NISTNCSTAR1-1D

Federal Building and Fire Safety Investigation of the

World Trade Center Disaster

Fire Protection and Life Safety

Provisions Applied to the Design and

Construction of WTC 1, 2, and 7 and

Post-Construction Provisions

Applied after Occupancy

Raymond A. Grill Duane A. Johnson

National Institute of Standards and Technology Technology Administrofion • U.S. Deparimenf of Commerce

NISTNCSTAR1-1D

Federal Building and Fire Safety Investigation of the

World Trade Center Disaster

Fire Protection and Life Safety

Provisions Applied to the Design and

Construction of WTC 1, 2, and 7 and

Post-Construction Provisions

Applied After Occupancy

Raymond A. Grill Duane A. Johnson

Rolf Jensen & Associates, Inc.

Septennber 2005

U.S. Department of Commerce

Carlos M. Gutierrez, Secretary

Technology Administration

Michelle O'Neill, Acting Under Secretary for Technology

National Institute of Standards and Technology

William Jeffrey, Director
Disclaimer No. 1

Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of Standards and Technology.

Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document,

however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline.

Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c).

In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been

provided to NIST under nondisclosure agreements.

Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code

since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the

properties and condition of the materials used, or changes to the original construction made over the life of the

buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining

compliance when implementing building codes. Where an Investigation report states whether a system was

designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating

whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met.

Use in Legal Proceedings

No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the

National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).

National Institute of Standards and Technology National Construction Safety Team Act Report 1-1

D

Natl. Inst. Stand. Technol. Natl. Constr. Sfty. Tm. Act Rpt. 1-1D, 168 pages (September 2005)

CODEN: NSPUE2

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 2005

For sale by the Superintendent of Documents, U.S. Government Printing Office

Internet: bookstore.gpo.gov — Phone: (202) 512-1800 — Fax: (202) 512-2250

Mail: Stop SSOP, Washington, DC 20402-0001
Abstract

This report was prepared to support the analysis of building and fire codes and standards of the National

Institute of Standards and Technology World Trade Center (WTC) Investigation. To best analyze the performance of WTC 1, 2, and 7 in response to the September 1 1, 2001, attacks, the provisions of the design and construction of the buildings must first be understood. The purpose of this report is to summarize the fire protection (both passive and active) and life safety provisions that were used to design

and construct WTC 1, 2. and 7 and to document the changes in building code regulations that occurred

after their construction.

Determination of the applicable building provisions was a multi-step task. First, documentation (such as drawings, memoranda, and New York City building regulations) was analyzed to identify the initial construction provisions at the times of construction of the three buildings. Second, New York City

building regulations, published since the time of construction, were analyzed to identify the new and

amended building provisions. Third, the building provisions were analyzed to detennine their applicability to the building characteristics of WTC 1, 2, and 7.

Ke\'u ords: Compartmentation. elevators, emergency power, fire alarm, fire protection, fire safety, fire sprinklers, high-rise buildings, inspections, interior finish, means of egress, pressurization, venting, voice

communication. World Trade Center.

NISTNCSTAR 1-1 D. WTC Investigation iii
Abstract

This page intentionally left blank.

iv NISTNCSTAR 1-1D, WTC Investigation
Table of Contents

Abstract iii

Table of Contents v

List of Figures xi

List of Tables xiii

List of Acronyms and Abbreviations xv

Metric Conversion Table xvii

Glossary xxi

Preface xxiii

Section I Fire Protection Summary for tlie World Trade Center Towers 1

Executive Summary 1

Chapter 1 Introduction 3

1.1 Purpose 3

1 .2 Introduction 3

Chapter 2 General 5

2.1 Applicable Codes and Standards 5

2.2 Building Summaries 6

Chapters

Construction 7

3 . 1 Construction Classification 7

3.2 Building Limitations 7

3.3 Secondary/Accessory Occupancies 7

3.4 Fire Resistance Ratings 7

3.5 Opening Protection 10

3.6 Separation of Occupancies 1

1

3.7 Firestopping 12

3 .8 Through Penetration Protection 13

3.9 Fire and Smoke Dampers 13

NIST NCSTAR 1-1D, WTC Investigation v
Table of Contents

Chapter 4 Interior Finish 15

4. 1 Interior Finish Flame Spread Ratings 1

5

4.2 Smoke Developed Ratings 16

4.3 Interior Trim 16

4.4 Floor Finish 16

Chapter 5 Means of Egress 1

7

5.1 General 17

5.2 Exits 18

5.3 Exit Width and Capacity 20

5.4 Doors 22

5.5 Exit Access 23

5.6 Staii-ways 24

5.7 Ramps 25

5.8 Handrails and Guardrails 26

5.9 Exit Signs 26

5.10 Means of Egress Lighting 27

Chapters

Fire Suppression 29

6. 1 Automatic Sprinkler Protection 29

6.2 Standpipes 29

6.3 Water Supply 30

Chapter 7 Fire Detection and Alarm 33

7. 1 Fire Alann System 33

7.2 Smoke and Heat Detector Locations 33

7.3 Manual Fire Alann Boxes 34

7.4 Audible/Visual Alann Notification Appliances 34

7.5 Communication System 34

Chapter 8 Elevators and Hoistways 37

8.1 General 37

vi NISTNCSTAR 1-1D, WTC Investigation
Table of Contents

Chapter 9 Special Features 39

9. 1 Emergency Power Systems 39

9.2 Public Garages 39

9.3 Smoke and Heat Venting 39

Chapter 10 References 41

Section II Fire Protection Summary for World Trade Center 7

Executive Summary 45

Chapter 11 Introduction 47

11.1 Purpose 47

1 1 .2 Introduction 47

Chapter 12 General 49

12.1 Applicable Codes and Standards 49

12.2 Building Summary 50

Chapter 13 Construction 51

13.1 Construction Classification 5

1

13.2 Building Limitations 51

13.3 Secondary/Accessory Occupancies 51

1 3.4 Fire Resistance Ratings 51

13.5 Opening Protection 54

13.6 Separation of Occupancies 55

13.7 Corapartmentation 56

13.8 Firestopping 57

13.9 Through Penetration Protection 57

1 3 . 1 0 Fire and Smoke Dampers 58

Chapter 14 Interior Finish 61

14.1 Interior Finish Flame Spread Ratings 61

14.2 Smoke Developed Ratings 62

NISTNCSTAR 1-1D, WTC Investigation vii
Table of Contents

14.3 Interior Trim 62

14.4 Floor Finish 62

Chapter 15

Means of Egress 63

15.1 General 63

15.2 Exits 64

1 5.3 Exit Width and Capacity 66

15.4 Doors 68

15.5 Exit Access 69

15.6 Stairways 70

15.7 Ramps 71

15.8 Handrails and Guardrails 72

15.9 Exit Signs 72

15.10 Means of Egress Lighting 73

Chapter 16

Fire Suppression .....75

16.1 Automatic Sprinkler Protection 75

16.2 Standpipes 76

16.3 Water Supply 77

Chapter 17 Fire Detection and Alarm 79

17.1 Fire Alarni System 79

1 7.2 Smoke and Heat Detector Locations 79

17.3 Manual Fire Alarm Boxes 81

1 7.4 Audible/Visual Alann Notification Appliances 81

17.5 Communication Systems 81

Chapter 18 Elevators and Hoistways 85

18.1 General 85

Chapter 19 Emergency, Electrical, and Standby Power Systems 87

19.1 Emergency Power Systems 87

vni NISTNCSTAR 1-1D, WTC Investigation
Table of Contents

Chapter 20

Special Features 89

20. 1 Smoke and Heat Venting 89

Chapter 21 Inspections ...91

21.1 Inspection Requirements 91

2 1 .2 Materials Requiring Inspection 92

Chapter 22 References 93

Section III Post-Construction Fire Protection and Life Safety Provisions for World

Trade Center 1, 2, and 7

Executive Summary 97

Chapter 23

Introduction 101

Chapter 24

General 103

24.1 Local Laws with Applicable Fire Protection/Life Safety Provisions 103

24.2 Building Summaries 103

Chapter 25

Construction 105

25.1 Construction Classification 105

25.2 Compartmentation 105

25.3 Firestopping 106

Chapter 26

Interior Finish 107

26.1 Floor Finish 107

Chapter 27

Means of Egress 109

27.1 General 109

27.2 Exits 109

27.3 Doors 109

27.4 Stair and Elevator Signs 109

27.5 Means of Egress Lighting 1 1

0

NISTNCSTAR 1-1D, WTC Investigation ix
Table of Contents

Chapter 28

Fire Suppression ....111

28.1 Automatic Sprinkler Protection 1 1

1

Chapter 29

Fire Detection and Alarm 113

29.1 Fire Alarm System 113

29.2 Smoke and Heat Detector Locations 1 14

29.3 Manual Fire Alarm Boxes 1 1

5

29.4 Audible/Visual Notification Appliances 1 1

6

29.5 Communication System 116

Chapter 30

Elevators and Hoistways 119

30.1 Elevator in Readiness 119

30.2 Locks 119

Chapter 31 Emergency, Electrical, and Standby Power Systems .....121

31.1 Emergency Power Systems 121

Chapter 32

Special Features 123

32.1 Smoke and Heat Venting 123

32.2 Smoke Control 124

32.3 Smoke Purge 124

32.4 Stair Pressurization 124

32.5 Fire Safety Plan 124

Chapter 33

Inspections .127

33.1 Materials Requiring Inspection 127

Chapter 34

Response to Retroactive Provisions ......129

Chapter 35

References ,....131

X NISTNCSTAR 1-1D, WTC Investigation
List of Figures

Figure P-1 . The eight projects in the federal building and fire safety investigation of the WTC

disaster xxv

NISTNCSTAR 1-1 D, WTC Investigation xi
List of Figures

This page intentionally left blank.

xii NISTNCSTAR 1-1 D, WTC Investigation
List of Tables

Table P-1 . Federal building and fire safety investigation of the WTC disaster xxiv

Table P-2. Public meetings and briefings of the WTC Investigation xxvii

Table 2-1 . Building characteristics used for design development 6

Table 12-1. Building characteristics used for design development 50

Table 24—1. Building characteristics 103

Table 34-1. Life safety and fire protection provisions required by Local Laws 130

NISTNCSTAR 1-1 D, WTC Investigation xiii
List of Tables

This page intentionally left blank.

xiv NISTNCSTAR 1-1 D, WTC Investigation
List of Acronyms and Abbreviations

Acronyms

A CT*A 4 ASIM ASTM International

BLNYL Building Lode oi the City oi New York (Local Law No. 76)

HVAL heating, ventilating, and air conditioning

T T LL Local Law to amend the New York City Administrative Code

NrrA National Fire Protection Association

NISI National Institute of Standards and Technology

PANYNJ Port Authority of New York and New Jersey

RS Reference Standard to the BCNYC

WTC World Trade Center

WTC 1 World Trade Center 1 (North Tower)

WTC 2 World Trade Center 2 (South Tower)

WTC 7 World Trade Center 7

Abbreviations

op degrees Fahrenheit

cfm cubic feet per minute

cm' square centimeters

ft foot

fe square feet

gal gallon

gpm gallons per minute

h hour

in. inch

in.' square inches

lb pound

min minute

V volt W watt

NISTNCSTAR 1-1D. WTC Investigation XV
List of Acronyms and Abbreviations

\

This page intentionally left blank.

XVI NISTNCSTAR 1-1D, WTC Investigation
Metric Conversion Table

To convert from to Multiply by

AREA AND SECOND MOMENT OF AREA

square foot (ft")

square inch (in.")

square inch (in.')

square v ard (yd')

square meter (m')

square meter (m')

square centimeter (cm')

square meter (m')

9.290 304 E-02

6.4516 E-04

6.4516 E+00

8.361 274 E-01

ENERGY (includes WORK)

kilowatt hour (kW h)

quad (1015 BtuIT)

therm (U.S.)

ton of TNT (energy equivalent) w att hour (W • h)

watt second (W s)

joule (J)

joule (J)

joule (J)

joule (J)

joule (J)

joule (J)

3.6 E+06

1.055 056 E+18

1.054 804 E+08

4.184 E+09

3.6 E+03

1.0 E+00

FORCE

dyne (dyn)

kilogram-force (kgf)

kilopond (kilogram-force) (kp)

kip(l kip= 1.000 Ibf)

kip(l kip=1.000 Ibf)

pound-force (Ibf)

newton (N) new ton (N)

newton (N)

newton (N)

kilonewton (kN)

newton (N)

l.OE-05

9.806 65 E+00

9.806 65 E+00

4.448 222 E+03

4.448 222 E+00

4.448 222 E+00

FORCE DIMDED BY LENGTH

pound-force per foot (Ibf/ft)

pound-force per inch (Ibf'in.)

newton per meter (N/m)

newton per meter (N/m)

1.459 390 E+01

1.751 268 E+02

HEAT FLOW RATE

calorieth per minute (calth/min)

calorieth per second (calth/s)

kilocalorieth per minute (kcallh'min)

kilocalorieth per second (kcalth/s)

watt (W)

watt(W)

watt (W)

watt (W)

6.973 333 E-02

4.184 E+00

6.973 333 E+01

4.184 E+03

NISTNCSTAR 1-1D. WTC Investigation xvii
Metric Conversion Table

To convert from to Multiply by

LENGTH

foot (ft) meter (m) 3.048 E-01

1 n Ii / 1 tT ^ IIIL 11 ^ 111 J

11 ICICI ^ 1 1 ^

inch (in.) centimeter (cm) 2.54 E+00

micron (m) meter (m) 1 .0 E-06

yard (yd) meter (m) 9.144 E-Gl

MASS and MOMENT OF INERTIA

kilogram-force second squared

per meter (kgf • s"/m) kilogram (kg) 9.806 65 E+00

LJUUIIU lUUl ^LILluICU \ lU 11 f k'llnfTrniTi rtiptpr cniiiirfH /Vcr . n"i~\ IVllUUlclIll IIICICI dliuchcu Vi^K "1 / 4 '>i4 ni 1 F-rc

pound inch squared (lb • in.') kilogram meter squared (kg m") 2.926 397 E-04

ton, metric (t) kilogram (kg) l.OE+03

ton, short (2.000 lb) kilogram (kg) 9.071 847 E+02

MASS DIVIDED BY AREA

pound per square foot (lb/ft") kilogram per square meter (kg/m') 4.882 428 E+00

pound per square mch

(not pound force) (lb/in.") kilogram per square meter (kg/m') 7.030 696 E+02

MASS niviDFn Rv 1 F\'r;TH

pound per foot (lb/ft) kilogram per meter (kg/m) 1.488 164 E+00

pound per inch (lb/in.) kilogram per meter (kg/m) 1.785 797 E+01

pound per yard (lb/yd) kilogram per meter (kg/m) 4.960 546 E-01

PRESSURE or STRESS (FORCE DIVIDED BY AREA)

kilogram-force per square centimeter (kgf/cm") pascal (Pa) 9.806 65 E+04

kilogram-force per square meter (kgf/m") pascal (Pa) 9.806 65 E+00

kilogram-force per square millimeter (kgf/mm") pascal (Pa) 9.806 65 E+06

kip per square inch (ksi) (kip/in.") pascal (Pa) 6.894 757 E+06

kip per square inch (ksi) (kip/in.") kilopascal (kPa) 6.894 757 E+03

pound-force per square foot (Ibf/ft") pascal (Pa) 4.788 026 E+01

pound-force per square inch (psi) (Ibf/in.') pascal (Pa) 6.894 757 E+03

pound-force per square inch (psi) (Ibf/in.') kilopascal (kPa) 6.894 757 E+00

psi (pound-force per square inch) (Ibf/in.") pascal (Pa) 6.894 757 E+03

psi (pound-force per square inch) (Ibf/in.') kilopascal (kPa) 6.894 757 E+00

xvin NISTNCSTAR 1-1 D, WTC Investigation
Metric Conversion Table

To convert from

TEMPER.\TURE

degree Celsius (°C)

degree centigrade

degree Fahrenheit (°F)

degree Fahrenheit (°F)

kelvin (K)

TEMPERATURE INTERVAL

degree Celsius (°C)

degree centigrade

degree Fahrenheit (°F)

degree Fahrenheit (°F)

degree Rankine {°R)

VELOCITY (includes SPEED)

foot per second (fl's)

inch per second (in./s)

kilometer per hour (km/h)

mile per hour (mi ll)

mile per minute (mi min)

VOLUME (includes CAPACITY)

cubic foot (ft')

cubic inch (in.'

)

cubic yard (yd')

gallon (U.S.) (gal)

gallon (U.S.) (gal)

liter (L)

ounce (U.S. fiuid) (n oz)

ounce (U.S. fluid) (fl oz)

to

kelvin (K)

degree Celsius (°C)

degree Celsius (°C)

kelvin (K)

degree Celsius (°C)

Multiply by

T/K = t/°C + 273.15

t/°C a t /deg. cent.

t/°C = (t/°F-32)/1.8 T/K = (t/°F + 459.67)/].

8

t/°C = T/K 2 273.15

kelvin (K) l.OE+00

degree Celsius (°C) 1 .0 E+00

degree Celsius (°C) 5.555 556 E-01

kelvin (K) 5.555 556 E-01

kelvin (K) 5.555 556 E-01

meter per second (m/s) 3.048 E-01

meter per second (m/s) 2.54 E-02

meter per second (m/s) 2.777 778 E-01

kilometer per hour (km/h) 1 .609 344 E+00

meter per second (m/s) 2.682 24 E+01

cubic meter (m')

cubic meter (m')

cubic meter (m')

cubic meter (m')

liter (L)

cubic meter (m')

cubic meter (m')

milliliter (mL)

2.831 685 E-02

1.638 706 E-05

7.645 549 E-01

3.785 412 E-03

3.785 412 E+00

1.0 E-03

2.957 353 E-05

2.957 353 E+01

NISTNCSTAR 1-1 D. WTC Investigation XIX
Metric Conversion Table

This page intentionally left blank

XX NISTNCSTAR 1-1 D, WTC Investigation
Glossary

active fire protection - A means to help prevent the loss of life and property from fire by extinguishing,

suppressing, or controlling a fire through functional systems. Sprinkler systems, fire alann systems, and

smoke control systems are examples of active fire protection.

area of refuge - A floor area to which egress is made through a horizontal exit or supplemental vertical

exit.

combustible - A material that is not determined to be noncombustible.

damper - A device installed in heating, ventilating, and air conditioning ductwork used to prevent the spread of fire and/or smoke. Dampers are provided to maintain a fire resistance rating of the assembly

being penetrated.

detector - An initiation device that automatically detects a change in state, such as presence of smoke,

high temperature, or abnormal rate of temperature rise.

fire alarm system - A system, automatic or manual, arranged to give a signal indicating a fire emergency

and initiate the appropriate response.

fire resistance rating - The time in hours that materials or their assemblies will withstand fire exposure

as determined by a fire test.

fireproofing - Materials or assemblies used to provide a fire resistance rating to a building component.

firestop - A solid or compact, tight closure to retard the spread of flames or hot gases within concealed

spaces.

initiation device - A system component that originates a change-in-state signal in the fire alann system.

An initiation device begins the life safety processes, such as evacuation; heating, ventilating, and air conditioning shut down; elevator recall; etc.

manual fire alarm box - A manually operated initiation device that originates a change-in-state signal in the fire alarm system.

means of egress - A continuous and unobstructed path of vertical and horizontal travel from any point in a building to a public way. The means of egress consists of the exit access, the exit, and the exit discharge.

noncombustible - A material that, in the form in which it is used in construction, will not ignite and bum

when subjected to fire. However, any material which liberates flammable gas when heated to any

temperature up to 1,380 °F for 5 min shall not be considered noncombustible.

NISTNCSTAR 1-1D, WTC Investigation xxi
Glossary

notification appliance - A fire alann system component such as a bell, horn, speaker, or strobe that provides audible, tactile, or visible outputs, or any combination thereof.

passive fire protection - Fire protection features that are incoiporated into the building construction or building materials that do not rely on active fire protection methods to limit fire ignition, fire growth, or material failure. Fire separations and divisions, sprayed fire-resistive material, and enclosing structural members with noncombustible materials are examples of passive fire protection.

smoke and heat venting - A process used to move products of combustion to the outdoor air.

xxn NISTNCSTAR 1-1D, WTC Investigation
Preface

Genesis of This Investigation

Immediately following the terrorist attack on the World Trade Center (WTC) on September 11, 2001, the Federal Emergency Management Agency (FEMA) and the American Society of Civil Engineers began

planning a building perfonnance study of the disaster. The week of October 7, as soon as the rescue and

search efforts ceased, the Building Perfonnance Study Team went to the site and began its assessment. This was to be a brief effort, as the study team consisted of experts who largely volunteered their time

away from their other professional commitments. The Building Perfonnance Study Team issued its report in May 2002. fulfilling its goal "to determine probable failure mechanisms and to identify areas of

fiiture investigation that could lead to practical measures for improving the damage resistance of buildings

against such unforeseen events."

On August 21, 2002, with funding from the U.S. Congress through FEMA, the National Institute of

Standards and Technology (NIST) announced its building and fire safety investigation of the WTC

disaster. On October 1, 2002, the National Construction Safety Team Act (Public Law 107-231), was

signed into law. The NIST WTC Investigation was conducted under the authority of the National

Construction Safet>' Team Act.

The goals of the investigation of the WTC disaster were:

• To investigate the building construction, the materials used, and the technical conditions that contributed to the outcome of the WTC disaster.

• To ser\ e as the basis for: - Improvements in the way buildings are designed, constructed, maintained, and used; - Improved tools and guidance for industry and safety officials; - Recommended revisions to current codes, standards, and practices; and - Improved public safety.

The specific objectives were:

1 . Determine why and how WTC I and WTC 2 collapsed following the initial impacts of the

aircraft and why and how WTC 7 collapsed;

2. Determine why the injuries and fatalities were so high or low depending on location,

including all technical aspects of fire protection, occupant behavior, evacuation, and

emergency response;

3. Determine what procedures and practices were used in the design, construction, operation,

and maintenance of WTC 1,2, and 7; and

4. Identify, as specifically as possible, areas in current building and fire codes, standards, and

practices that warrant revision.

NISTNCSTAR 1-1D, WTC Investigation xxiii
Preface

NIST is a nonregulatoiy agency of the U.S. Department of Commerce's Technology Administration. The

purpose of NIST investigations is to improve the safety and structural integrity of buildings in the United

States, and the focus is on fact finding. NIST investigative teams are authorized to assess building

perfonnance and emergency response and evacuation procedures in the wake of any building failure that has resulted in substantial loss of life or that posed significant potential of substantial loss of life. NIST

does not have the statutoiy authority to make findings of fault nor negligence by individuals or

organizations. Further, no part of any report resulting from a NIST investigation into a building failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action

for damages arising out of any matter mentioned in such report (15 USC 281a, as amended by Pubhc

Law 107-231).

Organization of the Investigation

The National Construction Safety Team for this Investigation, appointed by the then NIST Director, Dr. Arden L. Bement, Jr., was led by Dr. S. Shyam Sunder. Dr. William L. Grosshandler served as Associate Lead Investigator, Mr. Stephen A. Cauffman served as Program Manager for Administration,

and Mr. Harold E. Nelson served on the team as a private sector expert. The Investigation included eight

interdependent projects whose leaders comprised the remainder of the team. A detailed description of

each of these eight projects is available at http://wtc.nist.gov. The purpose of each project is summarized

in Table P-1, and the key interdependencies among the projects are illustrated in Fig. P-1.

Table P-1. Federal building and fire safety investigation of the WTC disaster.

Technical Area and Project Leader Project Purpose

Analysis of Building and Fire Codes and

Practices; Project Leaders: Dr. H. S. Lew

and Mr. Richard W. Bukowski

Document and analyze the code provisions, procedures, and

practices used in the design, construction, operation, and

maintenance of the structural, passive fire protection, and

emergency access and evacuation systems of WTC 1, 2, and 7. Baseline Structural Performance and

Aircraft Impact Damage Analysis; Project Leader: Dr. Fahim H. Sadek

Analyze the baseline performance of WTC 1 and WTC 2 under

design, service, and abnormal loads, and aircraft impact damage on

the structural, fire protection, and egress systems.

Mechanical and Metallurgical Analysis of

Structural Steel; Project Leader: Dr. Frank

W. Gayle

Determine and analyze the mechanical and metallurgical properties

and quality of steel, weldments, and connections from steel recovered from WTC 1 , 2, and 7. Investigation of Active Fire Protection Systems; Project Leader: Dr. David

D. Evans; Dr. William Grosshandler

Investigate the performance of the active fire protection systems in WTC 1, 2, and 7 and their role in fire control, emergency response, and fate of occupants and responders.

Reconstruction of Thermal and Tenability

Environment; Project Leader: Dr. Richard

G. Gann

Reconstruct the time-evolving temperature, thermal environment,

and smoke movement in WTC 1, 2, and 7 for use in evaluating the

structural performance of the buildings and behavior and fate of

occupants and responders.

Structural Fire Response and Collapse

Analysis; Project Leaders: Dr. John

L. Gross and Dr. Therese P. McAllister

Analyze the response of the WTC towers to fires with and without

aircraft damage, the response of WTC 7 in fires, the performance

of composite steel-trussed floor systems, and determine the most

probable structural collapse sequence for WTC I, 2, and 7. Occupant Behavior, Egress, and Emergency

Communications; Project Leader: Mr. Jason

D. Averill

Analyze the behavior and fate of occupants and responders, both

those who survived and those who did not, and the performance of

the evacuation system.

Emergency Response Technologies and

Guidelines; Project Leader: Mr. J. Randall Lawson

Document the activities of the emergency responders from the time

of the terrorist attacks on WTC 1 and WTC 2 until the collapse of

WTC 7, including practices followed and technologies used.

XXIV NISTNCSTAR 1-1D. WTC Investigation
Preface

laovemmeni.

Industry,

Professional,

Academic Inputs i

Public Inputs M

NIST WTC Investigation Projects

Nisr

Figure P-1. The eight projects in the federal building and fire safety

investigation of the WTC disaster.

National Construction Safety Team Advisory Committee

The NIST Director also established an advisory committee as mandated under the National Construction

Safety Team Act. The initial members of the committee were appointed following a public solicitation. These were:

• Paul Fitzgerald, Executive Vice President (retired) FM Global, National Construction Safety

Team Advisory Committee Chair

• John Barsom, President, Barsom Consulting, Ltd.

• John Bryan, Professor Emeritus, University of Maryland

• David Collins, President, The Preview Group, Inc.

• Glenn Corbett, Professor, John Jay College of Criminal Justice

• Philip DiNenno, President, Hughes Associates, Inc.

NIST NCSTAR 1-1D, WTC Investigation XXV
Preface

• Robert Hanson, Professor Emeritus, University of Michigan

• Charles Thornton, Co-Chaimian and Managing Principal, The Thomton-Tomasetti Group,

Inc.

• Kathleen Tiemey, Director, Natural Hazards Research and Applications Information Center,

University of Colorado at Boulder

• Fonnan Williams, Director, Center for Energy Research, University of California at San

Diego

This National Construction Safety Team Advisoty Committee provided technical advice during the Investigation and commentai'y on drafts of the Investigation reports prior to their public release. NIST

has benefited from the work of many people in the preparation of these reports, including the National

Construction Safety Team Advisoiy Committee. The content of the reports and recommendations,

however, are solely the responsibility of NIST.

Public Outreach

During the course of this Investigation, NIST held public briefings and meetings (listed in Table P-2) to

solicit input from the public, present preliminaiy findings, and obtain comments on the direction and

progress of the Investigation from the public and the Advisory Committee.

NIST maintained a publicly accessible Web site during this Investigation at http://wtc.nist.gov. The site contained extensive infonnation on the background and progress of the Investigation.

NIST's WTC Public-Private Response Plan

The collapse of the WTC buildings has led to broad reexamination of how tall buildings are designed,

constructed, maintained, and used, especially with regard to major events such as fires, natural disasters,

and teiTorist attacks. Reflecting the enhanced interest in effecting necessary change, NIST, with support

from Congress and the Administration, has put in place a program, the goal of which is to develop and

implement the standards, technology, and practices needed for cost-effective improvements to the safety

and security of buildings and building occupants, including evacuation, emergency response procedures,

and threat mitigation.

The strategy to meet this goal is a three-part NlST-led public-private response program that includes:

• A federal building and fire safety investigation to study the most probable factors that contributed to post-aircraft impact collapse of the WTC towers and the 47-story WTC 7

building, and the associated evacuation and emergency response experience.

• A research and development (R&D) program to (a) facilitate the implementation of

recommendations resulting from the WTC Investigation, and (b) provide the technical basis

for cost-effective improvements to national building and fire codes, standards, and practices

that enhance the safety of buildings, their occupants, and emergency responders.

xxvi NISTNCSTAR 1-1D. WTC Investigation
Preface

Table P-2. Public meetin(gs and briefings of the WTC Investigation.

Date Location Principal Agenda

June 24. 2002 New York City, NY Public meeting: Public comments on the Draft Plan for the pending WTC Investigation.

August 21, 2002 Gaithersburg. MD Media briefing announcing the formal start of the Investigation.

December 9, 2002 Washington, DC Media briefing on release of the Public Update and NIST request

for photographs and videos. April 8, 2003 New York City, NY Joint public forum with Columbia University on first-person

inter\'iews.

Apnl 29-30, 2003 Gaithersburg. MD NCST Advisory Committee meeting on plan for and progress on WTC Investigation with a public comment session. May 7, 2003 New York City, NY Media briefing on release of May 2003 Progress Report.

August 26-27, 2003 Gaithersburg, MD NCST Ad\'isnrv Committpp mpptino on status of the WTC

investigation with a public comment session. Npw Ynrk Cirv NY Media and public briefing on initiation of first-person data

collection projects.

December 2-3, 2003 Gaithersburg, MD NC^ST AHvisnrv r^ommittpp mpptinp on status and initial results and release of the Public Update with a public comment session. Fphniar\ 1 "> "'004 Npw York Cir\' NY Public meeting on progress and preliminary findings with public

rommpnts on issiips to bp ronsidprpH in formiilatino final recommendations.

June 18. 2004 New York City, NY IVtpHia/nuhlir hripfincr on rplpasp of Imtp "^(iOA Prntrj'/^^^ Rpiim'f

Iiinp ''7-7^ '^OOd vjalUlCl 5UUI lyiLJ NCST Advisory Committee meeting on the status of and

nrpliminar\^ findinos from thp WXC Invpstioation with a niihlir comment session. Mnri' ri nrr\ri l/" IF IN Ul LllUl UUK., IL Public viewing of standard fire resistance test of WTC floor svstpm at I InHprwTitprs F aboratorips Inr October 19-20, 2004 Gaithersburg. MD NCST Advisor)' Committee meeting on status and near complete

set of preliminary' findings with a public comment session. November 22, 2004 Gaithersburg, MD NCST Advisory Committee discussion on draft annual report to Congress, a public comment session, and a closed session to Hicpncc nrp-Hraft rprnmmpnHj^tion^; for WTC Invp^stipatinri Npw Ynrk Tin/ NY Media and public briefing on release of the probable collapse

spfiupnrp for thp WTC towprs and draft rpnorts for thp nroippts on

codes and practices, evacuation, and emergency response. June 23, 2005 New York City, NY Media and public briefing on release of all draft reports for the WTC towers and draft recommendations for public comment.

September 12-13,

2005

Gaithersburg. MD NCST Advisory Committee meeting on disposition of public

comments and update to draft reports for the WTC towers. September 13-15,

2005

Gaithersburg, MD WTC Technical Conference for stakeholders and technical community for dissemination of findings and recommendations

and opportunity for public to make technical comments.

• A dissemination and technical assistance program (DTAP) to (a) engage leaders of the construction and building community in ensuring timely adoption and widespread use of

proposed changes to practices, standards, and codes resulting from the WTC Investigation

and the R&D program, and (b) provide practical guidance and tools to better prepare facility owners, contractors, architects, engineers, emergency responders, and regulatory authorities

to respond to future disasters. The desired outcomes are to make buildings, occupants, and first responders safer in future disaster events.

NISTNCSTAR 1-1 D. WTC Investigation xxvn
Preface

National Construction Safety Team Reports on the WTC Investigation

A final report on the collapse of the WTC towers is being issued as NIST NCSTAR 1 . A companion

report on the collapse of WTC 7 is being issued as NIST NCSTAR lA. The present report is one of a set that provides more detailed documentation of the Investigation findings and the means by which these

technical results were achieved. As such, it is part of the archival record of this Investigation. The titles of the full set of Investigation publications are:

NIST (National Institute of Standards and Technology). 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Final Report on the Collapse ofthe World Trade

Center Towers. NIST NCSTAR 1. Gaithersburg. MD, September.

NIST (National Institute of Standards and Technology). 2006. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Final Report on the Collapse of World Trade Center 7. NIST NCSTAR 1 A. Gaithersburg, MD.

Lew, H. S., R. W. Bukowski, and N. J. Carino. 2005. Federal Building and Fire Safety Investigation of

the World Trade Center Disaster: Design, Construction, and Maintenance ofStructural and Life Safet}'

Systems. NIST NCSTAR 1-1. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Fanella, D. A., A. T. Derecho, and S. K. Ghosh. 2005. Federal Building and Fire Safety'

Investigation of the World Trade Center Disaster: Design and Construction ofStructural Systems.

NIST NCSTAR 1-1 A. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Ghosh, S. K., and X. Liang. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Comparison ofBuilding Code Structural Requirements. NIST

NCSTAR 1-lB. National Institute of Standards and Technology. Gaithersburg, MD, September.

Fanella, D. A., A. T. Derecho, and S. K. Ghosh. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Maintenance and Modifications to Structural

Systems. NIST NCSTAR 1-lC. National Institute of Standards and Technology. Gaithersburg,

MD, September.

