Project No. 4

Analysis of Active Fire 

Systems in WTC 1 

Robert J. Keough

Rolf Jensen & Associa

Raymond A. Grill, P.E., F

Arup Fire
Objectives

• Document the design and install

fire alarm systems and compare applicable code and standard re

• Document the normal operation 

alarm systems.

• Document modifications made t

alarm systems in WTC 1 and 2 fo1993 bombing.

• Document the performance of th

on September 11, 2001
Summary of Scope

• Task 1 –

Document the Fire Alarm 

and Installation and compdesigns to the applicable and standards

• Task 2 –

Document the normal exp

operation and provisions redundancy

• Task 3 –

Document the modificatio

the fire alarm system in W2 after 1993

• Task 4 –

Document the probable 

performance of the fire alsystem on September 11, 
Summary of Scope

• The primary source of information was los

during the collapse.

• Extensive review of documentation at PA i

Jersey.

• Additional information was requested by fo

visits to the Port Authority facilities in NJ.

• Extensive review of documentation was pe

at fire alarm manufacturer office in NJ.

• Extensive review of documentation perform

NIST.

• Interview of fire alarm project manager was 

performed in VA and at NIST.

• Reviewed information provided by NIST fro

witness interviews.
Summary of Scope

• Information used for this study originated 

– The Port Authority of New York and New – Silverstein Properties– City of New York– FEMA– Siemens

• Documents from the above list included th

many other organizations.

• Documentation was reviewed and analyzed 

factual information only.

• Judgment statements, opinions and 

findings/conclusions were omitted from ou
Task 1 & 2 – Design, Insta

Operation, Redundancy an

Compliance

• Provided a summary of the fire alarm sys

performance requirements.

• Documented the phased replacement of 

fire alarm system.

• Documented the design criteria, equipme

functions of the system, and installation the system.

• Documentation for WTC7 is very limited.
Fire Alarm Histor

•

Fire alarm replaced after Februar

bombing.

• Initial fire alarm purchase order s

March 17, 1993.

•

Fire alarm replacement separate

projects:

1. WTC1 and WTC22. WTC4 and WTC53. Concourse Level4. Sub-Grade Level
Fire Alarm Histor

•

WTC1 and WTC2 fire alarm 

projects divided into 3 phase

I. Installed back-bone head-end 

remote panels, and terminal c

II.

Transition detection, monitori

control from old to new systemalso included new warden telcore area speakers, and man

III. Expanded new system into te

and mechanical equipment ro
WTC1 & WTC2 Design A

•

Port Authority provided fire alarm system backbone archit

contractors to implement that described the core system iand hardware.

•

The PA also developed other specific design criteria as fo

–

Fire detection and interface device design criteria for device l

connections.

–

Audio and visual notification appliance design criteria for dev

and connections. 

–

Fire alarm riser/one line diagram criteria requiring a diagramm

interface cabinet, circuit, raceway, detection device type, and type.

–

Circuit performance criteria with forms for documenting test p

verification.

–

Contractor tie-in and pretest c

hecklist to docum

ent that the de

procedures have been followed.

–

Acceptance testing forms to document and assure the perform

monitoring, detection, and notification devices.

–

Project summary that reviews the deliverables required for th

through design, installation, acceptance, as-built documentatout.
Design Approac

Typical Wardens Phone Station1- Per Floor atCross Corridor Sprinkler Closet1 WF & 1 TSeach reporting EC TC TC ECto F

A System

ME

N

S 50

B EC

Primary Freight Lobby 1 Car - 

Typically C LA

DIES FA 17 A 

1 SSD Installed FS 49with Recall

EC TC TC EC

Electrical & Telephone Utility Closets1 SSD Installed in Each. 

