply the principle of a place for everyone within the stairway enclosure for this group. However, it was found by actual experiment

in the course of the investigations already described that the space

allotted per person in some existing methods that utilize this principle can be reduced.

Coming to those awake and alert, a different problem presents itself. Here the greatest need and quickest alarm will develop naturally on

the floor where the fire occurs. Other floors may not be involved at

all, or if so, not until a later time because of the fire resistance of the

building, particularly in its required enclosed shafts and stairways.

On the floor where the fire starts it is possible that panic will develop,

but this would hardly extend to all floors of the building at once. Here appears to be a reasonable field for the use of the method of

probable need. As a matter of fact, on reexamining the principal

methods for providing exits, we find that this principle is rather

generally recognized. Some do this directly by a rather drastic

reduction while others do so indirectly and partially by extremely

fiberal reductions in stairway sizes where sprinklers are present. The

net result in all cases is to provide less stairway space than would be

necessary for simultaneous use by all floors.

If this premise is accepted, and it seems necessary to do so unless

so large an area is allotted to stairways as to make the building of doubtful utility, the question arises how much reduction should be

made, or stating it another way, what is a reasonable probability of the number of floors that will need to be accommodated at one time.

One of the methods described sets a maximum for the 6 most densely

populated floors above the first. While this has a very evident merit

it takes no account of the problem created by high buildings. For

instance, a 7-story building and a 20-story building would each have

facilities for only 6 floors at a time. After reviewing this problem at length it appears that the probability would be better expressed by some other method. In the case of the lower buildings, flow takes

place; but in the case of high buildings a definite proportion of the

floors should be provided for at all times. As a reasonable assumption,

one-half of the floors above the first was selected and checked back

against values plotted to show the results of the survey of existing
44 Miscellaneous Publications, National Bureau of Standards

buildings segregated as to occupancy. The results showed that

current practice was substantially in accord with the percentage

chosen. The results were applied also to a number of plans of buildings and were submitted to representative architects for their opinions

as to their adequacy. Their reaction was favorable.

In the case of occupancy involving assembly there is virtually

unanimous agreement in existing methods on the flow principle, that

is, in providing for the escape of the occupants through exits proportioned to bring about a complete evacuation within a given maximum time. There appears to be no reason why this principle should

be altered and it has constituted the basis for dealing with this particular group.

It will thus be evident that a selection may be made of those fea- tures in existing methods that appear to have the most practical

usefulness when considered in relation to the principal groups constituting building occupants. No new principle is introduced but a more

logical application is effected. The method of arriving at actual

results in terms of units of exit width depends upon the use of several

simple divisional factors, as will be shown under the particular paragraphs to follow dealing with details.

7. CREDIT FOR ELEVATORS

In some methods examined, attempts were made to give a credit to elevators in computing aggregate exit width. This allowance was

so small, however, as to offer very slight reduction in required stairway space. Recognizing the growth in speed and other improvements in elevator construction, special attention was given to the

part that might be played by elevators in providing exit from buildings. Certainly these devices have the merit of being familiar means

of egress to which people would naturally turn in time of need.

It was assumed that automatic push-button elevators would not

be suitable. Although these have a considerable vogue in apartment

houses and small business buildings, their capacity and rate of speed

is not great. Furthermore, they are not subject to a single will as

in the case of an elevator operator, but to demands from many tenants. Their successful functioning in a time of emergency would be

problematical.

The potential usefulness of other passenger elevators appears to depend on the reliability of the operators and the ability to discharge

people at a reasonable rate. Testimony differs on the first point, some citing dereliction of elevator operators at critical times, while

others point to examples of heroism. The probability of the operators

staying on the job is at best uncertain. The possibilities of power

being cut off, of cars stopping between floors, and of smoke filling

shafts, also have to be considered.

As to the capacity and speed of elevators, one of the methods

examined made use of a formula indicating that 5 elevators were

about equal to one unit of stairway width, the exact relationship

varying with the number of persons that could be carried, the speed,

and the height of the building. A stairway of course, traverses the

entire height of the structure and furnishes some accommodations at each story, while the elevator can serve only 1 floor at a time. With

the modern high-speed elevator, however, running in an enclosed shaft,.
Design and Construction of Building Exits 45

the conditions are favorable for taking out a considerable number of

people. If an emergency is well sized up by some one in authority,

it can often be met by taking people from above the floor involved

to a lower floor, from which they can find their way to safety by means

of the stairways. Thus, the elevators do not necessarily have to descend to the street floor each time. Such a utilization of them

calls for intelligence and good discipline, qualities that cannot always

be safely assumed.

In general, a safer policy appears to be not to give direct credit

to elevators, but to recognize their availability in high buildings in

the stairway requirements. The presence of these devices makes it possible to apply the assumption of probability with greater confidence. With some possibility of flow out of the building down stair- ways in the case of low buildings and with modern elevators acting

as a valuable auxiliary in high buildings, proposed stairway requirements are considerably strengthened, while in the case of certain

occupancies for which floor space is required in the stairways for the

occupants of all floors, the elevators in use are likely to be of the pushbutton variety or else not able to carry a significant number of people

in case of fire. Thanks are due a large number of architects, engineers, building

officials, and others who supplied information and cooperated in

various ways. The procedure employed in the surveys was possible

only because of the courtesy of building managers who permitted

measurements and traffic counts to be taken in buildings under their

jurisdiction. Suggestions and criticism from numerous individuals

helped materially as the work progressed. Data on earlier traffic counts was supplied by J. Vipond Davies; the Illinois Central Railroad; and J. M. Tracy, superintendent of schools, Rochester, N. Y.

Others to whom particular acknowledgment should be made are Frank Burton, consulting engineer, Detroit, Mich.; C. Heller, consulting engineer, San Francisco, Calif.; Nolan D. Mitchell, structural

engineer, National Bureau of Standards; and Robert S. Moulton,

technical secretary, National Fire Protection Association, Boston,

Mass,
APPENDIX

VI. MEANS OF EGRESS

1. RECOMMENDATIONS

Throughout this study the ultimate object was to determine what

were suitable exit requirements for building codes. It was not in- tended to produce a complete manual of practice covering all conditions but to find the minimum that appeared to be necessary for the

usual occupancies. As the work proceeded, various tentative requirements were drawn up and compared with the results obtained in the

field studies. Eventually, a set of suggested requirements was formulated representing the consensus of the committee.

It was the intention to publish these findings as part of the series of

recommendations issued by the Department of Commerce Building

Code Committee. Before time came for publication, however, the

committee was discontinued. The suggested requirements, therefore,

could not be put out as one of its series, but there were requests for

issuance of a document giving the results of the studies and the interpretation placed upon them by the committee. Rather full footnotes

have been given in connection with the various recommendations to explain the reasoning leading to specific recommendations and to

illustrate their effect.

2. DEFINITIONS

The following terms shall, for the purpose of this chapter, have the

meanings indicated.

Approved.—As applied to a material, device, mode of construction, or testing agency, means approved by the building official under the

provisions of this code, or by other authority designated by law to give

approval in the matter in question.

Automatic.—As applied to a fire door or other protection for an

opening, means normally held in an open position and automatically

closed by a releasing device that is actuated by abnormal high temperature or by a rate of rise of temperature exceeding some fixed value.

Dwelling.—A building occupied exclusively as a residence for 1 or 2

families or as a boarding or rooming house serving not more than 15

persons with meals or sleeping accommodations, or both.

Exit.—As applied to a stairway or doorway, means constructed

and arranged as specified in this chapter.

Exit passageway.—An enclosed hallway or corridor connecting a

required exit to a street or an open space leading to a street. Fire wall.—A wall which subdivides a building or separates buildings to restrict the spread of fire, starting at the foundation and ex- tending through all stories to or above the roof, and having an ulti- mate fire resistance of at least 4 hours.

46
Design and Construction of Building Exits 47

Fire door.—A door construction consisting of door, frame, and sill, which under approved fire-test conditions meets the requirements for

the location in which it is to be used.

Fire window.—A window consisting of frame, sash, and glazing

which under approved fire-test conditions meets the requirements for the location in which it is to be used.

Floor area.—An area enclosed by exterior walls or by walls or partitions having at least 2 hours' ultimate fire resistance.

Grade.—(a) For buildings adjoining 1 street only, the elevation

of the sidewalk at the center of that wall which adjoins street; (b) for buildings adjoining more than 1 street, the average of the elevations of the sidewalk at centers of all walls adjoining streets; and (c) for buildings having no wall adjoining the street, the average level

of the ground (finished surface) adjacent to the exterior walls of the

building. All walls approximately parallel to and not more than 5

feet from a street line are to be considered as adjoining a street. Hereafter.—The time after this code is adopted.

Heretofore.—The time before this code is adopted.

Horizontal exit.—The opening or passage between any 2 floor areas, whether in the same structure or not, by means of a vestibule, by an

open-air balcony or bridge, or through a fire wall or a partition having an ultimate fire resistance of at least 2 hours.

Occupied.—As applied to a building, shall be construed as though

followed by the words, "or intended, arranged, or designed to be

occupied."

Place of assembly.—A room, floor area, or building seating or accom- modating 100 persons or more and used as a place for meetings, per- formances, and other gatherings.

Required.—Complying with a mandatory clause of this chapter.

Self-closing.—As applied to a fire door or other opening protective, means normally closed and equipped with an approved device which

will insure prompt closing after having been opened.

Sprinklered.—Equipped with an approved automatic sprinkler

system.

Stairway.—One or more flights of stairs and the necessary landings

and platforms connecting them, which provide a continuous and

uninterrupted passage from 1 story to another in a building or

structure.

Story.—That portion of a building included between a floor and

the floor or roof next above.

Street.—A highway or thoroughfare dedicated or devoted to public

use by legal mapping, user, or other lawful manner; and includes avenue, road, alley, lane, boulevard, terrace, concourse, driveway,

sidewalk.

Theater.—A place of assembly in which movable scenery is used or moving pictures are shown.

Ultimate fire resistance.—Resistance shown when tested under the

conditions prescribed in the standard fire test approved by the American Standards Association as "American Standard."

3. CLASSIFICATIONS

m Classifications of buildings by occupancy and by type of construction are to be found in the report of the Department of Commerce
48 Miscellaneous Publications, National Bureau of Standards

Building Code Committee entitled " Recommended Minimum Requirements for Fire Resistance in Buildings." 18 They are inserted

here prior to the exit requirements themselves in order to define terms

appearing in these requirements and to emphasize the close relationship existing between fire protection and exits. Sections 3-1 and 3-2

of that report are as follows: Section 3-1. Classification of Buildings by Occupancy.

Buildings or parts of buildings shall be classified by occupancy or use into the following groups:

Class 1—Public. Class 2.—Institutional. Class 3.—Residential. Class 4.—Business. Class 5.—Garages, hangars, barns. Each class is intended to embrace buildings or parts of buildings

as hereinafter defined and those of similar character or use. Where

there is any uncertainty as to the classification of a building, the

administrative building official shall fix the classification within which

it falls. Class 1. Public.—This classification includes buildings or parts

thereof in which people come together for transaction of public

business; for civic, political, social, or religious purposes; for educational purposes; or for entertainment or recreation; such as city halls,

churches, schools, theaters, and grandstands.

Class 2. Institutional.—This classification includes buildings or parts thereof in which people are harbored for medical, charitable, or other care or treatment or in which people are detained for penal

or correctional purposes; such as hospitals, sanitariums, homes for

the aged, prisons, and reformatories.

Class 3. Residential.—This classification includes buildings or parts thereof in which families or households live or in which sleeping

accommodations are provided, such as apartment houses, hotels,

dormitories, and dwellings.

Class 4. Business.—This classification includes buildings or parts

thereof in which goods are manufactured, stored, converted, or sold, or in which business or professional services are rendered; such as

factories, warehouses, stores, and office buildings.

Class 5. Garages, hangars, barns.—This classification includes

buildings or parts thereof used for the storage or repair of automotive

vehicles and airplanes, such as public and private garages and hangars; also for the keeping of horses and cattle, such as stables and riding

academies.

Section 3-2. Classification of Buildings by Type of Construction.

Construction shall be classified into 6 general types according to the character of materials employed and their method of assembly as follows: Type 1. Fully protected.

Type 2. Protected. Type 3. Heavy timber. Type 4. Masonry wall and joist. Type 5. Wood frame. Type 6. Unprotected metal.