Grill, R. A., and D. A. Johnson. 2005. Federal Building and Fire Safet}' Investigation ofthe World

Trade Center Disaster: Fire Protection and Life Safety Provisions Applied to the Design and

Construction of World Trade Center I, 2, and 7 and Post-Construction Provisions Applied after Occupancy. NIST NCSTAR 1-lD. National Institute of Standards and Technology. Gaithersburg,

MD, September.

Razza, J. C, and R. A. Grill. 2005. Federal Building and Fire Safet}' Investigation ofthe World

Trade Center Disaster: Comparison of Codes, Standards, and Practices in Use at the Time ofthe Design and Construction of World Trade Center 1, 2, and 7. NIST NCSTAR 1-lE. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Grill, R. A., D. A. Johnson, and D. A. Fanella. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Comparison of the 1968 and Current (2003) New

xxvm NIST NCSTAR 1-1 D, WTC Investigation
Preface

York City Building Code Provisions. NIST NCSTAR 1-lF. National Institute of Standards and

Technology. Gaithersburg, MD, September.

Grill, R. A., and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Amendments to the Fire Protection and Life Safety Provisions ofthe New

York Cit}- Building Code by Local Laws Adopted While World Trade Center 1, 2, and 7 Were in Use. NIST NCSTAR 1-lG. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Grill, R. A., and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Post-Construction Modifications to Fire Protection and Life Safety Systems

of World Trade Center 1 and 2. NIST NCSTAR 1-lH. National Institute of Standards and

Technology. Gaithersburg, MD, September.

Grill, R. A., D. A. Johnson, and D. A. Fanella. 2005. Federal Building and Fire Safety Investigation

of the World Trade Center Disaster: Post-Construction Modifications to Fire Protection, Life

Safety, and Structural Systems of World Trade Center 7. NIST NCSTAR l-ll. National Institute of

Standards and Technology. Gaithersburg, MD, September.

Grill, R. A., and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Design, Installation, and Operation ofFuel System for Emergency Power in World Trade Center 7. NIST NCSTAR 1-1 J. National Institute of Standards and Technology.

Gaithersburg, MD, September.

Sadek, F. 2005. Federal Building and Fire Safety Investigation ofthe World Trade Center Disaster:

Baseline Structural Performance and Aircraft Impact Damage Analysis ofthe World Trade Center

Towers. NIST NCSTAR 1-2. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Faschan, W. J., and R. B. Garlock. 2005. Federal Building and Fire Safety Investigation ofthe World Trade Center Disaster: Reference Structural Models and Baseline Performance Analysis of

the World Trade Center Towers. NIST NCSTAR I-2A. National Institute of Standards and

Technology. Gaithersburg, MD, September.

Kirkpatrick, S. W., R. T. Bocchicri, F. Sadek, R. A. MacNeill, S. Holmes, B. D. Peterson,

R. W. Cilke, C. Navarro. 2005. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Analysis ofAircraft Impacts into the World Trade Center Towers, NIST

NCSTAR 1-2B. National Institute of Standards and Technology. Gaithersburg, MD, September.

Gayle, F. W., R. J. Fields, W. E. Luecke, S. W. Banovic, T. Foecke, C. N. McCowan, T. A. Siewert, and

J. D. McColskey. 2005. Federal Building and Fire Safety Investigation ofthe World Trade Center

Disaster: Mechanical and Metallurgical Analysis ofStructural Steel. NIST NCSTAR 1-3. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Luecke, W. E., T. A. Siewert, and F. W. Gayle. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Contemporaneous Structural Steel

Specifications. NIST Special Publication 1-3A. National Institute of Standards and Technology.

Gaithersburg, MD, September.

NIST NCSTAR 1-1 D. WTC Investigation XXIX
Preface

Banovic, S. W. 2005. Federal Building and Fire Safety Investigation ofthe World Trade Center

Disaster: Steel Inventoiy and Identification. NIST NCSTAR 1-3B. National Institute of Standards

and Technology. Gaithersburg, MD, September.

Banovic, S. W., and T. Foecke. 2005. Federal Building and Fire Safety Investigation of the World

Trade Center Disaster: Damage and Failure Modes ofStructural Steel Components. NIST

NCSTAR 1-3C. National Institute of Standards and Technology. Gaithersburg, MD, September.

Luecke, W. E., J. D. McColskey, C. N. McCowan, S. W. Banovic, R. J. Fields, T. Foecke,

T. A. Siewert, and F. W. Gayle. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Mechanical Properties ofStructural Steels. NIST NCSTAR 1-3D.

National Institute of Standards and Technology. Gaithersburg, MD, September.

Banovic, S. W., C. N. McCowan, and W. E. Luecke. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Physical Properties ofStructural Steels. NIST

NCSTAR 1-3E. National Institute of Standards and Technology. Gaithersburg, MD, September.

Evans, D. D., R. D. Peacock, E. D. Kuligowski, W. S. Dols, and W. L. Grosshandler. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Active Fire Protection

Systems. NIST NCSTAR 1-4. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Kuligowski, E. D., D. D. Evans, and R. D. Peacock. 2005. Federal Building and Fire Safety

Investigation of the World Trade Center Disaster: Post-Construction Fires Prior to September II, 2001. NIST NCSTAR 1-4A. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Hopkins, M., J. Schoenrock, and E. Budnick. 2005. Federal Building and Fire Safet)' Investigation

ofthe World Trade Center Disaster: Fire Suppression Systems. NIST NCSTAR 1-4B. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Keough, R. J., and R. A. Grill. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Fire Alarm Systems. NIST NCSTAR 1-4C. National Institute of Standards

and Technology. Gaithersburg, MD, September.

Ferreira, M. J., and S. M. Strege. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Smoke Management Systems. NIST NCSTAR 1-4D. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Gann, R. G., A. Hamins, K. B. McGrattan, G. W. Mulholland, H. E. Nelson, T. J. Ohlemiller,

W. M. Pitts, and K. R. Prasad. 2005. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Reconstruction ofthe Fires in the World Trade Center Towers. NIST NCSTAR 1-5. National Institute of Standards and Technology. Gaithersburg, MD, September.

Pitts, W. M., K. M. Butler, and V. Junker. 2005. Federal Building and Fire Safety Investigation of

the World Trade Center Disaster: Visual Evidence, Damage Estimates, and Timeline Analysis.

NIST NCSTAR 1-5 A. National Institute of Standards and Technology. Gaithersburg, MD,

September.

XXX NIST NCSTAR 1-1D, WTC Investigation
Preface

Hamins, A., A. Maranghides, K. B. McGrattan, E. Johnsson, T. J. Ohlemiller, M. Donnelly,

J. Yang, G. Mulholland, K. R. Prasad, S. Kukuck, R. Anleitner and T. McAllister. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Experiments and

Modeling ofStructural Steel Elements Exposed to Fire. NIST NCSTAR 1-5B. National Institute of

Standards and Technology. Gaithersburg, MD, September.

Ohlemiller, T. J., G. W. Mulholland, A. Maranghides, J. J. Filliben, and R. G. Gann. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Fire Tests ofSingle

Office Workstations. NIST NCSTAR 1-5C. National Institute of Standards and Technology.

Gaithersburg, MD, September.

Gann, R. G., M. A. Riley, J. M. Repp, A. S. Whittaker, A. M. Reinhom, and P. A. Hough. 2005.

Federal Building and Fire Safety- Investigation ofthe World Trade Center Disaster: Reaction of

Ceiling Tile Systems to Shocks. NIST NCSTAR 1-5D. National Institute of Standards and

Technology. Gaithersburg, MD, September.

Hamins. A., A. Maranghides. K. B. McGrattan, T. J. Ohlemiller, and R. Anleitner. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Experiments and

Modeling ofMultiple Workstations Burning in a Compartment. NIST NCSTAR 1-5E. National

Institute of Standards and Technology. Gaithersburg, MD, September.

McGrattan, K. B.. C. Bouldin, and G. Forney. 2005. Federal Building and Fire Safety

Investigation of the World Trade Center Disaster: Computer Simulation ofthe Fires in the World

Trade Center Towers. NIST NCSTAR 1-5F. National Institute of Standards and Technology.

Gaithersburg, MD, September.

Prasad, K. R., and H. R. Baum. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Fire Structure Interface and Thermal Response ofthe World Trade Center

Towers. NIST NCSTAR 1-5G. National Institute of Standards and Technology. Gaithersburg,

MD, September.

Gross, J. L., and T. McAllister. 2005. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Structural Fire Response and Probable Collapse Sequence of the World Trade Center

Towers. NIST NCSTAR 1-6. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Carino, N. J., M. A. Stames, J. L. Gross, J. C. Yang, S. Kukuck, K. R. Prasad, and R. W. Bukowski.

2005. Federal Building and Fire Safety Investigation ofthe World Trade Center Disaster: Passive

Fire Protection. NIST NCSTAR 1-6A. National Institute of Standards and Technology.

Gaithersburg, MD, September.

Gross, J., F. Hervey, M. Izydorek, J. Mammoser, and J. Treadway. 2005. Federal Building and

Fire Safety Investigation of the World Trade Center Disaster: Fire Resistance Tests ofFloor Truss

Systems. NIST NCSTAR 1-6B. National Institute of Standards and Technology. Gaithersburg,

MD, September.

Zarghamee, M. S., S. Bolourchi, D. W. Eggers, O. O. Erbay, F. W. Kan, Y. Kitane, A. A. Liepins,

M. Mudlock, W. I. Naguib, R. P. Ojdrovic, A. T. Sarawit, P. R Barrett, J. L. Gross, and

NIST NCSTAR 1-1D, WTC Investigation xxxi
Preface

T. P. McAllister. 2005. Federal Building and Fire Safet}' Investigation of the World Trade Center

Disaster: Component, Connection, and Subsystem Structural Analysis. NISTNCSTAR 1-6C.

National Institute of Standards and Technology. Gaithersburg, MD, September.

Zarghamee, M. S., Y. Kitane, O. O. Erbay, T. P. McAllister, and J. L. Gross. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Global Structural

Analysis ofthe Response ofthe World Trade Center Towers to Impact Damage and Fire. NIST

NCSTAR 1-6D. National Institute of Standards and Technology. Gaithersburg, MD, September.

McAllister, T., R. W. Bukowski, R. G. Gann, J. L. Gross, K. B. McGrattan, H. E. Nelson, L. Phan,

W. M. Pitts, K. R. Prasad, F. Sadek. 2006. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Structural Fire Response and Probable Collapse Sequence of World Trade

Center?. (Provisional). NIST NCSTAR 1-6E. National Institute of Standards and Technology.

Gaithersburg, MD.

Gilsanz, R., V. Arbitrio, C. Anders, D. Chlebus, K. Ezzeldin, W. Guo, P. Moloney, A. Montalva,

J. Oh, K. Rubenacker. 2006. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Structural Analysis ofthe Response of World Trade Center 7 to Debris Damage

and Fire. (Provisional). NIST NCSTAR 1-6F. Nationallnstitute of Standards and Technology.

Gaithersburg, MD.

Kim, W. 2006. Federal Building and Fire Safety Investigation ofthe World Trade Center

Disaster: Analysis ofSeptember 11, 2001, Seismogram Data. (Provisional). NIST NCSTAR 1-6G.

National Institute of Standards and Technology. Gaithersburg, MD.

Nelson, K. 2006. Federal Building and Fire Safet}' Investigation ofthe World Trade Center

Disaster: The Con Ed Substation in World Trade Center 7. (Provisional). NISTNCSTAR 1-6H.

National Institute of Standards and Technology. Gaithersburg, MD.

Averill, J. D., D. S. Mileti, R. D. Peacock, E. D. Kuligowski, N. Groner, G. Proulx, P. A. Reneke, and

H. E. Nelson. 2005. Federal Building and Fire Safety Investigation ofthe World Trade Center Disaster:

Occupant Behavior. Egress, and Emergency Communication. NIST NCSTAR 1-7. National Institute of

Standards and Technology. Gaithersburg, MD, September.

Fahy, R., and G. Proulx. 2005. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Analysis ofPublished Accounts ofthe World Trade Center Evacuation. NIST

NCSTAR 1-7A. National Institute of Standards and Technology. Gaithersburg, MD, September.

Zmud, J. 2005. Federal Building and Fire Safet}- Investigation ofthe World Trade Center

Disaster: Technical Documentation for Sui-\>ey Administration. NISTNCSTAR 1-7B. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Lawson, J. R., and R. L. Vettori. 2005. Federal Building and Fire Safet}' Investigation of the World

Trade Center Disaster: The Emergency Response Operations. NISTNCSTAR 1-8. National Institute of

Standards and Technology. Gaithersburg, MD, September.

xxxii NISTNCSTAR 1-1D. WTC Investigation
Section I

Fire Protection Summary for

THE World Trade Center Towers
This page intentionally left blank.
Executive Summary

As part of the analysis of building and fire codes and standards of the National Institute of Standards and

Technology (NIST) World Trade Center (WTC) Investigation, this report supports the effort to detennine

the minimum construction requirements used in the design of WTC 1 and WTC 2. The purpose of this report is to summarize the fire protection (both passive and active) and life safety provisions used to design and construct WTC 1 and WTC 2.

Although the Port Authority of New York and New Jersey (PANYNJ) was not subject to the Building

Code of the City of New York (BCNYC), WTC 1 and WTC 2 were to be designed in accordance with the BCNYC and all applicable Reference Standards (RS). The initial building concept, including an early

concepmal design by Skidmore, Owings & Merrill, was based on the 1938 BCNYC. In 1965, PANYNJ

instructed the designers to follow the latest (second and third) drafts of the revised (what would become

the 1968) Code to take advantage of relaxations that could save on construction costs.

The BCNYC. building characteristics, and early design choices were used to determine the minimum

construction requirements for the design of WTC 1 and WTC 2. Because the BCNYC contains

requirements for various types of buildings, it was important to identify certain building requirements

early in the design. By identifying specific building characteristics, the designer can detennine which

requirements must be complied with and which requirements are not applicable.

The information included in Table E-1 was used to classify the buildings and determine the minimum

requirements within the BCNYC. Based on the height, area, primary occupancy classification, and no

sprinkler protection, the minimum construction type (permitted by the 1968 BCNYC) was I-B (3 h

protected) for both buildings. Fire resistance ratings for the structural components, fire divisions, and fire separations were based on this classification. Many of the means of egress, fire suppression, and fire alarm requirements were also based on the infoiTnation in Table E-1. An abbreviated list of the fire protection provisions is as follows. A complete list of the requirements is identified in the main body of

this report.

• A standpipe system was required.

• An automatic sprinkler system was only required in spaces below grade.

• A telephone and signaling system was required for fire department use in operating the standpipe system..

• Detectors were only required to sense smoke entering return grills of the heating, ventilating,

and air conditioning system and to shut down fans.

• Manual fire alarm boxes were not required.

• Audible/visual devices were not required.

NISTNCSTAR 1-1D, WTC Investigation 1
Executive Summary

• Although a fire alann and voice communication system was not required, a system was

installed.

• Exit signs and emergency lighting were required in specified spaces.

• An emergency power system was not required.

• Smoke and heat venting was required in certain shafts, including elevators.

• Stair pressurization was not required.

• A smoke purge system was not required.

Building Height

Number of Floors

Above Grade Footprint

Primary

Occupancy

Classification WTC 1 1,368 ft 110 42,900 ft- Group E (Business)

WTC2 1,362 ft 110 42,900 ft- Group E (Business)

Source: Merrit 2000a, 2000b; PANYNJ.

2 NISTNCSTAR 1-1D, WTC Investigation
Chapter 1 Introduction

1.1 PURPOSE

The purpose of this report is to summarize the major fire protection (both passive and active) and Hfe

safety provisions used to design and construct the World Trade Center (WTC) towers.

1.2 INTRODUCTION

The regulation of building construction is a direct resuk of the recognition that life safety is served by the

best available knowledge and practice. Codes and standards are created to establish minimum

requirements. Model codes have been published throughout the United States since 1905 (Boring 1981).

Through the use of technology advancements and serious incidents, such as fires, codes are developed

and later revised to continually implement increased knowledge. Establishing reference standards is just

as important to establishing codes. Referenced standards act as a technical basis of the code and provide

further methods of testing, installation and maintenance. Municipalities can adopt model building codes

and national standards or develop their own. Alteraatively, many municipalities throughout the United

States have adopted model building codes and national standards, and then amended portions as deemed

necessary. New York City, however, developed their own building code and provide a technical basis

with a mixture of nationally recognized standards (National Fire Protection Association, ASTM

International, American National Standards Institute, etc.) and New York City developed reference . standards (denoted by RS ##).

In accordance with the instructions issued by the Port Authority of New York and New Jersey (PANYNJ

or Port Authority) at the start of the project, construction drawings for the WTC were to confonn with the requirements of the Building Code of the City of New York (BCNYC), although as a so-called state compact under the U.S. Constitution, the Port Authority was exempt from state or local laws, including

the BCNYC. Any variations from the Code were to be called to the attention of the Port Authority for

final decision and authorization (Solomon 1975). Variances from the 1968 edition of the BCNYC, along

with the applicable provisions of the Code, will be identified (to the best extent possible) in this report.' This report summarizes the major provisions of the BCNYC. Readers interested in the more detailed

analysis should seek information directly from the BCNYC.

The design of the WTC towers took many years to develop. The initial design was to be in conformance

with the 1938 BCNYC. However, in 1965, a decision was made to use the provisions of the newly

proposed BCNYC (Kyle 1965). This decision included the rationale that (1) the new Code had been

reviewed by technical groups and modified to meet the major objections; (2) the Code would probably be

adopted before the WTC towers were constructed and (3) the Building Commissioner favored the approach of using advanced techniques in the design of the towers. Additionally, the PANYNJ

repeatedly pointed out that it was not subject to the provisions of the BCNYC (e.g., Tozzoli 1966). Drafts

The applicable provisions of the BCNYC, given throughout the report, are denoted by C26-###.

NISTNCSTAR 1-1D. WTC Investigation 3
Chapter 1

of the newly proposed code were used until December 1968 when the new BCNYC was adopted. The

December 6, 1968, BCNYC was referred to as the applicable building code for the constmction of WTC

1 and WTC 2 and is the base document for identifying the design and construction provisions in this report.

It was the policy of PANYNJ to follow the requirements of the BCNYC. Thus, since not all of the documentation used in the design and construction of the towers was identified, the assumption has been

made that the construction followed the requirements of the BCNYC. Where documentation was

identified, illustrating either confonnance with or deviation from a BCNYC provision, a reference has

been provided. This report does not evaluate whether or not the design provisions, indicated on drawings

and in coiTCspondence, were actually incoiporated in the construction of the towers, but merely identifies the provisions established in the design. Since the buildings no longer exist, it is generally impossible to verify the inclusion of specific design features beyond their being discussed in other documents.

4 NISTNCSTAR 1-1D, WTC Investigation
Chapter 2

General

2.1 APPLICABLE CODES AND STANDARDS

1. Building Code of the City of New York. 1968."

2. USASI 17.1 (1965) including Supplement A17.1a (1967) -USA Standard Safety Code for Elevators, Dumbwaiters. Escalators, and Moving Walks (as modified by Reference Standards

[RS] 18-1).

3. National Fire Protection Association (NFPA) 13 - Standard for the Installation of Sprinkler

Systems, 1966 (as modified by RS 17-2).

4. NFPA 22 - Standard for Water Tanks for Private Fire Protection. 1 962 (as modified by

RS 17).

5. NFPA 72 - Proprietary and Auxiliary Protective Signaling Systems, 1967 (as modified by

RS 17-5).

6. NFPA 80 - Installation of Fire Doors and Windows, 1 967 (as modified by RS 5-8).

7. NFPA 90A - Standard for the Installation of Air Conditioning and Ventilating Systems, 1967

(as modified by RS 13-1).

8. NFPA 204 - Guide for Smoke and Heat Venting, 1 96 1 (RS 5-11).

9. ASTM International (ASTM) E 84 - Standard Method of Test for Surface Burning

Characteristics of Building Materials. 1961 (as modified by RS 5-5).

10. ASTM E 1 19 - Standard Methods of Fire Tests of Building Construction and Materials, 1961

(as modified by RS 5-2).

11. RS 5-1 5 - Minimum Covering of Prestressing Steel for Various Fire Resistance Ratings.

12. RS 17-1 - Standpipe Construction.

13. RS 17-3 - Standards for the Installation of Fire, Sprinkler, Standpipe, Smoke Detection... and

other Alarm and Extinguishing Systems.

' Including the BCNYC Reference Standards that modify national standards as deemed necessary.

NISTNCSTAR 1-1D. WTC Investigation
Chapter 2

2.2 BUILDING SUMMARIES

Table 2-1. Building characteristics used for design development.

Building" Height

Number of Floors

Above Grade'' Footprint

Construction

Tvpe (1968

BCNYC)

Primary

Occupancy

Classification WTC r" 1,368 ft 110 42,900 ft- I-B Group E

(Business)

WTC 2'' 1.362 ft 110 42,900 ft- I-B Group E

(Business)

a. These buildings are localed inside the Borough of Manhattan Fire District without additional restrictions imposed based on its use and occupancy (C26-402. 1 , C26-403. 1 ).

b. Documentation indicates that the Concourse Level was treated as an underground street (Solomon 1975). Thus, the Plaza

level is the first floor.

c. WTC 1 characteristics are from Merritt 2000a. ^

d. WTC 2 characteristics are from Merritt 2000b. Source: Merrit 2000a, 2000b; PANYNJ.

6 NISTNCSTAR 1-1D, WTC Investigation
Chapter 3

Construction

3.1 CONSTRUCTION CLASSIFICATION

The minimum construction t}'pe permitted for both World Trade Center (WTC) towers was Class 1-B (3 h

protected)."

3.2 BUILDING LIMITATIONS

In accordance with Table 4-2 of the Building Code of the City of New York (BCNYC) the height and

area are not Hmited for an unsprinklered Class I-B construction building housing a Group E occupancy:

• Height - No Liinit

• Area - No Limit

3.3 SECONDARY/ACCESSORY OCCUPANCIES

Occupancy Fire Index

B-1 . Storage (Moderate Hazard) 3

B-2, Storage (Low Hazard, Garage) 2

C, Mercantile 2

F-4. Assembly (Restaurant) 1

3.4 FIRE RESISTANCE RATINGS

The minimum required fire resistance ratings listed as follows are in accordance with Table 3-4 of the BCNYC, unless noted otheru'ise. According to Solomon 1969 and Bracco 1969, the fire resistance

ratings of the buildings were designed in accordance with the BCNYC.

^ Because there was considered to be "no economic advantage" to design WTC 1 and WTC 2 to a higher construction

classification (i.e.. Class I-A). the buildings were constructed to the minimum construction class required by the BCNYC

(Feld 1987). Thus, all BCNYC requirements identified herein, which are dependent upon construction class, are given for Class I-B.

NISTNCSTAR 1-1 D. WTC Investigation 7
Chapter 3

Fire Resistance Rating

(Hours)

1. Exterior Bearing Walls 3

2. Exterior Non-bearing Walls having an Exterior

Separation of:'*

Three ft or less with 0 percent openings 2

Greater than 3 ft to less than 15 ft with 3V2 percent ^

protected openings

15 ft to less than 30 ft with 3'/2 percent openings^ IVi

30 ft or greater with unlimited openings NC^

3. Interior Walls:

Interior bearing walls and bearing partitions

Exit access con'idors (C26-604.2(h))

4. Enclosure of vertical exits, ^ exit passageways, hoistways, and

shafts

5. Columns, girders, trusses (other than roof trusses) and

framing:

Supporting one floor 2

Supporting more than one floor or a floor and roof 3

" When two or more buildings are constructed on the same lot and the combined floor area of the buildings does not exceed the

limits established by BCNYC Tables 4—1 and 4-2 for any one of the buildings, no fire-resistance rating shall be required for non-bearing portions of the exterior walls of those buildings facing each other, and there shall be no limitation on the pennitted amount of exterior openings.

' According to Solomon 1975, fire protected openings on exterior walls with a separation of less than 30 ft were omitted.

^ Noncombustible.

^ According to Solomon 1 975, corridor partitions were designed to meet 2 h construction to minimize the limitations of dead end corridors.

* See sections C26-504.6 and C26-604.8(i) for exceptions to shaft and stair enclosures requirements.

8 NISTNCSTAR 1-1D. WTC Investigation
Construction

Fire Resistance Rating

(Hours)

6. Structural members supporting a wall Same as required fire resistance of wall

supported, but not less than rating required for member by the class of

construction

7. Floor construction including beams 2

8. Roof construction - including beams, trusses, framing,

arches, domes, shells, cable supported roofs, and roof decks

(based on height of lowest member above floor):

15 ft or less VA

Greater than 15 ft to 20 ft 1

20 ft or more NC

9. Area of refuge separation (C26-604.5, C26-604.6) 2

10. Escalators not used as exits (C26-604.1 1)' Va

11. Enclosures:

Transformer vaults (greater than 35,000 V)

^ (National Fire Protection Association [NFPA] 70)

Emergency generator and fire pump rooms 2

Storage rooms (B-1 occupancy) greater than 75 ft' ^ (Table 5-1 note c)

Telephone closets l'"

Escalators thai connect tw o stories may be unenclosed. According to Solomon 1975, the original drawings indicated a 2 h rated shaft enclosure with louvers in a 1 'A h rated door for the telephone closets. Additionally, a variance was granted permitting the omission of dampers. The requirements were

changed in 1 969 to permit 1 h rated construction with 1 Vi h rated doors. The shaft requirements were eliminated and all floor openings left for future installation of cables had to be firestopped.

NISTNCSTAR 1-1D, WTC Investigation 9
Chapter 3

The minimum covering of prestressing steel shall comply with the requirements of Reference Standard

(RS) 5-15 (C26-502.2(d).

The design and installation provisions for fireproofmg are not specifically contained in the BCNYC. The

specific requirements for these provisions are derived from calculations, tests, and manufacturer's

requirements. Although, C26-501 and C26-502 require that the fire resistance rating of construction

assemblies and the protection of stnactural members shall comply with the requirements of the reference

standards of RS-5. Furthennore, the materials or combinations of materials shall be in accordance with

the specifications of materials used in the ASTM International (ASTM) E 1 19 test.

3.5 OPENING PROTECTION

1 . Openings in a 3 h rated Fire Division or Fire Separation wall

(C26-504.4 and Table 5-3).

Fire Resistance Rating

(Hours)

3 (Class A)

2. Openings in 2 h or 1 '/2 h rated Fire Division or Fire

Separation wall or vertical communication enclosure 1/4 (Class B)

(C26-504.4, C26-604.4(a), C26-1 800.6 and Table 5-3).

3. Openings in 1 h rated Fire Division or Fire Separation walls,

comdors or partitions (C26-504.4, C26-604.4(b) and % (Class B)

Table 5-3).

4. Openings in 1 h rated vertical communication enclosure. 1 (Class B)

5. Required protected openings in exterior walls (Class E or Class F)(C26-503. 1(b)).

"

Noncombustible mail slots not exceeding 40 in.' may be provided in corridor doors (C26-604.4(b)).

Noncombustible louvers may be installed in con idor doors opening into toilets, service sink closets and

electrical closets (C26-604.4(b))."

Openings in Fire Divisions and Fire Separations shall not exceed the size limits in Section C26-504.4(a).

In shafts that contain only one opening below the roof, no opening protective is required (C26-504.6(c)).

Exterior street floor exit doors with a fire separation distance of more than 1 5 ft need not have a fire resistance rating (C26-604.4(a)(l)).

" BCNYC does not limit the size of the louver, however, the Board of Standards and Appeals permits louvers of 2 ft" in Va h

rated doors (Solomon 1975).

10 NISTNCSTAR 1-1 D, WTC Investigation
Construction

Openings in elevator and dumbwaiter shafts shall comply with RS 18 (C26-504.6(c)).

3.6 SEPARATION OF OCCUPANCIES

Fire Resistance Rating

(Hours)

1. Fire Divisions

Between Group B-1 and B-2, C, E, or F-4, 3

2. Fire Separations

Between Groups E and B-2, C, or F-4. NR12,13

Between tenant spaces (C26-504.3(a)).

14 1

15

Spaces classified in occupancy groups having a higher fire index than the occupancy group classification of the building shall be separated by "Fire Divisions" constructed in accordance with

Section C26-504.1(a) and treated as separate buildings (C26-30 1.4(a)).

Spaces classified in occupancy groups having the same or lower fire index than the occupancy group

classification of the building shall be separated by "Fire Separations" constructed in accordance with

Section C26-504.1(b) (C26-301.4(b)).

When a building or space is used for muhiple purposes at different times, the building/space shall be

given a separate occupancy group classification for each of the activities. The design and construction

shall be in accordance with the most restrictive provisions that apply to any of the classifications (C26-301.6).

A minor variation of occupancy or use of a space is acceptable without multiple classifications if the

variation is normally associated with the occupancy classification and no specific danger or hazard is created (C26-301.6).

Fire divisions shall be constructed of noncombustible materials or assembly of noncombustible materials

to provide the fire-resistance ratings (C26-504.2). The following requirements apply:

1. Vertical fire divisions shall be continuous between foundation, roof, or horizontal fire divisions, and through any concealed space in floor or roof construction.

No Requirement.

Separations are not required between accessory business and mercantile activities limited in area to 100 ft', and closets 75 ft" or less in area (Table 5-1 notes b and c). The rated partition was coordinated to terminate at a I h rated ceiling in lieu of extending the partition to the underside of the

slab above (Solomon 1975). Solomon 1 969 confirms the use of 1 h fire resistance rated demising walls between tenant spaces.

NISTNCSTAR 1-1 D. WTC Investigation 11
Chapter 3

2. Horizontal fire divisions shall be continuous between exterior walls and/or vertical fire divisions.

3. Fire divisions shall be made smoketight at their junction with exterior walls.

4. Fire divisions may be offset if the construction between the offset divisions, including their supports, has the same fire-resistance rating as the fire division, with all hollow spaces within

the construction firestopped with noncombustible material.

5. Where combustible members such as joists, beams, or girders bear on, or frame into, vertical

fire divisions, such members shall not extend through the wall and shall have at least 4 in. of

solid noncombustible material below, at the sides, and at the ends of each such member.

6. Chases or recesses shall not be cut into fire divisions so as to reduce their thickness below

that required for the fire-resistance rating.

7. Vertical fire divisions that are hollow shall be firestopped with at least 4 in. of

noncombustible material so as to prevent passage of flame, smoke, or hot gases through the hollow spaces to the stoiy above or below, or to hollow spaces within connecting floor or roof construction.

3.7 FIRESTOPPING

All firestopping or fill materials shall consist of approved noncombustible materials that can be shaped,

fitted, and permanently secured in place (C26-504.7(a)).

Concealed spaces within partitions, walls, floors, roofs, stairs, fumng, pipe spaces, column enclosures,

etc., that would perniit passage of flame, smoke, fumes or hot gases from floor-to-floor shall be

firestopped or filled with noncombustible material in the following locations (C26-504.7):

1 . Hollow partitions and fun"ed spaces.

2. Concealed spaces within stair construction.

3. Ceiling spaces.

4. Exterior cornices.

5. Duct and pipe spaces (C26-504.5 and RS 13-1 Sec. 313 and 314).

6. Hollow vertical Fire Division (C26-504.2(i)).

The concealed space above a fire resistance rated ceiling shall be firestopped into areas not exceeding

3,000 ft-, except where (C26-502.5):

1 . Structural members within the concealed space are individually protected, or

2. The concealed space is sprinklered.

12 NISTNCSTAR 1-1D, WTC Investigation
Construction

3.8 THROUGH PENETRATION PROTECTION

Noncombustible pipes and conduits may pass through fire resistance rated construction provided the following (C26-504.5(b)):

1 . Space between the pipe or conduit and its sleeve or opening does not exceed 2 in. and is packed with noncombustible material.

2. Close-fitting metal escutcheons are provided on both sides of the construction.

3. Aggregate net area of openings does not exceed 25 in.' in any 100 ft" of wall or floor area. Openings in excess of this limit are not permitted unless tested as part of a rated assembly and

so protected.

Ceilings required to have a fire resistance rating may be pierced to accommodate noncombustible electric outlet boxes, recessed lighting fixtures, pipes and ducts as follows (C26-502.5(b)):

1. The aggregate area of outlet boxes and lighting fixtures does not exceed 16 in.' in each 90 ft' of ceiling area.

2. Ouflet boxes and lighting fixtures are constructed of steel at least 0.022 in. thick and sealed

tightly at the ceiling.

3. Additional or larger services are permitted only when tested as part of the assembly and

protected as provided in the test.

The concealed space above fire resistance rated ceilings may be used as a return air plenum if listed (tested) for that purpose provided (RS 13-1 Sec. 316(a)):

1 . All openings are tested as part of the assembly and protected in accordance with the test,

2. The integrity of firestopping is not destroyed,

3. No combustible materials are incorporated in the floor and ceiling construction, and

4. Electrical wiring is plenum rated (NFPA 70 Sec. 300-22).

3.9 FIRE AND SMOKE DAMPERS

Fire dampers shall be provided in accordance with RS 13-1 in each of the following locations

(C26-504.5):

1 . Duct penetrations of walls with a 2 h fire resistance rating or greater (RS 13-1 Sec. 902(a)).

2. Each opening in required vertical shaft enclosures (RS 13-1 Sec. 902(b)).

NISTNCSTAR 1-1D, WTC Investigation 13
Chapter 3

3. Each outlet or inlet opening in vertical shaft enclosure of duct systems serving two or more

floors (RS 13-1 Sec. 902(c)). As an alternate, dampers may be provided at each point where

the vertical duct pierces a floor it serves (RS 13-1 Sec. 902(c)).

4. Branch duct penetrations of vertical duct shaft enclosures (RS 13-1 Sec. 902(c)).

5. Fresh air intakes (RS 13-1 Sec. 902(e)).

6. Aluminum Class 1 duct penetrations of fire resistance rated floors (RS 13-1 Sec. 902(d)).

Fire dampers are not required at the following locations (RS 13-1 Sec. 903):

1. Non-aluminum or Class I vertical shaft branch duct penetrations with a cross-sectional area of

less than 20 in." which supply only air conditioning units discharging air at not over 4 ft above the floor (RS 13-1 Sec. 903(a)).

2. Non-aluminum or Class 1 duct penetrations of a floor (at one place only) with a crosssectional area of less than 20 in." which supply air conditioning units in one story only that discharge air at not over 4 ft above the floor (RS 13-1 Sec. 903(b)).

3. Duct penetrations in systems serving only one floor and used only for exhaust to the outside

and not penetrating a fire wall or fire partition or passing entirely through the vertical shaft enclosure (RS 13-1 Sec. 903(d)).

4. Branch ducts connected to a return riser where subducts are extended at least 22 in. upward

(RS 13-1 Sec. 903(e)).

5. Fire dampers shall be automatic closing VA h fire rated with a fusible link or other heat

actuated device rated approximately 50 °F above the maximum system operating temperature

(RS 13-1 Sec. 905(a)(g)).

Duct openings pennitted in fire resistance rated ceilings are required to be protected with fire dampers

(C26-502.5(b)).

Smoke dampers are required to be installed in the main supply duct and the main return duct in systems

over 15,000 cfm capacity (RS 13-1 Sec. 1003).

Smoke dampers are required to be arranged to close automatically when the system is not in operation, by

the operation of duct smoke detectors, and by the manual emergency fan stop (RS 13-1 Sec. 1003).

14 NISTNCSTAR 1-1D, WTC Investigation
Chapter 4

Interior Finish

4.1 INTERIOR FINISH FLAME SPREAD RATINGS

The minimum interior finish flame spread ratings as defined in ASTM International (ASTM) E 84 and

shown below are based on Table 5^ of the Building Code of the City of New York (BCNYC) and other

sections as noted.

1. Exits and shafts (C26-504. 10(c), C26-604.8(i)(3))

Corridors (C26-504. 10(c), C26-604.2(k)):

Group B-1

Groups B-2, C, E, F-4

16,17

Classification

Class A (0-25)

Class A (0-25)

Class A or B (0-75)

Rooms greater than 1.500 ft" (C26-504. 10(c)):

Groups B-1, B-2, F-4

Group E

Class A or B (0-75)

Class A, B, or C (0-225)

5.

Rooms less than 1,500 ft" (C26-504. 10(c)):

Groups B-1, B-2, E, F-4

Interior finish in kitchens, cooking spaces, pantries,

repair and maintenance shops, boiler rooms, and

incinerator combustion rooms (Table 5^ note f).

Class A, B, or C (0-225)

Class A or B (0-75)

When used in comdors. Class B finish material shall not extend more than 50 ft between separations of Class A finish material

that are at least 2 ft wide (BCNYC Table 5^ note b). Spaces through which it is necessary for occupants of an adjacent room to pass in order to reach the only exit are considered as corridors.

NISTNCSTAR 1-1 D, WTC Investigation 15
Chapter 4

4.2 SMOKE DEVELOPED RATINGS

Interior finish materials shall be limited to smoke developed ratings as defined in ASTM E 84 in the

locations specified:

1. Twenty-five or less in exits and corridors (C26-504. 10(d)).

2. One hundred or less in rooms where the net fiioor area per occupant is 10 ft' or less (C26-504. 10(d)).

No material shall be used in any interior location that upon exposure to fire will produce products that are more toxic in point of concentration than those given off by wood or paper (C26-504. 10(e)).

4.3 INTERIOR TRIM

Up to 20 percent of the aggregate wall and ceiling area of any room or corridor may be finished with

Class A, B, or C (0-225) materials and be exempt from the smoke developed rating requirements

(C26-504. 10(c)(4), C26-504. 10(d)). This allowance shall include the area of doors, folding partitions,

windows, glazing, skylights, luminous ceilings, trim, bases, chair rails, panels, moldings, etc.

4.4 FLOOR FINISH

Finish flooring in all exits shall be of noncombustible material (C26-504.13, C26-604.8(h)).

In all other areas, combustible finish flooring may be used when installed in accordance with

Section C26-504. 13(b).

16 NISTNCSTAR 1-1D, WTC Investigation
Chapter 5

Means of Egress

According to Feld (1987). the egress requirements were in accordance with the provisions of the Building

Code of the City of New York (BCNYC).

5.1 GENERAL

Clear width measurement is the net, unobstructed width of a means of egress without projections in such

width (C26-604.2(a), C26-604.3(b)):

1 . In corridors, projections up to 18 in. wide to the extent of 2 in. per unit of egress width are permitted if the total area of such projections does not exceed 5 percent of the area of the wall on which they occur (C26-604.2(a)).

2. Handrails shall project not more than 3'/2 in. and stringers 2 in. (each side) into the required

stair width (C26-604.8(b), C26-604.8(f)).

Headroom (C26-604.2(b), C26-604.3(c)):

1 . Corridor and exit passageway minimum height of 7 ft 6 in. for 75 percent of the floor area with no point less than 7 ft.

2. Projections from the ceiling shall be at least 7 ft above the floor and located so as not to obstruct full view of exit signs (C26-604.2(b), C26-604.3(c)).

Changes in level requiring less than two risers in a con idor or exit passageway shall be by a ramp

(C26-604.2(e), C26-604.8(d)(2)).

Obstructions to means of egress:

1 . The required width of a means of egress shall not be obstructed or reduced in any manner

(C26-604.2).

2. Corridors shall be kept free of combustible contents (C26-604.2).

3. All exterior means of egress elements, including exterior corridors and stairs, shall be

maintained free of ice and snow accumulation (C26-604.2, C26-604.9).

Corridors may be used as supply or return air ducts or plenums if equipped with an approved smoke

detector or thermostatic device to shut down fans (C26-604.2(j), RS 13-1 Sec. 316(d)).

Stairv,ays connecting two or more stories shall not be used as plenums (RS 13-1 Sec. 316(e)).

NISTNCSTAR 1-1D. WTC Investigation 17
Chapter 5

5.2 EXITS

Evei7 floor area shall be provided with at least two approved independent exits (C26-603.2).

PubHc garages shall be provided with at least two exits from each tier of parking (C26-709.8).

A minimum of two exits or exit access doors shall be provided from every room or space in which the occupant load exceeds the following limits (C26-603.1):

Occupancy Occupant Load

B (Storage) 50

C (Mercantile) 75

E (Business) 7.5

F (Assembly) 75

All required exits shall be located such that they are clearly visible, accessible, and have unobstructed

access at all times (C26-602.1).

In multi-tenant configurations, each tenant shall have access to the required numbers of exits without

passing through other tenant spaces (C26-602.2).

Whenever more than one exit or exit access is required from any room, space, or floor of a building, they

shall be located as remote from each other as practicable (C26-602.3).

Door openings to scissor stairs shall be at least 15 ft apart (C26-602.3).

All vertical exits shall extend in a continuous enclosure to discharge directly to an exterior space or at a yard, court, exit passageway, or street floor lobby of the required width and size to provide all occupants

with a safe access to an open exterior space. Where vertical exits sei'ving floors above grade continue in the same enclosure to serve floors below grade, the portion of such vertical exits above grade shall be

separated from the portion below grade by construction having at least a 1 h fire resistance rating, with

Va h self-closing doors opening in the direction of exit travel from the floors below grade (C26-602.4).

A maximum of 50 percent of the required number of vertical exits is permitted to discharge through a

single exit passageway (C26-604.3).

One hundred percent of the number of vertical exits may discharge through a street floor lobby if egress is provided in two different directions from discharge points to open exterior spaces remote from each other

(C26-604.3(h)(l)).

The clear width of an exit passageway serving two or more vertical exits shall be equal to 75 percent of

the width of all vertical exits it sei'ves (C26-604.3(b)).

18 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

The width of street floor lobbies serv ing as exit passageways shall be increased to accommodate the occupant load of all communicating spaces on the lobby floor that exit through them (C26-604. 3(h)(2)).

No openings other than exit doors are pennitted in exit passageways (C26-604.3(f)).

Openings between street floor lobbies serving as exit passageways and elevators or communicating

spaces and show windows protected in accordance with Section C26-604. 3(h)(3) are permitted.

Street floor lobbies serving as exit passageways may be occupied by newsstands, candy and tobacco

stands, infonnation booths, or similar occupancies if constructed of noncombustible materials, occupying

not more than 5 percent of the net lobby floor area, and if not reducing the required clear width at any

point (C26-604.3(h)(4)).

Horizontal and Supplemental Vertical Exits (C26-604.5 to C26-604.7):

1 . The occupant load capacity for vertical exits may be reduced by 50 percent when one area of

refuge is provided and by 66 percent when two or more areas of refuge are provided

(C26-603.3).

2. At least 3 ft' per person of clear public space, or space occupied by the same tenant or owner,

shall be provided within the area of refuge for the occupant load received in addition to its own occupant load (C26-604.5(b)).

3. Each area of refuge shall be provided with at least one vertical exit and when located above

the 1 1th floor, the vertical exit shall be supplemented by at least one elevator (C26-604.5(c)).

4. Access to an area of refuge, on the same floor, through a horizontal exit, may consist of

doors, balconies, bridges and tunnels (C26-604.6):

a. Doors must swing in the direction of exit travel and be self-closing having a fire resistance rating of 1 V2 h. Where areas of refuge are provided on both sides of a horizontal exit, two door openings shall be provided, each swinging in opposite directions

(C26-604.6(b)).

b. Balconies, bridges and tunnels serving as horizontal exits shall comply with

Section C26-604.6(c).

5. Access to an area of refuge on a floor nearer to the street, through a supplemental vertical

exit, may consist of enclosed interior stairs, ramps, or escalators (C26-604.7):

a. Supplemental vertical exits shall comply with the requirements for interior stairs, and

serv e no other purpose than to connect a floor area with an area of refuge with no

openings in the enclosure other than exit doors (C26-604.7).

b. Every supplemental vertical exit shall have a sign at the entrance stating EXIT TO AREA

OF REFUGE ON FLOOR (C26-604.7).

NISTNCSTAR 1-1D. WTC Investigation 19
Chapter 5

5.3 EXIT WIDTH AND CAPACITY

Occupant load shall be calculated based on the net floor areas in square feet divided by the occupant load

factor (square foot per person) or the actual number of occupants from whom each occupied space is designed, whichever is greater (C26-601.2):

1 . Non-simuhaneous Occupancy - The occupant load of toilets, locker rooms, meeting rooms,

storage rooms, employee cafeterias, and similar rooms or spaces that are not occupied at the same time as other rooms or spaces on the same floor may be omitted from the occupant load

calculation of the floor on which they are located (C26-601 .2(c)).

2. The occupant load of any space shall include the occupant load of all spaces that discharge

thi-Qugh it in order to gain access to an exit (C26-601.2).

Occupancy Occupant Load Factor

Business (offices) 100

Conference rooms (tables) 12

Conference rooms (chairs) 10

Dining spaces 12

Mercantile:

1 St floor/basement 25

All other floors 50

Assembly (fixed seats) No. of seats

Waiting space (standing) 4

Garages/parking 250

Storage rooms 200

Mechanical rooms 200

Where vertical exits serve more than one floor, only the occupant load of each floor considered

individually is used in computing the required capacity of exits at that floor, except where one floor is used by another as a means of egress (C26-60 1.1).

Exit capacity (width) shall not decrease in the direction of exit travel (C26-604.8).

20 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

The w idth of each means of egress component shall be that computed using the appropriate egress unit factor but not less than the minimum width prescribed for the component (C26-601.1, C26-601.3):

1. Where computations give fractional results, the next larger integral number of egress units or

integral number plus Vi shall be used (C26-601.3).

2. A fraction less than Vi may be neglected when constituting less than 10 percent of the total required number of egress units.

When a floor area has access to areas of refuge that comply with the requirements of Section C26-604.5,

the number of persons for whom vertical exits are to be pro\ ided may be reduced to 50 percent of the occupant load of the floor area when one area of refuge is provided, and may be reduce to 33 1/3 percent

of the floor area when two areas of refuge are provided (C26-603.3).

Egress capacity factors - capacity per egress unit (C26-601.1, C26-601.3):

1 . One unit of egress width is equal to 22 in.

2. Doors to outdoors at grade:

a. Occupancy Group B (Storage) - 75 persons per unit.

b. Occupancy Groups C (Mercantile), E (Business), and F (Assembly) - 100 persons per

unit.

3. Other exit and corridor doors:

a. Occupancy Group B (Storage) - 60 persons per unit.

b. Occupancy Group C (Mercantile), E (Business), and F (Assembly) - 80 persons per unit.

4. Stairs and escalators:

a. Occupancy Group B (Storage) - 45 persons per unit.

b. Occupancy Groups C (Mercantile), E (Business), and F (Assembly) - 60 persons per unit.

5. Ramps, corridors, exit passageways, horizontal exits:

a. Occupancy Group B (Storage) - 75 persons per unit.

b. Occupancy Groups C (Mercantile), E (Business), and F (Assembly) - 100 persons per

unit.

c. When ramp slope exceeds 1 in 10, the capacity shall be reduced by 25 percent (Table 6-1

note b).

Where a door is divided by muUions into two or more door openings, each opening shall be measured

separately in computing the number of egress units (Table 6-1 note m).

NISTNCSTAR 1-1D. WTC Investigation 21
Chapter 5

5.4 DOORS

Minimum nominal width shall be 32 in. except for corridor and exit door openings, which shall be 36 in. (C26-604.4(e)):

1 . Door jambs or stops and the door thickness when open shall not reduce the required width by more than 3 in. for each 22 in. of width (C26-604.4(e)).

2. In all cases where a door opening is divided by mullions into two or more door openings, the minimum nominal width of each such opening shall be 32 in. (C26-604.4{c)).

Maximum width of leaf (C26-604.4(e)) is 48 in.

Minimum height (C26-604.4(f)) is 6 ft 8 in.

Door jambs, stops, sills, and closers shall not reduce the clear opening to less than 6 ft 6 in. (C26-604.4(f)).

The floor on both sides of all exit and comdor doors shall be substantially level and have the same

elevation for a distance at least equal to the width of the leaf (C26-604.4(h)).

Where doors lead out of a building, the floor level inside may be IVi in. higher than the level outside

(C26-604.4(h)).

Exit doors, comdor doors sen'ing high hazard occupancy Group A spaces, and coixidor doors from rooms

required to have more than one door shall swing in the direction of egress (C26-604.4(g)).

Vertically sliding doors, rolling shutters, and folding doors shall not be used as exit doors or as corridor

doors (C26-604.4(d)).

Revolving doors designed and constructed in accordance with Section C26-604.4(m) are permitted to be

used as exits except that revolving doors shall not be used as interior exit access doors, at the foot of

stairs, or at the head of basement stairs (C26-604.4(d)).

Turnstiles designed and constmcted in accordance with Section C26-604.4(n) may also be permitted.

Power operated or power assisted manually operated doors may be used as exit or comdor doors provided

they remain closed in case of power failure and are manually operable. To be credited as a required exit,

power operated doors must swing in the direction of exit travel (C26-604.4(l)).

Exit doors and comdor doors shall noiTnally be kept in the closed position (C26-604.4(i)).

Latch bolts shall be provided on all exit doors and corridor doors to hold them in a closed position against

the pressure of expanding gases (C26-604.4(j)(l )(c)).

22 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

Obstruction of means of egress during door opening:

1 . Doors providing access to stairways or ramps shall not block stairs/ramps or stair landings or reduce the width of landings/stairs/ramps to less than 75 percent of the required width or to

less than the width of the door opening on them (C26-604.8(g), C26-604. 10(c)(4)).

2. No door shall swing over the sloping portion of a ramp (C26-604. 8(c)(4)).

Exit and corridor doors and doors providing access to areas of refuge shall be readily openable at all times

from the side from which egress is made without the use of a key (C26-604.4(j)(l)(a), C26-604.5(d)):

1 . Locks may be used in places where extra safeguards are required (banks, museums, etc.), subject to approval of the commissioner, provided the locks are equipped with electrical '

release devices for remote control in case of emergency (C26-604.4())( 1 )(a)(2)).

2. Doors opening into interior enclosed stairs shall not be locked from either side except that doors may be locked to prevent access to the stair from the outside at the street floor (C26-604.4G)(l)(b).

5.5 EXIT ACCESS

Minimum clear width of corridors shall be:

1 . Occupancy Groups B (Storage), C (Mercantile) - 36 in.

2. Occupancy Groups E (Business), F (Assembly) - 44 in.

The maximum travel distance shall not exceed the following limits. Travel distance shall be measured

along the natural and unobstructed path of travel. Where the path of travel is over an access stair, it shall be measured along an inclined straight line through the center of the outer edge of each tread (C26-601.4(a)(c), Table 6-1).

Occupancy Distance (Feet)'"

B-1 (Storage)

B-2 (Storage)

B-2 (Parking

garage)

" C (Mercantile)

E (Business)

F (Assembly < 75

persons)

100

125

100

150

200

150

'* Distances given are for unsprinklered conditions (BCNYC Table 6-1).

NISTNCSTAR 1-1 D, WTC Investigation 23
Chapter 5

The maximum dead-end distance shall not exceed the following limits (C26-604.2(d), Table 6-1):

Occupancy Distance (Feet)'^

B-1 (Storage) 50

B-2 (Storage) NR . C (Mercantile) 50

E (Business) 50

F (Assembly) ' 30

5.6 STAIRWAYS

Minimum clear width shall be at least 44 in. (C26-604.8(b)):

1 . The width of stairs shall be the clear width between walls, grilles, guard, or newel posts.

Stair stringer projections which do not exceed 2 in. on each side and handrail projections of

3'/2 in. are pennitted.

2. Vertical exits in pubhc garages may be 36 in. wide.

3. The minimum width of landings and platforms shall be at least the required width of the

stairway. On a straight run stair, landing and platfonn widths need not be more than 44 in.

Minimum headroom shall be at least 7 ft (C26-604.8(c)).

Maximum height between landings shall be 12 ft (C26-604.8(d)).

Treads and risers (C26-604.8(e), Table 6^):

1 . Maximum riser height:

a. Occupancy Group F (Assembly) - lYi in.

b. All others - IVa in.

2. Minimum tread depth - 9'/2 in. plus nosing

3. The sum of two risers plus one tread exclusive of the nosing shall not be less than 24 nor more than ISVz in.

4. Stair riser and tread dimensions shall be constant in any flight of stairs from story to story.

Curving or skewed stairs that confonn to Section C26-604. 8(e)(4) are pennitted to be used as exits.

Distances given are for unsprinklered conditions. When a corridor is completely enclosed in 2 h fire resistance rated construction with 1/2 h fire rated doors, the permissible length of dead end may be increased by 100 percent (C26-604.2(d)).

24 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

\Vhere exit stainvays serv ing floors above grade continue in the same enclosure to serve floors below

grade, the above and below grade portions shall be separated by 1 h fire resistance rated construction.

Stair identification signs shall be posted on the occupancy side of the stair door indicating the letter designation of the stair.

In buildings or in building sections more than three stories or 40 ft high with roofs having a slope of less than 20 degrees, access to the roof shall be provided by at least one interior stair. Access to set back roof

areas may be through a door or window opening to the roof

No openings of any kind are permitted into stair enclosures other than windows, fire department access

panels, and exit door.

Exterior stairs designed and constructed in accordance with Section C26-604.9 may be used as exits in lieu of interior stairs.

No exterior stair shall exceed 75 ft or six stories in height.

Escalators designed and constructed in accordance with Section C26-604.1 1 may be used as exits in lieu of interior stair.

5.7 RAMPS

The minimum clear width of exit ramps is 44 in. (C26-604.10, C26-604.8(b)).

Le\ el platforms or landings at least as wide as the ramp shall be provided at the top and bottom of all ramps and at intermediate levels as necessary:

1 . Level platforms shall be provided on each side of door openings into or from ramps.

2. Platforms shall be at least 3 ft wide; 5 ft when a door swings onto the platfonn.

Minimum headroom is 6 ft 8 in.

Changes in direction of travel shall be made only at landings (or platforms) (C26-604. 10(c)).

Ramps with a slope not greater than 1 in 12 at any place may be curved.

Ramps shall not have a slope steeper than 1 in 8 and sloping portions shall be at least 3 ft but not more

than 30 ft long between platforms or landings.

Level and ramped moving walkways designed and constructed in accordance with Section C26-604.12

may be used as exits (C26-604.12).

NISTNCSTAR 1-1 D. WTC Investigation 25
Chapter 5

5.8 HANDRAILS AND GUARDRAILS

Continuous handrails are required on both sides of all stairs, and all ramps with a slope exceeding 1 in 12:

1 . Stairs less than 44 in. wide may have a handrail on one side only.

2. Interaiediate handrails shall be provided to divide stairs more than 88 in. wide into widths

that maintain nominal muUiples of 22 in. and widths not greater than 88 in. nor less than

44 in.

3. Handrail height shall be 30 to 34 in. measured vertically above the nosing of treads.

4. Handrail ends shall be returned to walls and posts when tenninated.

5. Handrails shall provide a finger clearance of 1 Vi in. and shall project not more than SVi in. into the required stair width. v

Stair landings and platfonns shall be enclosed on sides by walls, grilles, or guards at least 3 ft height.

5.9 EXIT SIGNS

In all buildings, the location of every exit on eveiy floor shall be clearly indicated by approved EXIT

signs (C26-606.1).

EXIT signs shall be placed at an angle with the exit opening if such placement is required for the signs to serve their puipose.

In areas where the location of the exit may not be readily visible or understood (including long corridors

and open floor areas), directional signs shall be provided to sei"ve as guides from all portions of the corridor or floor.

The size, color and illumination of EXIT signs shall confonn to Section C26-606.3. Directional signs

shall confonn to Section C26-606.4.

All EXIT signs shall be illuminated at all times when the building is occupied.

Where a total of more than four signs (exit and/or directional) are required, all EXIT signs shall be

connected to circuits that are separate from the general lighting and power circuits. These circuits shall be

taken off ahead of the main switch or connected to an emergency lighting power source when such source

is provided.

Any door, passageway, stair, or other means of communication that is not an exit shall be so identified with a NOT AN EXIT sign and a sign indicating its use or puipose or a directional exit sign shall be

provided.

26 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

5.10 MEANS OF EGRESS LIGHTING

Corridors and exits shall be equipped with artificial lighting facilities to provide at least 5 ft candle

intensity floor lighting continuously during the time that conditions of occupancy of the building require

that the exits be available (C26-605.1).

Lighting shall be provided to illuminate changes in direction in and intersections of corridors, balconies,

exit passageways, stairs, ramps, escalators, bridges, tunnels, landings, and platfomis.

Illumination shall be arranged so that failure of any one light does not leave any area in darkness.

Where a total of more than four lights are required, exit lighting shall be connected to circuits that are separate from the general lighting and power circuits. The circuits shall be taken off ahead of the main

switch or connected to an emergency lighting power source when such source is provided.

NISTNCSTAR 1-1D. WTC Investigation 27
Chapter 5

This page intentionally left blank.

28 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 6

Fire Suppression

6.1 AUTOMATIC SPRINKLER PROTECTION

Automatic sprinkler protection shall be designed and installed in accordance with Section C26- 1703.1 and

Reference Standard (RS) 17-2 in the following areas:

1. Spaces in group B-1 > 500 ft".

2. Spaces in group B-1 < 500 ft' when required by the commissioner.

3. Spaces in group B-2 > 5,000 ft" or 75 ft in height.

4. Spaces in high-rise buildings classified as mercantile occupancy group C > 7,500 ft" in floor area or with an unenclosed stair or escalator between any two or more floors.

5. Regardless of occupancy, any story above grade and the first story below grade without

required ventilation.

a. All other stories below grade.

b. Sprinklers may be omitted in toilets, shower rooms, stair, and mechanical and electrical rooms.

A wet-pipe sprinkler system shall be provided throughout all areas requiring automatic sprinkler

protection. In areas subject to freezing, the sprinkler system shall be protected (insulation, heat trace, antifreeze solution) from freezing or a dry-pipe system shall be provided (C26-1703.13).

A sprinkler alarm system shall be provided when more than 36 heads are installed in any fire area or

section (C26-1 703.4).

6.2 STANDPIPES

Wet standpipes designed and installed in accordance with Section C26- 1702.1 and RS 17-1 shall be

provided (C26-1 702. 1(a)(1)):

The number and location of standpipes shall be such that every point of every floor can be reached by a 20 ft stream from a nozzle attached to not more than 125 ft of hose connected to a riser outlet valve

(C26-1702.4):

1. Standpipe risers and IVi in. hose valves shall be located within stairway enclosures

(C26-1702.5(a)).

NISTNCSTAR 1-1D, WTC Investigation 29
Chapter 6

2. When staii'way enclosures are not available within the 125 plus 20 ft distance (145 ft total),

risers and valves shall be located as near to the enclosure as practicable (C26- 1702.5(a)).

The highest riser shall be extended above the roof with a 3-way manifold with 2V2 in. hose valves

(C26-1702. 11(a)(2)).

A 2V2 in. hose outlet shall be provided at each standpipe riser on each floor served, and on the entrance

floor above the riser control valve, located between five and six ft above the landing or floor (C26-1702.1 1(a)(1)).

Hose stations shall be located at the standpipe risers, either inside or adjacent to the entrance of stairway

enclosures (C26-1 702.1 1(b)):

1. Hose stations shall be located to satisfy the 125 plus 20 ft (145 total) requirement

(C26-1702.1 1(b)(1)).

V

2. Hose shall be (C26-1 702. 11(c)):

a. 1 V2 in. unlined (flax-line) linen hose in Groups C, E, and F.

b. 2V2 in. (unhned) in Group B.

3. Auxiliai7 hose stations equipped with 1 '/2 in. (unlined) hose are pemiitted in Groups C, E,

and F (C26-1702.1 1(c)(4), C26-1702.1 1(d)).

Standpipe systems that include more than one riser shall have all risers cross-connected at, or below, the

street entrance floor level (C26-1 702. 10(a)).

Standpipe systems having more than one zone shall be ari'anged such that the risers supplied from each zone are cross-connected below, or in, the stoi-y of the lowest hose outlets from the water source in each zone (C26-1 702. 10(b)).

Standpipe risers shall be at least 4 in. in diameter where the riser height is 150 ft or less from the highest

hose outlet to the level of the entrance floor, 6 in. in diameter where greater than 150 ft (C26-1 702.7,

Table 17-1).

6.3 WATER SUPPLY

Standpipe systems shall have a primary water supply available at all times to eveiy hose outlet or made

available automatically when the hose valve at any outlet is opened (C26-1702.14).

Combinations of two or more of the following sources shall serve as the primary water supply

(C26-1702. 14(b)):

1 . Direct cormection to city water system.

2. Direct connection to a private yard main.

30 NISTNCSTAR 1-1D, WTC Investigation
Fire Suppression

3. Pressure tank(s).

4. Automatic fire pump (C26-1 702. 14(b)(5)).

a. In buildings higher than 300 ft, the automatic fire pump shall be used only for the lower

300 ft.

b. Zones above 300 ft shall be supplied by either a gravity or pressure tank.

5. An additional standpipe system water supply shall be provided for standpipes in buildings over 300 ft high (C26- 1702. 15(a)). The primary water supply to the standpipe system shall be supplemented by one or more manually operated fire pumps (C26-1 702. 1 5(a)).

At least one of the following automatic source of water supply shall be provided for sprinklers

(C26-1 703.8(a)):

1. Gravity tank(s).

2. Pressure tank(s).

3. Automatic fire pump.

4. Direct connection to public water system.

Domestic water supply may be used to supply cooling tower sprinklers and sprinklers installed in buildings classified in Occupancy Group E (Business) in accordance with Section C26-1703.9(e)

(C26-1 703.9 (c) and(d)).

Auxiliary sources of water supply for sprinkler systems may include a manually actuated fire pump or Siamese connection (C26-1 703.8(b)).

Combined Water Supplies:

1 . Fire pumps may simuhaneously serve as the required auxiliary water supply for standpipe

and sprinkler systems in accordance with Section C26-1 702. 15(d).

2. Tanks used to provide the required primary water supply to a standpipe system may also be

used as a supply for an automatic sprinkler system (C26-1 703.8(c)).

One standpipe system and one sprinkler system Siamese connection shall be provided for each 300 ft of

exterior building wall or fraction thereof facing each street or public space (C26- 1702.9(a),

C26-1 703.6(a)(1)). In addition:

1 . Modifications based on street frontage are permitted by Sections C26-1702.9(b)-(f).

2. Each Siamese connection shall be connected to a riser or to a cross connection connecting

other Siamese connections or risers (C26- 1702. 10(f)).

NISTNCSTAR 1-1D, WTC Investigation 31
In below grade sprinkler systems for garage occupancies, a sprinkler Siamese connection shall be provided within 50 ft of evei-y exit or entrance used by motor vehicles (C26-1703. 6(a)(2)).

Siamese connections for partial sprinkler systems shall be in accordance with

Section C26-1703.6(a)(3).

NISTNCSTAR 1-1D, WTC Investigation
Section I

Fire Protection Summary for

THE World Trade Center Towers
This page intentionally left blank.
Executive Summary

As part of the analysis of building and fire codes and standards of the National Institute of Standards and

Technology (NIST) World Trade Center (WTC) Investigation, this report supports the effort to determine

the minimum construction requirements used in the design of WTC 1 and WTC 2. The puipose of this report is to summarize the fire protection (both passive and active) and life safety provisions used to design and construct WTC 1 and WTC 2.

Although the Port Authority of New York and New Jersey (PANYNJ) was not subject to the Building

Code of the City of New York (BCNYC), WTC 1 and WTC 2 were to be designed in accordance with the BCNYC and all applicable Reference Standards (RS). The initial building concept, including an early

conceptual design by Skidmore, Owings & Merrill, was based on the 1938 BCNYC. In 1965, PANYNJ

instructed the designers to follow the latest (second and third) drafts of the revised (what would become

the 1968) Code to take advantage of relaxations that could save on construction costs.

The BCNYC, building characteristics, and early design choices were used to detennine the minimum

construction requirements for the design of WTC 1 and WTC 2. Because the BCNYC contains

requirements for various r>'pes of buildings, it was important to identify certain building requirements

early in the design. By identifying specific building characteristics, the designer can detemiine which

requirements must be complied with and which requirements are not applicable.

The information included in Table E-1 was used to classify the buildings and detennine the minimum

requirements within the BCNYC. Based on the height, area, primary occupancy classification, and no

sprinkler protection, the minimum construction type (permitted by the 1968 BCNYC) was I-B (3 h

protected) for both buildings. Fire resistance ratings for the structural components, fire divisions, and fire separations were based on this classification. Many of the means of egress, fire suppression, and fire alarm requirements were also based on the infonnation in Table E-1. An abbreviated list of the fire protection provisions is as follows. A complete list of the requirements is identified in the main body of

this report.

• A standpipe system was required.

• An automatic sprinkler system was only required in spaces below grade.

• A telephone and signaling system was required for fire department use in operating the standpipe system.

• Detectors were only required to sense smoke entering return grills of the heating, ventilating,

and air conditioning system and to shut down fans.

• Manual fire alann boxes were not required.

• Audible/visual devices were not required.

NISTNCSTAR 1-1 D. WTC Investigation 1
Executive Summary

Although a fire alann and voice communication system was not required, a system was

installed.

Exit signs and emergency lighting were required in specified spaces.

An emergency power system was not required.

Smoke and heat venting was required in certain shafts, including elevators.

Stair pressurization was not required.

A smoke purge system was not required.

Building Height

Number of Floors Above Grade Footprint

Primary

Occupancy

Classification WTC 1 1,368 ft 110 42,900 ft- Group E (Business)

WTC2 1.362 ft 110 42,900 ft- Group E (Business)

Source: Merrit 2000a, 2000b; PANYNJ.

2 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 1 Introduction

1.1 PURPOSE

The purpose of this report is to summarize the major fire protection (both passive and active) and hfe

safety provisions used to design and construct the World Trade Center (WTC) towers.

1.2 INTRODUCTION

The regulation of building construction is a direct resuh of the recognition that life safety is served by the best available knowledge and practice. Codes and standards are created to establish minimum

requirements. Model codes have been published throughout the United States since 1905 (Boring 1981).

Through the use of technology advancements and serious incidents, such as fires, codes are developed

and later revised to continually implement increased knowledge. Establishing reference standards is just as important to establishing codes. Referenced standards act as a technical basis of the code and provide

further methods of testing, installation and maintenance. Municipalities can adopt model building codes

and national standards or develop their own. Alternatively, many municipalities throughout the United

States have adopted model building codes and national standards, and then amended portions as deemed

necessary. New York City, however, developed their own building code and provide a technical basis

with a mixture of nationally recognized standards (National Fire Protection Association, ASTM

International, American National Standards Instimte, etc.) and New York City developed reference

standards (denoted by RS ##).

In accordance with the instructions issued by the Port Authority of New York and New Jersey (PANYNJ

or Port Authority) at the start of the project, construction drawings for the WTC were to conform with the requirements of the Building Code of the City of New York (BCNYC), although as a so-called state compact under the U.S. Constitution, the Port Authority was exempt from state or local laws, including

the BCNYC. Any variations from the Code were to be called to the attention of the Port Authority for

final decision and authorization (Solomon 1975). Variances from the 1968 edition of the BCNYC, along

with the applicable provisions of the Code, will be identified (to the best extent possible) in this report.' This report summarizes the major provisions of the BCNYC. Readers interested in the more detailed

analysis should seek information directly from the BCNYC.