" BS BH14 (1931).
Design and Construction oj Building Exits 49

Type 1. Fully protected.—Fully protected construction is that in

which walls are of masonry or of reinforced concrete and the structural members are of incombustible materials having an ultimate fire resistance sufficient to withstand the hazard involved in the occu- pancy, but not less than 4 hours for bearing walls, fire walls, party

walls, piers, columns, trusses, and for girders which support walls;

2){ hours for walls and girders not otherwise specified, floors including

beams and girders, and for roofs; and in which the degree of fire resistance for other construction features and the materials acceptable

for the purpose are as given in chapter ll. 19 Type 2. Protected — -Protected construction is that in which walls

are of masonry or reinforced concrete and the structural members

have an ultimate fire resistance of not less than 4 hours for fire walls

and party walls; 3 hours for bearing walls, piers, trusses other than

roof trusses, and columns and girders supporting walls; 2 hours for

walls, columns, and girders not otherwise specified; 1 }{ hours for floors,

including beams and girders, roof trusses except as provided for in

section 11-2-3, and for roofs except as provided for in section 11-8-1

;

and in which the degree of fire resistance required for other construction features and the materials acceptable for the purpose are as given in chapter 11 (of BH14).

Type 3. Heavy timber.—Heavy-timber construction is that in which

walls are of masonry or reinforced concrete and the interior framing

is of timbers, or, in part, of protected steel or reinforced concrete having an ultimate fire resistance of at least 1 hour, except for roof

trusses as specified in section 11-2-4, the plank floors and roof being

arranged in heavy solid masses and smooth flat surfaces, avoiding

thin sections, sharp projections, and concealed or inaccessible spaces;

and in which the degree of fire resistance required for other construction features and the materials acceptable for the purpose are

as given in chapter 11 (of BH14).

Type J+. Masonry wall and joist.—Masonry-wall and joist construction is that not included in type 3 in which the exterior walls are of masonry or reinforced concrete and the interior framing is partly

or wholly of wood or unprotected iron or steel. Type 5. Wood frame.—Wood-frame construction is that in which

structural parts and materials are of wood or are dependent upon a wood frame for support, including construction having an incombustible exterior veneer. Type 6. Unprotected metal.—Unprotected-metal construction is that

in which the imposed loads are carried by an unprotected metal frame

and in which the exterior walls and roof are of sheet metal or other

incombustible material.

19 The reference to chapter 11 is to the same chapter number in BS BH14 (1931).
50 Miscellaneous Publications, National Bureau oj Standards

Section 7-1. Application of Chapter. 20 7-1-1. New Buildings.

Buildings hereafter erected, except dwellings,21 shall be provided

with exit facilities in accordance with the requirements of this chapter.

These regulations shall be taken as the minimum necessary for the

conditions stated. For unusually hazardous conditions the building

official may order additional exit facilities to assure the safety of

the occupants.

7-1-2. Existing Buildings.

Buildings heretofore erected, except dwellings, which are not provided with exit facilities as prescribed in this chapter for buildings

hereafter erected and in which the existing exit facilities are inadequate in the judgment of the building official for the safety of the

occupants, shall be provided with such good and sufficient stairways,

fire escapes,

22 or other means of egress as shall be specified in a written

order by him.23 7-1-3. Alterations.24 No buildings shall hereafter be altered so as to reduce the number

or width of exits to less than required for buildings hereafter erected.

No change of occupancy whether necessitating physical alterations or not shall be made in any building unless such building conforms

with the requirements of this chapter applying to new buildings of

the proposed new use.

2° The chapter numbering as set forth in the report of the Department of Commerce Building Cede Com

mittee entitled "Recommended Practice for Arrangement of Building Codes " (BS BH8 (1925)) is given oh

the assumption that the chapter would be the seventh in a complete series of building-code requirements.

21 No practical way has been found to require exits in dwellings beyond those customarily supplied as a matter of convenience. It is true that there is considerable loss of life in such structures. This could be

considerably reduced by attention to proper construction, adequate fire-stopping, proper spacing of heating

appliances from combustible construction, and other details of fire protection where a large degree of im- provement is possible over many present buildings. Such details may be consulted in the report Recom- mended Minimum Requirements for Small Dwelling Construction (BS BH18 (1932)). A further suggestion made by the committee on fundamental equipment of the President's conference on home building and home ownership in the conference report entitled "House Design, Construction, and Equipment",

was that sprinkler heads placed in especially hazardous locations, such as over the heater in the basement and in the kitchen, offered additional security where such measures were practicable.

22 Fire escapes are recognized only as supplemental y means of egress for the purpose of this chapter. Where used, they should conform in design and construction to the Building Exits Code as approved by

the American Standards Association.

23 Testimony of building officials indicates that the securing of adequate exit facilities in existing buildings

is much more difficult than in the case of new buildings. The installation of fire escapes has been the

usual solution to this problem in the past and will probably continue to be chosen as the easiest one. Modern practice condemns the use of fire escapes on new buildings, but their use on existing buildings is often the only means of providing sufficient egress facilities without prohibitive cost. Because they are an emergency device and but infrequently used, their maintenance is often neglected. These devices are exposed

to snow and ice, and are often inadequately lighted. Fire from wall openings along the path of travel may render a fire escape useless. For these and other reasons fire escapes are regarded as particularly unsatisfactory as a means of egress.

2* A wide range of remodeling and alteration projects are continually going on. Changes in occupancy must be provided for specifically. In both instances it is preferable that exit facilities should equal those

required for a new building of the same occupancy. While the owner of a building may be put to considerable inconvenience and expense to meet retirements eiual to those for new buildings, there appears to be no reason why the occupants should not be assured the same degree of safety as occupants of buildings

erected for the specific purpose. In other words, if the owner wishes to profit from the alteration he should

not expect to do so at the expense of hazard to the tenant. It will frequently happen that the existing exit

facilities are ample for the use of the new occupancy and therefore no changes will be required. Many occupancy changes do not require physical alterations of the buildings, as, for example, changing

a dwelling into a rooming house. The increase in population may be sufficient to put the building into another occupancv class requiring more exits but when there are no alterations the matter seldom comes

to the building official's attention. Such changes are so frequent and the possible hazard so great that it should be specifically providad, as here, that no change of occupancy of any kind shall be made unless the

exits are adequate. All such cases should be referred to the building official for authority to make the

change.
Design and Construction of Building Exits 51

Section 7-2. Kinds of Exits.

Exits 25 shall consist of stairways, horizontal exits, passageways,

doorways providing direct exit to a street or to an exterior open

space leading to a street; or ramps, designed, constructed, and ar- ranged as specified in this chapter.

Section 7-3. Minimum Number of Exits.

7-3-1. Room Doorways.26 Where floor areas are divided into rooms every room occupied by

100 or more persons shall have at least 2 doorways as remote from

25 The term "exits" refers to the means of egress mandatory under recommended minimum require- ments. Means of egress provided in addition to the exit s contained in the recommended minimum require- ments are not subject to regulations of width, construction, etc. However, in order to distinguish between

such means of egress and the exits required, the latter must be so marked that their function is plainly evi- dent to any occupants. (See sec. 7-13.) Hallways, lobbies, and ordinary room doorways, except in special

cases, are not considered as exits since they serve only as a means of reaching an exit. Requirements cover- ing the width of hallways and lobbies have been included in order to maintain necessary relationships between their width and those of exits to which they are connected. No decrease in width of the means

of egress can be permitted in the direction of exit travel or "bottle necks" would be created, thus materially reducing the egress efficiency. This principle is elementary.

Fire towers or smokeproof towers have long been regarded as very desirable means of egress and believed by some to possess certain advantages not found in the ordinary enclosed stairway. Their principal characteristic is that they are reached by means of vestibules or balconies opening to the outer air, so that smoke

and fire cannot directly enter the stairway from the building itself. Some codes make their installation mandatory in buildings over a certain height. However, to give special credit to fire towers seems illogical because a certain amount of exit width must be provided in any event in order to provide egress for a given

population. In recent years many questions have been raised as to the supposed advantages of fire towers. Opinions have been advanced by competent persons to the effect that these towers, while desirable, do not possess sufficient extra advantage over the enclosed stairway to justify making their use mandatory. They might well be provided because of their immunity from smoke in cases where the extra expense involved in its construction is not a deciding factor. Where used, the details of construction for fire towers should be at least equal

to those recommended in the Building Exits Code, as approved by the American Standards Association. The term "exit passageway" has a special meaning as indicated by the definition. (See p. 46.) Ordinarily it denotes a fire-resistive corridor leading from the base of a stairway to the outside of the building.

It also includes corridors such as are frequently found in theaters and other places of assembly, which furnish a means of getting from emergency courts, so-called, to the street.

26 Eoom doorways, while not in themselves exits, except in special cases, provide means of reaching an

exit. However, there is a point at which it becomes necessary in the interests of safety to make certain re- quirements for such doorways. As a matter of convenience requirements concerning them are presented here. One of the fundamental principles of exit design is that every building, regardless of its size or the number

of occupants, should have a certain minimum number of exits, the number varying with the class cf occu- pancy. This section deals not only with the minimum number of exits in buildings of different occupancy, but also with exits from different portions of the building. In formulating the requirements the room may be taken as the starting point of travel to the street. A

minimum of 100 persons has been chosen as the limit at which 2 room doorways are required. At the rate

of travel estimated through doorways. 60 persons per minute per 22-inch unit of width, a room occupied by

100 persons could be emptied through 2 doorways in approximately 1 minute. This is a safe interval of time to be assumed in arriving at emergency requirements. Calculations for the required aggregate width

of doorways are provided in section 7-8-1 of this chapter, but section 7-3-1 is concerned only with the mini- mum number of such doorways. The expression "as remote from each other as practicable" is used several times in this report and has been inserted to give both the designer and building official some latitude in regard to the arrangement of

exits. In some codes, exits are required to be "as remote from each other as possible". The most remote arrangement of doors in a room would be in the diagonally opposite corners. In figure 1, two situations are presented in which it may not be feasible for various reasons to provide such an arrangeROR

20

POP

20

POP

too

POP

/so

POP

POP

ZO

POP

20

POP

20

POP

20

POP

20

Figure 1.

Doorways placed "as remote as practicable."
52 Miscellaneous Publications, National Bureau oj Standards

each other as practicable, at least 1 of which shall lead directly, or through a corridor or other open space, to an exit and any other doorway may lead into an adjoining room from which there is access to an exit or exits. 7-3-2. Ground-Floor Exits.27 When a floor area has direct exit to a street or to an exterior open

space leading to a street and is occupied by 100 or more persons or is ment. Both the room with a population of 100 and that with 150 are, however, considered sufficiently safe as to exit facilities. Permitting 1 of the required room doorways to lead into another room having access to an exit allows

for flexibility in design. Since the adjoining room must have access to an exit safety is not sacrificed. This

provision prohibits the designing of a succession of rooms, 1 leading into the next, with the end room only having access to an exit. A correct design for room doorways from 2 or more rooms is shown in figure 2.

ZOO IQO

V- V N

Figure 2.

Doorway location for connecting rooms occupied by 100 or more persons. " A ground-floor exit is one that is so situated that it leads from a floor or story directly to a street. In

fixing 100 persons as the limit beyond which 2 or more exits are required from these floors the same reasoning

is used as in fixing the limit for rooms. If the limit were fixed at any lower figure, many small shops with narrow frontages would be required to have 2 front entrances, as a rear entrance is often impracticable for the small shop. In view of the small population found in these shops even with an area of 3,000 square feet, the limit fixed should be safe under ordinary conditions. The expression "direct exit to a street" used in this section means that the floor area communicates

directly with the street either by a doorway, or by a short flight of steps. Throughout the chapter certain exits are required to lead directly to a street, or to an exterior open space

leading to a street. This expression is used to permit the designer to discharge the occupants into a yard

or court which in turn communicates with the street, either directly or through properly protected passage- ways, as illustrated in the sketch below. This method is considered to be satisfactory for egress purposes and permits flexibility in the design of the building. It assumes that the same principle applies here as to

all exit facilities, namely, that they shall never diminish in the direction of exit travel.