The design of the WTC towers took many years to develop. The initial design was to be in conformance

with the 1938 BCNYC. However, in 1965, a decision was made to use the provisions of the newly

proposed BCNYC (Kyle 1965). This decision included the rationale that (I) the new Code had been

reviewed by technical groups and modified to meet the major objections; (2) the Code would probably be

adopted before the WTC towers were constructed and (3) the Building Commissioner favored the approach of using advanced techniques in the design of the towers. Additionally, the PANYNJ

repeatedly pointed out that it was not subject to the provisions of the BCNYC (e.g., Tozzoli 1966). Drafts

The applicable provisions of the BCNYC, given throughout the report, are denoted by C26-###.

NISTNCSTAR 1-1D, WTC Investigation 3
Chapter 1

of the newly proposed code were used until December 1968 when the new BCNYC was adopted. The

December 6, 1968, BCNYC was referred to as the applicable building code for the construction of WTC

1 and WTC 2 and is the base document for identifying the design and constixiction provisions in this report.

It was the policy of PANYNJ to follow the requirements of the BCNYC. Thus, since not all of the documentation used in the design and construction of the towers was identified, the assumption has been

made that the construction followed the requirements of the BCNYC. Where documentation was

identified, illustrating either conformance with or deviation from a BCNYC provision, a reference has

been provided. This report does not evaluate whether or not the design provisions, indicated on drawings

and in con'espondence, were actually incorporated in the construction of the towers, but merely identifies the provisions established in the design. Since the buildings no longer exist, it is generally impossible to verify the inclusion of specific design features beyond their being discussed in other documents.

4 NISTNCSTAR 1-1D, WTC Investigation
Chapter 2

General

2.1 APPLICABLE CODES AND STANDARDS

1. Building Code of the City of New York, 1968."

2. USASI 17.1 (1965) including Supplement A 17. la (1967) -USA Standard Safety Code for Elevators, Dumbwaiters. Escalators, and Moving Walks (as modified by Reference Standards

[RS] 18-1).

3. National Fire Protection Association (NFPA) 1 3 - Standard for the Installation of Sprinkler

Systems, 1966 (as modified by RS 17-2).

4. NFPA 22 - Standard for Water Tanks for Private Fire Protection, 1 962 (as modified by

RS 17).

5. NFPA 72 - Proprietary and Auxiliary Protective Signaling Systems, 1967 (as modified by

RS 17-5).

6. NFPA 80 - Installation of Fire Doors and Windows, 1967 (as modified by RS 5-8).

7. NFPA 90A - Standard for the Installation of Air Conditioning and Ventilating Systems, 1967

(as modified by RS 13-1).

8. NFPA 204 - Guide for Smoke and Heat Venting, 1961 (RS5-11).

9. ASTM International (ASTM) E 84 - Standard Method of Test for Surface Burning

Characteristics of Building Materials, 1961 (as modified by RS 5-5).

10. ASTM E 1 19 - Standard Methods of Fire Tests of Building Construction and Materials, 1961

(as modified by RS 5-2).

11. RS 5-15 - Minimum Covering of Prestressing Steel for Various Fire Resistance Ratings.

12. RS 17-1 - Standpipe Construction.

13. RS 17-3 - Standards for the Installation of Fire, Sprinkler, Standpipe, Smoke Detection... and

other Alarm and Extinguishing Systems.

^ Including the BCNYC Reference Standards that modify national standards as deemed necessary.

NISTNCSTAR 1-1 D. WTC Investigation
Chapter 2

2.2 BUILDING SUMMARIES

Building^ Height Above Grade" Footprint

Construction

BCNYC)

Primary

Classification WTC r 1,368 ft no 42,900 ft- 1-B Group E

(Business)

WTC 2'^ 1,362 ft 110 42,900 ft- 1-B Group E

(Business)

a. These buildings are located inside the Borough of Manhattan Fire District without additional restrictions imposed based on its use and occupancy (C26-402, 1 , C26-403. 1 ). b. Documentation indicates that the Concourse Level was treated as an underground street (Solomon 1975). Thus, the Plaza

level is the first floor.

c. WTC 1 characteristics are from Merritt 2000a. ^

d. WTC 2 characteristics are from Merritt 2000b. Source: Merrit 2000a, 2000b; PANYNJ.

6 NISTNCSTAR 1-1D, WTC Investigation
Chapter 3

Construction

3.1 CONSTRUCTION CLASSIFICATION

The minimum construction type permitted for both World Trade Center (WTC) towers was Class I-B (3 h

protected).^

3.2 BUILDING LIMITATIONS

In accordance with Table 4-2 of the Building Code of the City of New York (BCNYC) the height and

area are not limited for an unsprinklered Class I-B construction building housing a Group E occupancy:

• Height - No Limit

• Area - No Limit

3.3 SECONDARY/ACCESSORY OCCUPANCIES

Occupancy Fire Index

B-1, Storage (Moderate Hazard) 3

B-2, Storage (Low Hazard, Garage) 2

C, Mercantile 2

F-4, Assembly (Restaurant) 1

3.4 FIRE RESISTANCE RATINGS

The minimum required fire resistance ratings listed as follows are in accordance with Table 3^ of the BCNYC, unless noted otherwise. According to Solomon 1969 and Bracco 1969, the fire resistance

ratings of the buildings were designed in accordance with the BCNYC.

Because there was considered to be "no economic advantage" to design WTC 1 and WTC 2 to a higher construction

classification (i.e., Class I-A). the buildings were constructed to the minimum construction class required by the BCNYC

(Feld 1987). Thus, all BCNYC requirements identified herein, which are dependent upon construction class, are given for Class I-B.

NISTNCSTAR 1-1D, WTC Investigation 7
Chapter 3

Fire Resistance Rating

(Hours)

1. Exterior Bearing Walls 3

2. Exterior Non-bearing Walls having an Exterior

Separation of:"*

Three ft or less with 0 percent openings 2

Greater than 3 ft to less than 15 ft with 3 '/a percent ^

protected openings

1 5 ft to less than 30 ft with 3 Vi percent openings^ 1 Vi

30 ft or greater with unlimited openings NC^

3. Interior Walls:

Interior bearing walls and bearing partitions 3

Exit access corridors (C26-604.2(h)) 1^

4. Enclosure of vertical exits, ^ exit passageways, hoistways, and

^

shafts

5. Columns, girders, trusses (other than roof trusses) and

framing:

Supporting one floor 2

Supporting more than one floor or a floor and roof 3

^ When two or more buildings are constructed on the same lot and the combined floor area of the buildings does not exceed the

limits established by BCNYC Tables 4-1 and 4-2 for any one of the buildings, no fire-resistance rating shall be required for non-bearing portions of the exterior walls of those buildings facing each other, and there shall be no limitation on the permitted amount of exterior openings.

' According to Solomon 1975, fire protected openings on exterior walls with a separation of less than 30 ft were omitted.

* Noncombustible.

^ According to Solomon 1975, corridor partitions were designed to meet 2 h construction to minimize the limitations of dead end corridors.

** See sections C26-504.6 and C26-604.8(i) for exceptions to shaft and stair enclosures requirements.

8 NISTNCSTAR 1-1D, WTC Investigation
Construction

Fire Resistance Rating

(Hours)

6. Structural members supporting a wall Same as required fire resistance of wall

supported, but not less than rating required for member by the class of

construction

7. Floor construction including beams 2

8. Roof construction - including beams, trusses, framing,

arches, domes, shells, cable supported roofs, and roof decks

(based on height of lowest member above floor):

15 ft or less I'/.

Greater than 15 ft to 20 ft 1

20 ft or more NC

9. Area of refuge separation (C26-604.5, C26-604.6) 2

1 0. Escalators not used as exits (C26-604. 1 1

)'* Va

1 1 . Enclosures:

Transformer vaults (greater than 35,000 V)

^ (National Fire Protection Association [NFPA] 70)

Emergency generator and fire pump rooms 2

Storage rooms (B-1 occupancy) greater than 75 ft"

^ (Table 5-1 note c)

Telephone closets l'"

Escalators that connect two stories may be unenclosed. According to Solomon 1975, the original drawings indicated a 2 h rated shaft enclosure with louvers in a 1 Vi h rated door for the telephone closets. Additionally, a \ ariance was granted permitting the omission of dampers. The requirements were

changed in 1 969 to permit 1 h rated construction with 1 Vi h rated doors. The shaft requirements were eliminated and all floor openings left for future installation of cables had to be firestopped.

NISTNCSTAR 1-1 D. WTC Investigation 9
Chapter 3

The minimum covering of prestressing steel shall comply with the requirements of Reference Standard

(RS) 5-15 (C26-502.2(d).

The design and installation provisions for fireproofmg are not specifically contained in the BCNYC. The

specific requirements for these provisions are derived from calculations, tests, and manufacturer's

requirements. Although, C26-501 and C26-502 require that the fire resistance rating of construction

assemblies and the protection of structural members shall comply with the requirements of the reference

standards of RS-5. FurtheiTnore, the materials or combinations of materials shall be in accordance with

the specifications of materials used in the ASTM International (ASTM) E 119 test.

3.5 OPENING PROTECTION

Fire Resistance Rating

(Hours)

1 . Openings in a 3 h rated Fire Division or Fire Separation wall

(C26-504.4 and Table 5-3).

3 (Class A)

2. Openings in 2 h or 1

'/> h rated Fire Division or Fire

Separation wall or vertical communication enclosure 1 Vi (Class B)

(C26-504.4, C26-604.4(a), C26-1 800.6 and Table 5-3).

3. Openings in 1 h rated Fire Division or Fire Separation walls,

comdors or partitions (C26-504.4, C26-604.4(b) and Va (Class B)

Table 5-3).

4. Openings in 1 h rated vertical communication enclosure. 1 (Class B)

5. Required protected openings in exterior walls (Class E or Class F)(C26-503. Kb)).

^

Noncombustible mail slots not exceeding 40 in." may be provided in corridor doors (C26-604.4(b)).

Noncombustible louvers may be installed in corridor doors opening into toilets, service sink closets and

electrical closets (C26-604.4(b))."

Openings in Fire Divisions and Fire Separations shall not exceed the size limits in Section C26-504.4(a).

In shafts that contain only one opening below the roof, no opening protective is required (C26-504.6(c)).

Exterior street floor exit doors with a fire separation distance of more than 1 5 ft need not have a fire resistance rating (C26-604.4(a)(l)).

BCNYC does nol limit the size of the louver, however, the Board of Standards and Appeals permits louvers of2ff in^h

rated doors (Solomon 1975).

10 NISTNCSTAR 1-1 D, WTC Investigation
Construction

Openings in elevator and dumbwaiter shafts shall comply with RS 18 (C26-504.6(c)).

3.6 SEPARATION OF OCCUPANCIES

Fire Resistance Rating

(Hours)

1. Fire Divisions

Between Group B-1 and B-2, C, E, or F-4 3

2. Fire Separations

Between Groups E and B-2, C, or F-4. NR12.13

Between tenant spaces (C26-504.3(a)).

14 1

15

Spaces classified in occupancy groups having a higher fire index than the occupancy group classification of the building shall be separated by "Fire Divisions" constructed in accordance with

Section C26-504.1(a) and treated as separate buildings (C26-30 1.4(a)).

Spaces classified in occupancy groups having the same or lower fire index than the occupancy group

classification of the building shall be separated by "Fire Separations" constructed in accordance with

Section C26-504.1(b) (C26-30 1.4(b)).

When a building or space is used for multiple purposes at different times, the building/space shall be

given a separate occupancy group classification for each of the activities. The design and construction

shall be in accordance with the most restrictive provisions that apply to any of the classifications

A minor variation of occupancy or use of a space is acceptable without multiple classifications if the

variation is normally associated with the occupancy classification and no specific danger or hazard is created (C26-301.6).

Fire divisions shall be constructed of noncombustible materials or assembly of noncombustible materials

to provide the fire-resistance ratings (C26-504.2). The following requirements apply:

1. Vertical fire divisions shall be continuous between foundation, roof, or horizontal fire divisions, and through any concealed space in floor or roof construction.

' No Requirement. " Separations are not required between accessory business and mercantile activities limited in area to 100 ft", and closets 75 ft" or less in area (Table 5-1 notes b and c). The rated partition was coordinated to terminate at a 1 h rated ceiling in lieu of extending the partition to the underside of the

slab above (Solomon 1975). Solomon 1969 confirms the use of 1 h fire resistance rated demising walls between tenant spaces.

NIST NCSTAR 1-1D, WTC Investigation 1

1

(C26-301.6).
Chapter 3

2. Horizontal fire divisions shall be continuous between exterior walls and/or vertical fire divisions.

3. Fire divisions shall be made smoketight at their junction with exterior walls.

4. Fire divisions may be offset if the construction between the offset divisions, including their supports, has the same fire-resistance rating as the fire division, with all hollow spaces within

the construction firestopped with noncombustible material.

5. Where combustible members such as joists, beams, or girders bear on, or frame into, vertical

fire divisions, such members shall not extend through the wall and shall have at least 4 in. of

solid noncombustible material below, at the sides, and at the ends of each such member.

6. Chases or recesses shall not be cut into fire divisions so as to reduce their thickness below

that required for the fire-resistance rating.

7. Vertical fire divisions that are hollow shall be firestopped with at least 4 in. of

noncombustible material so as to prevent passage of flame, smoke, or hot gases through the hollow spaces to the story above or below, or to hollow spaces within connecting floor or roof construction.

3.7 FIRESTOPPING

All firestopping or fill materials shall consist of approved noncombustible materials that can be shaped,

fitted, and pennanently secured in place (C26-504.7(a)).

Concealed spaces within partitions, walls, floors, roofs, stairs, furring, pipe spaces, column enclosures,

etc., that would pemiit passage of flame, smoke, fumes or hot gases from floor-to-floor shall be

firestopped or filled with noncombustible material in the following locations (C26-504.7):

1 . Hollow partitions and furred spaces.

2. Concealed spaces within stair construction.

3. Ceiling spaces.

4. Exterior cornices.

5. Duct and pipe spaces (C26-504.5 and RS 1 3-1 Sec. 3 1 3 and 3 14).

6. Hollow vertical Fire Division (C26-504.2(i)).

The concealed space above a fire resistance rated ceiling shall be firestopped into areas not exceeding

3,000 ft", except where (C26-502.5):

1 . Structural members within the concealed space are individually protected, or

2. The concealed space is sprinklered.

12 NISTNCSTAR 1-1 D, WTC Investigation
Construction

3.8 THROUGH PENETRATION PROTECTION

Noncombustible pipes and conduits may pass through fire resistance rated construction provided the following (C26-504.5(b)):

1 . Space between the pipe or conduit and its sleeve or opening does not exceed 2 in. and is packed with noncombustible material.

2. Close-fitting metal escutcheons are pro\'ided on both sides of the construction.

3. Aggregate net area of openings does not exceed 25 in." in any 100 ft" of wall or floor area. Openings in excess of this limit are not permitted unless tested as part of a rated assembly and

so protected.

Ceilings required to have a fire resistance rating may be pierced to accommodate noncombustible electric outlet boxes, recessed lighting fixtures, pipes and ducts as follows (C26-502.5(b)):

1 . The aggregate area of outlet boxes and lighting fixtures does not exceed 1 6 in." in each 90 ft^ of ceiling area.

2. Outlet boxes and lighting fixtures are constructed of steel at least 0.022 in. thick and sealed

tightly at the ceiling.

3. Additional or larger sers ices are permitted only when tested as part of the assembly and

protected as provided in the test.

The concealed space above fire resistance rated ceilings may be used as a return air plenum if listed (tested) for that purpose provided (RS 13-1 Sec. 316(a)):

1 . All openings are tested as part of the assembly and protected in accordance with the test,

2. The integrity of firestopping is not destroyed,

3. No combustible materials are incorporated in the floor and ceiling construction, and

4. Electrical wiring is plenum rated (NFPA 70 Sec. 300-22).

3.9 FIRE AND SMOKE DAMPERS

Fire dampers shall be provided in accordance with RS 13-1 in each of the following locations

(C26-504.5):

1 . Duct penetrations of walls with a 2 h fire resistance rating or greater (RS 13-1 Sec. 902(a)).

2. Each opening in required vertical shaft enclosures (RS 13-1 Sec. 902(b)).

NISTNCSTAR 1-1D, WTC Investigation 13
Chapter 3

3. Each outlet or inlet opening in vertical shaft enclosure of duct systems serving two or more

floors (RS 13-1 Sec. 902(c)). As an alternate, dampers may be provided at each point where

the vertical duct pierces a floor it serves (RS 13-1 Sec. 902(c)).

4. Branch duct penetrations of vertical duct shaft enclosures (RS 13-1 Sec. 902(c)).

5. Fresh air intakes (RS 13-1 Sec. 902(e)).

6. Aluminum Class I duct penetrations of fire resistance rated floors (RS 13-1 Sec. 902(d)).

Fire dampers are not required at the following locations (RS 13-1 Sec. 903):

1 . Non-aluminum or Class I vertical shaft branch duct penetrations with a cross-sectional area of

less than 20 in." which supply only air conditioning units discharging air at not over 4 ft above the floor (RS 13-1 Sec. 903(a)).

2. Non-aluminum or Class 1 duct penetrations of a floor (at one place only) with a cross- sectional area of less than 20 in.' which supply air conditioning units in one story only that discharge air at not over 4 ft above the floor (RS 13-1 Sec. 903(b)).

3. Duct penetrations in systems serving only one floor and used only for exhaust to the outside

and not penetrating a fire wall or fire partition or passing entirely through the vertical shaft enclosure (RS 13-1 Sec. 903(d)).

4. Branch ducts connected to a return riser where subducts are extended at least 22 in. upward

(RS 13-1 Sec. 903(e)).

5. Fire dampers shall be automatic closing 1 Vi h fire rated with a fusible link or other heat

actuated device rated approximately 50 °F above the maximum system operating temperature

(RS 13-1 Sec. 905(a)(g)).

Duct openings pennitted in fire resistance rated ceilings are required to be protected with fire dampers

(C26-502.5(b)).

Smoke dampers are required to be installed in the main supply duct and the main return duct in systems

over 15,000 cfm capacity (RS 13-1 Sec. 1003).

Smoke dampers are required to be arranged to close automatically when the system is not in operation, by

the operation of duct smoke detectors, and by the manual emergency fan stop (RS 13-1 Sec. 1003). .

14 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 4

Interior Finish

4.1 INTERIOR FINISH FLAME SPREAD RATINGS

The minimum interior finish flame spread ratings as defined in ASTM International (ASTM) E 84 and

shown below are based on Table 5^ of the Building Code of the City of New York (BCNYC) and other

sections as noted.

1. Exits and shafts (C26-504. 10(c), C26-604.8(i)(3))

2. Corridors (C26-504. 10(c), C26-604.2(k)):

Group B-1

Groups B-2, C, E, F-4

16.17

Classification

Class A (0-25)

Class A (0-25)

Class A or B (0-75)

3. Rooms greater than 1,500 ft" (C26-504. 10(c)):

Groups B-1, B-2, F-4

Group E

Class A or B (0-75)

Class A, B, or C (0-225)

4. Rooms less than 1 ,500 ft" (C26-504. 1 0(c)):

Groups B-1. B-2, E. F-4

5. Interior finish in kitchens, cooking spaces, pantries,

repair and maintenance shops, boiler rooms, and

incinerator combustion rooms (Table 5^ note f).

Class A, B, or C (0-225)

Class A or B (0-75)

When used in comdors. Class B finish matenal shall not extend more than 50 ft between separations of Class A finish material

that are at least 2 ft wide (BCNYC Table 5-^ note b). Spaces through which it is necessary for occupants of an adjacent room to pass in order to reach the only exit are considered as

corridors.

NISTNCSTAR 1-1D. WTC Investigation 15
Chapter 4

4.2 SMOKE DEVELOPED RATINGS

Interior finish materials shall be limited to smoke developed ratings as defined in ASTM E 84 in the locations specified:

1 . Twenty-five or less in exits and corridors (C26-504. 1 0(d)).

2. One hundred or less in rooms where the net floor area per occupant is 10 ft" or less (C26-504. 10(d)).

No material shall be used in any interior location that upon exposure to fire will produce products that are more toxic in point of concentration than those given off by wood or paper (C26-504. 10(e)).

4.3 INTERIOR TRIM

Up to 20 percent of the aggregate wall and ceiling area of any room or corridor may be finished with

Class A, B, or C (0-225) materials and be exempt from the smoke developed rating requirements

(C26-504. 10(c)(4), C26-504. 10(d)). This allowance shall include the area of doors, folding partitions,

windows, glazing, skylights, luminous ceilings, trim, bases, chair rails, panels, moldings, etc.

4.4 FLOOR FINISH

Finish flooring in all exits shall be of noncombustible material (C26-504.13, C26-604.8(h)).

In all other areas, combustible finish flooring may be used when installed in accordance with

Section C26-504. 13(b).

16 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 5

Means OF Egress

According to Feld (1987), the egress requirements were in accordance with the provisions of the Building

Code of the City of New York (BCNYC).

5.1 GENERAL

Clear width measurement is the net, unobstructed width of a means of egress without projections in such

width (C26-604.2(a), C26-604.3(b)):

1 . In corridors, projections up to 18 in. wide to the extent of 2 in. per unit of egress width are permitted if the total area of such projections does not exceed 5 percent of the area of the wall on which they occur (C26-604.2(a)).

2. Handrails shall project not more than 3'/2 in. and stringers 2 in. (each side) into the required

stair width (C26-604.8(b), C26-604.8(f)).

Headroom (C26-604.2(b), C26-604.3(c)):

1. Corridor and exit passageway minimum height of 7 ft 6 in. for 75 percent of the floor area with no point less than 7 ft.

2. Projections from the ceiling shall be at least 7 ft above the floor and located so as not to obstruct ftiU view of exit signs (C26-604.2(b), C26-604.3(c)).

Changes in level requiring less than two risers in a corridor or exit passageway shall be by a ramp

(C26-604.2(e), C26-604.8(d)(2)).

Obstructions to means of egress:

1 . The required width of a means of egress shall not be obstructed or reduced in any manner

(C26-604.2).

2. Corridors shall be kept free of combustible contents (C26-604.2).

3. All exterior means of egress elements, including exterior corridors and stairs, shall be

maintained free of ice and snow accumulation (C26-604.2, C26-604.9).

Corridors may be used as supply or return air ducts or plenums if equipped with an approved smoke

detector or thennostatic device to shut down fans (C26-604.2(j), RS 13-1 Sec. 316(d)).

Stairways connecting two or more stories shall not be used as plenums (RS 13-1 Sec. 316(e)).

NISTNCSTAR 1-1 D, WTC Investigation 17
Chapter 5

5.2 EXITS

Every floor area shall be provided with at least two approved independent exits (C26-603.2).

Pubhc garages shall be provided with at least two exits from each tier of parking (C26-709.8).

A minimum of two exits or exit access doors shall be provided from every room or space in which the occupant load exceeds the following limits (C26-603.1):

Occupancv Occupant Load

B (Storage) 50

C (Mercantile) 75

E (Business) J5

'

F (Assembly) 75

All required exits shall be located such that they are clearly visible, accessible, and have unobstructed

access at all times (C26-602.1).

In multi-tenant configurations, each tenant shall have access to the required numbers of exits without

passing through other tenant spaces (C26-602.2).

Whenever more than one exit or exit access is required from any room, space, or floor of a building, they

shall be located as remote from each other as practicable (C26-602. 3).

Door openings to scissor stairs shall be at least 15 ft apart (C26-602.3).

All vertical exits shall extend in a continuous enclosure to discharge direcfly to an exterior space or at a yard, court, exit passageway, or street floor lobby of the required width and size to provide all occupants

with a safe access to an open exterior space. Where vertical exits serving floors above grade continue in the same enclosure to serve floors below grade, the portion of such vertical exits above grade shall be

separated from the portion below grade by construction having at least a 1 h fire resistance rating, with

h self-closing doors opening in the direction of exit travel from the floors below grade (C26-602.4).

A maximum of 50 percent of the required number of vertical exits is permitted to discharge through a

single exit passageway (C26-604.3).

One hundred percent of the number of vertical exits may discharge through a street floor lobby if egress is provided in two different directions from discharge points to open exterior spaces remote from each other

(C26-604.3(h)(l)).

The clear width of an exit passageway serving two or more vertical exits shall be equal to 75 percent of

the width of all vertical exits it serves (C26-604.3(b)).

18 NISTNCSTAR 1-1 D, WTC Investigation
Means of Egress

The width of street floor lobbies serving as exit passageways shall be increased to accommodate the occupant load of all communicating spaces on the lobby floor that exit through them (C26-604.3(h)(2)).

No openings other than exit doors are pemiitted in exit passageways (C26-604.3(f)).

Openings between street floor lobbies serving as exit passageways and elevators or communicating

spaces and show windows protected in accordance with Section C26-604. 3(h)(3) are pennitted.

Street floor lobbies serving as exit passageways may be occupied by newsstands, candy and tobacco

stands, information booths, or similar occupancies if constructed of noncombustible materials, occupying

not more than 5 percent of the net lobby floor area, and if not reducing the required clear width at any

pomt (C26-604.3(h)(4)).

Horizontal and Supplemental Vertical Exits (C26-604.5 to C26-604.7):

1. The occupant load capacity for vertical exits may be reduced by 50 percent when one area of

refuge is provided and by 66 percent when two or more areas of refuge are provided

(C26-603.3).

2. At least 3 ft" per person of clear public space, or space occupied by the same tenant or owner,

shall be provided within the area of refuge for the occupant load received in addition to its own occupant load (C26-604.5(b)).

3. Each area of refuge shall be provided with at least one vertical exit and when located above

the 1 1th floor, the vertical exit shall be supplemented by at least one elevator (C26-604.5(c)).

4. Access to an area of refuge, on the same floor, through a horizontal exit, may consist of

doors, balconies, bridges and tunnels (C26-604.6);

a. Doors must swing in the direction of exit travel and be self-closing having a fire resistance rating of 1 Vi h. Where areas of refuge are provided on both sides of a

horizontal exit, two door openings shall be provided, each swinging in opposite directions

(C26-604.6(b)).

b. Balconies, bridges and tunnels serving as horizontal exits shall comply with

Section C26-604.6(c).

5. Access to an area of refuge on a floor nearer to the street, through a supplemental vertical

exit, may consist of enclosed interior stairs, ramps, or escalators (C26-604.7):

a. Supplemental vertical exits shall comply with the requirements for interior stairs, and

serve no other purpose than to connect a floor area with an area of refuge with no

openings in the enclosure other than exit doors (C26-604.7).

b. Every supplemental vertical exit shall have a sign at the entrance stating EXIT TO AREA

OF REFUGE ON FLOOR (C26-604.7).

NISTNCSTAR 1-1D, WTC Investigation 19
Chapter 5

5.3 EXIT WIDTH AND CAPACITY

Occupant load shall be calculated based on the net floor areas in square feet divided by the occupant load

factor (square foot per person) or the actual number of occupants from whom each occupied space is designed, whichever is greater (C26-601.2):

1. Non-simultaneous Occupancy - The occupant load of toilets, locker rooms, meeting rooms,

storage rooms, employee cafeterias, and similar rooms or spaces that are not occupied at the same time as other rooms or spaces on the same floor may be omitted from the occupant load

calculation of the floor on which they are located (C26-601 .2(c)).

2. The occupant load of any space shall include the occupant load of all spaces that discharge

through it in order to gain access to an exit (C26-601 .2).

Occupancy

Business (offices)

Conference rooms (tables)

Conference rooms (chairs)

Dining spaces

Mercantile:

1 st floor/basement

All other floors

Assembly (fixed seats)

Waiting space (standing)

Garages/parking

Storage rooms

Mechanical rooms

Occupant Load Factor

100

12

10

12

25

50

No. of seats

4

250

200

200

Where vertical exits serve more than one floor, only the occupant load of each floor considered

individually is used in computing the required capacity of exits at that floor, except where one floor is used by another as a means of egress (C26-601.1).

Exit capacity (width) shall not decrease in the direction of exit travel (C26-604.8).

20 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

The width of each means of egress component shall be that computed using the appropriate egress unit factor but not less than the minimum width prescribed for the component (C26-601.1, C26-601.3):

1 . Where computations give fractional results, the next larger integral number of egress units or

integral number plus Vi shall be used (C26-601.3).

2. A fraction less than Vi may be neglected when constituting less than 10 percent of the total required number of egress units.

When a floor area has access to areas of refuge that comply with the requirements of Section C26-604.5,

the number of persons for whom vertical exits are to be provided may be reduced to 50 percent of the occupant load of the floor area when one area of refuge is provided, and may be reduce to 33 1/3 percent

of the floor area when two areas of refuge are provided (C26-603.3).

Egress capacity factors - capacity per egress unit (C26-601.1, C26-601.3):

1 . One unit of egress width is equal to 22 in.

2. Doors to outdoors at grade:

a. Occupancy Group B (Storage) - 75 persons per unit.

b. Occupancy Groups C (Mercantile), E (Business), and F (Assembly) - 100 persons per

unit.

3. Other exit and corridor doors:

a. Occupancy Group B (Storage) - 60 persons per unit.

b. Occupancy Group C (Mercantile), E (Business), and F (Assembly) - 80 persons per unit.

4. Stairs and escalators:

a. Occupancy Group B (Storage) - 45 persons per unit.

b. Occupancy Groups C (Mercantile), E (Business), and F (Assembly) - 60 persons per unit.

5. Ramps, corridors, exit passageways, horizontal exits:

a. Occupancy Group B (Storage) - 75 persons per unit.

b. Occupancy Groups C (Mercantile), E (Business), and F (Assembly) - 100 persons per

unit.

c. When ramp slope exceeds 1 in 10, the capacity shall be reduced by 25 percent (Table 6-1

note b).

Where a door is divided by muUions into two or more door openings, each opening shall be measured

separately in computing the number of egress units (Table 6-1 note m).

NISTNCSTAR 1-1D, WTC Investigation 21
Chapter 5

5.4 DOORS

Minimum nominal width shall be 32 in. except for corridor and exit door openings, which shall be 36 in. (C26-604.4(e)):

1 . Door jambs or stops and the door thickness when open shall not reduce the required width by more than 3 in. for each 22 in. of width (C26-604.4(e)).

2. In all cases where a door opening is divided by mullions into two or more door openings, the minimum nominal width of each such opening shall be 32 in. (C26-604.4(c)).

Maximum width of leaf (C26-604.4(e)) is 48 in.

Minimum height (C26-604.4(f)) is 6 ft 8 in.

Door jambs, stops, sills, and closers shall not reduce the clear opening to less than 6 ft 6 in. (C26-604.4(f)).

The floor on both sides of all exit and comdor doors shall be substantially level and have the same

elevation for a distance at least equal to the width of the leaf (C26-604.4(h)).

Where doors lead out of a building, the floor level inside may be IVi in. higher than the level outside

(C26-604.4(h)).

Exit doors, comdor doors serving high hazard occupancy Group A spaces, and corridor doors from rooms

required to have more than one door shall swing in the direction of egress (C26-604.4(g)).

Vertically sliding doors, rolling shutters, and folding doors shall not be used as exit doors or as corridor

doors (C26-604.4(d)).

Revolving doors designed and constructed in accordance with Section C26-604.4(m) are permitted to be

used as exits except that revolving doors shall not be used as interior exit access doors, at the foot of

stairs, or at the head of basement stairs (C26-604.4(d)).

Turnstiles designed and constructed in accordance with Section C26-604.4(n) may also be permitted.

Power operated or power assisted manually operated doors may be used as exit or corridor doors provided

they remain closed in case of power failure and are manually operable. To be credited as a required exit, power operated doors must swing in the direction of exit travel (C26-604.4(l)).

Exit doors and corridor doors shall nonnally be kept in the closed position (C26-604.4(i)).

Latch bolts shall be provided on all exit doors and corridor doors to hold them in a closed position against

the pressure of expanding gases (C26-604.4(j)(l)(c)).

22 NISTNCSTAR 1-1 D, WTC Investigation
Means of Egress

Obstruction of means of egress during door opening:

1 . Doors providing access to stairways or ramps shall not block stairs/ramps or stair landings or reduce the width of landings/stairs/ramps to less than 75 percent of the required width or to less than the width of the door opening on them (C26-604.8(g), C26-604. 10(c)(4)).

2. No door shall swing over the sloping portion of a ramp (C26-604. 8(c)(4)).

Exit and corridor doors and doors providing access to areas of refuge shall be readily openable at all times

fi-om the side from which egress is made without the use of a key (C26-604.4())(l)(a), C26-604.5(d)):

1 . Locks may be used in places where extra safeguards are required (banks, museums, etc.), subject to approval of the cominissioner, provided the locks are equipped with electrical release devices for remote control in case of emergency (C26-604.4(j)(l)(a)(2)).

2. Doors opening into interior enclosed stairs shall not be locked from either side except that doors may be locked to prevent access to the stair from the outside at the street floor (C26-604.4(j)(l)(b).

5.5 EXIT ACCESS

Minimum clear width of corridors shall be:

1 . Occupancy Groups B (Storage), C (Mercantile) - 36 in.

2. Occupancy Groups E (Business), F (Assembly) - 44 in.

The maximum tra\ el distance shall not exceed the following limits. Travel distance shall be measured

along the natural and unobstructed path of travel. Where the path of travel is over an access stair, it shall be measured along an inclined straight line through the center of the outer edge of each tread (C26-601.4(a)(c), Table 6-1).

Occupancy Distance (Fect)'^

B-1 (Storage)

B-2 (Storage)

B-2 (Parking

garage)

C (Mercantile)

E (Business)

F (Assembly < 75

persons)

100

125

100

150

200

150

Distances given are for unsprinklered conditions (BCNYC Table 6-1).

NISTNCSTAR 1-1D, WTC Investigation 23
Chapter 5

The maximum dead-end distance shall not exceed the following limits (C26-604.2(d), Table 6-1):

Occupancy Distance (Feet)^^

B-1 (Storage) 50

B-2 (Storage) NR : C (Mercantile) 50

E (Business) 50

F (Assembly) 30

5.6 STAIRWAYS

Minimum clear width shall be at least 44 in. (C26-604.8(b)):

1 . The width of stairs shall be the clear width between walls, grilles, guard, or newel posts.