THEA TEB

passage w/?y COU&T

Figure 3.-

Discharge from a theater into a court, thence through a passageway to the street.
Design and Construction of Building Exits 53

3,000 square feet or more in area, it shall be provided with at least 2 exits. 7-3-3. Floor-Area Exits. 28 A floor area not having direct exit to a street or to an exterior open

space leading to a street shall have access to at least 2 exits; provided,

that in the following cases there shall be access to at least 1 exit: Floor areas 3,000 square feet or less in buildings of type 1, fully

protected, or type 2, protected construction, whose occupancies come

under class 3, residential, class 4, business, or class 5, garages, hangars,

barns

;

Floor areas 3,000 square feet or less in buildings of other types of construction not over 2 stories in height, whose occupancies come

under class 4, business, or class 5, garages, hangars, barns;

Floor areas 6,000 square feet or less devoted to office occupancy in

buildings of type 1, fully protected, or type 2, protected construction,

when the maximum distance to an exit does not exceed 50 feet; Floor areas 6,000 square feet or less used for manufacturing purposes in buildings of type 1, fully protected, or type 2, protected construction, when the maximum distance to an exit does not exceed

50 feet and the buildings are sprinklered throughout.

7—3—4. Exits for Institutional Occupancies.29 For occupancies coming under class 2, institutional, those portions

of a floor area which exceed 3,000 square feet occupied by bedridden

patients shall have a horizontal exit, ramp, or doorway leading directly

28 It has been an accepted principle of exit design that in general every floor area should be provided with not less than 2 exits. While the principle is undoubtedly sound, slight modifications result in econ- omy in construction without necessarily affecting the safety of the occupants. Buildings in which people

sleep or are harbored for care, or in which public assemblies are held, require better exit facilities than

buildings housing only able-bodied and alert persons and containing no sleeping quarters. This does not imply a lowering of standards for the latter group of buildings but does recognize a distinction between

the two classes. This distinction is based on the relative ability of the occupants to evacuate the buildings promptly in an emergency. The provisions of this chapter adhere to the requirement of 2 exits, except in certain cases in which it is considered safe to permit a relaxation. Low-hazard occupancies in buildings of fire-resistive construction, buildings having a slight density of population, and sprinklered factories constitute the only exceptions

that should be permitted within the occupancy groups cited. In addition, certain specified conditions must not be exceeded. As a check against these requirements, a survey of modern buildings was con- ducted in several cities to determine current practice in the design of exits. The findings of this survey

indicated that modern architectural practice favored the permitted exceptions. Floor areas of public and institutional buildings should always be provided with not less than 2 exits, regardless of the area or type of construction. Within the limitations just given, however, and where

the contents of the building are not such as to constitute a hazardous occupancy, an area of 3,000 square

feet may be taken as the general limit of safety for 1 stairway, except when the building is of fire-resistive construction and additional factors of safety in the form of sprinkler protection or short distances to exits are provided. In such cases, a limit of 6,000 square feet has been considered safe. This recognizes the tendency in modern office-building design to provide a tower section of comparatively small area. In

permitting 1 stairway in these towers under certain conditions the fire resistance of the buildings was considered, as was also the probability of the use of elevators. It has long been recognized that in very high

buildings it is a physical impossibility for most persons to descend to the street by means of stairways, and

that some dependence must be placed on the elevators. A further consideration is the possibility of re-entering at a floor beneath the fire in the case of a fire- resistive building. With the fire-resistive floors and protected openings characteristic of this type of construction such a procedure is practical. Normally, when there is but 1 stairway in a tower, this will be

used as the service stairway from floor to floor. The practice of locking doors of stairways so that a person

cannot re-enter at a lower floor impairs the usefulness of the stairway, both for service and escape purposes, and is to be condemned. The maximum of 3,000 square feet area for residential construction having 1 stairway was set some time

before intensive studies of low-rental housing had been initiated. Some of these studies point to the need

of an area approximately 10 percent greater in the case of the so-called "cross-plan" type having 4 apart- ments to a floor using a common stairway. This is required in order to meet standards of light, ventilation, minimum room area, privacy, and other factors held to be essential.

29 Buildings of institutional occupancy require special provisions for means of egress. A study of records over a period of years shows that a large loss of life has occurred in buildings of this class as a result of fires. The fire records do not state directly that the exits were a contributing cause of loss of life, but the facts point to the need for special exit facilities in these buildings. There are many records of institutional fires in which the occupants have been carried to safety by attendants and firemen, in some cases through windows, indicating that the conventional exits had been rendered impassable. The mental and physical

condition of the occupants is such that the ordinary protected exit adequate for buildings of other occu- pancy will not suffice for the institutional building. Helplesis children, bedridden and incarcerated
54 Miscellaneous Publications, National Bureau oj Standards

outside the building not less than 48 inches wide so located that no

point in such portions is more than 100 feet from such horizontal exit,

ramp, or doorway leading directly outside the building; provided that

in buildings sprinklered throughout this distance may be increased

to 150 feet. 7-3-5. Exits for Places of Assembly.30 7-3-5-1. Rooms. Every room, tier, balcony, or other space used as a place of as- sembly shall have at least two means of exit.

7-3-5-2. Buildings. Exits for buildings used as places of assembly shall be supplied as

follows:

Not less than 2 exits when 600 persons or less are accommodated in

each room, balcony, tier, or other space; not less than 3 exits when

more than 600 but not more than 1,000 persons are accommodated; and not less than 4 exits when more than 1,000 persons are accommodated.

7-3-5-3. Separation of Theater Stairways.si Exit stairways serving theaters located in buildings containing

other occupancies shall be separate and independent from the stair- ways serving other occupancies in the building.

Exit stairways serving theater balconies above the first shall be

separate from other stairways.

7-3-6. Boiler Room Exits.32 Every building, in which steam boilers, or apparatus using or producing gas or vapor, are placed below curb level, in addition to

patients, the feeble-minded, and hopelessly insane may require special exit facilities and assistance in an

emergency. The horizontal exit, while it does not always provide a direct means of exit to the exterior of the building, does permit egress to a protected portion of the building from which there is access to an exit leading to the

exterior. Both the horizontal exit and enclosed ramp are particularly applicable to the institutional build- ing housing bedridden persons because of the facility with which beds may be transferred from one section

to another. Their use in buildings housing occupants of other than normal mentality and occupants physically unfit is especially to be recommended because of the difficulty of getting such persons into stair en- closures in the first place, and the slow movement down the stairs after egress has been assured. With the spread of fire restricted by the walls of the horizontal exit, a much longer period of time can be utilized to evacuate the area on the safe side of the horizontal exit. There is a further necessary limitation of the requirements for institutional occupancies in the case of such institutions as prisons and reformatories where escape of occupants must be prevented. In view of the gravity of the problem, it seems advisable to leave the provisions for exit facilities to the designers of prisons and to the officials upon whom rests the responsibility for guarding of their charges. Some formal certifica- tion that the exits provided on the plans are sufficient in the judgment of the designer and the responsible prison official might well be made in order to make it clear upon whom the responsibility rests for this feature of the building.

so Places of assembly may be considered in two groups, one consisting of rooms used as places of assembly,

the other of buildings entirely devoted to places of assembly. As a general proposition, places of assembly

are those buildings or rooms in which people congregate for civic, political, social, or religious purposes, or

for entertainment; such as court rooms, churches and theaters. Classified by occupancy, they are a part of

class 1, public, but, due to the fact that they include a large density of population, they are generally considered to require special treatment in the matter of minimum number of exits. The internal arrangements

of theaters, such as width of aisles, spacing between seats, and other details have not been taken up as they

fall naturally into a chapter on special occupancy provisions not covered at the time this chapter was pre- pared. Details concerning them will be found in the Building Exits Code, 1934 edition, approved as American Tentative Standard by the American Standards Association.

31 A theater, by definition, is a special form of place of assembly in which there is provision for movable

scenery, or in which moving pictures are displayed. It presents hazards beyond those customarily met

in other places of assembly. The presence of scenery, and of projection booths and screens, is a special fire and smoke hazard. Performances are presented while the space is darkened, thus presenting greater

possibility of panic than in ordinary places of assembly. In order to avoid any interference with the flow of people from a theater, the theater stairways need to be independent of any other stairways in the building. It is obvious that with any arrangement of stair- ways in which the use is common to all, the uninterrupted flow of traffic is impossible, and jams are likely to occur at the intersection of the two streams of traffic. Any stoppage of the orderly discharge of a crowd,

as from a theater, is likely to develop panic conditions, regardless of how serious the fire which necessitated evacuation may be. To eliminate any such possibility, free and uninterrupted exit must be assured.

32 In the case of isolated occupancies, such as small tailor shops or hat-cleaning shops, it is assumed that a reasonable interpretation will be placed upon the requirement by the building official if in his judgment,

adequate safety of the occupants is secured.
Design and Construction oj Building Exits 55

the exit stairways shall have stairs or a stationary iron ladder leading

directly to the street from the story in which such boiler or such

apparatus is located, or some other additional exit by means of an

enclosed stairway or a horizontal exit. Section 7-4. Location of Exits.

7-4-1. Distance to Exits.33 Exits shall be so located that no point in a floor area, room or

space, served by them is more than 100 feet distant from an exit,

measured along the line of travel; provided, that in office buildings,

and in buildings sprinklered throughout, this distance shall be not more than 150 feet. 34 In the case of floor areas subdivided into apartments or small rooms, as in office buildings and hotels, the distance

shall be taken from the corridor entrance to such rooms to the

nearest exit. 7-4-2. Distribution of Exits.35 Where a floor is required to have 2 exits, they shall be placed as remote from each other as practicable.

33 The requirement fixing the maximum distance which must be traveled to reach an exit is the chief

factor controlling the location of exits. It is not sufficient to require a certain minimum number of exits; the building regulations must go further and limit the distance traveled to reach an exit in order to locate them within the immediate reach of the occupants, and thus prevent any serious delay in reaching the

exit.In some codes this distance depends upon the occupancy; in others, the type of construction controls. The distance of 100 feet has been selected as a practical compromise between the two methods and as repre- senting a reasonal maximum which might be imposed. Special occupancies possessing unusual hazards

will, of course, require shorter distances but these distances may well be left to the judgment of the building

official. A hazard classification useful for reference is contained in the Building Exits Code approved by the American Standards Association.

Office buildings, because of the character of the occupancy, the low-hazard contents of the building, and

the customary subdivision of the floor areas, are permitted an increase in this distance up to 150 feet. Sprinklered buildings also have been permitted an increase on the assumption that fires in such buildings

will be checked promptly before assuming sufficient proportions to cut off the line of retreat. In the case of undivided floor areas, the distance to the exit is measured in a straight line. In other cases, the distance is measured along the normal path of travel, such as corridors or hallways, from the room

entrance to the nearest exit.

3^ For exceptions to this requirement, see section 7-3-3.

35 Proper distribution of exits is very important. Elsewhere maximum distances from a given point on

the floor are given, but this does not prevent concentrating all stairways near a given point with the result that all might be cut off by a single fire. So vital is this requirement that some experienced officials advocate

V - -i

><:x K

7

7

! Figure 4.

Distribution of stairways in a building where services are in a central core.
56 Miscellaneous Publications, National Bureau oj Standards

Where more than 2 exits are required, they shall be distributed as uniformly as practicable within or around the floor area, room or space they are to serve.

7-4-3. Outlets from Exits.36 An exit stairway shall lead either directly or through an exit passageway to a street or to an exterior open space leading to a street, except as follows:

# In buildings of type 1, fully protected, or type 2, protected construction, devoted to office, or class 3, residential occupancy, such stairway

may terminate in a hallway or lobby; provided that when there are

stores, restaurants, or other business occupancies within or opening

a definite method of separating exits by expressing a minimum distance as a percentage of the longest wall

of the building. This method has certain disadvantages, since it prohibits installations as shown in figure 4. Such layouts would seem to be reasonably safe, although the exits are not as remote from each other as

possible, nor in compliance with the percentage of wall-length rule. Having in mind that no 2 buildings

are alike, it was deemed best in the interests of practical design to word the requirement as given. Where

2 exits only are required, it is assumed that they will be so placed as to make them accessible to all the oc- cupants of the floor without subjecting both the exits to the possibility of being cut off by fire.

36 The theory of exit design contemplates a safe, unobstructed path of travel of undiminished width from

the starting point to the street. For the last portion of this travel, the path from the foot of the stairway to the street, an ideal arrangement would consist of all stairways discharging either directly into the street or through a protected passageway leading directly to the street, the latter device being considered the best substitute for direct discharge to the street. Practical considerations, however, suggest modifications of

this arrangement in certain occupancies. The economic requirements of use of modern buildings are such that lobbies with plate-glass windows

opening into ground-floor spaces are a desirable feature for certain occupancies, and it has been deemed

impractical to require such lobbies to be completely closed off. The survey of current practice in construction made in connection with the preparation of these requirements revealed that large numbers of buildings

are being built with stairways terminating in lobbies having windows and doors opening upon the first- floor area. Office buildings and hotels are representative of this type of arrangement. Apartment buildings having apartments, restaurants, and shops opening into ground-floor corridors and lobbies are also found so frequently as to constitute the rule rather than the exception. This current practice has been recogrized

in permitting exceptions for office and residential buildings, but it has been safeguarded by requiring

sprinkler protection for commercial occupancies opening on such corridors and lobbies. It was believed that

this protection would compensate for the safety lost by the departure from the ideal requirement of a pro- tected passageway. Inasmuch as plate glass soon shatters under heat, the expression "opening upon" a corridor should be construed to include occupancies having windows but not necessarily doors in the cor- ridor walls. A further desirable protection in some locations where plate-glass windows open upon public lobbies

consists of metal or fire-resistive shutters to cover the glass area. These shutters operate automatically by some form of sensitive releasing device. In the building of institutional occupancy at least one avenue of safety leading directly to the street should be provided. The remaining stairways may be permitted to discharge into hallways or lobbies leading to the street, and extra protection for these hallways may be omitted in order to permit their utilization as service corridors for those rooms which open thereon. In the case of department stores permission to allow one-half the stairways from the upper floors to dis- charge directly into the first-floor area recognizes a special situation. In these buildings such a method

appears to be customary procedure and comparatively unobjectionable in case the building is of fire-resistive construction and completely sprinklered. Here again, direct discharge to the street is regarded as pref- erable, but not always practicable. When one-half of the population of the upper floors find their way

out from the first-floor area the aggregate width of doorways must take into account the width of the stair- ways from the upper floors in order to prevent a jam at the doorways.

Places of assembly, due to the fact that the entire population is visible at one time, are particularly exposed

to the possibility of panic conditions. It is, therefore, extremely desirable that a rapid discharge of the oc- cupants be effected without any delays or interruptions. For this reason a limit is necessary for the distance

of upward travel which will avoid any waiting in line to secure entrance to stairways or ramps. Appreciating that the nonfire-resistive building offers more opportunity for spread of fire than the fire-resistive building, the distance of upward travel permitted in the nonfire-resistive building has been restricted. To insure egress to the street from areas below grade, at least 1 stairway is required to lead up directly

to the street or to a passageway leading to a street. This provision has particular reference to densely oc- cupied areas, such as department-store basements, or basement workshops, but the principle is applicable

to all areas below grade. As an emergency line of retreat in the event that stairways are cut off below, provision has been made for a single stairway leading to the roof. Provision for 2 stairways by means of which persons can cross over by way of the roof and descend by a stairway not cut off was considered but has not been required. There are various theories exemplified in present code requirements on the role played by stairways lead- ing to the roof. Some codes require all stairways serving the upper stories to continue on through; others require 2 to go through on the theory that a person can escape up by 1, cross over the roof, and then descend through the other. Other provisions recognize the use of a passageway from 1 stairway to another in the topmost story as a substitute for crossing over by way of the roof. With present-day architecture involving numerous set-backs on high buildings, the value of stairways leading to the roof in these buildings is problematical. There seems to be a need for rationalizing the treatment of this subject. In the case of buildings

of moderate height and with flat roofs there is a chance that a person who finds his downward path blocked may turn to the roof, and he may either escape by the roof of an adjoining building of similar height, or be taken down ladders by the fire department. Accordingly, the requirement has been made that at least 1 stairway shall continue through the roof in the case of structures whose height is limited because of the nature of their construction. The exits survey showed that stair doors leading to roofs are frequently kept

locked, and served to emphasize that such means of escape are dependable only as a last resort and are not

to be considered in any way as a substitute for properly constructed stairways leading to the street.
Design and Construction of Building Exits 57

upon the hallway or lobby, such occupancies shall be provided with an approved sprinkler system; 37 in buildings whose occupancy comes

under class 2, institutional, at least 1 exit stairway shall discharge

directly or through an exit passageway to the street or to an exterior

open space leading to a street and the remaining stairways may dis- charge into a hallway or lobby; in buildings of type 1, fully protected,

or type 2, protected construction, occupied as stores and sprinklered

throughout not more than one-half of the exit stairways from upper

floors may discharge into the ground-floor area; provided, that unobstructed aisles at least as wide as the stairways are maintained

from such stairways to the exit doorways.

In places of assembly no required exit shall discharge by means of upward travel through a vertical distance of more than 15 feet in

buildings of type 1, fully protected, or type 2, protected construction nor by more than 6 feet in buildings of other types of construction;

provided, that in places of assembly occupied by not more than 150

persons such vertical distance shall not be limited.

Where there are 2 or more exit stairways serving floor areas below

grade at least 1 shall lead up directly to the street, or to an exterior

open space or exit passageway leading to a street. In buildings of other than type 1, fully protected, or type 2, protected construction, more than two stories high above grade with

roofs having a pitch of 1 foot in 4 feet or less, at least 1 exit stairway

shall continue through the roof. Section 7-5. Relation of Population to Exits.

7-5-1. Determination of Population.

The number of persons used in determining the necessary exit

facilities on any given floor shall be the actual number 38 to occupy

the floor but in no case less than that determined by dividing the

following areas per person into the gross area 39 within the perimeter

of the building serving each particular occupancy at the given floor

level; for occupancies not specified the building official shall, by rule,

establish the ratio to be used:

37 Provision might well be made to allow the building official to make exemptions in the case of minor

occupancies not of great fire hazard.

38 In many instances floor areas are designed to accommodate a fixed number of persons and that number is customarily stated in the application for the permit. It is the intent of this section to make use of the actual number of persons contemplated by the design when it is known, or perhaps is fixed by other regulations such as labor laws. In case no actual number is stated, or known, the number of persons is, of course, determined on the basis of the areas given in this section. However, a minimum is also provided for regardless of what the design may contemplate in order to insure safety.

39 It should be noted particularly that gross rather than net areas are to be used in determining the population in case it is not known. The dimensions of exits as determined in subsequent sections of the report are proportioned to the number

of occupants to be accommodated. The determination of the number of occupants on any floor becomes

then of first importance in designing exits. There are numerous methods used in codes for making these

calculations and very little agreement as to the assumptions. A method of determination involving least laborious calculation, but which gives results believed to be in reasonable accord with actual conditions is the most useful. Areas based on counts of occupants of buildings of different occupancy should be used by

the building official to determine the population. Some years ago Rudolph P. Miller, as superintendent of buildings of Manhattan, prepared a tabulation showing the density of population in workshops in the city of New York. The tabulation resulted from

population counts in connection with "exit orders" in 500 workshops and factories. The occupants of each story of the buildings investigated were determined as accurately as possible and the area occupied per

person computed from the gross area of the story. As might be expected the tabulation revealed a wide

variation in areas per person ranging from 19 to 560 square feet. This variation is accounted for by the differ- ent kinds of industries represented in the tabulation. The average for the entire group of buildings in the table was 107 square feet per person, which corresponds very closely with the average figure of 100 square feet per person adopted by the committee for this occupancy. A census of the Equitable Building in New York City, taken in 1924, was made available to the committee

through the courtesy of C. T. Coley, operating manager of that building. Here, again, there was a considerable variation, ranging from 43 square feet to 2fi0 square feet per person, but the average was 107. The figures given are based on the net rentable area. When converted into terms of gross area they may

range from 10 to 25 percent higher. On the other hand, they are based on the persons regularly employed
58 Miscellaneous Publications, National Bureau oj Standards

Areas per person Occupancy: (square feet) Dance hall, lodge room, and places of assembly 15

Store:Street floor and sales basement 30

Other floors 60

School, courtroom, and other similar public; restaurant 40

Office, factory, and workroom 100 Hotel and apartment 125

Institutional 150 Warehouse, storage, and garage 300

In places of assembly, theaters, dance halls, lodge rooms, and

similar occupancies when seating arrangements are used or con- templated, the seating capacity shall be established by allowing

6 square feet per person in that portion occupied by the audience.

The population of basements or portions of basements or of mezzanine floors shall be determined according to the occupancy.

The population of a mezzanine floor discharging through a floor below shall be added to the population of such floor. 7-5-2. Population Limited.40 It shall be unlawful to occupy any part of a building by a greater

number of persons than that for which exits have been provided in

accordance with this chapter.

in the building and do not take into account visitors, customers, or other transients. This increase in population is probably sufficient to bring the gross areas per person very closely in line with the committee's recommended figure of 100 square feet for office buildings. The table of areas per person applies also to mixed occupancies provided the adjacent corridor areas, shafts, and service spaces are distributed to the several occupancies in proper proportions to obtain the

gross area devoted to any one occupancy. For example, in figure 5 with 2 occupancies on a given

floor of 12,000 square feet area, the area devoted exclusively to the 2 occupancies being 4,000 and 6,000 square

feet, the proportion of the remaining 2,000 square feet of space utilized by^orridors, elevator shafts, and

service rooms, allocated to each occupancy will be 4,000/10,000 and 0,000/10,000, or 800 square feet and 1,200 square feet, respectively. XXx KITCHEN

DANCE FLOO&

6OO0SQ FT

\

RESTAURANT

tOOOSQ FT

TOTAL fl&Eti = /2t OOOSQ FT

Figuee 5.-Example for computation oj amount of service area allotted to mixed

occupancies.

If the general occupancy contains a minor occupancy, as, for example, a kitchen in a restaurant, the area contained in the minor occupancy is to be added to the general occupancy and the population determined by dividing the total area by the area per person for the general occupancy.

*o When the exit facilities for a building have once been designed, the number of occupants of that building must be limited to the exit facilities provided. The requirements are thus definitely connected to administrative sections and insure that penalty provisions in the administrative chapter of the code will apply.
Design and Construction oj Building Exits 59

Section 7-6. Stairways.

7-6-1. Width.

7-6-1-1. Minimum Width." The minimum unobstructed width of every exit stairway, except

for handrails projecting inward not more than 3% inches on each side, shall be not less than 2 units of 22 inches each; provided, that in in- stitutional occupancies, exit stairways serving bedridden patients, shall be not less than 48 inches in width; and provided, further, that in

buildings whose occupancy comes under class 4, business, or class 5, garages, hangars, barns, and which are occupied by a single tenant 42 and limited in occupancy to 50 persons, and in case of exit stairways

leading to roofs other than roof gardens and similar occupancies, such

width shall be at least 36 inches.

7-6-1-2. Aggregate Widths

Exit stairways shall be supplied in accordance with the following

requirements, using the limitations and assumptions 44 given in this

chapter.

41 In the opinion of many who have studied the matter, 22 inches can be taken as the width of a file of people in motion. Its origin is said to be in experience gained in the Army. A stairway width of 44 inches will permit 2 files of people to move freely down the stairs at the same time. In occupancies where

fire drills are common, the 44-inch width permits the orderly movement of 2 files where individuals walk

side by side. This width is measured between walls, or from wail to center line of hand rail or balustrade,

in case 1 side of the stairway is open. It is the intention of this section to prohibit any building construction such as beams, columns, chimneys, etc., from encroaching on this space and reducing the required width. For wide stairways, the rounding or splaying of corners on landings is considered advantageous in elimi- ating points at which obstruction might occur to the forward movement of traffic.

42 This provision permits small stores, manufacturing and storage buildings, and office buildings occu- pied by 1 tenant as, for example, a real-estate company's building, to have 36-inch stairs. This width is believed sufficient for the number of occupants allowed and permits some economy in construction. Where

roofs are occupied as restaurants or used for recreation, etc., the stairways are required to be at least 44

inches, but where they are not used for such purposes 36 inches is permitted.