Stair stringer projections which do not exceed 2 in. on each side and handrail projections of

3V2 in. are permitted.

2. Vertical exits in public garages may be 36 in. wide.

3. The minimum width of landings and platfonns shall be at least the required width of the stairway. On a straight run stair, landing and platforai widths need not be more than 44 in.

Minimum headroom shall be at least 7 ft (C26-604.8(c)).

Maximum height between landings shall be 12 ft (C26-604. 8(d)).

Treads and risers (C26-604.8(e), Table 6-4):

1. Maximum riser height:

a. Occupancy Group F (Assembly) - IVi in.

b. All others - TA in.

2. Minimum tread depth - in. plus nosing

3. The sum of two risers plus one tread exclusive of the nosing shall not be less than 24 nor more than ISVz in.

4. Stair riser and tread dimensions shall be constant in any flight of stairs from story to story.

Curving or skewed stairs that conform to Section C26-604. 8(e)(4) are permitted to be used as exits.

'"^ Distances given are for iinsprinklered conditions. When a corridor is completely enclosed in 2 h fire resistance rated construction with 1/2 h fire rated doors, the permissible length of dead end may be increased by 100 percent (C26-604.2(d)).

24 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

Where exit stairways serving floors above grade continue in the same enclosure to serve floors below

grade, the above and below grade portions shall be separated by 1 h fire resistance rated construction.

Stair identification signs shall be posted on the occupancy side of the stair door indicating the letter designation of the stair.

In buildings or in building sections more than three stories or 40 ft high with roofs having a slope of less than 20 degrees, access to the roof shall be provided by at least one interior stair. Access to set back roof

areas may be through a door or window opening to the roof

No openings of any kind are pennitted into stair enclosures other than windows, fire department access

panels, and exit door.

Exterior stairs designed and constructed in accordance with Section C26-604.9 may be used as exits in

lieu of interior stairs.

No exterior stair shall exceed 75 ft or six stories in height.

Escalators designed and constructed in accordance with Section C26-604.1 1 may be used as exits in lieu of interior stair.

5.7 RAMPS

The minimum clear width of exit ramps is 44 in. (C26-604.10, C26-604.8(b)).

Lev el platforms or landings at least as wide as the ramp shall be provided at the top and bottom of all ramps and at intermediate levels as necessary:

1 . Level platforais shall be provided on each side of door openings into or from ramps.

2. Platforms shall be at least 3 ft wide; 5 ft when a door swings onto the platform.

Minimum headroom is 6 ft 8 in.

Changes in direction of travel shall be made only at landings (or platfomis) (C26-604. 10(c)).

Ramps with a slope not greater than 1 in 12 at any place may be curved.

Ramps shall not have a slope steeper than 1 in 8 and sloping portions shall be at least 3 ft but not more

than 30 ft long between platforms or landings.

Level and ramped moving walkways designed and constructed in accordance with Section C26-604.12

may be used as exits (C26-604.12).

NISTNCSTAR 1-1 D, WTC Investigation 25
Chapter 5

5.8 HANDRAILS AND GUARDRAILS

Continuous handrails are required on both sides of all stairs, and all ramps with a slope exceeding 1 in 12:

1. Stairs less than 44 in. wide may have a handrail on one side only.

2. Intennediate handrails shall be provided to divide stairs more than 88 in. wide into widths

that maintain nominal multiples of 22 in. and widths not greater than 88 in. nor less than

44 in.

3. Handrail height shall be 30 to 34 in. measured vertically above the nosing of treads.

4. Handrail ends shall be returned to walls and posts when tenninated.

5. Handrails shall provide a tmger clearance of I'/z in. and shall project not more than 3'/2 in. into the required stair width. \

Stair landings and platfonns shall be enclosed on sides by walls, grilles, or guards at least 3 ft height.

5.9 EXIT SIGNS

In all buildings, the location of every exit on every floor shall be clearly indicated by approved EXIT

signs (C26-606.1).

EXIT signs shall be placed at an angle with the exit opening if such placement is required for the signs to serve their purpose.

In areas where the location of the exit may not be readily visible or understood (including long corridors

and open floor areas), directional signs shall be provided to serve as guides from all portions of the corridor or floor.

The size, color and illumination of EXIT signs shall confonn to Section C26-606.3. Directional signs

shall conform to Section C26-606.4.

All EXIT signs shall be illuminated at all times when the building is occupied.

Where a total of more than four signs (exit and/or directional) are required, all EXIT signs shall be

connected to circuits that are separate from the general lighting and power circuits. These circuits shall be

taken off ahead of the main switch or connected to an emergency hghting power source when such-source

is provided.

Any door, passageway, stair, or other means of communication that is not an exit shall be so identified

with a NOT AN EXIT sign and a sign indicating its use or purpose or a directional exit sign shall be

provided.

26 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

5.10 MEANS OF EGRESS LIGHTING

Corridors and exits shall be equipped with artificial lighting facilities to provide at least 5 ft candle

intensity' floor lighting continuously during the time that conditions of occupancy of the building require

that the exits be available (C26-605.1).

Lighting shall be provided to illuminate changes in direction in and intersections of corridors, balconies,

exit passageways, stairs, ramps, escalators, bridges, tunnels, landings, and platforms.

Illumination shall be arranged so that failure of any one light does not leave any area in darkness.

Where a total of more than four lights are required, exit lighting shall be connected to circuits that are separate from the general lighting and power circuits. The circuits shall be taken off ahead of the main

switch or connected to an emergency lighting power source when such source is provided.

NISTNCSTAR 1-1 D, WTC Investigation 27
Chapter 5

This page intentionally left blank.

28 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 6

Fire Suppression

6.1 AUTOMATIC SPRINKLER PROTECTION

Automatic sprinkler protection shall be designed and installed in accordance with Section C26-1 703.1 and

Reference Standard (RS) 17-2 in the following areas:

1. Spaces in group B-1 > 500 ft".

2. Spaces in group B-1 < 500 ft' when required by the commissioner.

3. Spaces in group B-2 > 5,000 ft' or 75 ft in height.

4. Spaces in high-rise buildings classified as mercantile occupancy group C > 7,500 ft' in floor area or with an unenclosed stair or escalator between any two or more floors.

5. Regardless of occupancy, any story abo\ e grade and the first story below grade without

required ventilation.

a. All other stories below grade.

b. Sprinklers may be omitted in toilets, shower rooms, stair, and mechanical and electrical rooms.

A wet-pipe sprinkler system shall be prox ided throughout all areas requiring automatic sprinkler

protection. In areas subject to freezing, the sprinkler system shall be protected (insulation, heat trace, antifreeze solution) from freezing or a dry-pipe system shall be provided (C26-1703.13).

A sprinkler alarm system shall be provided when more than 36 heads are installed in any fire area or section (C26-1 703.4).

6.2 STANDPIPES

Wet slandpipes designed and installed in accordance with Section C26- 1702.1 and RS 17-1 shall be

provided (C26-1702.1(a)(l)):

The number and location of standpipes shall be such that every point of every floor can be reached by a 20 ft stream from a nozzle attached to not more than 125 ft of hose connected to a riser ouflet valve

(C26-1702.4):

1 . Standpipe risers and 2I/2 in. hose valves shall be located within stairway enclosures

(C26-1 702.5(a)).

NISTNCSTAR 1-1 D. WTC Investigation 29
Chapter 6

2. When stairway enclosures are not available within the 125 plus 20 ft distance (145 ft total), risers and valves shall be located as near to the enclosure as practicable (C26- 1702.5(a)).

The highest riser shall be extended above the roof with a 3-way manifold with IVi in. hose valves

(C26-1702. 11(a)(2)).

A IVi in. hose outlet shall be provided at each standpipe riser on each floor served, and on the entrance

floor above the riser control valve, located between five and six ft above the landing or floor (C26-1702. 11(a)(1)).

Hose stations shall be located at the standpipe risers, either inside or adjacent to the entrance of stairway

enclosures (C26-1702.1 1(b)):

1. Hose stations shall be located to satisfy the 125 plus 20 ft (145 total) requirement

(C26-1702. 11(b)(1)).

2. Hose shall be (C26-1702. 11(c)):

a. 1 Vi in. unlined (flax-line) linen hose in Groups C, E, and F.

b. IVi in. (unlined) in Group B.

3. Auxiliary hose stations equipped with VA in. (unlined) hose are permitted in Groups C, E,

and F (C26-1 702. 11 (c)(4), C26-1702.1 1(d)).

Standpipe systems that include more than one riser shall have all risers cross-connected at, or below, the

street entrance floor level (C26-1 702. 10(a)).

Standpipe systems having more than one zone shall be arranged such that the risers supplied from each zone are cross-connected below, or in, the story of the lowest hose outlets from the water source in each zone (C26-1702. 10(b)).

Standpipe risers shall be at least 4 in. in diameter where the riser height is 150 ft or less from the highest

hose outlet to the level of the entrance floor, 6 in. in diameter where greater than 150 ft (C26-1 702.7,

Table 17-1).

6.3 WATER SUPPLY

Standpipe systems shall have a primary water supply available at all times to every hose outlet or made

available automatically when the hose valve at any outlet is opened (C26-1702.14).

Combinations of two or more of the following sources shall serve as the primary water supply

(C26-1702. 14(b)):

1 . Direct connection to city water system.

2. Direct connection to a private yard main.

30 NISTNCSTAR 1-1D. WTC Investigation
Fire Suppression

3. Pressure taiik(s).

4. Automatic fire pump (C26-1 702. 14(b)(5)).

a. In buildings higher than 300 ft. the automatic fire pump shall be used only for the lower

300 ft.

b. Zones ahoxe 300 ft shall be supphed by either a gravity or pressure tank.

5. An additional standpipe system water supply shall be provided for standpipes in buildings over 300 ft high (C26-1702. 15(a)). The primary water supply to the standpipe system shall be supplemented by one or more manually operated fire pumps (C26- 1702. 15(a)).

At least one of the following automatic source of water supply shall be provided for sprinklers

(C26-1703.8(a)):

1 . Grax ity tank(s).

2. Pressure tank(s).

3. Automatic fire pump.

4. Direct connection to public water system.

Domestic water supply may be used to supply cooling tower sprinklers and sprinklers installed in buildings classified in Occupancy Group E (Business) in accordance with Section C26- 1703.9(e)

(C26-1703.9 (c)and (d)).

Auxiliary sources of water supply for sprinkler systems may include a manually actuated fire pump or Siamese connection (C26-1 703.8(b)).

Combined Water Supplies:

1 . Fire pumps may simultaneously serve as the required auxihary water supply for standpipe

and sprinkler systems in accordance with Section C26- 1702. 15(d).

2. Tanks used to pro\ ide the required primary water supply to a standpipe system may also be

used as a supply for an automatic sprinkler system (C26- 1703. 8(c)).

One standpipe system and one sprinkler system Siamese connection shall be provided for each 300 ft of

exterior building wall or fraction thereof facing each street or public space (C26- 1702.9(a),

C26-1703.6(a)(l)). In addinon:

1 . Modifications based on street frontage are permitted by Sections C26-1 702.9(b)-(f).

2. Each Siamese connection shall be connected to a riser or to a cross connection connecting

other Siamese connections or risers (C26- 1702.10(f)).

NISTNCSTAR 1-1 D. WTC Investigation 31
Chapter 6

3. In below grade sprinkler systems for garage occupancies, a sprinkler Siamese connection shall be provided within 50 ft of every exit or entrance used by motor vehicles (C26-1703.6(a)(2)).

4. Siamese connections for partial sprinkler systems shall be in accordance with

Section C26-1703.6(a)(3).

32 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 7

Fire Detection and Alarm

7.1 FIRE ALARM SYSTEM

A fire alann system was not required by the Building Code of the City of New York (BCNYC) at the time of design and construction of World Trade Center (WTC) 1 and WTC 2, but smoke detectors were

required to be provided to prevent the recirculation of smoke through certain heating, ventilating, and air conditioning (HVAC) systems (C26- 1300.7(a)). A sprinkler alann system shall be provided when more

than 36 heads are installed in any fire area or Section (C26 1703.4). (Note that the underground spaces

and parking garage were originally sprinklered.)

A local water flow alann unit shall be provided (outdoor water motor or electric alarm gongs) where there

is no watchman with watch service (Reference Standard [RS] 17-2 Sec. 3721).

Central station water flow alarm service is desirable but does not waive the local alarm requirement

(RS 17-2 Sec. 3721).

7.2 SMOKE AND HEAT DETECTOR LOCATIONS

HVAC Systems (C26-1300.7(a), RS 13-1):"°

1 . In systems over 5,000 cfm capacity, thermostatic devices shall be provided for automatic fan

shut-down as follows (RS 13-1 Sec. 1002):

a. 1 25 °F (max) devices located in the return air stream prior to exhaust or dilution by

outside air(RS 13-1 Sec. 1002(a)).

b. 50 °F (max) above maximum operating temperature devices located in the main supply

duct down stream of the filters (RS 13-1 Sec. 1002(b)).

c. Where thermostatic devices are installed in systems utilizing recirculated air on floors protected by sprinkler or fire alarm systems, fans shall automatically shut down on alann

(RS 13-1 Sec. 1005).

2. In systems over 15,000 cfm capacity smoke detectors shall be provided for automatic fan

shutdown as follows (RS 13-1 Sec. 1003).

a. Smoke detectors shall be located in the main supply duct downstream of the filters (RS 13-1 Sec. 1003(b)).

A Port Authority fire safety report contained in Appendix A of NIST NCSTAR 1 -1 H indicates that smoke detectors were

installed on each floor at return air ducts. The NIST NCSTAR 1-lH report is one of the companion documents from this Investigation. A list of these documents appears in the Preface.

NIST NCSTAR 1-1D, WTC Investigation 33
Chafjter 7

b. Smoke detectors shall be arranged to provide audible and visual annunciation at a local supervisory control board in the building in accordance with RS 13-1 Sec. 1003(c).

3. In systems utilizing recirculated air, smoke detectors shall be provided for automatic fan shut- down when any of the following conditions exists (RS 13-1 Sec. 1003(a)):

a. System supplies an exit passageway, or a space leading from elevators to a street or to the

exterior.

b. System supplies spaces on more than one story or spaces in different fire areas in the same story.

c. Where the area of a building or space served is over 20,000 ft" in mercantile or indoor

assembly occupancies.

d. Where there is a duct opening in a required 2 h fire resistance rated interior Fire Division.

e. Where a duct passes through a firewall,

f Where a comdor is used as a plenum.

4. Systems incorporating automatic exhaust in lieu of automatic fan shutdown are acceptable

provided they are equipped with smoke detectors (RS 13-1 Sec. 1004).

5. Each installation shall be equipped with a manual emergency stop for quick shut down of the

fan(s) in case of fire (RS 13-1 Sec. 1001).

7.3 MANUAL FIRE ALARM BOXES

No requirement per BCNYC.

7.4 AUDIBLEA/ISUAL ALARM NOTIFICATION APPLIANCES

No requirement per BCNYC.

7.5 COMMUNICATION SYSTEM

In every building more than 300 ft high, a telephone and signaling system shall be provided for fire department use in operating the standpipe system (C26- 1702.21, C26- 1704.7(a)).

The standpipe telephone system shall be as follows:

1 . System shall permit communication by pennanent telephones in the following locations

(C26-1704.7(b)):

a. Pump rooms.

b. Entrance floor.

34 NISTNCSTAR 1-1 D. WTC Investigation
Fire Detection and Alarm

c. Gravity tank rooms.

d. Each floor near main standpipe riser.

2. The system shall be a selective ringing, common talking system supplied by a 24 V direct current power source (C26- 1704.7(b)).

3. Peraianent wall telephones shall be provided with 6 in. gongs except in the pump room where

a loud speaking receiver shall be provided (C26-1 704.7(c)).

4. Where portable phones are used, jacks protected by break-glass boxes shall be provided

(C26- 1704.7(c)).

a. At least three portable phones shall be provided for each standpipe installation, kept in a dedicated, locked cabinet located in the main hall of the entrance floor (C26-] 704.7(d)).

b. A pilot light shall be provided over the cabinet to indicate if the system is in use or a

receiver is off the hook (C26-1704.7(e)).

5. Manual, individually coded sending stations shall be located in the main corridor of the building arranged to transmit a signal to alarm sounding devices (C26- 1 704.7(f)( 1 )). The

system shall be installed in accordance with RS 17-3 (C26- 1704.7(f), C26- 1704.8).

6. An 8 in. gong shall be provided in the pump rooms and in elevator shafts at intervals not exceeding 10 floors (C26- 1704.7(f)(1))-

7. Adjacent to each telephone station and near the main standpipe riser, a closed circuit strap

key connected in series with the box circuit of the signal sending station shall be provided

(C26- 1704.7(f)(2)).

NISTNCSTAR 1-1D, WJC Investigation 35
Chapter 7

This page intentionally left blank.

36 NIST NCSTAR 1-1D, WTC Investigation
Chapter 8

Elevators and Hoistways

8.1 general

Elevators or escalators shall be provided in accordance with Section C26- 1800.1 and Reference Standard

(RS) 18-1 in all new buildings exceeding four stories in height (C26-604.1(a), C26- 1800.6(d)).

1 . When areas of refuge are provided above the 1 1 th floor of a building, they shall be served by

at least one elevator (C26-604.5(c)).

2. Escalators may be used as exits in lieu of interior stairs (C26-604.1 1, C26- 1800.6(g).

In every building exceeding 100 ft in height, at least one elevator shall be kept available for immediate

use by the fire department during all hours (C26- 1702.22, C26- 1800.8)."'

In buildings exceeding 150 ft in height, there shall be an operator available at all times (C26- 1800.8).

Automatic passenger elevators shall be equipped with emergency controls for fire department use (RS 18-1 Rule 210.13).

1 . A two-position keyed switch shall be provided at a main floor of each elevator or group of

elevators for recall to the main floor in accordance with RS 18-1 Rule 210.13(a).

2. A keyed switch shall be provided in or adjacent to an operating panel of each elevator to

initiate emergency service in accordance with RS 18-1 Rule 210.13(b).

Fire drills shall be conducted in accordance with the fire safety plan at least once every 3 months for

existing buildings during the first 2 years. Thereafter, fire drills shall be conducted at least once every

6 months. The occupants of the building, other than building service employees, shall not be required to leave the floor or use the exits during the drill.

According to Bracco 1969, all passenger elevators were capable of being recalled to their respective lobbies using manual

controls. The control over-rides all individual floor hall calls, preventing manual or heat activation from calling a car to a "fire

floor'" and makes the car available for manual operation by the Fire Department. This arrangement is similar to requirements

for emergency operation added by LL 5/1973, to which the elevators were retrofit later.

NISTNCSTAR 1-1 D. WTC Investigation 37
Chapter 8

\

This page intentionally left blank.

38 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 9

Special Features

9.1 EMERGENCY POWER SYSTEMS

No requirement per Building Code of the City of New York (BCNYC).

9.2 PUBLIC GARAGES

A public garage used exclusively for parking of vehicles having fuel storage tanks of 26 gal capacity or

less is classified in storage Occupancy Group B-2 (C26-709.2(b)).

All floors shall be concrete or equivalent noncombustible material and columns shall be protected from

vehicle impact or designed to resist lateral forces in accordance with Section C26-902.4 (C26-709.3).

Public garages shall be ventilated in accordance with Section C26-709.7.

Ramps serving as required exits shall be enclosed in 2 h fire resistance rated construction with vehicle

openings at each parking tier protected by a 3 gpm per linear foot deluge type sprinkler water curtain

(C26-709.9).

9.3 SMOKE AND HEAT VENTING"

Elevator and dumbwaiter shafts shall be in accordance with RS 18-1.

Other closed shafts shall be as follows:'^

1. All closed shafts having an area exceeding 4 ft' shall be provided with a smoke vent having

an area of at least 3 1/2 percent of the maximum shaft area at any floor but not less than ft' (C26-504.6(d)).

2. Smoke vents may be windows, louvers, skyhghts, vent ducts or similar devices

(C26-504.6(d)).

3. Vent ducts shall be enclosed by construction having the same fire resistance rating as required for the shaft and extend vertically, diagonally, or horizontally in accordance with

Sec. C26-504.6(d)(l)(2).

~ A Port Authority fire safety report contained in Appendix A of NIST NCSTAR 1-lH indicates that a smoke purge

configuration (not yet required by BC>JYC) for the heating, ventilating, and air conditioning system was installed. Requirements for smoke purge systems were adopted in LL 16-1984. The original design omitted vents from closed shafts (Solomon 1975).

NIST NCSTAR 1-1D, WTC Investigation 39
Chapter 9

4. Of the total required vent area for shafts at least 1/3 shall be clear to the outdoors either in the

form of fixed louvers, ridge vents, or hooded or goose-necked openings (C26-504.6(e)).

5. As an alternate, skylights or trap doors may be an'anged to open automatically by fusible link or other mechanical device when subjected to 160 °F fixed temperature or 15-20 °F per min

temperature rise (C26-504.6(e)).

6. The remaining portion of the required vent area may be a window or skylight glazed with

plain glass not more than 1/8 in. thick or slow burning plastic (C26-504.6(e)).

Machine Rooms.

1 . Any compartment containing machinery that communicates with a shaft enclosure shall comply with all requirements for shafts (C26-504.6(f)).

2. The required louver or glazing shall not be located in any door leading into such compartment

(C26-504.6(f).

40 NISTNCSTAR 1-1D, WTC Investigation
Chapter 10

References

Boring, D.F., J.C. Spence, and W.G. Wells. 1981. Five Protection Through Modern Building Codes.

American Iron and Steel Institute, Washington, D.C., October.

Bracco, M. 1969. Office Correspondence to J. R. Endler, May 26.

City Publishing Center Department of General Services. 1968. The City ofNew York Building Code.

New York, NY, December 6.

Feld, Lester S. 1987. Memorandum to Robert J. Linn (Deputy Director for Physical Facilities, WTD),

January 15.

Kyle, John M. 1965. Memorandum to Malcolm P. Levy (Chief), June 22.

Merritt and Harris, Inc. 2000a. Property Condition Assessment of World Trade Center Portfolio One

World Trade Center. New York, NY, December 6.

Merritt and Harris, Inc. 2000b. Property- Condition Assessment of World Trade Center Portfolio Two

World Trade Center. New York, NY, December 6.

NIST (National Institute of Standards and Technology). 2003. Progress Report on the Federal Building

and Fire Safety Investigation ofthe World Trade Center Disaster. Washington, DC, May.

PANYNJ (Port Authority of New York and New Jersey). 1976. Report on Fire Safety of the World

Trade Center. New York, NY, January.

Robertson, Leslie E. 1965. Letter to Malcolm P. Levy (Port of New York Authority), April 26.

Solomon, Joseph H. 1969. Correspondence to Malcolm P. Levy (Chief), June 6.

Solomon, Joseph H. 1975. Correspondence to Malcolm P. Levy (General Manager WTC Operations),

February 18.

Tozzoli, Guy F. 1966. Memorandum to John M. Kyle (Chief Engineer), May 19.

NISTNCSTAR 1-1D, WTC Investigation 41
Chapter 10

This page intentionally left blank.

42 NISTNCSTAR 1-1 D, WTC Investigation
Section II

Fire Protection Summary for

World Trade Center 7
s

This page intentionally left blank.

0
Executive Summary

As part of the analysis of building and fire codes and standards of the National Institute of Standards and

Technology (NIST) World Trade Center (WTC) Investigation, this report supports the effort to detemiine

the minimum construction requirements used in the design of WTC 7. The purpose of this report is to summarize the fire protection (both passive and active) and life safety provisions used to design and

construct WTC 7.

Although the Port Authority of New York and New Jersey (PANYNJ or Port Authority) was not subject

to the Building Code of the City of New York (BCNYC), WTC 7 was intended to be designed in accordance with the BCNYC and all applicable reference standards. Based on citations in the construction documents, the 1968 BCNYC, including amendments to January 1, 1985, appears to have

been used for the design and construction provisions of WTC 7.

The BCNYC, building characteristics, and early design choices were used to determine the minimum

construction requirements for the design of WTC 7. Because the BCNYC contains requirements for various types of buildings, it is crucial to identify applicable building requirements early in the design.

By identifying specific building characteristics, a designer is able to detennine which requirements must

be complied with and which requirements are not applicable.

The building summaries in Table E-1 were used to classify the building and detennine the minimum

requirements of the BCNYC. Based on the height, area, primary occupancy classification, and

installation of a fire sprinkler and standpipe system, the minimum construction type (permitted by the BCNYC) was type I-C (2 h protected). However, some documentation, including some building

drawings and specifications for bidders on the contract for fireproofing the structural steel, indicate a type

1-B (3 h) classification. No documents were found containing measured thicknesses of fireproofing

which might settle this difference. Fire resistance ratings for the structural components, fire divisions,

and fire separations were based on this classification. In this report, type 1-C is assumed, but the

possibility exists that the actual classification might have been 1-B. Many of the means of egress, fire suppression, and fire alarm requirements were also based on the building summaries of Table E-1. An

abbreviated list of the fire protection requirements is as follows. A complete list of the requirements is identified in the main body text of this report.

• Standpipes were required.

• A complete automatic sprinkler system was required.

• A Class E fire alarm and communication system was required.

• A telephone and signaling system was required for fire department use in operating the standpipe system.

• Detectors were required in certain locations of the building and the heating, ventilating, and

air conditioning system.

NISTNCSTAR 1-1D, WTC Investigation 45
Executive Summary

• Manual fire alann boxes were required.

• Audible/visual devices were required.

• Exit signs and emergency lighting were required in selected spaces.

• An emergency power system was required.

• Smoke and heat venting was required in selected spaces.

• A smoke purge system was required.

• Stair pressurization was not directly required but could be used as an alternative to eliminate

smoke and heat venting requirements.

Table E-1. Building characteristics used to determine BCNYC requirements.

Building Height

Number of Floors Above Grade Footprint

Frimary

Occupancy

Classification WTC 7 618 ft 47 48,000 ft- Group E (Business)

Source: PANYNJ.

46 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 11

Introduction

11.1 PURPOSE

The purpose of this report is to summarize the fire protection (passive and active) and life safety

provisions used to design and construct World Trade Center (WTC) 7.

11.2 INTRODUCTION

The regulation of building construction is a direct result of the recognition that life safety is served by the

best available knowledge and practice. Codes and standards are created to establish minimum

requirements. Model codes have been published throughout the United States since 1905 (Boring 1981).

Through the use of technology improvements and as a result of serious incidents, such as fires, codes are developed and later revised to continually implement increased knowledge. Establishing reference

standards is just as important as establishing codes. Reference standards act as a technical basis of the code and provide methods of testing, installation and maintenance. Municipalities can adopt model

building codes and national standards or develop their own. Alternatively, many municipalities

throughout the United States have adopted model building codes and national standards, and then amend

portions as deemed necessary. New York City, however, developed their own building code and

provided a technical basis with a mixture of nationally recognized standards (National Fire Protection

Association, ASTM International, American National Standards Institute, etc.) and New York City

developed reference standards (denoted by RS ##).

In accordance with the instructions issued by the Port Authority of New York and New Jersey (PANYNJ

or Port Authority) at the start of the project, construction drawings for the WTC were to confonn with the requirements of the Building Code of the City of New York (BCNYC), although as a so-called state compact under the U.S. Constitution, it was exempt from state or local laws, including the BCNYC.

Based on citations m the construction documents, the 1968 edition of BCNYC, including amendments to January 1, 1985,"'' has been used for citing the design and construction requirements for WTC 7. The

applicable provisions of the BCNYC given throughout this report are denoted by C26-###.

As stated previously, it was the policy of the Port Authority to follow the requirements of the BCNYC.

Where documentation was identified, illustrating either conformance or deviation from the BCNYC

provision, a reference has been provided. This report does not evaluate whether or not the design

provisions were actually incorporated in the design of WTC 7, but merely identifies the provisions used in the design.

The year is an assumption based on the years of building construction and a reference to the 1983 edition of NFPA 13 located on sprinkler drawing PFP-1 of the construction documents.

NISTNCSTAR 1-1 D. WTC Investigation 47
Chapter 1

1

This page intentionally left blank.

48 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 12

General

12.1 APPLICABLE CODES AND STANDARDS

1. Building Code of the City of New York, 1968 including amendments to January 1, 1985.'^ '^

2. Local Law No. 5, Fire Safety Requirements and Controls. January 18. 1973.

3. Local Law No. 16. March 27. 1984."^

4. American National Standards Institute A 17.1 - Safety Code for Elevators and Escalators and

Supplement A17.1 -85a, 1984 (as modified by Reference Standards (RS) 18).

5. National Fire Protection Association (NFPA) 13 - Standard for the Installation of Sprinkler

System, 1983 (as modified by RS 17-2).

6. NFPA 22 - Standard for Water Tanks for Private Fire Protection. 1981.

7. NFPA 72A - Standard for the Installation, Maintenance and Use of Local Protective

Signaling Systems for Guard's Tour. Fire Alann and Super\ isor\' Serv ice, 1979 (as modified

by RS 17).

8. NFPA 72B - Standard for the Installation, Maintenance and Use of Auxiliary, Protective

Signaling Systems for Fire Alarm Ser\ ice, 1982 (as modified by RS 17).

9. NFPA 72C - Standard for the Installation, Maintenance and Use of Remote Station

Protective Signaling Systems for Fire Alarm and Super\ isor\' Serv ice. 1982 (as modified by

RS 17).

10. NFPA 72D - Standard for the Installation, Maintenance and Use of Proprietary Protective

Signaling Systems. 1979 (as modified by RS 17).

11. NFPA 72E - Standard on Automatic Fire Detectors, 1978 (as modified by RS 17).

12. NFPA 80 - Installation of Fire Doors and Windows, 1979 (RS 5-8).

^ Including the Building Code Reference Standards that modify national standards as deemed necessary-. This edition of the BCNYC includes Local Laws No. 5 and No. 1 6. See footnote 1

.

According to Syska 1 984d. the building was completely sprinklered and pro\'ided with a standpipe system. Class E fire alarm system (with voice communication), manual pull stations and smoke detection systems to comply with Local Law No. 5. ^ According to Syska 1984a, the building was designed in compliance with Local Law No. 16.

NISTNCSTAR 1-1 D. WTC Investigation 49
Chapter 12

12.2

13. NFPA 90A - Standard for the Installation of Air Conditioning and Ventilating Systems, 1981

(asmodifiedby RS 13-1).

14. NFPA 204 - Guide for Smoke and Heat Venting, 1968 (RS 5-11).

15. ASTM International (ASTM) E 84 - Standard Method of Test for Surface Burning

Characteristics of Building Materials, 1961 (as modified by RS 3-2).

16. ASTM E 1 19 - Standard Methods of Fire Tests of Building Construction and Materials, 1961

(as modified by RS 3-1).

17. RS 5-15

18. RS 5-17

19. RS 5-18

20. RS 17-1

21. RS 17-3

other Alann and Extinguishing Systems.

22. RS 1 7-3 A - Standards for the Installation of Class E Fire Alarm Signal Systems.

23. RS 17-3B - Standards for the Installation of Modified Class E Fire Alarm Signal Systems.

BUILDING SUMMARY

Tab e 12-1. Building characteristics used for design development.

Building"'^ Height

Number of Floors

Above Grade Footprint

Construction Type

(1968 BCNYC)

Primary

Occupancy

Classiflcation WTC 7 618 ft 47 48,000 ft- I-C (but some

documents cite 1-B)

Group E

(Business)

Source: PANYNJ.

""^ This building is located inside the Borough of Manhattan Fire District without additional restrictions imposed based on its use and occupancy (C26-402.1, C26-403.1).

50 NISTNCSTAR 1-1D, WTC Investigation
Chapter 13

Construction

13.1 CONSTRUCTION CLASSIFICATION

The minimum construction type permitted for the building was I-C (2 h protected).''"

13.2 BUILDING LIMITATIONS

In accordance with Table 4-2 of the Building Code of the City of New York (BCNYC) the height and

area are not limited for a sprinklered Class I-C construction building housing a Group E occupancy.

• Height - No Limit

• Area - No Limit

13.3 SECONDARY/ACCESSORY OCCUPANCIES

Occupancy Fire Index

B-1, Storage (moderate hazard) 3

B-2, Storage (low hazard, garage) 2

C, Mercantile 2

F-4, Assembly (restaurant) 1

13.4 FIRE RESISTANCE RATINGS

The minimum required fire resistance ratings listed as follows are in accordance with Table 3^ of the BCNYC, unless noted otherwise. The fire resistance ratings are based on the test procedures of reference

standard RS 3-1.

All BCNYC requirements identified herein, which are dependent upon construction class, are given for Class I-C.

NIST NCSTAR 1-1D. WTC Investigation 5

1
Chapter 13

Fire Resistance Rating

(Hours)

1. Exterior bearing walls , 2

2. Exterior non-bearing walls having an exterior

separation of:^'

3 ft or less with 0 percent openings 2

2

15 ft to less than 30 ft with 3 V2 percent openings ,

Greater than 3 ft to less than 1 5 ft with percent

protected openings

30 ft or greater with unlimited openings NC

3. Interior walls:

Walls and partitions (structurally bearing) 2

Corridors (C26-604.2(h))

^ 1

4. Enclosure of vertical exits^^, exit passageways, hoistways ^ and shafts

5. Columns, girders, trusses (other than roof trusses) and

framing:

Supporting one floor 1

V

Supporting more than one floor or a floor and roof 2

32

" When two or more buildings are constructed on the same lot and the combined floor area of the buildings does not exceed the

limits established by Tables 4-1 and 4-2 for any one of the buildings, no fire resistance rating shall be required for nonbearing portions of the exterior walls of those buildings facing each other, and there shall be no limitation on the permitted amount of exterior openings. Noncombustible.

See Sections C26-504.6 and 26-604.8(1) for exceptions to shaft and stair enclosures requirements.

52 NISTNCSTAR 1-1 D, WTC Investigation
Construction

6. Structural members supporting a wall

7. Floor construction including beams

8. Roof construction - Including beams, trusses, framing,

arches, domes, cable supported roofs and roof decks - above

floor to lowest member:

15 ft or less

15 ft to 20 ft

20 ft or more

Fire Resistance Rating

(Hours)

Same as required fire resistance of wall

supported, but not less than rating required for member by the class of

construction.

r/2

l34

1^^ orO^^'

The minimum covering of prestressing steel shall comply with the requirements of RS 5-15

(C26-502.2(d).

Materials which are not noncombustible. as defined in article 2 of the BCNYC, may be used in non-bearing construction elements if they fall into one of the following categories:

a. Materials having a structural base of noncombustible material as defined in article 2, and having a surface not over 1/8 in. thick which w hen tested in accordance with the provisions of reference standard RS 3-2 have a flame spread rating not higher than 50.

b. Materials which when tested in accordance with the provisions of reference standard RS 3-2 have a surface flame spread

rating not higher than 25 without evidence of continued progressive combustion, and which are of such composition that surfaces which would be exposed by cutting through the material in any way would not have a flame spread rating higher

than 25 without evidence of continued progressive combustion.

Applies to occupancy groups: A, B-1 , B-2, and D-1 . See also footnote 34. Applies to all occupancy groups other than those indicated in footnote 35. Fire retardant treated wood complying with the requirements of Section C26-502.6 may be used. See also footnote 34.

NISTNCSTAR 1-1D, WTC investigation 53
Chapter 13

13.5 OPENING PROTECTION

1 . Openings in a 3 h rated Fire Division or Fire Separation wall

(C26-504.4 and Table 5-3).

2. Openings in 2 h or 1 Vi h rated Fire Division or Fire

Separation wall or vertical coiTiiTiunication enclosure IV2 (Class B)

(C26-504.4, C26-604.4(a), C26-1 800.6 and Table 5-3).

3. Openings in 1 h rated Fire Division or Fire Separation walls,

corridors or partitions (C26-504.4, C26-604.4(b) and % (Class B)

Table 5-3).

4. Openings in 1 h rated vertical communication enclosure. 1 (Class B)

5. Required protected openings in exterior walls (Class E or Class F) (C26-503. 1(b)).

Noncombustible mail slots not exceeding 40 in." may be provided in corridor doors (C26-604.4(b)).

Noncombustible louvers may be installed in corridor doors opening into toilets, service sink closets, and

electrical closets (C26-604.4(b)).

Openings in Fire Divisions and Fire Separations should not exceed the size limits as follows

(C26-504.4(a)):

Fire Resistance Rating

(Hours)

3 (Class A)

1 . In buildings that are not sprinklered no opening through a fire division or a fire separation

shall exceed 120 ft' in area, with no dimension greater than 12 ft, and the aggregate width of

all openings at any level shall not exceed 25 percent of the length of the wall.

2. Where the areas on both sides of a fire division or fire separation are sprinklered in accordance with the construction provisions of article 17, the size of the opening may be

150 ft" in area, with no dimension greater than 15 ft.

3. In buildings fully sprinkled in comphance with the provisions of article 17, the size and

aggregate width of openings through the fire divisions or fire separations shall be unlimited.

4. When a fire division or fire separation serves as a horizontal exit also, it shall have no

opening other than door openings not exceeding 56 ft" in area, the aggregate width of all openings at any level shall not exceed 25 percent of the length of the wall.

In shafts that contain only one opening below the roof, no opening protective is required (C26-504.6(c)).

54 NISTNCSTAR 1-1D, WTC Investigation
Construction

Exterior street floor exit doors with a fire separation distance of more than 15 ft need not have a fire resistance rating (C26-604.4(a)(l)).

Openings in elevator and dumbwaiter shafts shall comply with RS 18 (C26-504.6(c)).

13.6 SEPARATION OF OCCUPANCIES

Fire Resistance Rating

(Hours)

1. Fire Divisions

Between Group B-1 and B-2,C,E or F-4. 3

2. Fire Separations

Between Groups E and B-2, C or F-4. NR"'

Between tenant spaces (C26-504.3(a)). 1

Separate Building (Building Section) - Spaces classified in occupancy groups having a higher fire index

than the occupancy group classification of the building shall be separated by "Fire Divisions" constructed

in accordance with Section C26-504.1(a) and treated as separate buildings (C26-30 1.4(a)).

Separate Spaces - Spaces classified in occupancy groups having the same or lower fire index than the occupancy group classification of the building shall be separated by "Fire Separations" constructed in accordance with Section C26-504.1(b) (C26-30 1.4(b)).

Multiple occupancy or use - When a building or space is used for multiple purposes at different times, the building/space shall be given a separate occupancy group classification for each of the activities. The

design and construction shall be in accordance with the most restrictive provisions that apply to any of the

classifications (C26-301.6).

A minor variation of occupancy or use of a space is acceptable without multiple classifications if the

variation is normally associated with the occupancy classification and no specific danger or hazard is created (C26-301.6).

Fire divisions shall be constructed of noncombustible materials or assembly of noncombustible materials

to provide the fire-resistance ratings (C26-504.2). The following requirements apply:

1. Vertical fire divisions shall be continuous between foundation, roof, or horizontal fire divisions, and through any concealed space in floor or roof construction.

No requirement.

** Separations are not required between accessory business and mercantile activities limited in area to 100 fr, and closets 75 ft' or less in area (Table 5-1 notes b and c).

NISTNCSTAR 1-1D, WTC Investigation 55
Chapter 13

2. Horizontal fire divisions shall be continuous between exterior walls and/or vertical fire divisions.

3. Fire divisions shall be made smoketight at their junction with exterior walls.

4. Fire divisions may be offset if the construction between the offset divisions, including their supports, has the same fire-resistance rating as the fire division, with all hollow spaces within

the construction firestopped with noncombustible material.

5. Where combustible members such as joists, beams, or girders bear on, or frame into, vertical

fire divisions, such members shall not extend through the wall and shall have at least 4 in. of

solid noncombustible material below, at the sides, and at the ends of each such member.

6. Chases or recesses shall not be cut into fire divisions so as to reduce their thickness below

that required for the fire-resistance rating.

7. Vertical fire divisions that are hollow shall be firestopped with at least 4 in. of

noncombustible material so as to prevent passage of flame, smoke, or hot gases through the hollow spaces to the story above or below, or to hollow spaces within connecting floor or roof construction.

13.7 COMPARTMENTATION

All new buildings classified in occupancy group E (Business) having air-conditioning and/or mechanical

ventilation systems that serve more than the floor on which the equipment is located, and unsprinklered

floor areas^^ more than 40 ft above curb level, shall be subdivided by fire separations into spaces or compartments as indicated below (C26-504.1):

1 . All unsprinklered floor areas shall be segregated by 1 h fire separations into spaces or compartments not to exceed 7,500 ft".

2. Where the floor area exceeds 10,000 ft', at least one of the subdividing fire separations shall be of 2 h construction, creating areas of refuge, complying with section C26-604.5 except that the requirement for an elevator in each area shall not apply.

3. The floor area or any subdivided area may be increased to not more than 15,000 ft' if complete area protection by approved devices for the detection of products of combustion

other than heat is provided within such increased area and provided further that at least one of

the subdividing fire separations shall be of 2 h construction where the floor area exceeds

15,000 ft", creating areas of refuge complying with C26-604.5 as noted in 2 above. The

acfivation of the detectors shall have the same effect as section C26-1 704.5(f).

4. Compartmentation is not required when complete sprinkler protection is provided.

The floor area shall be defined as the area within exterior walls and excluding any areas enclosing stairs, corridors, elevators, and shafts. (C26-504.1)

56 NISTNCSTAR 1-1D, WTC Investigation
Construction

13.8 FIRESTOPPING

All firestopping or fill materials shall consist of approved noncombustible materials that can be shaped,

fitted and permanently secured in place (C26-504.7(a)).

Concealed spaces within partitions, walls, floors, roofs, stairs, fiirring, pipe spaces, column enclosures,

etc. that would permit passage of flame, smoke, fiimes or hot gases from floor to floor shall be firestopped

or filled with noncombustible material in the following locations (C26-504.7):

1. Hollow partitions and furred spaces.

2. Concealed spaces within stair construction.

3. Ceiling spaces.

4. Exterior cornices.

5. Duct and pipe spaces (C26-504.5 and RS 13-1 Sec. 313 and 314).

6. Hollow spaces where combustible trim and finish is permitted.

7. Hollow vertical Fire Division (C26-504.2(i)).

The concealed space above a fire resistance rated ceiling shall be firestopped into areas not exceeding

3,000 fr, except where (C26-502.5):

1. Structural members within the concealed space are individually protected, or

2. The concealed space is sprinklered.

Firestopping shall not be required where (C26-502.5(a)(l)):

1 . The structural members within the concealed space are individually protected with materials

having the required fire resistance rating.

2. The ceiling is not an essential part of the fire resistive assembly

3. A concealed space is sprinklered in accordance with the construction requirements of

article 17.

13.9 THROUGH PENETRATION PROTECTION

Noncombustible pipes and conduits may pass through fire rated construction provided the following

(C26-504.5(b)):

1 . Space between the pipe or conduit and its sleeve or opening does not exceed 2 in. and is packed with noncombustible material.

NISTNCSTAR 1-1 D, WTC Investigation 57
Chapter 13 '

'

2. Close-fitting metal escutcheons are provided on both sides of the construction.

3. Aggregate net area of openings does not exceed 25 in." in any 100 ft' of wall or floor area. Openings in excess of this limit are not peraiitted unless tested as part of a rated assembly and

so protected.

Ceilings required to have a fire resistance rating may be pierced to accommodate noncombustible electric outlet boxes, recessed lighting fixtures, pipes and ducts as follows (C26-502.5(b)):

1. The aggregate area of outlet boxes and hghting fixtures does not exceed 16 in." in each 90 ft^ of ceiling area.

2. Outlet boxes and lighting fixtures are constructed of steel at least 0.022 in. thick and sealed

tightly at the ceiling.

3. Additional or larger services are peraiitted only when tested as part of the assembly and

protected as provided in the test.

The concealed space above fire rated ceilings may be used as a return air plenum if listed (tested) for that purpose provided (RS 13-1 Sec. 316):

1 . All openings are tested as part of the assembly and protected in the test,

2. The integrity of firestopping is not destroyed,

3. No combustible materials are incorporated in the floor and ceiling construction, and

4. Electrical wiring is plenum rated (NFPA 70 Sec. 300-22).

13.10 FIRE AND SMOKE DAMPERS

Fire dampers shall be provided in accordance with RS 13-1 in the following locations (C26-504.5(a)):

1. Duct penetrations of walls with a 2 h fire resistance rafing or greater (RS 13-1 Sec. 902(a)).

2. Each opening in required vertical shaft enclosures (RS 13-1 Sec. 902(b)).

3. Each outlet or inlet opening in vertical shaft enclosure of duct systems serving two or more

floors (RS 13-1 Sec. 902(c)).

4. As an alternate, dampers may be provided at each point where the vertical duct pierces a floor

it serves (RS 13-1 Sec. 902(c)).

5. Branch duct penetrations of vertical duct shaft enclosures (RS 13-1 Sec. 902(c)).

6. Fresh air intakes (RS 13-1 Sec. 902(e)).

7. Aluminum Class I duct penetrations of fire resistance rated floors (RS 13-1 Sec. 902(d)).

58 NISTNCSTAR 1-1 D, WTC Investigation
Construction

Fire dampers are not required at the following locations (RS 13-1 Sec. 903):

1 . Non-aluminum or Class I vertical shaft branch duct penetrations with a cross-sectional area of

less than 20 in.' which supply only air conditioning units discharging air at not over 4 ft above the floor (RS 13-1 Sec. 903(a)).

2. Non-aluminum or Class 1 duct penetrations of a floor (at one place only) with a crosssectional area of less than 20 in." which supply air conditioning units in one story only that discharge air at not over 4 ft above the floor (RS 13-1 Sec. 903(b)).

3. Duct penetrations in systems serv ing only one floor and used only for exhaust to the outside

and not penetrating a fire wall or fire partition or passing entirely through the vertical shaft enclosure (RS 13-1 Sec. 903(d)).

4. Branch ducts connected to a return riser where subducts are extended at least 22 in. upward

(RS 13-1 Sec. 903(e)).

Fire dampers should be automatic closing Wi h fire rated with a fusible link or other heat actuated device

rated approximately 50 °F above the maximum system operating temperature (RS 13-1 Sec. 905(a)(g)).

Duct openings permitted in fire resistance rated ceilings shall be protected with fire dampers

(C26-502.5(b)).

Smoke dampers shall be installed in the main supply duct and the main return duct in systems over

15,000 cfm capacity (RS 13-1 Sec. 1003).

Smoke dampers shall be arranged to close automatically \\'hen the system is not in operation, by the operation of duct smoke detectors, and by the manual emergency fan stop (RS 13-1 Sec. 1003).

NISTNCSTAR 1-1D, WTC Investigation 59
Chapter 13

This page intentionally left blank.

60 NIST NCSTAR 1-1 D, WTC Investigation
Chapter 14

Interior Finish

14.1 INTERIOR FINISH FLAME SPREAD RATINGS

The minimum interior finish flame spread ratings below are based on Table 5^ of the Building Code of

the City of New York (BCNYC) and other sections as noted.

Classification

1. Exits and shafts (C26-504. 10(c), C26-604.8(i)(3))

2. Corridors (C26-504. 10(c), C26-604.2(k)):^''-^'

Group B-1

Groups B-2, C, E, F-4

3. Rooms greater than 1,500 ft- (C26-504. 10(c)):

Groups B-1, B-2, F-4

Group E

4. Rooms less than 1 ,500 ft^ (C26-504. 1 0(c)):

GroupsB-l,B-2, E, F-4

5. Interior finish in kitchens, cooking spaces, pantries, repair

and maintenance shops, boiler rooms and incinerator

combustion rooms (Table 5-4 note f).

Class A (0-25)

Class A (0-25)

Class A or B (0-75)

Class A or B (0-75)

Class A, B or C (0-225)

Class A, B or C (0-225)

Class A or B (0-75)

When used in corridors. Class B finish material should not extend more than 50 ft between separations of Class A finish material that are at least 2 fit wide (Table 5-4 note b). Spaces through which it is necessary for occupants of an adjacent room to pass in order to reach the only exit are considered as

corridors.

NISTNCSTAR 1-1 D. WTC Investigation 61
Chapter 14

14.2 SMOKE DEVELOPED RATINGS

Twenty-five or less in exits and corridors (C26-504. 10(d)).

One hundred or less in rooms where the net floor area per occupant is 10 ft" or less (C26-504. 10(d)).

No material shall be used in any interior location that upon exposure to fire will produce products that are more toxic in point of concentration than those given off by wood or paper (C26-504. 10(e)).

14.3 INTERIOR TRIM

Up to 20 percent of the aggregate wall and ceiling area of any room or corridor may be finished with

Class A, B, or C (0-225) materials and be exempt from the smoke developed rating requirements

(C26-504. 10(c)(4), C26-504. 10(d)). This allowance shall include the area of doors, folding partitions,

windows, glazing, skylights, luminous ceilings, trim, bases, chair rails, panels, moldings, etc.

14.4 FLOOR FINISH

Finish flooring in all exits shall be of noncombustible material (C26-504.13, C26-604.8(h)).

In all other areas, combustible finish flooring may be used when installed in accordance with

Section C26-504. 13(b).

62 NISTNCSTAR 1-1D, WTC Investigation
Chapter 15

Means of Egress

15.1 GENERAL

Clear width measurement is the net, unobstructed width of a means of egress without projections in such

width (C26-604.2(a), C26-604.3(b)):

1 . hi corridors, projections up to 18 in. wide to the extent of 2 in. per unit of egress width are permitted if the total area of such projections does not exceed 5 percent of the area of the wall on which they occur (C26-604.2(a)).

2. Handrails shall project not more than 3 'A in. and stringers 2 in. (each side) into the required

stair width (C26-604.8(b), C26-604.8(f)).

Headroom (C26-604.2(b), 604.3(c)):

1 . Corridor and exit passageway minimum height of 7 ft 6 in. for 75 percent of the floor area with no point less than 7 ft.

2. Projections from the ceiling shall be at least 7 ft above the floor and located so as not to obstruct full view of exit signs (C26-604.2(b), 604.3(c)).

Changes in level requiring less than two risers in a corridor or exit passageway shall be by a ramp

(C26-604.2(e), C26-604.8(d)(2)).

Obstructions to means of egress:

1 . The required w idth of a means of egress shall not be obstructed or reduced in any manner

(C26-604.2).

2. Corridors shall be kept free of combustible contents (C26-604.2).

3. All exterior means of egress elements, including exterior corridors and stairs, shall be

maintained free of ice and snow accumulation (C26-604.2, C26-604.9).

Corridors may be used as supply or return air ducts or plenums if equipped with an approved smoke

detector or thermostatic device to shutdown fans (C26-604.2(j), Reference Standard [RS] 13-1

Sec. 316(d)).

Stairways connecting two or more stories shall not be used as plenums (RS 13-1 Sec. 316(e)).

NISTNCSTAR 1-1 D. WTC Investigation 63
Chapter 15

15.2 EXITS

Every floor area shall be provided with at least two approved independent exits (C26-603.2).

A minimum of two exits or exit access doors shall be provided from every room or space in which the occupant load exceeds the following limits (C26-603.1):

Occupancy Load

B (Storage) 50

C (Mercantile) 75

E (Business) 75

F (Assembly) \ 75

All required exits shall be located such that they are clearly visible, accessible and have unobstructed

access at all times (C26-602.1).

In multi-tenant configurations, each tenant shall have access to the required numbers of exits without

passing through other tenant spaces (C26-602.2).

Whenever more than one exit or exit access is required from any room, space or floor of a building, they

shall be located as remote from each other as practicable (C26-602.3). The minimum distance between

such doors shall be the greater of 30 ft or be one-third the maximum travel distance of the floor, provided,

however, that where such distance will result in travel distances exceeding those authorized in section

C26-601.1, additional vertical exits shall be provided (C26-602.3).

All vertical exits shall extend in a continuous enclosure to discharge directly to an exterior space or at a yard, court, exit passageway or street floor lobby of the required width and size to provide all occupants

with a safe access to an open exterior space. Where vertical exits serving floors above grade continue in the same enclosure to serve floors below grade, the portion of such vertical exits above grade shall be

separated from the portion below grade by construction having at least a 1 h fire resistance rating, with

Va h self-closing doors opening in the direction of exit travel from the floors below grade (C26-602.4).

A maximum of 50 percent of the required number of vertical exits is pemiitted to discharge through a

single exit passageway (C26-604.3).

One hundred percent of the number of vertical exits may discharge through a street floor lobby if egress is provided in two different directions from discharge points to open exterior spaces remote from each other

(C26-604.3(h)(l)).

The clear width of an exit passageway serving two or more vertical exits shall be equal to 75 percent of

the width of all vertical exits it serves (C26-604.3(b)).

The width of street floor lobbies serving as exit passageways shall be increased to accommodate the occupant load of all communicating spaces on the lobby floor that exit through them (C26-604.3(h)(2)).

64 NISTNCSTAR 1-1 D, WTC Investigation
Means of Egress

No openings other than exit doors are permitted in exit passageways (C26-604.3(f)).

Openings between street floor lobbies serving as exit passageways and elevators or communicating

spaces and show windows protected in accordance with Section C26-604.3(h)(3) are pennitted.

Street floor lobbies serving as exit passageways may be occupied by newsstands, candy and tobacco

stands, information booths or similar occupancies if constructed of noncombustible materials, occupying

not more than 5 percent of the net lobby floor area, and if not reducing the required clear width at any

point (C26-604.3(h)(4)).

Honzontal and Supplemental Vertical Exits (C26-604.5 to C26-604.7):

1. The occupant load capacity for vertical exits may be reduced by 50 percent when one area of refuge is provided and by 66 percent when two or more areas of refuge are provided

(C26-603.3).

2. At least 3 ft" per person of clear public space, or space occupied by the same tenant or owner,

shall be provided within the area of refuge for the occupant load received in addition to its own occupant load (C26-604.5(b)).

3. Each area of refuge shall be provided with at least one vertical exit and when located above

the 1 1th floor, the vertical exit should be supplemented by at least one elevator

(C26-604.5(c)).

4. Access to an area of refuge, on the same floor, through a horizontal exit, may consist of

doors, balconies, bridges, and tunnels (C26-604.6):

a. Doors must swing in the direction of exit travel and be self-closing having a fire resistance rating of 1 Vz h. Where areas of refuge are provided on both sides of a

horizontal exit, two door openings shall be provided, each swinging in opposite directions

(C26-604.6(b)).

b. Balconies, bridges and tunnels serving as horizontal exits shall comply with Section

C26-604.6(c).

^

5. Access to an area of refuge on a floor nearer to the street, through a supplemental vertical

exit, may consist of enclosed interior stairs, ramps, or escalators (C26-604.7):

a. Supplemental vertical exits shall comply with the requirements for interior stairs, and

ser\ e no other purpose than to connect a floor area with an area of refuge with no

openings in the enclosure other than exit doors (C26-604.7).

b. Every supplemental vertical exit shall have a sign at the entrance stating EXIT TO AREA

OF REFUGE ON FLOOR (C26-604.7).

NISTNCSTAR 1-1D, WTC Investigation 65
Chapter 15

15.3 EXIT WIDTH AND CAPACITY

Occupant load - Calculated based on the net floor area in square feet divided by the occupant load factor (square foot per person) or the actual number of occupants for whom each occupied space is designed,

whichever is greater (C26-601.2):

1 . Non-simultaneous Occupancy - The occupant load of toilets, locker rooms, meeting rooms,

storage rooms, employee cafeterias, and similar rooms or spaces that are not occupied at the same time as other rooms or spaces on the same floor may be omitted from the occupant load

calculation of the floor on which they are located (C26-601 .2(c)).

2. The occupant load of any space shall include the occupant load of all spaces that discharge

through it in order to gain access to an exit (C26-601 .2).

Occupancy Occupant Load Factor

Business (offices) _ , 100

Conference rooms (tables) 12

Conference rooms (chairs) 1

0

Dining spaces 12

Mercantile:

1 St floor/basement 25

All other floors 50

Assembly (fixed seats) No. of seats

Waiting space (standing) 4

Garages/parking 250

Storage rooms 200

Mechanical rooms 200

Where vertical exits serve more than one floor, only the occupant load of each floor considered

individually is used in computing the required capacity of exits at that floor, except where one floor is used by another as a means of egress (C26-601.1).

Exit capacity (width) shall not decrease in the direction of exit travel (C26-604.8).

66 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

The width of each means of egress component shall be that computed using the appropriate egress unit factor but not less than the minimum width prescribed for the component (C26-601.1, C26-601.3):

1 . Where computations give fractional results, the next larger integral number of egress units or

integral number plus Yi shall be used (C26-601.3).

2. A fraction less than V2 may be neglected when constituting less than 10 percent of the total required number of egress units.

When a floor area has access to areas of refuge that comply with the requirements of section C26-604.5,

the number of persons for whom vertical exits are to be provided may be reduced to 50 percent of the occupant load of the floor area when one area of refuge is provided, and may be reduce to 33 1/3 percent

of the floor area when two areas of refuge are provided (C26-603.3).

Egress capacity factors - capacity per egress unit (C26-601.1, C26-601.3):

1 . One unit of egress width is equal to 22 in.

2. Doors to outdoors at grade:

a. Occupancy Group B (Storage) - 75 persons per unit

b. Occupancy Groups C (Mercantile), E (Business), and F (Assembly) - 100 persons per

unit

3. Other exit and corridor doors:

a. Occupancy Group B (Storage) - 60 persons per unit

b. Occupancy Group C (Mercantile), E (Business), and F (Assembly) - 80 persons per unit

4. Stairs and escalators:

a. Occupancy Group B (Storage) - 45 persons per unit

b. Occupancy Groups C (Mercantile), E (Business), and F (Assembly) - 60 persons per unit

5. Ramps, corridors, exit passageways, horizontal exits:

a. Occupancy Group B (Storage) - 75 persons per unit

b. Occupancy Groups C (Mercantile), E (Business), and F (Assembly) - 100 persons per

unit

c. When ramp slope exceeds 1 in 10, the capacity shall be reduced by 25 percent (Table 6-1

note b).

Where a door is divided by muUions into two or more door openings, each opening should be measured

separately in computing the number of egress units (Table 6-1 note m).

NISTNCSTAR 1-1D, WTC Investigation 67
Chapter 1

5

15.4 DOORS

Minimum nominal width shall be 32 in. except for corridor and exit door openings which shall be 36 in. (C26-604.4(e)):

1 . Door jambs or stops and the door thickness when open shall not reduce the required width by more than 3 in. for each 22 in. of width (C26-604.4(e)).

2. In all cases where a door opening is divided by mullions into two or more door openings, the minimum nominal width of each such opening shall be 32 in. (C26-604.4(c)).

Maximum width of leaf (C26-604.4(e)) shall be 48 in.

Minimum height (C26-604.4(f)) shall be 6 ft 8 in.

Door jambs, stops, sills, and closers should not reduce the clear opening to less than 6 ft 6 in. (C26-604.4(f)).

The floor on both sides of all exit and coiTidor doors shall be substantially level and have the same

elevation for a distance at least equal to the width of the leaf (C26-604.4(h)).

Where doors lead out of a building, the floor level inside may be IVi in. higher than the level outside

(C26-604.4(h)).

Exit doors, corridor doors serving high hazard occupancy Group A spaces, and corridor doors from rooms

required to have more than one door shall swing in the direction of egress (C26-604.4(g)).

Vertically sliding doors, rolling shutters, and folding doors shall not be used as exit doors or as corridor

doors (C26-604.4(d)).

Revolving doors designed and constructed in accordance with Section C26-604.4(m) are pennitted to be

used as exits except that revolving doors shall not be used as interior exit access doors, at the foot of

stairs, or at the head of basement stairs (C26-604.4(d)).

Turnstiles designed and constructed in accordance with Section C26-604.4(n) may also be pennitted.

Power operated or power assisted manually operated doors may be used as exit or corridor doors provided

they remain closed in case of power failure and are manually operable. To be credited as a required exit,

power operated doors must swing in the direction of exit travel (C26-604.4(l)).

Exit doors and corridor doors shall nonnally be kept in the closed position (C26-604.4(i)).

Latch bolts shall be provided on all exit doors and corridor doors to hold them in a closed position against

the pressure of expanding gases (C26-604.4(j)(l)(c)).

68 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

Obstruction of means of egress during door opening:

1 . Doors providing access to stairways or ramps shall not block stairs/ramps or stair landings or reduce the width of landings/stairs/ramps to less than 75 percent of the required width or to

less than the width of the door opening on them (C26-604.8(g), C26-604. 10(c)(4)).

2. No door shall swing over the sloping portion of a ramp (C26-604. 8(c)(4)).

Exit and corridor doors and doors providing access to areas of refuge shall be readily openable at all times

from the side from which egress is made without the use of a key (C26-604.4(j)(l)(a), C26-604.5(d)):

1 . Locks may be used in places where extra safeguards are required (banks, museums, etc.), subject to approval of the commissioner, provided the locks are equipped with electrical release devices for remote control in case of emergency (C26-604.4(j)(l)(a)(2)).

2. Doors opening into interior enclosed stairs shall not be locked from either side except that doors may be locked to prevent access to the stair from the outside at the street floor (C26-

604.4G)(l)(b).

15.5 EXIT ACCESS

Minimum clear width of corridors:

1 . Occupancy Groups B (Storage), C (Mercantile) - 36 in.

2. Occupancy Groups E (Business), F (Assembly) - 44 in.

The maximum length of exit access travel shall not exceed the following limits, measured from the most

remote point in an area, to the center of an exit door. Travel distance shall be measured along the natural and unobstructed path of travel. Where the path of travel is over an access stair, it shall be measured

along an inclined straight line through the center of the outer edge of each tread.

Occupancy Distance (Fcct)^'

B-1 (Storage) 150

B-2 (Storage) 175

B-2 (Parking Garage) 150

C (Mercantile) 200

E (Business) 300

F (Assembly < 75 persons) 200

Distances given are for sprinklered conditions (Table 6-1).

NIST NCSTAR 1-1 D. WTC Investigation 69
Chapter 15

The maximum dead-end distance shall not exceed the following limits:

T^l C^^O M /> <i f Ia^ £in^\'

D-i ( storage

j

JU

B-2 (Storage) NR

C (Mercantile) 50

E (Business) 50

F (Assembly) 30

Exterior corridors designed and constructed in accordance with Section C26-604.2(f) may be used as a means of egress. . ^

15.6 STAIRWAYS

Minimum clear width shall be at least 44 in. (C26-604. 8(b)):

1. The width of stairs shall be the clear width between walls, grilles, guard, or newel posts.

Stair stringer projections which do not exceed two in. on each side and handrail projections of

3'/2 in. are pemiitted.

2. Vertical exits in public garages may be 36 in. wide.

3. The minimum width of landings and platfonns should be at least the required width of the stairway. On a straight run stair, landing and platform widths need not be more than 44 in.

Minimum headroom shall be at least 7 ft (C26-604.8(c)).

Maximum height between landings shall be 12 ft (C26-604.8(d)).

Treads and risers (C26-604.8(e), Table 6-4):

1 . Maximum riser height - IV^ in.

a. Occupancy Group F (Assembly) - IVi in.

b. All others - IVa in.

2. Minimum tread depth - in. plus nosing

Distances given are for unsprinklered conditions. When a corridor is completely enclosed in 2 h fire resistance rated construction with 'A h fire rated doors, the pennissible length of dead ends may be increased by 100 percent (C26-604.2(d)).

70 NISTNCSTAR 1-1D, WTC Investigation
Means of Egress

3. The sum of two risers plus one tread exclusive of the nosing shall not be less than 24 nor more than ISVi in.

4. Stair riser and tread dimensions shall be constant in any flight of stairs from story to story.

Curving or skewed stairs that conform to Section C26-604. 8(e)(4) are peraiitted to be used as exits.

Where exit stairways serv ing floors above grade continue in the same enclosure to serve floors below

grade, the above and below grade portions shall be separated by 1 h fire resistance rated construction.

Stair identification signs shall be posted on the occupancy side of the stair door indicating the letter designation of the stair.

In buildings or in building sections more than three stories or 40 ft high with roofs having a slope of less than 20 degrees, access to the roof shall be provided by at least one interior stair. Access to set back roof

areas may be through a door or window opening to the roof.

No openings of any kind are permitted into stair enclosures other than windows, fire department access panels and exit doors.

Exterior stairs designed and constructed in accordance with Section C26-604.9 may be used as exits in lieu of interior stairs.

No exterior stair shall exceed 75 ft or six stories in height.

Escalators designed and constructed in accordance with Section C26-604.ll may be used as exits in heu

of interior stairs.

15.7 RAMPS

The minimum clear width of exit ramps is 44 in. (C26-604.10, C26-604.8(b)).

Level platforms or landings at least as wide as the ramp shall be provided at the top and bottom of all ramps and at intermediate levels as necessary:

1 . Level platforms shall be provided on each side of door openings into or from ramps.

2. Platforms shall be at least 3 ft wide, 5 ft when a door swings onto the platform.

Minimum headroom shall be 6 ft 8 in.

Changes in direction of travel shall be made only at landings (or platforms) (C26-604. 10(c)).

Ramps with a slope not greater than 1 in 1 2 at any place may be curved.

Ramps shall not have a slope steeper than 1 in 8 and sloping portions shall be at least 3 ft but not more

than 30 ft long between platforms or landings.

NISTNCSTAR 1-1 D, WTC Investigation 71
Chapter 15

Level and ramped moving walkways designed and constructed in accordance with Section C26-604.12

may be used as exits.

15.8 HANDRAILS AND GUARDRAILS

Continuous handrails are required on both sides of all stairs, and all ramps with a slope exceeding 1 in 12:

1 . Stairs less than 44 in. wide may have a handrail on one side only.

2. Intennediate handrails shall be provided to divide stairs more than 88 in. wide into widths

that maintain nominal multiples of 22 in. and widths not greater than 88 in. nor less than

44 in.

3. Handrail height shall be 30 to 34 in. measured vertically above the nosing of treads.

4. Handrail ends shall be returned to walls and posts when tenninated.

5. Handrails shall provide a finger clearance of Wi in. and shall project not more than 31/2 in. into the required stair width.

Stair landings and platforms shall be enclosed on sides by walls, grilles, or guards at least 3 ft height.

15.9 EXIT SIGNS

In all buildings, the location of every exit on every floor shall be clearly indicated by approved EXIT

signs (C26-606.1).

EXIT signs shall be placed at an angle with the exit opening if such placement is required for the signs to serve their purpose.

In areas where the location of the exit may not be readily visible or understood (including long corridors

and open floor areas), directional signs shall be provided to serve as guides from all portions of the corridor or floor.

The size, color and illuinination of EXIT signs shall confonn to Section C26-606.3. Directional signs

shall confonn to Section C26-606.4.

All EXIT signs shall be illuminated at all times when the building is occupied.

Where a total of more than four signs (exit and/or directional) are required, all EXIT signs shall be

connected to circuits that are separate from the general lighting and power circuits. These circuits shall be

taken off ahead of the main switch or connected to an emergency lighting power source when such source

is provided.

Any door, passageway, stair, or other means of communication that is not an exit shall be so identified with a NOT AN EXIT sign and a sign indicating its use or purpose or a directional exit sign shall be

provided.

72 NISTNCSTAR 1-1 D, WTC Investigation
Means of Egress

15.10 MEANS OF EGRESS LIGHTING

Corridors and exits shall be equipped with artificial lighting facilities to provide at least 2 ft candle

intensity' floor lighting continuously during the time that conditions of occupancy of the building require

that the exits be available (C26-605.1(a)).