43 The minimum number of stairways must be provided to meet previous requirements and these stair- ways must be so distributed that the distance traveled to reach a stairway does not exceed the limits otherwise fixed. The total aggregate width is then computed by the method described in section 7-6-1-2, and if additional width is required the designer is given the option of providing extra stairways or of in- creasing the width of those required to fulfill the other two conditions. Experienced designers have stated

that the number of stairways in the majority of buildings is governed by the minimum number and maximum distance to an exit. This is probably true in buildings having a slight density of population, such as the average office building. The requirements for aggregate width take into account the advantages and disadvantages of the various methods in use. The type of construction of the building does not affect the aggregate width of stairways. The class of occupancy does, however, control the aggregate width of stairways as indicated by the divi- sion factors as given on page 60. Buildings in which people sleep or are housed for care or medical treat- ment are provided with greater stairway width for a given population per floor than buildings housing

alert, active persons. In arriving at the division factors, the traffic studies provided valuable information. These counts were made for various occupancies and were obtained under sufficiently varying conditions to give a general

average. The studies took into account not only the rate of movement on stairs but also the capacity of

stairs of different width. This enabled the committee to determine whether any advantage in either flow

or capacity was gained by using wide stairs in preference to narrower ones. In buildings in which people sleep or are housed for care of any sort, it is desirable that the stairs be made

large enough to provide a place of refuge for the population if the need arises. On the other hand, the office building or store, containing a population necessarily alert and able-bodied, need not use its stairs as a place of refuge, since it is unusual for a fire to gain much headway before being discovered and the occu- pants given an opportunity to escape. The typical 44-inch stair having return landings will accommodate 64 persons in a 10-foot story height assuming 2 persons for each tread and 1 person for each 1H square feet of platforms and landings. This is absolute capacity and will permit little if any movement. As a practical matter, however, it is unlikely

that the stairway will ever be called upon to accommodate its full capacity, since some of the occupants

of the lower stories are certain to escape during the first few minutes of the alarm, and thus provide more

room for the remaining population. At the rate of flow found in stairways in which people are moving

without interference with one another, 45 persons can be discharged per minute for each 22 inches cf stairway width. A few typical examples of the computation for aggregate width of exits are given in the ensuing paragraphs. Given an office building 21 stories in height and 36,000 square feet in area for the first 12 stories in its height and 24,000 square feet in area for the remaining 9 stories. The population per floor, unless known, will be assumed at 36,000/100=360 persons on a typical floor within the first 12 stories. By this section 360/60 will

result in six 22-inch units of exit stairway for the floors up to and including the 12th where the set-back

occurs for this particular case. At the 13th floor which is 24,000 square feet in area the population would be

24,000/100 = 240. Then 240/60=four 22-inch units of exit stairway required for that floor and those above.

It should be noted, of course, that concentration of population on an intermediate floor may change the

aggregate width of exit stairways for that floor and, inasmuch as exit width cannot diminish in the direction

of exit travel, this would fix the width of the exit stair ways from that floor downward to eventual discharge

.

Given a hotel building 16 stories in height and 15,000 square feet in area. An auditorium of 1,500 square

feet i located on the 5th floor. The population on the typical floors will be 15,000/125, or 120 per floor.
60 Miscellaneous Publications, National Bureau of Standards

The aggregate number of units of width necessary for exit stair- ways shall be determined for each floor of a building by dividing

the population of each occupancy on that floor by 30 in the case of

occupancies coming under class 2, institutional, and class 3, residential, and by 60 in the case of other occupancies, except as otherwise

specifically provided for in this section.

Exit stairways in places of assembly having the main entrance at the street level and not communicating with any other occupancy

in the same building shall be determined on the basis of 100 persons

per unit of exit width.

In determining the aggregate width of exit stairways in any building, if the result contains a fraction, 12 inches of width shall be added

for a fraction of one-half or less and 1 unit of width for a fraction

greater than one-half.

If the required total number of units of exit width is greater than

the total number of units of exit width for the minimum number of

exit stairways of the minimum permissible width, the additional

width 45 shall be provided by additional stairways or by increasing

the width of the minimum number of exit stairways.

7-6-1-3. Changes in Stairway Width. The width of exit stairways shall not decrease in the direction of

exit travel.

7-6-1-4. Exit Stairways Serving Floor Areas Below Graded

The aggregate width of exit stairways serving areas below grade

shall be at least equal to that required for such stairways serving similar occupancies above grade in accordance with the provisions of this chapter.

Under section 7-0-1-2, 120/30= four 22-inch units, or two 44-inch stairways will be required. At the 5th

floor, two 44-inch stairways will be required for the normal population of this floor. The portion of the auditorium occupied by the audience is 1,300 square feet. This will accommodate 1,300/6 or 217 persons. To accommodate this number of occupants 217/60 or four 22-inch additional units of exit width must be provided from the 5th floor down.

In a theater having a population of 1,000 persons in the balcony, the provisions of section 7-6-1-2 would

include it as a place of assembly having the main entrance at the street level and the aggregate stairway width would then be computed at the rate of 100 persons per unit of exit width, that is, 1,000/100=10 units

of stairway width would be required. If conditions of maximum distance to an exit were satisfied, two

66-inch stairways and two 44-inch stairways or any other grouping using the 10 aggregate units of width would fulfill the condition. The exit doorways for the orchestra population would be computed according

to the provisions of section 7-8-1. Given a school building 3 stories high and 14,400 square feet in area. The population per floor will be

14,400/40 or 360 persons. 380/60, or six 22-inch units of stairway width will be required. These may be

supplied as three 44-inch or two 66-inch stairways, depending on the distance to the exits. Given a 3-story factory, 80,000 square feet in area. 60,000/100=600 persons per floor. 600/60=ten 22-inch units of stairway required which could be satisfied by 4 stairways, 2 containing 2 units each and 2 containing

3 units each. Given an 8-story department store 30,000 square feet in area. The upper floor population would be

30,000/60 or 500 per floor. 500/60=9 units of stairway width would then be required. The sales basement

population would be 30,000/30= 1,000 persons. 1,000/60= 17 units of stairway width would then be required, from the sales basement. To illustrate the effect of the requirements in the case of different occupancies and to compare these requirements with current practice as found in the field survey, figures 6 to 15 on pages 61-64 have been pre- pared. The solid line representing requirements starts at the minimum set by section 7-3-3. Points

indicated on figures 8 to 15 represent actual conditions found in buildings during the survey.

44 Concerning minimum number of exits, see section 7-3; locations of exits, see section 7-4; relation of population to exits, see section 7-5.

45 After conditions of minimum number of stairways and minimum width of stairways are satisfied, the

designer may distribute the computed width exceeding the minimum in any way he sees fit as long as the maximum distance to an exit is not exceeded. For example, if 2 stairways of 2 units each would satisfy the

conditions of minimum number of stairways and maximum distance to an exit, but the computations re- quired 6 units of width, an additional stairway could be provided, or 1 unit could be added to each of the

stairways.

46 Some codes require stairways from areas below grade to be increased in width over those required from

areas above grade by amounts ranging from 50 to 100 percent. The particular application is to stores, but under this code the aggregate width of stairs from store basements is already twice that of stairs from upper

stories due to the assumed areas per person. Considered in this light, no further increase is necessary but basement stairs should be required to be at least equal to the width of stairs from upper stories. Studies,

of movement show that for short distances the rate of flow up stairways approximates that downward.

62 Miscellaneous Publications, National Bureau of Standards

<? 100. o

•oo o sspao iqooo /sooo eapoo zspco &yx>o 35.000 <qoaa 45,000 sopoo sspoo &opoo (jooo 70000 ispoo FLOO& tf&EA lli SQUfi&E F££T Figure 8.

Results of exits survey compared with curve adopted for office buildings.

o

o

o o

o

o o Jfioo topoo 15,000 zopoo zspoo 30,000 33,000 FLOOfZ /ri SQUfi&E FEET Figure 9.-

Results of exits survey compared with curve adopted for stores.

perp ?nson 60pe oer vi

1—

o"" —0—

jooo icpoo i«ooo 20,000 is/too 30,000 34000 FLOO& rtMErt //V SQO/1SE FEET Figure 10.

Results of exits survey compared with curve adopted for factories.
Design and Construction of Building Exits 63-

o c oo —

"

o

o c 3—a -crc

28."

.5,000 (0.000 15,000 ZS.OOO ZS.OQO 30,000 35,000 FLOOR IN SQUfiZE FEET

Figure 12.Results of exits survey compared with curve adopted for apartments..

IO.OOO J5,OQO ZO.OOO ZS.OOO FLOOR /9&E# IN SOU/T/SE FEET Figure 13.

Results of exits survey compared with curve adopted for hotels and'

dormitories.
64 Miscellaneous Publications, National Bureau of Standards

7-6-2. Construction.

7-6-2-1. Materials.*? Stairs and landings of exit stairways shall be constructed of incombustible materials; provided, that combustible materials may be used

for stairs and landings of interior exit stairways in buildings of type 3, heavy-timber construction not over 4 stories in height, in buildings of

type 4, masonry-wall and joist construction, and of interior and exterior exit stairways for buildings of type 5, wood-frame construction.

Exit stairways shall have solid treads.

o — O/SO on30jc perun oo °00 o o

5.000 IS.000 20.000 25,000 30,000 FLOOR ftREfl IN SQUfi&E FEET

3S.OOQ Figure 14.

Results of exits survey compared with curve adopted for hospitals and

institutions.

IOO ZOO 300 AGO SOO COO 700 800 900 IOGO II OO IZOO 1300 1400 1500 POPULATION PER, PCOOfS Figure 15.

Results of exits survey compared with curve adopted for places of assembly.

47 In view of the fact that stairways are required to be enclosed in partitions of incombustible materials, it was considered consistent to keep the materials of the stairways themselves in harmony with the rest of the

building. There is a point, based on judgment, where combustible materials should be allowed, and a natural point is that of the height of type 4, masonry-wall and joist construction. Accordingly, combustible

materials were allowed for stairs and landings of interior exit stairways in buildings of type 3, heavy-timber

construction, not over 4 stories in height, in buildings of type 4, masonry-wall and joist construction, and of

interior and exterior exit stairways in buildings of type 5, wood-frame construction. It should be remembered that interior exit stairways are required to be enclosed in fire-resistive partitions as provided in section

7-6-3-1. Handrails are not required to be of fire-resistive material.
Design and Construction of Building Exits 65

7-6-2-2. Treads and Risers.* 3 Treads and risers of stairs in exit stairways shall be so proportioned

that the sum of the height of 2 risers, in inches, and the width of 1 tread, in inches, is not less than 24 nor more than 25; that no riser shall be greater than 7% inches in height and no tread less than 9 inches in width, exclusive of nosing. Treads shall be not less than

12 inches in width where flights of less than 3 risers are permitted.

Treads less than 10 inches wide 49 shall have nosings. Treads shall be of uniform width and risers of uniform height in any 1 flight.

Winders shall not be used in exit stairways.

7-6-2-3. Required Landings.' No flight of stairs shall have a vertical rise of more than 12 feet between floors or landings; provided, that in exit stairways in buildings whose occupancy comes under class 1, public, such vertical rise shall not exceed 8 feet. The length and width of landings shall be not less than the width

of exit stairways in which they occur; provided, in straight runs the

minimum distance between risers on landings and platforms shall not

be required to be more than 44 inches.

7-6-2-4. Changes in Floor Levels In buildings whose occupancy comes under class 1, public, flights

of less than 3 risers shall not be used at entrances or elsewhere in connection with required exits. To overcome lesser differences in level,

gradients not exceeding 1 foot in 10 feet shall be used.

7-6-2-5. Handrails.** Exit stairways shall have enclosing walls or well-secured balustrades

or guards on both sides; when less than 44 inches in width they shall

have handrails on at least 1 side; when 44 inches or more in width,

they shall have handrails on both sides.

48 Of the several rules in use for proportioning treads and risers, the one given in this section seems to give

results more nearly in agreement with current practice. The matter of the slope of stairs seems to be a very- important point, affecting as it does, the comfort and safety of the use of the stairs. A high riser and narrowtread make a steep stair which may become very hazardous under fire conditions. On the other hand, a very low riser and wide tread make travel slow and may render the stair as unsafe as risers and treads of the

other extreme. The possibility of the risers being made too high or too low has been overcome by fixing a maximum for the riser height and a minimum for the tread width. Some recent studies have been made on the relation of tread width to riser height and other features affect ing the use of stairways. Curves plotted for the three well-known rules for proportioning treads and risers

of stairways and one or two suggested curves indicate that in the range of riser heights ordinarily found in buildings the tread widths vary only slightly. However, further study of this phase of stairway design appears advisable. For further discussion of the subject, consult articles in the November and December 1933

issues of Architecture entitled "Rake, Riser, and Tread"; and "More Anent the Stair Rule", and "More

Anent Stairway Design", in the January and February 1931 issues of Pencil Points. Stairways which wind as they descend thus causing a dilference in width between their inner and outer ends are also hazardous, because there is no uniform width of tread in any one step. As a consequence the

user must feel his way carefully and the usual rate of descent is slowed up. There is also an ever-present

possibility of tripping because of the varying footing. Winders are frequently graceful in appearance and

it is often desirable to make use of them from an artistic standpoint, particularly in dwellings and monumental buildings. The requirement given does not prohibit their use on monumental stairs, but does

exclude their use in exit stairways. « The measurement of tread width under this requirement means the run as measured horizontally from

the face of 1 riser to the face of the next. m An unbroken length of stairway extending for some distance creates an effect of steepness that is dis- concerting to many people and offers no relief from the fatigue imposed in descending. By breaking up the

length of travel through the use of landings, a desirable effect is produced both as regards the appearance of steepness and in providing welcome change from steady descent. The provisions of this section are intended

to accomplish these purposes. The vertical height permitted between landings has been decreased in the

case of public buildings because of a greater number of people to be accommodated and the greater possibilities of panic in public gatherings.

s 1 Short flights of stairs are particularly objectionable and flights of less than 3 risers should not be per- mitted in public buildings. When the exits are crowded, the stairs are not readily visible and tripping or stumbling is likely to occur. Ramps are much more suitable for such buildings provided the gradient is kept low enough for safe travel.

52 Handrails are essential in stairways to provide support for persons descending and it is desirable that each file of persons should have its own support.

Rails also serve as guides to indicate changes from flight to landing, change of direction, and proportion

of rise to tread in locations where visibility is poor, or where attention has been diverted to other than

travel on the stair.
66 Miscellaneous Publications, National Bureau of Standards

When the width of an exit stairway is 88 inches or more there shall

be an intermediate handrail continuous between landings; provided,

that the number and positions of intermediate handrails shall be such

that there shall be not more than 66 inches between adjacent handrails; and provided further, that in schools, there shall be an intermediate handrail when the width of the exit stairway exceeds 66. inches.

7-6-3. Enclosures.

7-6-3-1. Construction." Exit stairways in buildings whose occupancies come under class 1„

public, class 2, institutional, class 4, business, or class 5, garages,, hangars, barns, shall be enclosed with walls or partitions having an

ultimate fire resistance of at least 2 hours, and in buildings whose

occupancies come under class 3, residential, shall be enclosed with

walls or partitions having an ultimate fire resistance of at least 1 hour; provided, that portions of the enclosure outside the walls of the- building shall have an ultimate fire resistance of at least 1 hour. On

buildings not over 45 feet in height the building official may waive the

requirement for enclosure of portions of such stairway outside of the

building walls if all openings in the building walls below or within 10

feet horizontally of such stairways are protected by approved fire doors or stationary fire windows.

Whenever an exit stairway is so constructed that the severaL

flights are not directly above one another, the necessary connecting

hallways shall be enclosed in partitions, floors, and ceilings of the same ultimate fire resistance as required for the type of construction

of the building in which they occur but not less than 1 hour in anycase, and openings into such hallways shall be provided with approved,

fire doors.

7-6-3-2. Openings. 54 No openings except the necessary doorways, and windows opening;

to the exterior of the building, shall be permitted in exit-stairway

enclosures. Doorways opening into exit stairways shall be equipped,

with approved self-closing fire doors; provided, that in schools and

institutional buildings approved automatic fire doors so arranged thai

they can be readily closed may be permitted in lieu of self-closing

63 The enclosure of the stairway serves several purposes. It provides a safe line of travel by means of" which the occupants may proceed protected from the flames; it serves as a barrier to upward spread of

flames; it prevents smoke from rising to floors above and obstructing egress; and it affords firemen access- to the building for rescue of the occupants or for fighting the fire. In order that these four objectives, may be accomplished it is essential that the partitions forming the enclosures have a substantial degree of

fire resistance. One hour fire resistance has been fixed as the minimum. Unless the occupants are re- moved within that period, the possibility of their eventual removal, if necessary, is extremely remote.. The requirements of fire resistance of enclosures varies also with the class of occupancy, being somewhat; more severe in those buildings in which large crowds assemble or in which the combustible content is high. Any opening in a stairway enclosure is admittedly a point of weakness which decreases its efficiency. Good strategy requires that such points of weakness in a defense erected against fire should be made a&

few, as small, and as well protected as practicable. This is the intent of the requirements of this section.

Self-closing fire doors are required as a general rule in all doorways of stair enclosures except for those doors which open directly to the exterior or into a protected passageway. In schools and institutional buildings in which the stairways are used extensively as service stairways, automatic fire doors are per- mitted in order that these doors may stand open to permit traffic to pass easily. However, as a safety pro- vision it is required that these doors be arranged so that they may be easily closed in an emergency. It is. contemplated that fusible links and weights or checks controlled by a fusible link will be employed to, close these doors in the event of fire. Anticipating that these devices may fail to function, it is further required that evidence be submitted to the building official that other suitable means are provided to close the doors. For example, smoke may rise from a fire and penetrate the stairway to such an extent that the- stairway becomes impassable and yet sufficient heat may not be generated to melt the fusible link and

automatically close the door. Therefore, certain persons must be designated as a part of the fire drills of" the buildings to insure these doors being closed, manually, if necessary, and evidence must be furnished; the building official that such means are maintained and not simply designated.
Design and Construction of Building Exits 67

fire doors when satisfactory evidence is furnished the building official that adequate devices are installed and maintained for closing such

doors in case of fire; and provided, further, that in buildings not over

three stories in height whose occupancy comes under class 3, residential, approved self-closing wood-slab doors of a minimum thickness of

1% inches may be permitted.

7-6-4. Moving Stairs.55 Moving stairs which operate normally in the direction of exit travel

may be given credit as exit stairways provided they conform to all requirements of this chapter that are applicable.

Section 7-7. Ramps.56 Ramps serving as exits shall not exceed in slope 1 foot in 10 feet. Ramps may be substituted for exit stairways. Ramps serving as

exits shall comply with all the requirements for exit stairways that

are applicable. When a doorway opens into a ramp the floor of the

ramp shall comply with the requirements for inclined exit passageways given in this chapter.

Ramps shall be provided with an approved nonslip surface.

Section 7-8. Doorways.

7-8-1. Width.57 No exit doorway shall have a width of less than 36 inches; provided,

that in institutional occupancies doorways serving as exits for bedridden patients shall be not less than 48 inches in width.

The aggregate width of exit doorways on any floor serving more

than 100 persons shall be not less than at the rate of 22 inches for each

100 persons on that floor. « The increasing use of moving stairs in department stores and even in office buildings requires some

recognition of these devices as means of egress. They are, however, required to conform to all of the provisions of this chapter that apply to width, enclosure, and hand rails, if they are to receive credit as required

stairs. Obviously the requirement for landings between stories of more than a given height as contained

in section 7-6-2-3 does not apply. All moving stairs for which credit is given as constituting required means of egress should be of the horizontal tread type. The cleat type is not recognized as a required means

of egress.

{6 Ramps are recognized as equal in all respects to a stairway as a means of egress when meeting the re- quirements of stairways pertaining to width and enclosure. For certain occupancies, such as schools and

institutions, they are believed to be more satisfactory and their use in these buildings is recommended. The slope of the ramp and the character of the walkway surface are important points in the construction which should be checked carefully by the building official. As will be evident from a consideration of figures on page 37, ramps have a rate of discharge between that of stairways and level passageways. While

this is an added recommendation in their favor as compared with stairways, it has been considered unwise

further to complicate the requirements by giving them a special rating. Extensive studies summarized on page 38, were made on rates of flow through doorways with the object

of determining an average rate which could be used in calculating the required width of doorways. The

studies were made under sufficiently varying conditions and included enough different classes of occupancy

to give results which represented a fair average. Consistent with the requirements for stairway width, the aggregate width of doorways has been expressed

in terms of units of 22 inches. This is regarded as a proper basis of computation since it permits one file of persons for each unit of width. Although the studies of flow through doorways revealed that travel was

seldom, if ever, in files, yet in buildings in which fire drills are maintained it is essential that the width

of doorways be made to accommodate such methods of egress, and in other buildings it serves as a factor of

safety. In speaking of width of doorways, the clear width between jambs is intended. In other words, when a doorway containing 2 doors has 2 separate openings each would be measured separately while if these doors merely meet at the center without the intervention of a mullion the opening would be measured as a whole. The conclusion from the studies made by other agencies and confirmed by the committee's studies was

that rate of travel through doorways with doors fastened open could be maintained at the rate of 60 persons

per minute per 22-inch width. This rate was found to be constant up to a width of about 6 feet, beyond

which the rate diminished as the doorway became wider, indicating that 6 feet is about the maximum

efficient width. Beyond this width it would seem more desirable to introduce additional doors. Exit-doorway widths for ground-floor areas into which no population from upper floors is discharged are readily computed. However, when a portion or all of the upper-floor population must find its way out from the bottom of a stairway through aisles in the floor area as in department stores, or through lobbies, hallways, or passageways as in office buildings, allowance must be made for this condition. In sketch 1, figure 16, since none of the population of the upper floors passes through the ground-floor

area, the exit-doorway width for the ground-floor area is figured simply at the rate of 100 persons per 22 inches
68 Miscellaneous Publications, National Bureau of Standards

Credit of 50 percent of a unit shall be allowed for 12 inches or more

of width added to 1 or more full 22-inch units of doorway width.

The aggregate width of exit doorways to the outside of a building

from aisles, lobbies, hallways, or passageways in which a single exit

stairway discharges shall be at least equal to the width of the exit

stairway. If there is more than one such exit stairway, the exit doorways to the outside shall be at least equal in aggregate width to three-fourths the combined width of the exit stairways. The aggregate width of the exit doorways shall be further increased at the rate

of 22 inches per 100 persons for any additional persons on the floor served by such exit doorways.

of exit-doorway width. This would result in a total required width of 2 units or 44 inches in the ease shown. However, because the minimum number of doorways required by section 7-3-2 would be 2 and because

each doorway must be at least 36 inches wide, two 36-inch doorways must be provided. In sketch 2, figure 16, 1 stairway discharges into a passageway at the ground-floor level and the persons coming down the stairway must find their way out through this passageway to the street. The width of the doorway leading from this passageway must, then, under the requirement, equal the width of the stairway

plus an increment of width sufficient to accommodate the portion of the ground-floor population served by

the passageway. The determination of what part of the ground-floor population is served by the passage- way is a matter for the individual designer, subject to the approval of the building official. In the case shown it is assumed that one-half of the ground-floor population would leave through the passageway, which would make it necessary to add 1 unit of exit width to the width of the stairway, giving a total of 66 inches as the required width of the doorway leading from the passageway. The other door serving the

ground-floor population would have to be at least 1 unit wide by calculation, but would be further gov- erned by the requirement of 36 inches minimum width. In sketch 3, figure 16, 2 stairways discharge into a passageway which also serves a portion of the groundfloor population. Under the requirement the doorway width leading from the passageway would be M

(44+44) plus 22 inches for the portion of the ground-floor population served, as explained in the previous example. This would result in a total of 88 inches, which would be satisfied by two 44-inch doorways. The

other doorway serving the ground-floor population would be 36 inches wide as before. 5

Figure 16.