Lighting shall be provided to illuminate changes in direction in and intersections of corridors, balconies,

exit passageways, stairs, ramps, escalators, bridges, tunnels, landings, and platfonns.

Illumination shall be arranged so that failure of any one light does not leave any area in darkness.

Where a total of more than four lights are required, exit lighting shall be cormected to an emergency

power source or to approved storage battery equipment (C26-605.2(a)).

NISTNCSTAR 1-1 D. WTC Investigation 73
Chapter 15

This page intentionally left blank.

74 NIST NCSTAR 1-1 D, WTC Investigation
Chapter 16

Fire Suppression

16.1 AUTOMATIC SPRINKLER PROTECTION

Automatic sprinkler protection shall be designed and installed in accordance with Section C26- 1703.1 and

Reference Standard (RS) 1 7-2 in the following areas:

1. Spaces in group B-1 > 500 ft".

2. Spaces in group B-1 < 500 ft" when required by the commissioner.

3. Spaces in group B-2 > 5,000 ft" or 75 ft in height.

4. Spaces in high-rise buildings classified as mercantile occupancy group C > 7,500 ft" in floor area or with an unenclosed stair or escalator between any two or more floors.

5. Showroom spaces exceeding 7,500 ft" in area located more than 40 ft above curb level in new

and existing buildings classified in occupancy group E, 100 ft or more in height having air- conditioning and/or mechanical ventilation systems that serve more than the floor in which

the equipment is located.

6. Regardless of occupancy, any story above grade and the 1st story below grade without

required ventilation:

a. All other stories below grade.

b. Sprinklers may be omitted in toilets, shower rooms, stair, and mechanical and electrical rooms.

7. Catering establishments and banquet halls with an occupancy load of 300 or more persons.

8. Spaces in occupancy group F-4 located more than 75 ft above curb level.

9. Notwithstanding the requirement of other sections, new high rise buildings in occupancy

group E (Business).

A wet-pipe sprinkler system should be provided throughout all areas requiring automatic sprinkler

protection (C26-1703.13). In areas subject to freezing the sprinkler system shall be protected (insulation,

heat trace, antifreeze) or a dry-pipe system shall be provided (C26-1703.13).

A sprinkler alarm system shall be provided in accordance with RS 17-2 and RS 17-3 or in accordance

with RS 17-3 A or RS 17-3B if a class E or modified class E fire alarm system is provided (C26- 1703.4).

NISTNCSTAR 1-1D, WTC Investigation 75
Chapter 16

A sprinkler alann system shall be provided when more than 36 heads are installed in any fire area or

section.

16.2 STANDPIPES

Wet standpipes designed and installed in accordance with Section C26- 1702.1 and RS 17-1 shall be

provided (C26-1 702. 1(a)(1)).

The number and location of standpipes shall be such that every point of every floor can be reached by a 20 ft stream from a nozzle attached to not more than 125 ft of hose connected to a riser outlet valve

(C26-1702.4):

1. Standpipe risers and IVi in. hose valves shall be located within stairway enclosures

(C26-1702.5(a)).

2. When stairway enclosures are not available within the 125 plus 20 ft distance (145 ft total), risers and valves shall be located as near to the enclosure as practicable (C26-1 702.5(a)).

The highest riser shall be extended above the roof with a 3-way manifold with IVi in. hose valves

(C26-1702. 11(a)(2)).

A 2V2 in. hose outlet shall be provided at each standpipe riser on each floor served, and on the entrance floor above the riser control valve, located between 5 and 6 ft above the landing or floor (C26-1702. 11(a)(1)).

Hose stations shall be located at the standpipe risers, either inside or adjacent to the entrance of stairway

enclosures (C26-1702.1 1(b)):

1. Hose stations shall be located to satisfy the 125 plus 20 ft (145 ft total) requirement

(C26-1 702. 11(b)(1)).

2. Hose shall be (C26- 1702. 11(c)):

a. 1 V2 in. unlined (flax-line) linen hose in Groups C, E, and F.

b. 2/2 in. (unlined) in Group B.

3. Auxiliary hose stations equipped with IVi inch (unlined) hose are permitted in Groups C, E,

and F (C26-1702. 11(c)(4), C26-1702. 11(d)).

Standpipe systems that include more than one riser shall have all risers cross-connected at, or below, the

street entrance floor level (C26-1 702. 10(a)).

Standpipe systems having more than one zone shall be arranged such that the risers supplied from each zone are cross-connected below, or in the story of the lowest hose outlets from the water source in each

zone (C26-1 702. 10(b)).

76 NISTNCSTAR 1-1D, WTC Investigation
Fire Suppression

Standpipe risers shall be at least 4 in. in diameter where the riser height is 150 ft or less from the highest

hose outlet to the level of the entrance floor, 6 in. in diameter where greater than 150 ft (C26- 1702.7,

Table 17-1).

16.3 WATER SUPPLY

Standpipe systems shall have a primary water supply available at all times to every hose outlet or made

available automatically when the hose valve at any outlet is opened (C26-1702.14).

Combinations of two or more of the following sources shall serve as the primary water supply

(C26-1702. 14(b)):

1. Direct cormection to city water system.

2. Direct connection to a private yard main.

3. Gravity tank(s).

4. Pressure tank(s).

5. Automatic fire pump (C26-1 702. 14(b)(5)):

a. In buildings higher than 300 ft, the automatic fire pump shall be used only for the lower

300 ft.

b. Zones above 300 ft shall be supplied by either a gravity or pressure tank.

6. An additional standpipe system water supply shall be provided for standpipes in buildings over 300 ft high (C26- 1702. 15(a)). The primary water supply to the standpipe system should

be supplemented by one or more manually operated fire pumps (C26-1 702. 15(a)).

At least one of the following automatic sources of water supply shall be provided for sprinklers

(C26-1703.8(a):

1 . Gravity tank(s).

2. Pressure tank(s).

3. Automatic fire pump.

4. Direct connection to public water system.

Domestic water supply may be used to supply cooling tower sprinklers and sprinklers installed in buildings classified in Occupancy Group E (Business) in accordance with Section C26-1703.9(e)

(C26-1 703.9 (c) and(d)).

Auxiliary sources of water supply for sprinkler systems may include a manually actuated fire pump or Siamese connection (C26-1703.8(b)).

NISTNCSTAR 1-1 D, WTC Investigation 77
Chapter 16

Combined Water Supplies:

1 . Fire pumps may simultaneously serve as the required auxiliary water supply for standpipe

and sprinkler systems in accordance with Section C26-1 702. 15(d).

2. Tanks used to provide the required primary water supply to a standpipe system may also be

used as a supply for an automatic sprinkler system (C26-1703.8(c)).

One standpipe system and one sprinkler system Siamese connection shall be provided for each 300 ft of

exterior building wall or fraction thereof facing each street or public space (C26- 1702.9(a),

C26-1703.6(a)(l)):

1 . Modifications based on street frontage as pemiitted by Sections C26-1702.9(b)-(f).

2. Each Siamese connection shall be connected to a riser or to a cross connection connecting

other Siamese connections or risers (C26- 1702. 10(f)).

3. In below grade sprinkler systems for garage occupancies, a sprinkler Siamese connection shall be provided within 50 ft of every exit or entrance used by motor vehicles (C26- 1703.6(a)(2)).

4. Siamese connections for partial sprinkler systems shall be in accordance with

Section C26-1703.6(a)(3).

78 NISTNCSTAR 1-1D, WTC Investigation
Chapter 17

Fire Detection and Alarm

17.1 FIRE ALARM SYSTEM

New buildings classified in occupancy group E 75 ft or more in height and existing buildings in occupancy group E 100 or more ft in height are required to be provided with a Class E (or modified

Class E) fire alarm and communication system including loud speakers, two-way voice, and a fire command station. (C26-1704.1(a)(9), C26-1704.4(g)(h), C26-1704.5(f)(g), C26-1704.8)

A sprinkler alarm system shall be provided when more than 36 heads are installed in any fire area or

section (C26-1 703.4).

A local water flow alarm unit shall be provided (outdoor water motor or electric alann gongs) where there

is no watchman with watch service (Reference Standard [RS] 17-2 Sec. 3721).

Central station water flow alarm service is desirable, but does not waive the local alarm requirement

(RS 17-2 Sec. 3721).

17.2 SMOKE AND HEAT DETECTOR LOCATIONS

Heating, Ventilating, and Air Conditioning (HVAC) Systems (C26-1 300.7(a), RS 13-1):

1. In HVAC systems over 2,000 cfm capacity, approved smoke detectors shall be provided for automatic fan shut-down in (RS 13-1 Sec. 4-3 and 4-4):

a. The main supply duct on the downstream side of the filters.

b. The return air stream, prior to exhausting from the building or being diluted by outside

air.

Exception 1 : The smoke detector in the return air stream may be omitted in systems of

less than 15,000 cfm capacity.

Exception 2: Both detectors may be omitted provided that the system is less than

15,000 cfm capacity, the entire system is within the space served and such space is protected by an area smoke detection system.

2. In HVAC systems serving more than the floor on which the equipment is located, an approved product of combustion ionization detecting device or a combination of an approved

smoke detecting device and an approved fixed temperature thermostatic device shall be

located at the return shaft at each floor and so located as to monitor each inlet to the air return

shaft (RS 13-1 Sec. 4-3.2(c)).

NISTNCSTAR 1-1D, WTC Investigation 79
Chapter 17

3. In HVAC systems utilizing recirculated air, smoke detectors shall be provided for automatic

fan shut-down when any of the following conditions exists (RS 13-1 Sec. 4-5.4):

a. System supplies an exit passageway, or a space leading from elevators to a street or to the

exterior.

b. System supplies spaces on more than one story or spaces in different fire areas in the same story.

c. Where the area of a building or space sei'ved is over 15,000 ft' in mercantile or indoor

assembly occupancies.

d. Where there is a duct opening in a required 2 h fire resistance rated interior fire division.

e. Where a duct passes through a firewall.

f Where a corridor is used as a plenum. ^

Specific occupancy requirements:

1. In a Class E fire alann system, ceiling mounted ionization smoke detectors or combination

smoke/heat detectors shall be installed at each elevator landing immediately above a call button (C26-1 704.5(f)(8)). A building equipped throughout with an automatic sprinkler

system including a water flow alarai shall be exempt from the installation of the detectors

provided the water flow alarni has the same effect mentioned below (C26-1704.5(f)(10)).

2. The activation of a smoke detector in any elevator lobby shall only annunciate at the

fire command station. The activation of both smoke detectors in any elevator lobby

shall cause selected elevators to return non-stop to the designated level (RS 18-1,

Rule211.3b(6)(a and b)).

3. Activation of an elevator landing detector shall (C26-1 704.5(f)(8)):

a. Sound continuously throughout the floor of alarm and floor above.

b. Sound fire alann signal at the fire command station, mechanical control center and

regularly assigned location of the fire safety director.

c. Operate the information display system.

d. Stop the air supply into and air return from the floor where activated by approved remote

control reversible fire shutters or by automatically shutting down supply and return air fans.

e. Activate air exhaust fans and dampers in smoke shafts and/or pressurizing fans in stair enclosures.

4. In addition to the smoke detector requirement, in a building equipped throughout with an

automatic sprinkler system, a waterflow alann when activated shall initiate Phase I emergency recall operation (RS 18-1, Rule 21 1.3).

80 NISTNCSTAR 1-1D, WTC Investigation
Fire Detection and Alarm

17.3 MANUAL FIRE ALARM BOXES

The boxes shall be installed in accordance with NFPA 72.

At least one fire alarai sending station shall be provided in each stoiy located in each path of escape with

additional stations installed so that no point on any floor is more than 200 ft from the nearest station (RS 17-3A. Sec. 7(a)).

Operation of a manual station shall automatically transmit a fire alami signal to the fire department via a

central station and sound an alarm continuously on the floor where activated and the floor above

(C26-1 704.5(f)(4)).

Fire alarm (Class E) sending stations shall be painted red with a diagonal white stripe painted or applied

to sending stations which transmit a fire alarm signal to the fire department via a central station (C26- 1704.6(e)).

17.4 AUDIBLEA/ISUAL ALARM NOTIFICATION APPLIANCES

In a Class E fire alarm system, loudspeakers capable of being operated from the fire command station should be provided on each floor, and in each elevator and stair enclosure (C26-1 704.8(a)).

Loudspeakers shall be located so that their operation will be heard clearly above ambient noise

(C26-1704.5(f)(5)).

The loudspeaker amplifier system shall be so designed and installed that approximately 50 percent of the system shall remain operable for the transmission and audibility of signal and intelligibility of voice

communication over the loudspeaker system throughout the building, in the event the other 50 percent

becomes inoperable (C26-1 704.5(f)(7)).

Recessed speakers shall be located not more than 10 ft from the entrance to each required exit (RS 17-3 A,

Sec. 8(b)).

17.5 COMMUNICATION SYSTEMS

In every building more than 300 ft high, a telephone and signaling system shall be provided for fire department use in operating the standpipe system (C26-1702.21, C26-1704.7(a)).

Standpipe Telephone System:

1. System shall pennit communication by permanent telephones in the following locations

(C26-1704.7(b)):

a. Pump rooms.

b. Entrance floor.

c. Gravity tank rooms.

NISTNCSTAR 1-1D, WTC Investigation
Chapter 17

d. Each floor near main standpipe riser.

2. The system shall be a selective ringing, common talking system supplied by a 24-volt direct current power source (C26- 1704.7(b)).

3. Peraianent wall telephones shall be provided with 6 inch gongs except in the pump room

where a loud speaking receiver should be provided (C26- 1704.7(c)).

4. The telephones in the pump room shall be equipped with a loudspeaking receiver so that a voice can be distinctly heard at a distance of at least 1 5 ft from the receiver.

5. Where portable phones are used, jacks protected by break-glass boxes shall be provided

(C26- 1704.7(c)):

a. At least three portable phones shall be provided for each standpipe installation, kept in a

dedicated, locked cabinet located in the main hall of the entrance floor (C26- 1704.7(d)).

b. A pilot light shall be provided over the cabinet to indicate if the system is in use or a

receiver is off the hook (C26- 1704.7(e)).

Standpipe Signaling Devices:

1. Manual, individually coded sending stations shall be located in the main corridor of the building airanged to transmit a signal to alarm sounding devices (C26- 1704.7(f)(1)). System

shall be installed in accordance with RS 17-3 (C26- 1704.7(f), C26-1704.8).

2. An 8 inch gong shall be provided in the pump rooms and in elevator shafts at intervals not exceeding 10 floors (C26- 1704.7(f)(1)).

3. Adjacent to each telephone station and near the main standpipe riser, a closed circuit strap

key connected in series with the box circuit of the signal sending station shall be provided

(C26-1 704.7(f)(2)).

In a Class E fire alann signal system, the standpipe fire line telephone and signaling system may be

combined with the fire alarm system provided (C26- 1704.7(g)):

1 . The alanns and two-way voice communication with the fire command station include the pump and gravity tank rooms.

2. A designated floor station of the Class E system is located at or near the main standpipe riser on every floor. A two-way communication capability shall be provided between the fire command station and the following locations (C26- 1704.8(a)(2)):

1 . A designated floor warden station on each floor.

2. Mechanical control center.

82 NISTNCSTAR 1-1 D. WTC Investigation
Fire Detection and Alarm

3. Elevators.

4. Air-handling control rooms.

5. Elevator machine rooms. A floor warden station shall be located between required stairways, vertical exits or other exits (RS 17-3B7.b):

1 . System shall include a telephone type handset at the floor warden station with integral

signaling to the fire command station.

2. Warden stations may be part the speaker system.

NISTNCSTAR 1-1D, WTC Investigation 83
Chapter 1

7

This page intentionally left blank.

84 NIST NCSTAR 1-1 D, WTC Investigation
Chapter 18

Elevators and Hoistways

18.1 GENERAL

Elevators or escalators shall be provided in accordance with Section C26- 1800.1 and RS 18-1 in all new

buildings exceeding four stories in height (C26-604.1(a), C26-1 800.6(d)):

1. When Areas of Refuge are provided above the 1 1th floor of a building, they shall be served

by at least one elevator (C26-604.5(c)).

2. Escalators may be used as exits in lieu of interior stairs (C26-604.1 1 and C26- 1800.6(g)).

In every building exceeding 1 75 ft in height, at least one elevator shall be kept available for immediate

use by the fire department during all hours (C26-1 702.22, C26-1 800.8).

In buildings exceeding 150 ft in height, there shall be an operator available at all times (C26- 1800.8).

Automatic passenger elevators shall be equipped with emergency controls for fire department use (Reference Standard [RS] 18-1 Rule 210.13):

1 . A two-position keyed switch shall be provided at a main floor of each elevator or group of

elevators for recall to the main floor in accordance with RS 18-1 Rule 2 10. 13. a.

2. A keyed switch shall be provided in or adjacent to an operating panel of each elevator to

initiate emergency service in accordance with RS 18-1 Rule 210.13.b.

NISTNCSTAR 1-1 D, WTC Investigation 85
Chapter 18

This page intentionally left blank.

86

NISTNCSTAR 1-1 D, WTC Investigation
Chapter 19

Emergency, Electrical, and Standby Power Systems

19.1 emergency POWER SYSTEMS

An emergency power system shall be provided in high-rise buildings in occupancy group E and have

capacity to operate equipment such as (C26-610.1, C26-610.3):

1. Fire pumps.

2. At least three elevators at one time, with manual transfer to other elevators.

3. Alarm systems.

4. Communications systems.

5. Emergency lighting, if battery packs are not available.

6. Ventilating systems used for smoke venting or control.

7. Stair pressurization.

NISTNCSTAR 1-1 D. WTC Investigation
Chapter 19

\

This page intentionally left blank.

88 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 20

Special Features

20.1 SMOKE AND HEAT VENTING

Elevator and dumbwaiter shafts shall be vented in accordance with Reference Standard (RS) 18-1.

Other closed shafts shall be vented as follows:

1 . All closed shafts having an area exceeding 4 ft' shall be provided with a smoke vent having an area of at least 3 '/2 percent of the maximum shaft area at any floor but not less than '/2 ft" (C26-504.6(d)).

2. Smoke vents may be windows, louvers, skylights, vent ducts, or similar devices

(C26-504.6(d)).

3. Vent ducts shall be enclosed by construction having the same fire resistance rating as required for the shaft and extend vertically, diagonally, or horizontally in accordance with

Sections C26-504.6(d)(l and 2).

4. Of the total required vent area for shafts at least one-third shall be clear to the outdoors either

in the fonn of fixed louvers, ridge vents, or hooded or goose-necked openings

(C26-504.6(e)).

5. As an alternate, skylights or trap doors may be used arranged to open automatically by fusible

link or other mechanical device when subjected to 160 °F fixed temperature or 15 °F to 20 °F

per min temperature rise (C26-504.6(e)).

6. The remaining portion of the required vent area may be a window or skylight glazed with

plain glass not more than 1/8 in. thick or slow burning plastic (C26-504.6(e)).

Machine Rooms:

1 . Any compartment containing machinery that communicates with a shaft enclosure shall comply with all requirements for shafts (C26-504.6(f)).

2. The required louver or glazing shall not be located in any door leading into such compartment

(C26-504.6(f)).

NISTNCSTAR 1-1 D, WTC Investigation 89
Chapter 20

\

This page intentionally left blank.

90

NISTNCSTAR 1-1 D, WTC Investigation
Chapter 21

Inspections

21.1 INSPECTION REQUIREMENTS

The following requirements shall apply to the inspection of all materials which, in their use, are regulated

by the provisions of the code:

1 . Controlled inspection - All such materials which are designated for "controlled inspection"

under the provisions of the code shall be inspected and/or tested to verify compliance with

code requirements. Unless otherwise provided by code provisions, all required inspection

and test of materials designated for "controlled inspection" shall be made and witnessed by or under the direct superv ision of an architect or engineer retained by or on behalf of the owner

or lessee, who shall be, or shall be acceptable to, the architect or engineer who prepared or supervised the preparation of the plans; and the architect or engineer by whom, or under

whose direct supervision, the required inspections and tests are made and witnessed shall file with the department signed copies of all required inspection and test reports, together with his signed statement that the material and its use or incorporation into the work comply with code

requirements, unless the filing of such reports and statements is specifically waived by code

provisions (C26-1 06.3(a)).

2. Semi-controlled inspection - All such materials that are not designated for controlled

inspection under the provisions of the code shall be subject to semi-controlled inspection and,

as such, shall be inspected and/or tested to verify compliance with code requirements by the person superintending the use of the material or its incorporation into the work, except that all required inspections and tests may, at the option of the owner or lessee, be made and

witnessed by or under the direct supervision of any architect or engineer retained by or on

behalf of the owner or lessee, who shall be, or shall be acceptable to, the architect or engineer

who prepared or superv ised the preparation of the plans. The person superintending the use of the material or its incorporation into the work, or the architect or engineer by or under

whose direct superv ision the required inspections and tests are made and witnessed, as the case may be, shall file with the department signed copies of all required inspection and test reports, together with his signed statement that the material and its use or incorporation into the work comply with code requirements, unless the filing of such reports and statement is specifically waived by code provisions (C26- 106.3(b)).

3. Off-site inspection - In all cases where code provisions require that the inspection and/or test of materials be made off-site, or prior to actual use or incorporation into the work, the inspector shall mark or cause to be marked for identification all units (or packages of units) of

the material inspected; and the reported results of such inspection shall state that the material was so marked for identification (C26-1 06.3(c)).

NISTNCSTAR 1-1 D, WTC Investigation 91
Chapter 21

21.2 MATERIALS REQUIRING INSPECTION

The installation of all required sprayed fire-resistive material of structural members except those encased

in concrete shall be subject to the controlled inspection requirements (C26-502.2(f)).

The installation of all required firestopping shall be subject to the controlled inspection requirements

(C26-504.7(h)).

92 NISTNCSTAR 1-1D, WTC Investigation
Chapter 22

References

Friedlander, Robert. 1 985. Building Code ofthe City ofNew York and Registration ofArchitects.

New York. NY.

PANYNJ (Port Authority of New York and New Jersey). 7 World Trade Center Fire Safety Plan.

New York, NY.

Syska and Hennessy. 1 984a. 7 World Trade Center Basic Design Schematics for Electrical,

November 5.

Syska and Hennessy. 1984b. 7 World Trade Center Basic Design Schematics for Fire Protection,

November 5.

Syska and Hennessy. 1984c. 7 World Trade Center Basic Design Schematics for Heating, Ventilating

and Air Conditioning, November 5.

Syska and Hennessy. 1984d. 7 World Trade Center Simtmaiy ofMechanical and Electrical Systems.

May 1.

NISTNCSTAR 1-1 WTC Investigation 93
Chapter 22

This page intentionally left blank.

94 NISTNCSTAR 1-1D, WTC Investigation
Section III

Post-Construction Fire Protection

AND Life Safety Provisions for

World Trade Center 1 , 2, and 7
,1^

This page intentionally left blank.
Executive Summary

As part of the analysis of building and fire codes and standards of the National Institute of Standards and

Technology (NIST) World Trade Center (WTC) Investigation, this report supports the effort to document

the change in building code regulations that occurred after the construction of WTC 1, 2, and 7. The

purpose of this report is to summarize the applicable fire protection (both passive and active) and life safety provisions that were adopted after the design and construction of the WTC 1, 2, and 7.

The WTC complex was a network of buildings constructed and maintained under the jurisdiction of the Port Authority of New York and New Jersey (PANYNJ). Facilities of the PANYNJ are not subject to the requirements of the local building codes, although the PANYNJ voluntarily followed the New York City

codes where applicable. In accordance with the instructions issued by the Port Authority at the start of

the WTC project, construction drawings for the WTC were to conform to the requirements of the Building Code of the City of New York (BCNYC).

The City of New York does not use a national model building code. Since the first pubhshed model

building code in the United States in 1905, municipalities have been given the opportunity to adopt a model building code(s) or develop their own code(s). New York City has taken the approach to develop

their own building code while incorporating technical and installation requirements by referencing

nationally recognized standards (National Fire Protection Association, ASTM International, American

National Standards Institute, etc.) and New York City developed reference standards (denoted by RS).

As time passed and experience was gained, the provisions of the BCNYC changed. Depending on the requirements of the changes in the BCNYC, new buildings (and some existing buildings) were required to meet the revised design and construction provisions. Generally, changes to the building code effect new

buildings and only affect existing buildings when a major aheration or a change in occupancy occurs. However, some of the provisions of the BCNYC were made retroactive, thus, effecting existing buildings.

The revised provisions in the BCNYC that were applicable to WTC 1, 2, and 7 are summarized in this

report.

Determination of the applicable building provisions was a multi-step task. First, documentation, such as drawings, memorandums and New York City building regulations, were analyzed to identify the initial construction pro\ isions at the times of construction of WTC 1, 2, and 7. Second, New York City building

regulations, published since the times of construction, were analyzed to identify the new and amended

building provisions. Third, the building provisions were analyzed to determine their applicabihty to the building characteristics of WTC 1, 2, and 7.

The revised provisions of the building code affect WTC 1 and WTC 2 differently from WTC 7. All of the requirements that were adopted by the City of New York subsequent to the 1968 edition of the Building

Code should have been implemented in the original design of WTC 7 since the local laws containing the revised construction provisions all predate the time of construction (1985) of WTC 7. However, all of the code provisions that were passed subsequent to the 1968 edition of the Building Code were not required

to be implemented in WTC 1 and WTC 2 since the local laws came into effect after the time of

NISTNCSTAR 1-1 D. WTC Investigation 97
Executive Summary

construction (1971) of WTC 1 and WTC 2. Only the applicable retroactive provisions were required to be implemented.

The applicable local laws that provided changes to fire protection and life safety provisions in the BCNYC are as follows:

• Local Law No. 5, Fire Safety Requirements and Controls (effective date immediately except

as noted), January 18, 1973.

• Local Law No. 16, Local Laws of the City of New York for the Year 1984 (effective date

immediately except as noted), March 27, 1984.

• Local Law No. 33, Local Laws of the City of New York for the Year 1978 (effective date

immediately), October 6, 1978.

• Local Law No. 54, Local Laws of the City of New York for the Year 1970 (effective date

immediately), November 17, 1970.

• Local Law No. 55, Local Laws of the City of New York for the Year 1976 (effective date

immediately), November 1, 1976.

• Local Law No. 84, Fire Safety Pressurization Requirements in Certain Office Buildings

(effective date immediately), December 13, 1979.

• Local Law No. 86, Dates for Compliance with the Local Laws Enacted for Fire Safety

Requirements and Controls in Certain Buildings (effective date immediately),

December 13, 1979.

The following is a summary of the post construction (retroactive) provisions that were required to be

implemented in WTC 1 and WTC 2. These provisions should have been implemented in the initial construction of WTC 7.

• Compartmentation of floor areas creating areas of refuge, unless complete sprinkler

protection is provided. The commissioner may waive the compartmentation provision and

accept an alternative measure fulfilling the intent of the code. One-third of the total floor area must be in compliance by February 7, 1973, with at lest two-thirds of the total floor area in compliance by August 7, 1984. Full compliance must be provided by February 7, 1988.

• Stair and elevator signs are required to be provided for by October 1, 1985.

• Emergency lighting shall be provided with secondary power by April 1, 1987.

• Exit signs shall be provided with secondary power by April 1, 1987.

• Provide sprinklers for showroom spaces over 7,500 ft" in area and located more than 40 fit above curb level.

98 NISTNCSTAR 1-1D, WTC Investigation
Executive Summary

• Provide sprinklers for catering establishments and banquet halls with an occupant load of

300 or more persons.

• Provide sprinklers for spaces in occupancy group F-4 (Assembly) located more than 75 ft above curb level.

• Install a Class E or modified Class E fire alarni and communication system including loud

speakers, two-way voice, manual fire alanti boxes and a fire command station.

• Provide the appropriate number of elevators ready for immediate use by the fire department.

• Provide a fire safety plan.

• Remove locks from elevator and hoistway doors, except elevators used exclusively for

freight, by April 1, 1987.

• Provide at least one smoke shaft by which smoke and heat can be mechanically vented to the outdoors by September 13, 1982. In lieu of the smoke shaft, a stair pressurization system(s) can be installed in all interior enclosed stairs. Or, provide a sprinkler system throughout.

One-third of the sprinkler system must be installed by December 13. 1981, with two-thirds of

the system completed by December 13, 1982. Full compliance must be provided by

December 13, 1983. The commissioner may extend the time requirements upon approval.

In addition to the retroactive provisions incorporated since the 1968 BCNYC, Local Laws added

requirements for new construction that were applicable to the design and construction of WTC 7, but were not applicable to the design and construction of WTC 1 and WTC 2. These requirements are

identified below:

• Class 1-B. unsprinklered, occupancy group E (Business) was changed from allowing

unlimited height and area to limiting Class I-B unsprinklered buildings to 75 ft in height with

an unlimited area.

• All hollow spaces shall be firestopped or filled with noncombustible materials, where

combustible trim and finish is permitted.

• Only v.'ool carpet assemblies are permitted to be installed in lobby areas, exit passageways

and convenient stairs.

• Flammabihty requirements of carpets and carpet assemblies were changed.

• Provisions for adequate means of egress in the opinion of the commissioner or fire protection

as the commissioner shall direct. Provisions include:

- Stair doors may be locked on the stair side above the street floor except that at intervals of four stories or less, the doors shall be openable from the stair side without the use of a key. Doors with automatic unlocking systems that are activated by the fire alarm system,

are deemed as openable from the stair side.

NISTNCSTAR 1-1 D. WTC Investigation 99
Executive Summary

- The minimum distance between vertical exits shall be the greater of 30 ft or one-third the maximum travel distance of the floor.

- New high-rise buildings in occupancy group E (Business) shall be sprinklered.

- An emergency power system shall be provided in all group E (Business) high-rise

buildings.

- A smoke control system shall be provided for in all group E (Business) occupancies.

- A smoke purge system shall be provided for in all group E (Business) occupancies.

- All sprayed fire-resistive material shall be subject to the controlled inspection

requirements of the BCNYC.

The PANYNJ and various consultants continuously evaluated the life safety and fire protection features of the WTC. Chapter 12 of this report contains a summary of how the local law provisions were complied with. Some of the local law provisions were complied with prior to the passage of the local law

requirements. During the time of the 1975 WTC fire, the New York Board of Fire Underwriters stated,

"The Fire Safety Program of the World Trade Center is an excellent one" and "In the overall, these towers may be considered as among the safest buildings in New York City" (refer to Appendix A in NIST

NCSTAR 1-lH). However, the same report cites problem areas such as , ". . . fireproofing of the steel may be missing in places; ... fire rating of shafts is just above minimum requirements; wiring ducts under

the floor (as in many other buildings), have questionable fire resistance and construction hazards and

deficiencies due to incomplete construction are still present."

100 NIST NCSTAR 1-1D, WTC Investigation
Chapter 23

Introduction

The regulation of building construction results from the recognition that life safety is served by the best

a\ ailable knowledge and practice. As technology changes and serious incidents occur, such as fires, building codes are developed and revised. Model codes have been published throughout the United States since 1905 (Boring 1981). Referenced standards adopted by the codes provide a technical basis for implementation of the code requirements and provide detailed methods of testing, installation, and

maintenance. Municipalities can either adopt a model building code(s) or develop their own code(s).

Additionally, many municipalities throughout the United States adopt model building codes and amend

the code as deemed necessary. New York City, however, has taken the approach to develop their own

building code while providing technical support and installation requirements from a mixture of

nationally recognized standards (National Fire Protection Association, ASTM International, American

National Standards Institute, etc.) and New York City developed reference standards (denoted by RS).

The World Trade Center (WTC) complex was constructed under the jurisdiction of the Port Authority of

New York and New Jersey (PANYNJ or Port Authority). Facilities of the PANYNJ are not technically

subject to the requirements of the local building codes, although the PANYNJ voluntarily followed the New York City codes where applicable. In accordance with the instructions issued by the Port Authority

at the start of the WTC project, construction drawings for the WTC were to confonn to the requirements

of the Building Code of the City of New York (BCNYC) (Solomon 1975).

New technology and serious incidents, such as fires, bring about the need for change in the provisions of

the BCNYC. As the years pass, the building code becomes outdated and requires revisions. In the city of

New York, local laws are passed to address the changes and are later incorporated in the BCNYC. The

requirements in the local laws generally affect only new construction and major alteration projects.

However, in some cases, requirements include retroactive provisions that are applicable to existing

buildings within the effective date. The effective date of a local law is a crucial piece of infonnation that will determine how a local law will affect a building.

WTC I, 2, and 7 were affected differently by the local laws presented herein since the buildings were

constructed under different editions of the BCNYC. WTC 1 and WTC 2 were constructed under the 1968

edition of the BCNYC. The 1968 edition of the BCNYC, including amendments to January 1, 1985, was

used to provide the fire protection and life safety provisions during the design and construction phases

(base building) of WTC 7. It is important to understand that all of the local laws in this report dated

before the amended date above have already been included in the base building construction of WTC 7. In contrast, there are certain local laws in this report, with retroactive requirements, that are applicable to the base building of WTC I and WTC 2. Without an applicable retroactive effective date, existing

conditions are permitted to remain, even if a new provision has changed the requirements of the BCNYC.

However, when tenant modifications or major aherations to the base building are performed, the modification (or major alteration) is required to meet the most current provision at the time of installation.

NISTNCSTAR 1-1D, WTC Investigation 101
Chapter 23

The reference standards within the BCNYC have been deaU with differently throughout the years and are complex to summarize. Amendments, deletions, and additions to the reference standards of the BCNYC

have been adopted through Local Laws, Board of Standards and Appeals calendar numbers, and Building

Department amendments. As previously stated, reference standards within the BCNYC contain both

nationally recognized standards and New York City developed reference standards. Due to the complex manner with which reference standards are dealt with in the BCNYC, a complete detail of the revised

provisions within the BCNYC reference standards cannot be detailed in this report. Where a specific

section of the New York City developed reference standard has been amended, deleted, or added, it shall be noted in this report. Otherwise, it is understood that the reference standard of the BCNYC refers to a

nationally recognized standard and has merely been updated to a more recent edition of the national

standard. Since nationally recognized standards do not contain retroactive effective dates, an updated

edition of a nationally recognized standard would therefore only affect major renovations or tenant modifications.