Example for computation of doorway widths. The permission for several stairways to discharge into a passageway only three-quarters the combined

width of these stairways is an apparent variation of the rule that the exit width should never diminish in the direction of exit travel. Actually, in terms of potential-flow capacity there is no change, since the pas- sageway can discharge at a rate four-thirds as fast as the stairways. In the case of 1 stairway, the reduction

is not necessary because ordinary design would require a passageway as wide as the stairway whether this width were needed for exit purposes or not. In the case of several stairways, however, the sum of their width would create an unreasonable and unnecesary width of passageway. In the above examples, occupants have been provided with means of escape involving a combination of doorways, passageways, and stairways. The width of stairways is determined by the population of upper

floors as set forth in section 7-6-1. The width of the doorways leading from the building is determined in the manner just explained. The width of the passageways connecting these doorways with the base of the stairways is governed by the width of the doorways as set forth in section 7-9-1. The width of doorways

entering stairways at any given floor may vary with the population on that floor. It was noted at the fire drill of a large building in which the stairway from the upper floors discharged into the hallways serving the ground floor, that a stoppage occurred at the ground-floor exit door due to the join- ing of the streams of traffic from the stairway and the ground floor, indicating that, although the exit doorway was wide enough for the ground-floor population, its width had not been increased to care for the

discharge from the stairway. The stoppage was sufficient to back up the stream of traffic to such an extent

that the occupants of the stairway were compelled to remain stationary until the doorway had been cleared and the forward movement down the stairs could be resumed. Panic spreads quickly under such conditions and a jam with consequent blocking of the stairway would seem almost inevitable in case of actual fire

,
Design and Construction of Building Exits 69

The width of exit doorways at the foot of exit stairways or at the

head of exit stairways serving basements shall be at the rate of at

least 20 inches 68 for each unit of exit stairway served.

7-8-2. Hanging of Doors.59 The doors of exit doorways shall swing in the direction of exit travel

and shall be so hung and arranged that they shall not obstruct the

travel along an exit passageway, stairway, or other required exit; provided, that a door swung flat against a wall is not considered an

obstruction ; and provided, further, that no door shall at any point in

its swing reduce the width of an exit stairway by more than 18 inches.

Except in occupancies coming under class 3, residential, exit doorways to a street or an exterior open space leading to a street, shall have

the doors, including the doors of vestibules, so hung as to swing out- wardly when opening; but this requirement shall not be construed to

prohibit the use of doors swinging both inwardly and outwardly or of doors sliding horizontally when used in shipping and receiving rooms in

occupancies coming under class 4, business, nor in class 5, garages,

hangars, barns, nor of sliding doors when used in connection with a

horizontal exit. Doors leading from rooms occupied by 50 or more persons shall be

hung to swing in the direction of exit travel. No door of an exit doorway shall open immediately on a flight of

stairs, but a landing at least the width of the door shall be provided

between such door and such stairs. 7-8-3. Revolving Doors.60 Kevolving doors may be used as doors in exit doorways, except in

places of assembly, in schools, and in occupancies coming under class

2, institutional.

m In most cases the doorways at the foot of stairways can be made the same width as the stairways and

where possible this should be done. It has been recognized that in straight run flights of stairs some practical difficulty would be encountered in making the doorway the same width as the stairway, and for that reason the doorway width has been reduced by a maxmum of 2 inches for each unit of stairway width. m It will be noted that the doors of exit doorways and doors leading from rooms occupied by 50 or more

persons are required to swing in the direction of exit travel. Exit doorways are those required by the provisions of this chapter and include doorways required to complete the enclosure of stairways, doorways

leading to the exterior of the building which are also classified as "exits", and doorways opening into

exit passageways. This permits the doors of classrooms containing less than 50 persons to swing in either direction at the

option of the architect. An inwardly swinging door is regarded by some school authorities as giving the

classroom teacher better control over the pupils in case of fire. Residential buildings are exempted from the requirement that all exterior exit doors shall swing outwardly. While this may represent a possible relaxation in the requirements, in view of current practice it seems to be

a reasonable one. It takes into account the probability that the occupants will not arrive at the exit doors

in a crowd, but that opportunity will be afforded for opening the doors before the maximum use of the doorway is necessary.

6" Revolving doors are given credit as a means of egress in buildings of certain occupancies when limited

in use as required by the provisions of section 7-8-3. Certain advantages are claimed over the swinging

door in ease of operation and protection against the elements. Considered solely as a means of egress, however, the revolving door has not been given the same credit as the swinging door. Mechanical operation may not be sure and rate of discharge is generally slower, particularly when large crowds of people must be accommodated, and while these doors may possess collapsible features, investigation has shown

that unless properly maintained the probability of collapse at the time when needed is uncertain. For

these reasons, revolving doors have not been recognized as exits in places of assembly, in schools, in insti- tutional buildings, and at the base of required stairways in all buildings, but their use has not been prohibited for other than exit purposes.

, The studies of rate of flow through doorways did not indicate that an increase in width of revolving doors

increased the flow through them to any appreciable extent. The revolving door in actual practice is a 1- line door, i. e., accommodates but 1 file of persons. At the normal revolving speed 1 person can be accom- modated in the space between each 2 leaves of the door, but observations made on these doors in actual

use indicate that this flow is not steady. Also, unless properly maintained, as the doors become worn from

use, the revolving speed is likely to increase, thus hampering a normal flow of persons through the doorway.

These considerations led to the decision that only part credit should be given revolving doors as means of

egress. To insure safe egress it was decided to limit the total number of revolving doors that might be used to 50 percent of the required exit width, and to guard against the possibility of the revolving door failing to function, due either to mechanical faults or to the pressure of a crowd against the door, it is required that revolving doors be supplemented by swinging doors.
70 Miscellaneous Publications, National Bureau of Standards

Credit for revolving doors serving exit doorways shall be made only

at the rate of one-half unit of exit width for each door. Such doors

shall not be located immediately at the foot of exit stairways. Such

doors shall not exceed 50 percent of the required width of exit doors

and there shall be at least one swinging door for each revolving door

in the same general exit opening.

7-8-4. Door Fastenings.61 Fastenings on doors serving exit doorways shall be such that the

doors may be readily opened from the inside without the use of keys

during the time when the building is occupied, but this requirement

shall not apply to the doors of rooms where persons are under legal

restraint.

Section 7-9. Exit Passageways.62 7-9-1. Width.

The clear width of exit passageways shall be at least equal to the

width of the exit doorways leading from them to the exterior of the building.

7-9-2. Enclosures.

7-9-2-1. Construct]on.63 The walls of exit passageways shall have an ultimate fire resistance

of not less than 2 hours.

6 UNITS

POP

GOO

3 UNITS

AC3 UNITS

POP

€00

3 UNITS

,€ UA//T5-

2

^q-J UN/TS

POP

GOO

-3 UNI TS

3 u/v/TS

J Z 3

Figure 17.Example for computation of exit passageway widths.

61 The survey of exit facilities in buildings revealed that many exit doors are kept locked during the time

-when the buildings are occupied, and testimony of building officials indicates that this practice is extremely

difficult to prevent. Nevertheless, the necessity of detecting such violations is of primary importance. Doorways, passageways, and stairways may be of ample size and properly designed and distributed to accommodate the population, yet one padlocked exit door may be sufficient to defeat every effort to secure

safe and prompt egress. Exit doors are not usually locked in an effort to invite calamity; they are locked

as a matter of operating convenience or because of poor maintenance, and it is only by conscientious inspection and the exercise of vigilance on the part of building inspectors and fire marshals, reinforced by severe

penalties for violations, that such practices can be abolished. In requiring the width of exit passageways to be at least equal to the width of exit doorways leading from

thorn to the exterior of the building, an attempt was made to simplify the method of design and eliminate any unnecessary computations. It is obvious that there is no advantage in making the passageway any

wider than the door or doors at the ends and hence, once the exit doorway width has been established, all that is required is that the passageway shall have the same width. w The passageway must provide protection to the occupants for an interval adequate to evacuate the space served by the passageway. To do this, the enclosure must have sufficient fire resistance to withstand flame and smoke penetration for at least the time required to complete the evacuation with some margin of safety

to allow for an interval between the start of the fire and the sounding of the alarm. This section, which is taken from the Building Code Committee's report entitled " Recommended Minimum Requirements for Fire Resistance in Buildings", is intended to provide this protection.
Design and Construction of Building Exits 71

The floors and ceilings of exit passageways shall have an ultimate

fire resistance at least equal to that required for the t}rpe of construction of the building in which they occur, but not less than iy2 hours.

7-9-2-2. Openings.^

No openings other than the exit doorways leading into or out of an

exit passageway, and windows to the outer air, shall be permitted.

Exit doorways, except those from enclosed stairways discharging

into exit passageways and those to the exterior of the building, shall be equipped with approved self-closing fire doors.

7-9-3. Inclined Exit Passageways.65 To overcome differences in level within exit passageways gradients

of not more than 1 foot in 10 feet or flights of stairs having not less than 3 risers shall be used; provided, that at a doorway leading into an exit passageway or at the foot of an exit stairway, the floor shall be level across the entire width of such passageway and along its length

in the case of the doorway for a distance of not less than 12 inches on

each side of the doorway, and in the case of an exit stairway for a

distance of not less than 25 inches at the foot of such stairway.

Section 7-10. Hallways.

The width 66 of a hallway shall be at least equal to the width of the

exit doorway to which it leads.

^ As in the stairway enclosure, it is necessary that the openings in the passageway be kept at a minimum. An exception to the requirement might be made in the case of doors to toilet rooms or service closets.

65 From the very nature of the passageway it is frequently necessaiT that difference of elevation be over- come, as in the case of a passageway leading occupants of the orchestra floor of a theater to grade level. Flights of stairs are objectionable for obvious reasons. Ramps, on the other hand, are very desirable, if space permits and the slope can be kept within reasonable limits. In order to make the walkway safe and

to avoid tripping or falling at doorwaj^s or at the foot of stairways, certain level landings are required by

this section as illustrated in figure 18.

LEVEL

!

RP.MP

tjasats.1'' *- -»

LEVEL LEV£L RflMP

•4 GfiMP

III •J RfRMP fSPMP

Figure 18.

Level landings required on inclined passageways.

66 The required width of exit doorways which controls hallway width is given in section 7-8-1.
72 Miscellaneous Publications, National Bureau oj Standards

Section 7-11. Horizontal Exits.67 The width 68 of horizontal exits shall be determined in the same manner as the width of exit doorways.

Horizontal exits shall be equipped with at least one approved fire door; provided, that when located in fire walls or party walls there

shall be an approved fire door on each side of such walls, one of which

shall be a swinging, self-closing fire door.69 The floor area on either side of a horizontal exit shall be sufficient to hold the occupants of both floor areas, allowing not less than 3 square feet net clear area per person.

There shall be at least one exit accessible to or from the space on

each side of a horizontal exit.

«? Horizontal exits are considered to be a very effective means of egress, particularly for those portions of institutional occupancies where, in case of emergency, bedridden patients must be removed from the

floor area exposed to fire. The horizontal exit is a most practical device for providing means of egress from one floor area of a building

to an adjoining one, or from one building to a connecting building. Equipped with self-closing or auto- matic fire doors the space on the far side of the exit becomes a place of refuge having sufficient fire resistance

to enable the occupants to make their escape in an orderly manner. Some examples of horizontal exits are given in figure 19.

4

hop. _^ ex/rs~^

GPOUNO FLOOR UPPER FLOOR.

UPPER FLOOR Figure 19.- UPPER PL OOR Various types of horizontal exits.

If all of the effectiveness of the horizontal exit is to be utilized, it is necessary that sufficient clear space be provided on each side to hold all of the occupants of the areas on both sides. This space may consist of

aisles or open spaces providing at least 3 square feet of standing room per person. This is the minimum

space which will permit movement; more is desirable if possible, but the minimum will serve the purpose

of a place of refuge. Elevator lobbies are frequently so constructed with fire-resistive walls and fire doors that they may serve as places of refuge. These are practically all clear space. Having reached the place of refuge on the safe side of a horizontal exit it is not contemplated that the occupants remain there indefinitely, although to do so may be safe. Access must be provided to additional

exits which lead to the street as the place of ultimate safety. Such additional exits may consist of doorways

or other horizontal exits leading to the exterior or to hallways communicating with a stairway, or to hori- zontal exits leading to a connecting building, or stairways leading to the street may be provided on each side

of the horizontal exit. Whatever the method employed access must finally be had to a stairway or ramp

leading to the street.

68 The minimum and aggregate width of horizontal exits is determined in the same manner as that for exit doorways given in section 7-8-1.

69 From an exit standpoint, provision for a door on each side of a fire wall may prove to be awkward. Two

doors are, however, necessary to meet fire-resistance requirements. A desirable arrangement would provide

a vestibule on one side of the wall so that the occupants will not be confronted with the problem of opening two doors at almost the same instant.
Design and Construction of Building Exits 73

Horizontal exits complying with the requirements of this section

may be substituted for stairways or other exits.70 Vestibules, open-air balconies, or bridges serving as horizontal

exits shall be constructed of incombustible materials and their clear

width shall be at least equal to the width of the exit doorway opening

into them.