Chapters 3 through 1 1 present a summary of the minimum requirements of the revised BCNYC

provisions that have been added or amended by the Local Laws. Chapter 12 is a brief suinmary of how

the revised provisions were implemented in WTC 1 and WTC 2.

102 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 24

General

24.1 LOCAL LAWS WITH APPLICABLE FIRE PROTECTION/LIFE SAFETY

PROVISIONS

1 . Local Law No. 5, Fire Safety Requirements and Controls (effective date immediately except

as noted), January 18, 1973.

2. Local Law No. 16, Local Laws of the City of New York for the Year 1984 (effective date

immediately except as noted), March 27, 1984.

3. Local Law No. 33, Local Laws of the City of New York for the Year 1978 (effective date

immediately), October 6, 1978.

4. Local Law No. 54, Local Laws of the City of New York for the Year 1970 (effective date

immediately), November 17, 1970.

5. Local Law No. 55, Local Laws of the City of New York for the Year 1976 (effective date

immediately), November 1, 1976.

6. Local Law No. 84, Fire Safety Pressurization Requirements in Certain Office Buildings

(effective date immediately), December 13, 1979.

7. Local Law No. 86, Dates for Compliance with the Local Laws Enacted for Fire Safety

Requirements and Controls in Certain Buildings (effective date immediately),

December 13, 1979.

24.2 BUILDING SUMMARIES

Table 24-1. Building characteristics.

Building Height

Number of Floors Above Grade Footprint

Construction

Type (1968

BCNYC)

Primary Occupancy

Classification WTC 1 1.368 ft 1 10 42,900 ft- I-B Group E (Business)

WTC 2 L362ft 110 42,900 ft- I-B Group E (Business)

WTC 7 618ft 47 48,000 ft- I-C (some

documents cite 1-B)

Group E (Business)

Source: Merrii 2000a, 2000b; PANYNJ.

NISTNCSTAR 1-1D, WTC Investigation 103
Chapter 24

This page intentionally left blank.

104 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 25

Construction

25.1 CONSTRUCTION CLASSIFICATION

The Building Code of the City of New York (BCNYC) of December 16, 1968, did not limit the height or

area of a construction Class I-B, unsprinklered, occupancy group E (Business) building. However,

Local Law No. 16 amended Table 4-1, Area and Height Limitations of Unsprinklered Buildings and

Spaces, and limited the height (of the previously mentioned characteristics) to 75 ft while the area remained unlimited.

25.2 COMPARTMENTATION

All new buildings classified in occupancy group E (Business),'*'' and existing office buildings, 100 ft or more in height ha\ ing air-conditioning and/or mechanical ventilation systems that serve more than the

floor on which the equipment is located, unsprinklered floor areas,''"'' more than 40 ft above curb level,

shall be subdivided by fire separations into spaces or compartments as required (C26-504.1, added by

Local Law [LL] 5, Sec. 6):

1. All unsprinklered floor areas shall be segregated by 1 h fire separations into spaces or compartments not to exceed 7.500 ft'.

2. Where the floor area exceeds 10,000 ft', at least one of the subdividing fire separations shall be of 2 h construction, creating areas of refuge, complying with section C26-604.5 except that the requirement for an elevator in each area shall not apply.

3. The floor area or any subdivided area may be increased to not more than 15,000 ft' if complete area protection by approved devices for the detection of products of combustion

other than heat is provided within such increased area and provided further that at least one of

the subdividing fire separations shall be of 2 h construction where the floor area exceeds

15.000 ft', creating areas of refuge complying with C26-604.5 as noted in 2 above. The

activation of the detectors shall have the same effect as section C26- 1704.5(f).

4. In existing building, existing 1 h fire separations may be accepted in heu of the 2 h fire separation provided all of the requirements of 2 and 3 above are complied with.

5. Compartmentation is not required when complete sprinkler protection is provided.

LL 161 984 removed "all new buildings classified in occupancy group E (Business)" leaving the compartmentation

requirements of C26-504.1 to existing office buildings 100 fit or more in height due to sprinkler requirements.

The floor area shall be defined as the area within exterior walls and excluding any areas enclosing stairs, corridors, elevators, and shafts.

NISTNCSTAR 1-1 D, WTC Investigation 105
Chapter 25

6. Existing office buildings 100 ft or more in height shall comply with the requirements as follows:

a. At least one-third of the total floor area of the building not in compliance with the requirements above on February 7, 1973, shall comply with the requirements above by

December 13, 1981. Complete plans showing such compliance shall be filed with, and a pennit secured from the commissioner, by September 13, 1980 (LL 5, Sec. 6, dates revised by LL 86, Sec. 1).

b. At least two-thirds of the total floor area of the building not in compliance with the requirements above on February 7, 1973, must be in compliance on or before

August 7, 1984 (LL 5, Sec. 6, dates revised by LL 86, Sec. 1).

c. Full compliance must be provided on or before Februai^ 7, 1988 (LL 5, Sec. 6, dates

revised by LL 86, Sec. 1).

7. In existing office building 100 ft or more in height, the commissioner may waive or modify

the above requirements and accept alternatives fulfilling the intent of the requirements if compliance would cause practical difficulty or undue hardship. Where compliance with the

time requirements above would cause undue hardship, the commissioner, with the approval

of the fire commissioner, may extend the time for compliance (LL 5, Sec. 6, revised by

LL86, Sec. 1).

25.3 FIRESTOPPING

Where combustible trim and finish is permitted, all hollow spaces shall be firestopped at 10 ft intervals or

shall be sohdly filled with noncombustible materials (C26-504.7(f), added by LL 16, Sec. 28).

106 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 26

Interior Finish

26.1 FLOOR FINISH

Carpets and carpet assemblies shall not be installed in required exits, except that wool carpeting may be

installed in lobby areas, exit passageways and convenient stairs (C26-504. 13(d), added by LL 16, Sec. 32).

The flammability requirements of carpets and carpet assemblies, when used as a floor covering, shall be

as follows (C26-504. 13(d), added by LL 16, Sec. 32):

1 . All carpets and underlayments shall pass a methanine pill test in accordance with RS 5-20.

2. Carpets and carpet assemblies shall be tested for at least a 15 min critical radiant flux exposure in accordance with RS 5-20:

a. Where carpets and carpet assemblies are installed in corridors, the minimum critical radiant flux shall be 0.5 W/cm".

b. Where carpets and carpet assemblies are installed in other general areas, the minimum

critical radiant flux shall be 0.4 W/cm'.

3. Carpets and carpet assemblies shall be tested for smoke development ratings in accordance

with RS 5-20 and shall not exceed 300 within the first 4 min for the flaming or no-flaming

mode.

4. The manufacturer of the carpets and carpet assemblies shall submit a certificate from an

independent laboratory acceptable to the commissioner showing the complete test data

results, prior to final acceptance.

NISTNCSTAR 1-1 D, WTC Investigation 107
Chapter 26

1

This page intentionally left blank.

108 NIST NCSTAR 1-1 D, WTC Investigation
Chapter 27

Means of Egress

27.1 GENERAL

Every structure existing on December 6, 1968, that does not provide exit facilities in accordance with the Building Code of the City of New York (BCNYC) provisions and contain, in the opinion of the commissioner, inadequate means of egress shall be provided with such means of egress or fire protection

as the commissioner shall direct (C26-600.3, added by Local Law [LL] 54, Sec. 5).

27.2 EXITS

The minimum distance between vertical exit doors shall be the greater of 30 ft or one-third the maximum

travel distance of the floor, provided, however, that where such distance will result in travel distances

exceeding those authorized in section C26-601.1, additional vertical exits shall be provided (C26-602.3

amended by LL 16, Sec. 35).

27.3 DOORS

Doors opening into interior stair enclosures shall not be locked from either side with the following

exceptions (C26-604.4(j){l)(b). amended by LL 5, Sec. 9):

1 . Doors may be locked to prevent access to the stair at the street floor.

2. In buildings classified in occupancy group E, 100 ft or more in height and existing office buildings 100 ft or more in height, the doors may be locked on the stair side above the street floor except that at intervals of four stories or less, doors shall be openable from the stair side without the use of a key to perniit reentry at such floors.

3. The door on every floor where a keyed switch is required by the provisions of article 18 shall be openable from the stair side without the use of a key to pennit reentry at such floors.

4. When a locked door is provided with an automatic fail safe system for opening such door in the event of the activation of any automatic fire detecting device or when any elevator in readiness as provided in section C26- 1800.8 is activated, such door shall be deemed as openable from the stair side. Stair reentry signs required by C26-608.5 shall specify that reentry is provided only during fire emergencies.

27.4 STAIR AND ELEVATOR SIGNS

Buildings classified in occupancy group E (Business), occupied or arranged to be occupied for an occupant load of more than 100 persons above or below the street level or more than a total of

NISTNCSTAR 1-1 D, WTC Investigation 109
Chapter 27

500 persons in the entire building and any existing office building with an occupant load more than

100 persons shall be provided with signs as follows (C26-608.1, added by LL 5, Sec. 11):

1. A sign shall be posted and maintained on eveiy floor at the elevator landing. The sign

shall read "IN CASE OF FIRE, USE STAIRS UNLESS OTHERWISE INSTRUCTED".

(C26-608.2, added by LL 5, Sec. 11).

2. Floor numbermg signs on every floor (C26-608.3, added by LL 5, Sec. 11).

3. Stair and elevator identification signs (C26-608.4, added by LL 5, Sec. 11).

4. Stair reentry signs (C26-608.5, added by LL 5, Sec. 1 1

).

5. All existing buildings not already subject to the requirements of this section as of

January 18, 1973 shall comply with these requirements by October 1, 1985 (C26-608.7(c),

amended by LL 16, Sec. 49). \

27.5 MEANS OF EGRESS LIGHTING

Where a total of more than four lights are required, exit lighting shall be connected to an emergency

power source or to storage battery equipment. The exit lighting may be on circuits that are separate from

the general lighting and power circuits, taken off ahead of the main switch. The requirements of this section shall be provided by April 1, 1987 (C26-605.2, added by LL 16, Sec. 45).

Where a total of more than four exit signs are required, the signs shall be connected to an emergency

power source or to storage battery equipment. The exit lighting may be on circuits that are separate from

the general lighting and power circuits, taken off ahead of the main switch. The requirements of this section shall be provided by April 1, 1987 (C26-606.2(b), added by LL 16, Sec. 46).

110 NISTNCSTAR 1-1D, WTC Investigation
Chapter 28

Fire Suppression

28.1 AUTOMATIC SPRINKLER PROTECTION

New automatic sprinkler system requirements were added to section C26- 1703.1 of the Building Code of

the City of New York (BCNYC) as follows (Local Law [LL] 5, Sec. 15 and LL 16, Sec. 64). Automatic

sprinklers are required in the following locations:

1 . Showroom spaces exceeding 7,500 ft' in area located more than 40 ft above curb level in new

and existing buildings classified in occupancy group E (Business), 100 ft or more in height

having air-conditioning and/or mechanical ventilation systems that serve more than the floor

in which the equipment is located (LL 5, Sec. 15). This existing condition must be corrected

by January 18, 1976.

2. Catering establishments and banquet halls with an occupancy load of 300 or more persons

(LL 16, Sec. 64).

3. Spaces in occupancy group F-4 (Assembly) located more than 75 ft above curb level (LL 16, Sec. 64).

4. Notwithstanding the requirements of showrooms above, new high-rise buildings in occupancy group E (Business) (LL 16, Sec. 64).

NISTNCSTAR 1-1 D. WTC Investigation 111
Chapter 28

\

This page intentionally left blank.

112 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 29

Fire Detection and Alarm

29.1 FIRE ALARM SYSTEM

New buildings classified in occupancy group E (Business), 75 ft or more in height and existing buildings

in occupancy group E (Business) 100 or more ft in height are required to be provided with a Class E fire alarm and communication system including loud speakers, two-way voice and a fire command station in accordance with RS 17-3 A. (C26- 1704. 1(a)(9), C26- 1704.4(g), C26- 1704.5 (f), added by Local Law

[LL] 5, Sec. 21, 23, and 25, amended by LL 16, Sec. 72);

1 . It shall be a special electrically supervised approved direct wire, radio or combination thereof

fire alarm system consisting of an interior fire alarm and voice communicating system so arranged that the operation of any station will identify its location at the fire command

station, at the mechanical control center and at the regularly assigned location of the fire safety director (C26-1704.5(f)(l), added by LL 5, Sec. 25).

2. Audible signal devices indicating operation of the fire alarm signal system shall be provided

at the fire command station, mechanical control center and the regularly assigned location of

the fire safety director (C26- 1704.5(f)(3), added by LL 5, Sec. 25).

3. The fire alarm system may be sounded over loud speakers in accordance with RS 1 7-3 A so

located that their operation will be heard clearly above any ambient noise, and shall be

controlled from the fire command station in such a manner that the fire alarm signal can be

sounded on the individual floors or throughout the building (C26-1 704.5 (f)(5), added by

LL 5, Sec. 25).

4. Provision shall be made whereby the fire command station may permit the floor station to make announcements over the loud speaker system (C26-1 704.5(f)(6), added by LL 5, Sec. 25).

5. Existing office buildings 100 ft or more in height shall comply with the requirements of this secfion by September 13, 1981 (C26-1704.5(f)(12), added by LL 5, Sec. 25, amended by

LL86, Sec. 3).

6. In existing office buildings 100 ft or more in height where compliance would cause practical

difficulty or undue hardship, the commissioner may waive or modify the requirements of

C26-1407.5(f)(l-9) and accept alternatives fulfilling the intent of the requirements

(C26-1704.5(f)(l 1), added by LL 5, Sec. 25).

NISTNCSTAR 1-1 D, WTC Investigation 113
Chapter 29

Fire alann or communication systems installed prior to December 13, 1980, in existing office buildings

1 00 ft or more in height, may be incorporated or installed in a modified Class E fire alarni signal system

in accordance with RS 17-3B (C26- 1704.5(g), added by LL 5, Sec. 25). The requirements of the modified Class E system are the same as the Class E system mentioned above except:

1 . The provision whereby the fire command station may permit the floor station to make

announcements over the loud speaker system is not required.

2. Other differences mentioned below.

A fire command station shall be located in the lobby of the building on the entrance floor as part of the elevator control panel or immediately adjacent thereto. The fire command station shall contain the following (C26-1704.8(b), added by LL 5, Sec. 30):

1. The loud speaker and communication capability described in section C26- 1704.8(a).

2. The audible alann signal required in section C26- 1704. 5(f)(g).

3. Manually reset information display system to indicate the floor where the alarm was

activated.

4. Means to control the sounding devices on any floor or throughout the building.

5. Means to manually transmit a fire alarm signal to the fire department.

6. Means for silencing the audible alarm signals when the loud speakers are in use and for activating the audible alami systems automatically when use of the loud speakers are tenninated.

7. Display lamps to include on/off condition of air-handling systems unless such lamps are provided in the mechanical control center.

8. Existing office buildings 100 ft or more in height shall comply with the requirements by

September 13, 1981 (C26-1 704.8(c), added by LL 5, Sec. 30, amended by LL 86, Sec. 3).

29.2 SMOKE AND HEAT DETECTOR LOCATIONS

An approved products of combustion ionization detecting device or a combination of an approved smoke

detecting device and an approved fixed temperature theiTnostatic device shall be installed at each elevator

landing. The device shall be located in the ceiling immediately above a call button (C26- 1704.4(h),

C26-1 704.5(f)(8), added by LL 5, Sec. 25).

Activafion of an elevator landing detector should (C26-1704. 5(f)(9), added by LL 5, Sec. 25):

1 . Sound continuously throughout the floor of alann and floor above.

2. Cause a fire alarm signal to be transmitted to the fire department.

114 NISTNCSTAR 1-1D, WTC Investigation
Fire Detection and Alarm

3. Sound fire alarm signal at the fire command station, mechanical control center and regularly

assigned location of the fire safety director.

4. Operate the infonnation display system.

5. Stop the air supply into and air return from the floor where activated by approved remote

control reversible fire shutters or by automatically shutting down supply and return air fans.

6. Activate air exhaust fans and dampers in smoke shafts and/or pressurizing fans in stair enclosures.

An approved products of combustion ionization detecting device or a combination of an approved smoke

detecting device and an approved fixed temperature thennostatic device shall be located at the air return

shaft at each floor and so located as to monitor each inlet to the air return shaft (RS 13-1 Sec. 1006, added

by LL 5, Sec. 34).

A building equipped throughout with an automatic sprinkler system including a water flow alarm shall be

exempt from the installation of any detectors required at each elevator landing and return air shaft, as mentioned above, provided (C26-1704.5(f)(10), added by LL 5, Sec. 25):

1 . The water flow alarm has the same effect specified for the elevator landing detector

mentioned above.

2. In addition to the smoke detector requirement, in a building equipped throughout with an

automatic sprinkler system, a waterflow alarm when activated shall initiate Phase 1 (Rule 21 1.3a) emergency recall operation (RSI 8-1, Rule 21 1.3b(2)).

Approved and operational smoke detecting devices shall be installed in mechanical rooms, electrical switch gear rooms and electric and telephone closets over 75 ft" in all buildings in all occupancy groups

(C26-1705.2(b), added by LL 16, Sec. 78).

29.3 MANUAL FIRE ALARM BOXES

At least one fire alarm sending station shall be provided in each story located in each path of escape with

additional stations installed so that no point on any floor is more than 200 ft from the nearest station (RS 17-3 A and B, Sec. 7(a), added by LL 5, Sec. 39 and 40).

Operation of a manual station shall automatically transmit a fire alarm signal to the fire department via a

central station and sound an alarm continuously on the floor where activated and the floor above

(C26-1704.5(f)(4), added by LL 5, Sec. 25).

Fire alarm (Class E) sending stations shall be painted red with a diagonal white stripe painted or applied

to sending stations which transmit a fire alarm signal to the fire department via a central station (C26-1 704.6(e), amended by LL5, Sec. 27).

All fire alarm stations installed or relocated after April 1, 1984, shall be installed so that the handle is approximately 4 ft from the floor (C266- 1704.6, amended by LL 16, Sec. 76).

NISTNCSTAR 1-1 D, WTC Investigation 115
Chapter 29

A designated station on each floor shall have the capability of operating the loud speakers for that floor (RS 17-3 A, Sec. 7(i), added by LL 5, Sec. 39). This is not a requirement of the modified class E fire alarm system.

29.4 AUDIBLEA/ISUAL NOTIFICATION APPLIANCES

In a Class E fire alann system, loudspeakers capable of being operated from the fire command station

shall be provided on each floor, and in each elevator and stair enclosure (C26-1 704.8(a), added by LL 5, Sec. 30).

The loudspeaker amplifier system shall be so designed and installed that approximately 50 percent of the

system shall remain operable for the transmission and audibility of signal and intelligibility of voice

communication over the loudspeaker system throughout the building, in the event the other 50 percent

becomes inoperable (C26- 1704.5(f)(7), added by LL 5, Sec. 25). This is not a requirement of the modified Class E fire alarm system.

^

Loudspeakers shall be located so that their operation will be heard clearly above ambient noise

(C26-1704.5(f)(5), added by LL 5, Sec. 25).

Recessed and surface mounted speakers shall be located not more than 1 0 ft from the entrance to each

required exit (RS 17-3A and B, Sec. 8(b), added by LL 5, Sec. 39 and 40).

The alann sounding devices may be utilized for other audio purposes including building security if means

are provided to insure fire alarm priority (RS 17-3A and B, Sec. 8(c), added by LL 5, Sec. 39 and 40).

29.5 COMMUNICATION SYSTEM

In a Class E fire alann signal system, the standpipe fire line telephone and signaling system may be

combined with the fire alann system provided (C26-1 704.7(g), added by LL 5, Sec. 28):

1. The alarms and two-way voice communication with the fire command station include the pump and gravity tank rooms.

2. A designated floor station of the Class E system is located at or near the main standpipe riser on every floor.

New and existing buildings classified in occupancy group E (Business), 100 ft or more in height shall be

provided with the following (C26- 1704.8, added by LL 5, Sec. 30):

1 . Loudspeakers on each floor of the building, in each elevator and each stair enclosure, which

shall be capable of being operated from the fire command station.

116 NISTNCSTAR 1-1 D, WTC Investigation
Fire Detection and Alarm

2. A two-way communication with capability between the fire command station and the following locations:

a. A designated floor warden station on each floor.

b. Mechanical control center.

c. Elevators.

d. Air-handling.

e. Elevator machine rooms. A floor warden station shall be located between required stairways, vertical exits, or other exits (RS 1 7- 3A and B. Sec. 7(b), added by LL 5, Sec. 39 and 40):

1 . System shall include a telephone type handset at the floor warden station with integral

signaling to the fire command station.

2. Warden station may be part of the speaker system.

NISTNCSTAR 1-1 D, WTC Investigation 117
Chapter 29

This page intentionally left blank.

118 NISTNCSTAR 1-1D, WTC Investigation
Chapter 30

Elevators and Hoistways

30.1 elevator in readiness

In buildings classified in occupancy group E (Business), 100 ft or more in height, and in existing office buildings 100 ft or more in height, the number of elevators that shall be kept available for immediate use by the fire department is as follows (C26- 1800.8, added by Local Law [LL] 5. Sec. 31):

1 . Where a floor is serviced by three or less elevator cars, every car shall be kept available.

2. Where a floor is serviced by more than three elevator cars, at least three elevator cars with a

total rated load capacity of not less than 6,000 lb shall be kept available for every floor. Such

cars shall include not more than two cars which service all floors and at least one other car in another bank servicing that floor. If the total load capacity of all cars servicing the floor is

less than 6.000 lb, all cars shall be kept available.

3. Elevators which have automatic or continuous pressure operation shall be controlled by

keyed switches meeting the requirements of RS 18-1.

4. In high-rise buildings classified in occupancy group E (Business), all other automatically

operated cars shall have manual operation capability.

Notwithstanding the retroactive provisions in C26-1801.1, existing office buildings 100 ft or more in height shall comply with the requirements of this section by September 13, 1981.

30.2 LOCKS

In high-rise buildings and existing high-rise buildings, no switch, lock, or device of any kind shall be

installed on any floor on or above the street floor on any elevator car or elevator hoistway door, except

elevators used exclusively for freight, that shall prevent opening of such doors by anyone not having a key, unless fire department access to cars and hoistways is provided for by a city-wide standard key.

Existing high-rise buildings shall comply with this requirement by April 1, 1987 (C26-1801.4, added by

LL 16, Sec. 80).

NISTNCSTAR 1-1 D, WTC Investigation 119
Chapter 30

This page intentionally left blank.

120 NIST NCSTAR 1-1D, WTC Investigation
Chapter 31

Emergency, Electrical, and Standby Power Systems

31 .1 emergency power systems

An emergency power system shall be provided in high-rise buildings in occupancy group E (Business)

(C26-610.3, added by Local Law [LL] 16, Sec. 50).

Emergency power shall be provided having the capacity to operate the following equipment, where such

equipment is installed (C26-610.1, added by LL 16, Sec. 50):

1 . Fire pumps.

2. At least three elevators at one time, with manual transfer to other elevators.

3. Alarm systems.

4. Communications systems.

5. Emergency lighting, if battery packs are not provided.

6. Ventilating systems used for smoke venting or control.

7. Stair pressurization.

Emergency power generation equipment shall be registered with the Department of Environmental

Protection, Bureau of Air Resources in accordance with the requirements of Section 1403.2-3.09 of the Administrative Code (C26-610.2, added by LL 16, Sec. 50).

NISTNCSTAR 1-1D. WTC Investigation 121
Chapter 31

This page intentionally left blank.

122 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 32

Special Features

32.1 SMOKE AND HEAT VENTING

Buildings classified in occupancy group E (Business), 100 ft or more in height, having air-conditioning

and/or mechanical ventilation systems that serve more than the floor on which the equipment is located,

shall be provided with at least one smoke shaft by means of which smoke and heat shall be mechanically

vented to the outdoors as provided in RS 5-17 (C26-504. 15(b)) (Local Law [LL] 5, Sec. 7). RS 5-17 was

added by LL 5, Sec. 32.

Existing office buildings, 100 ft or more in height, having air-conditioning and/or mechanical ventilation

systems that serve more than the floor on which the equipment is located, shall be provided with at least one smoke shaft by means of which smoke and heat shall be mechanically vented to the outdoors as pro\ ided in RS 5-17 or in lieu of such smoke shaft(s), all interior enclosed stairs other than a fire tower or access stairs may be provided with a system of pressurization for fire emergency use (C26-504. 15(c))

(LL 5 Sec. 7, revised by LL 86, Sec. 2):

1 . Where the pressurization system(s) option has been chosen, the system(s) shall be provided in accordance with RS 5-18.

2. The smoke and heat venting requirements shall be completed by September 13, 1982.

New Buildings that are sprinklered throughout shall be exempt from the smoke shaft requirements

(C26-504.15(b)) (LL 5, Sec 7).

Existing buildings that are sprinklered throughout shall be exempt from the smoke shaft and optional stair pressurization requirements under the following conditions (C26-504. 15(b)) (LL 86, Sec 2):

1 . The installation shall proceed in conformance with a schedule acceptable to the commissioner.

2. At least one-third of the total floor area of the building, including but not limited to the entrance lobby, corridors and elevator landing areas, is sprinklered by December 13, 1981.

3. At least two-thirds of the total floor area of the building is sprinklered by December 13, 1982.

4. The building is sprinklered throughout by December 13, 1983.

5. Where compliance with the time requirements would cause undue hardship, the commissioner, with approval of the fire commissioner, may extend the time for compliance.

NISTNCSTAR 1-1D, WTC Investigation 123
Chapter 32

32.2 SMOKE CONTROL

Smoke control shall be installed in all buildings classified in occupancy group E (Business) as follows

(C26-1300.8(a), added by LL 16, Sec. 53):

1 . Ventilation systems supplying different occupancy groups shall not be interconnected,

provided however that a ventilation system may serve two occupancy groups located on the same floor when the accessory use occupies less than 20 percent of the floor area occupied by

the principal use.

2. Ventilation systems supplying corridors shall not be interconnected with systems serving

other spaces, except that this requirement shall not apply to floors used exclusively as office space in buildings classified in occupancy group E (Business) which are fully sprinklered.

3. A ventilation system supplying any part of a means of egress shall not be interconnected with

any other ventilation system.

4. A ventilation system supplying public areas and assembly spaces shall have smoke detecting

devices that will shut down the system upon detecting smoke.

5. Either a combined heat and smoke damper or independent heat and smoke dampers shall be

installed at any penetration of construction required to have a fire resistance rating., unless

otherwise provided by section C26-504.5.

32.3 SMOKE PURGE

In all buildings classified in occupancy group E (Business), there shall be provided a system of

mechanical means of sufficient capacity to exhaust 6 air changes per hour or 1 cfm/ft", whichever is greater, from the largest floor in the building, using either dedicated fan equipment or the building

ventilation system aiTanged to shut down automatically with manual override capability to exhaust one

floor at a time through a roof or an approved location on an exterior wall other than a lot line wall

(C26-1 300.8(b), added by LL 16, Sec. 53).

32.4 STAIR PRESSURIZATION

Stair pressurization is not directly required by code in an occupancy classified as group E (Business). As

previously stated in Section 32.1 of this report, stair pressurization can be used to eliminate the requirement of smoke and heat venting. If stair pressurization is provided, each stair shall be protected in accordance with RS 5-18 (RS 5-18 added by LL 5, Sec. 33, amended by LL 84, Sec. 3).

32.5 FIRE SAFETY PLAN

A fire safety plan for fire drill and evacuation procedures shall be submitted to the commissioner. The

applicable parts of the fire safety plan shall be distributed to the tenants and service employees. All

occupants of the building shall participate and cooperate in carrying out the provisions of the fire safety

plan (C19-161.2, added by LL 5, Sec. 1).

124 NISTNCSTAR 1-1D, WTC Investigation
Special Features

One employee (of the building owner) shall be designated as fire safety director and one or more

employees as deputy fire safety director. Such employees shall each have a certificate of fitness,

qualifying him to conduct fire drills, evacuations, and related activities such as organizing, training and

superv ising a fire brigade.

During fire emergencies, the primary responsibility of the fire safety director shall be the supervision and

manning of a fire command station and the direction and execution of the evacuation as provided in the

fire safety plan. Such activities shall be subject to fire department control. A fire brigade consisting of qualified building service employees shall be selected by the fire safety

director.

Fire drills shall be conducted in accordance with the fire safety plan at least once every 3 months for existing building during the first 2 years. Thereafter, fire drills shall be conducted at least once every

6 months. The occupants of the building, other than building service employees, shall not be required to

lea\'e the floor or use the exits during the drill.

NISTNCSTAR 1-1 D. WTC Investigation 125
Chapter 32

\

This page intentionally left blank.

126 NISTNCSTAR 1-1 D, WTC Investigation
Chapter 33

Inspections

33.1 MATERIALS REQUIRING INSPECTION

The installation of all required sprayed fire-resistive material of structural members except those encased

in concrete shall be subject to the controlled inspection requirements in C26- 106.3(a), C26-502.2(f),

added by Local Law No. 55.

NISTNCSTAR 1-1 D. WTC Investigation 127
Chapter 33

\

This page intentionally left blank.

128 NISTNCSTAR 1-1D. WTC Investigation
Chapter 34

Response to Retroactive Provisions

The Port Authority of New York and New Jersey (PANYNJ) and various consuhants continuously

e\ aluated the hfe safety and fire protection features of the World Trade Center (WTC). In response to the Local Laws of New York City, a fire in 1975, a bombing in 1993, and many other fires, the life safety and

fire protection features of WTC 1 and WTC 2 were enhanced. Throughout the years, numerous studies and plans were created. The reports generated by the studies gave recommendations with numerous

alternatives to equivalently comply with the intent of the code. Eventually, for one reason or another, the provisions of these Local Laws were addressed, and in many instances were exceeded (see Table 12-1).

Additionally, since the PANYNJ did not merely comply with the minimum requirements, some of the

local law provisions were complied with prior to the development of the Local Law requirements. During

the time of the 1975 WTC fire, the New York Board of Fire Underwriters stated, "The Fire Safety

Program of the World Trade Center is an excellent one" and "In the overall, these towers may be

considered as among the safest buildings in New York City" (stated in a document contained in Appendix A of NIST NCSTAR 1-lH).

NISTNCSTAR 1-1 D, WTC Investigation 129
Chapter 34

Table 34-1. Life safety and fire protection provisions required by Local Laws.

Provision Approach adopted by PANYNJ

Compartmentation No (sprinkler alternative was chosenf

Stair and elevator signs Yes

Secondary power supply for exit signs and lights Exceeded''

Smoke and heat shaft or stair pressurization Exceeded*^ (not required since building was sprinklered)

Elevators in readiness Exceeded''

Class E fire alarm system Exceeded*

Fire command station Yes'

Removal of locks on elevators and hoistway doors Yes

Fire protection and fire safety plans Yes

Emergency power Exceeded*

a. In 1976, a plan to vertically compartmentalize WTC 1 and WTC 2 was chosen. But. in the mid-1980s, a program to fully sprinkler WTC 1 and WTC 2 was initialed, eliminating the compartmentation requirements. Documentation indicates that in 1993, WTC 1 was approximately 95 percent completed and approximately 85 percent complete in WTC 2. By 2000, the

office floors of WTC 1 and WTC 2 were sprinklered except for electric and telephone closets, most toilet rooms, the main

lobby and the B-6 Level Mechanical Equipment Room (Merritt 2000a, 2000b).

b. Provided with separate feeders and emergency generators.

c. Smoke purge and pressurization of corridors with 1 00 percent fresh air was provided.

d. All passenger elevators are capable of being recalled and makes the car available for manual operation by the Fire Department.

e. Many components of the fire alann system were above code requirements at the time of Local Law No. 5. After the 1993 bombing, a completely new system was installed complying with the most current provisions at the time of installation, f Each tower did not have an individual fire command station at the time of the 1993 bombing. Part of the enhancement after the bombing included providing Fire Command Stations in the lobby of each building,

g. Was not retroactively required, but was provided. Sources: PANYNJ; Appendix A, NIST NCSTAR 1-lH; Rivera 1993; Merritt 2000a, 2000b.

130 NIST NCSTAR 1-1 D, WTC Investigation
Chapter 35

References

Boring, D.F.. J.C. Spence, and W.G. Wells. 1981. Fire Protection Through Modern Building Codes.

American Iron and Steel Institute, Washington. DC, October.

City Publishing Center Department of General Services. 1968. The City ofNew York Building Code.

New York, NY, December 6.

Merrit and Harris, Inc. 2000a. Property Condition Assessment of World Trade Center Portfolio, One

World Trade Center. New York, NY, December 6.

Merrit and Harris, Inc. 2000b. Property Condition Assessment of World Trade Center Portfolio, Two

World Trade Center. New York, NY, December 6.

PANYNJ (Port Authority of New York and New Jersey). 1976. Report on Fire Safety of the World Trade

Center. New York, NY, January.

PANYNJ (Port Authority of New York and New Jersey). 7 World Trade Center Fire Safety Plan. New

York, NY.

Rivera, CM. 1 993. Fire and Building Codes and the Jurisdiction and Compliance ofFederal, State Authorities and Foreign Government Buildings. The City of New York Fire Department. New York,

NY, March 25.

Solomon, J. 1975. Emery Roth and Sons, New York, NY, personal communication to M. Levy, World

Trade Center Operations, New York, NY. February 18.

NISTNCSTAR 1-1D. WTC Investigation 131