Doorways or windows opening on, below, or within 10 feet of such

vestibules, balconies, or bridges shall be equipped with approved

self-closing fire doors or approved stationary fire windows.

Where there is a difference in level between the connected floor areas, gradients of not more than 1 foot in 10 feet shall be provided.

No stairs or steps shall be used in a horizontal exit. 71 Section 7-12. Modifications in Required Exit Widths.72 There shall be no reduction in required width along the line of exit

travel, except as specifically permitted in this chapter.

Section 7-13. Exit Designation.73 7-13-1. Exit Signs.

Exits shall be indicated by suitable signs or lights at all times when

the building is occupied. In places of assembly accommodating more

than 100 persons exits shall be plainly marked by approved signs,

sufficiently illuminated when such places are occupied, to be readily

distinguished.

In places of assembly exit lights and lights used for the illumination of exit signs and lights for the lighting of halls, corridors, and

any other parts of places of assembly used by the audience, except

the general auditorium lighting, shall be fed independently of the

stage lighting, and shall be controlled only from the lobby or other

convenient place in the front of the house.

In buildings where exit lights or signs or the exits themselves are not visible from every point in a hallway or undivided floor area, suitable directional signs indicating the location of the exit shall be

provided.

70 This provision is intended to prevent the substitution of a horizontal exit on a single floor for a stairway- running through the entire height of the building. Its effect would be to provide a horizontal exit on each

floor served by the stairway allowed to be eliminated. Such an arrangement may sometimes be advantageous as is shown in the following example: A factory containing 3 floors of 60,000 square feet each has a fire wall extending up through the building dividing it into 2 approximately equal sections each of which contains 2 stairways. By providing a horizontal exit of suitable size in the wall, 1 stairway can be eliminated on each side of the wall, reducing the total number of stairways in the building from 4 to 2.

71 Where the bridge or balcony is not enclosed and the climate such as to involve the possible blocking of the doors by snow or ice, it is desirable to place the level of the bridge floor below the level of the building

floor by the height of an ordinary riser—1% inches. Otherwise the building-floor level and the balcony or

bridge-floor level may be the same.

7 * Concerning reduction in doorway width where the population from 2 or more stairways merges, see section 7-8-1.

73 Adequate exit marking, although often neglected, is an essential feature to secure safe egress. This is particularly true in those buildings frequented by transients, who cannot be expected to be familiar with

the location of exits. In many codes, places of assembly for religious gatherings are exempted from the provisions of this sec- tion. There seemed no more reason for exempting such assemblies than for assembly rooms used for a

political gathering. The hazard appears equal in either case and fire records testify that churches are not more immune to the dangers of fire than many other buildings in which nonreligious gatherings are held. Properly designed and placed exit signs should not detract from the beauty of the interior of a church and

there can be no question as to their value in promoting safe egress should a fire occur. The requirements of section 7-13-1 are based on the recommendations of the National Electrical Safety Code. The reasonableness of the requirements for exit designation would seem to be so obvious as to make their

incorporation in a code unnecessary. Yet the most casual observation will reveal how infrequently the

provisions are carried out. In these days of high-speed elevators the tenant of the average office building,

hotel, or apartment house may not even know the location of the stairway and certainly has but small

occasion to use it to the extent of becoming familiar with it at different floor levels. This fact emphasizes

the importance of marking the street-level door of the stairway so that there can be no mistaking when that

level has been reached. In the confusion attending a fire the occupants might easily follow the stairway down into the basement and lose valuable time in seeking egress to the street unless the street level was

clearly marked.
74 Miscellaneous Publications, National Bureau oj Standards

Exit stairways shall be so arranged or marked as clearly to indi- cate the level at which there is direct exit to a street or to an exterior

open space leading to a street. 7-13-2. Lighting.

Exits and hallways leading to them shall be kept adequately

lighted at all times when the building is occupied.

Artificial light shall be provided whenever natural light is inadequate.

In buildings whose occupancy comes under class 1, public, or

class 2, institutional, the artificial lighting required by this subsection

shall be separate and independent from that serving other parts of

the building.

Section 7-14. Maintenance.74 Exits, and other means of escape when permitted, shall at all times

be maintained in good, safe, usable condition, and shall at all times

be kept free and clear of obstructions and shall be readily accessible.

Exits shall be kept free from combustible material or decorations.

No part of an exit shall be used for storage. The space under stairs shall be kept clear and free. No fire-extinguishing apparatus, radiator, steam or other riser shall be placed in an exit or in a hallway

leading to it, nor in an aisle of a floor area in which seating accommodation is provided, unless placed in such a manner as not to interfere

with free travel, and unless heating apparatus is guarded by substantial metal screens.

7* It is the intent of this section that exits shall at all times be kept in an unobstructed condition and free from combustible materials, including decorations which may be hung in stairways or hallways and pro- vide a possible fire hazard. There is at least one instance on record in which such decorations in a stair- way were ignited and not only rendered the stairway impassable but communicated the fire to other portions of the building. Maintenance of exit facilities is one of the most difficult provisions of building regulations to enforc8 according to building officials. Exit doors are locked; self-closing fire doors are wedged in the open position; stairways and passageways are utilized for the storage of materials, combustible as well as incombustible; fire escapes are blocked and the lower swinging portion is permitted to rust and become unusable;

to mention only a few of the violations of maintenance provisions. During the survey of exit facilities made in connection with the preparation of egress requirements, the

condition of the exits was investigated carefully to determine how closely the maintenance provisions were

being carried out. The conditions were most deplorable. Scarcely a building was inspected which did not show a violation in one form or another, the most common being the wedging of self-closing fire doors and the utilization of stairways and hallways as storage space for combustible materials. It would soem

that unless frequent and thorough inspections necessary to secure proper administration of code maintenance provisions were carried out, coupled with sufficiently severe penalties for infraction of rules, much

of the effort and careful planning necessary to provide proper exit facilities would be at least partially neutralized by inadequate maintenance.
INDEX TO RECOMMENDATIONS

A Page

Aisle width 57 Application of chapter VI 50 Approved, definition of 46

Areas: Assumed per person 58 For various occupancies 58 Below grade 56,60 Stairways serving in types 1 and 2 buildings. - 53 In other types of construction 53 Alterations involving: Changes of occupancy 50 Physical changes 50 Automatic fire doors: Definition 46 Required - 66,71,72 B

Balconies: Horizontal exits 47,73 Population of - - 58 Separate stairways for 54 Basements:

Population of 58 Stairways from 60 Boiler-room exits 54 Bridges as horizontal exits 47, 73 Buildings: Existing 50 New 50 D

Definitions 46 Department stores: Aisles 57 Aggregate exit widths 59 Location of exits 55 Minimum number of exits 51 Minimum width of exits 59, 67 Stairways ending in first-floor area 57 Distance to an exit: Maximum permitted 55 Special limitations 55 Doors: Automatic fire 46 Fastenings 70 Fire 66,71,72,73 Opening on stairs 69 Revolving 69,70 Swing not to create obstruction 69 Hanging 69 Doorways:

Aggregate width 67, 68 Minimum number 51,52 Minimum width 67 Dwellings excepted from requirements 50 E

Enclosures: Of lobbies 56 Of passageways 70 Of ramps 66,67 Of stairways 66 Openings into 66 Existing buildings: Dwellings excepted... 50 Inadequate exit facilities 50

Exit: Designation 73 Lighting 74 Signs 73,74

Exits: Aggregate width of 59,67 Distribution of -- 55,56 Kinds 51 Lighting 74 Location 55 Minimum number 51, 52, 53, 54 Minimum width 59,67 Modifications in required width. 73 Relation of copulation to... 57 Signs 73

F -rage Factory exits: Aggregate width 59 Location 55 Minimum number 51, 52, 53 Minimum width 59,67 Fire escapes 50 Fire doors: Definition 47 Required 66,71,72,73 Fire walls, definition of 46

Fire window:

Definition 47 Stationary required 66, 73 Floor area: Definition 47 Maximum distance to stairway 55 Minimum number of stairways 52, 53, 54 Floor exits: Aggregate width 59 Distribution 55,56 Minimum number of, exceptions 53 Minimum width 59,67 Floor level, changes in 71 Fractions: How treated when computing 60 Aggregate stairway width 60 G

Grade:

Definition .... 47 Stairways serving areas below in types 1 and 2 buildings 60 In other types of construction 53 Gradients: Maximum permitted 67,71

Stairs in connection with.. 71 Ground-floor exits: Aggregate width 52 Distribution 55,56 Minimum number 53 Minimum width 67 H

Hallways: Openings into 51 Width 71 Handrails required 65 Horizontal exits: Aggregate width 72 Definition 47 Differences in level 73 Doors in connection with 72 Exits on each side of 72 Exterior openings near 73 Fire resistance of walls and partitions 47 Floor area on each side of 72 Materials 73 Minimum width 72 Substitution for stairways 73 Hospitals. See: Institutional occupancies.

Institutional occupancies: Aggregate width of exits 59, 67 Distribution of exits 55 Doorway widths 67 Horizontal exits required 53 Minimum number of exits 51 Minimum width of exits 59, 67 Stairways to outside 56 K

Kinds of exits: Doorways 67 Horizontal exits 72 Passageways 70 Ramps 67 Recognized as required exits 51 Stairways 59 75
76 INDEX

L Page

Landings: Length... 65 Required... 65 Vertical distance between 65 Width.... 65 Lighting of: Stairways 74 Passageways, etc 74 Exit signs 73 Lobbies:

Clear space when served by horizontal exits. . 72 Enclosure when stairways terminate in 56 Location of exits: Distribution 55 Maximum distance to exits 55 Outlets from exits 56 M

Maintenance: Combustible material 74 Obstructions 74 Space under stairs.. 74 Storage 74 Materials for: Stairs 64 Stairway enclosures 66 Walls and partitions 66 Maximum distance to an exit 55 Mezzanine, population of 58 Minimum number of exits 51 Minimum width of exits 59,67 Modifications in exit width 73 Moving stairs, requirements for 67 N

New buildings: Application of chapter to 50 Dwellings excepted 50 Number of exits: For boiler rooms 54 For rooms 51 For ground-floor areas 52 For other floor areas 53 For institutional occupancies 53 For places of assembly 54 Minimum 51 O

Office buildings: Aggregate exit width 59,67 Location of exits 55 Minimum number of exits 51 Minimum width of exits 59, 67 Outlets from exits 56

Passageways:

Aggregate width 70 Definition of exit passageway 46 Enclosure 70 Inclined 71 Minimum width 70 Openings in enclosure 71 Places of assembly: Aggregate width of exits 59, 67 Definition 47 Marking of exits 73 Minimum number of exits 54 Minimum width of exits 59, 67 Theater stairways to be separate 54 Population: Determination of 57 Limited by requirements 58 Relation of exits to 57

Maximum slope 67 Requirements for 67 Substituted for stairways 67

Risers. See: Treads and risers. Required, definition of 47 Room exits. 51

Schools: Aggregate exit width 59,67 Assembly halls in 54 Doors into stairways 66 Location of exits. 55 Minimum number of exits 51 Minimum width of exits 59,67

Self-closing: Definition 47 Fire doors required. _ 66 , 71 , 72, 73 Signs: At street level in stairways 73 Directional 73 Lighting of 73 Location of 73 When required 73 Sprinklers: Affecting minimum distance to an exit 55 Affecting minimum number of stairways 53 Definition.. 47 Stairways: Aggregate width — 59, 67 Changes in floor level 65 Construction of enclosures 66 Definition 47 Distribution of 55 Exterior 64 Handrails 65 Lighting 74 Location of 55 Materials 64 Minimum number 53 Minimum width 59 Moving 67' Not continuous 66 Openings 66 Outlet from 56 Treads and risers 65

Street, definition of 47' Theaters: ^

Aggregate width of exits 59 Definition 47 Minimum number of exits 54 Minimum width of exits 59, 67 Population 57 Stairways to be separate 54 Aggregate width of exits 59,67

Tier, stairways for 54 Treads and risers, rule for width and height... 65 U

Ultimate fire resistance, definition of 47 Unit:

Definition 59 Width of 59 V

Vestibules as part of horizontal exits 73 W

Winders prohibited 65 Windows:

Permitted in exit enclosures 66 Protected where near exits 73 O