Typical Tenant Fire Alarm/Fire SuppressionPanel - Reporting to Base Bldg F

A System

Alarm-Waterflow-Supervisory-Trouble

PELV
Design Approac

Typical Strobe Layout
Additional Quality Ass

•

Written Acceptance Test Proce

•

Contractor Tie-In & Pre-Test C

•

Circuit Test Forms
Fire Alarm Equipment & 

•

Fire Command Station

•

Operation Control Center

•

Base Building Fire Alarm Equipme

•

Detection, Monitoring, Control Dev

Circuits

•

Notification Appliance Devices & C

•

Warden & Fireman Telephones & C
Fire Command Stati

(Features required by New York 

1. An audible alarm signal.2. Emergency voice and alarm communication capability.3. Means for silencing the audible alarm signals when the lo

and for activatin

g the audible alarm syst

e

m automatically 

speakers is terminated.

4. A means to control the alarm sounding devices on all floo5. A manually reset the information display.6. Manual controls and display lamps to include on/off condi

systems.

7. A Standpipe Fire Line Telephone system with the capabili

announcements over the emergency voice and alarm com

8. A two-way communication system connected to a design

a

station on each floor, the mechanical control center, elevacontrol rooms, and elevator mac

hine rooms.

9. Means to manually transmit a fire alarm signal to the fire d

central station of a franchised operating company.

10. Means for testing the display, alarms, and connection to t
Fire Command Stat

AnnunciatorDisplay Speaker Floor Switches

Floor WardenTelephone Switches

Remote ConcourseFire Alarm Panels

RemoFire A

WTC1 FIR

E ALARM PANELS

Speaker Floor Switches

Fireman Telephone 

V Switches oice Evac Common Control Switches
Fire Command Stat

WTC2 FireAlarm Panels

Concourse Fire Alarm Panels

SubGrade Fire Alarm Panels

Network Command Center(Not Shown)

WTC2
Operation Control C

Remote WTC1 Fire Alarm Panels

Remote WTC1 Fire Alarm Panels

Remote WFire Alarm 

Network Command Center(Not Shown)

Fire Alarm Printers

NetworkCommand Centers

Note: SubGrade, WTC5, and WTC4 fire alarm panels are located on the wall behind the photographer.
Base Building Fire Alarm Equipment 

MXLV NCC

FCS RFCS RFCS RFCS

TOW ER 1 FCS

M XL-VR

CONCO URSE

X -NET

S UBGRADE

X -N ET

TO

W

E

R 1

XNET

TRANSPONDER

M XL-VR

XNET

TRANSPONDER

M XL-VR

XNET

TRANSPONDER

M XL-VR

XNET

TRANSPONDER

M XL-VR

XNET

TRANSPONDER

M XL-VR

XNET

TRANSPONDER

M XL-VR

XNET

TRANSPONDER

M XL-VR

XNET

TRANSPONDER

M XL-VR

XNET

TRANSPONDER

M XL-VR

XNET

TRANSPONDER

TOW ER 1 TO W ER 2 CO NCOURSE SUBG RADE

M XLV NCC M XLV N CC M XLV NCC M XLV N CC

RFCS RFCS RFCS RFCS

O CC

W TC 4

X -NET

W TC 5

X -N ET

W TC 4 W TC 5 TOW ER 1 TOW ER 2

M XLV NCC M XLV NCC M XLV N CC

C 

C

FCS

TOW ER 2

MXLV NCC

FCS 

C O NCO URSE

X -NET

S UBGRA

X -NET

CONCO URSE SU

M XLV N CC M XLV 

TO

W

E

R 2

TOW ER 2 FCS

XNET
Detection, Monitoring & Contr

•

Addressable open area ioniz

ation smoke detecto

•

Addressable high-air velocity open area ioniz

atio

detectors (ILI-1A)

•

Addressable duct ionization smoke detectors –

h

(ILI-1B)

•

Addressable open area photoelectric smoke dete

•

Addressable open area photoelectric smoke dete

heat detector (ILPT-1)

•

Addressable open area rate compensated heat d

135)

•

Addressable single input monitor modules (TRI-6

•

Addressable dual input monitor modules (TRI-60

•

Addressable single input with relay control outpu

60R)

•

Addressable single-action pull stations (MS-MI)
Detection, Monitoring & Contr

1. ELEV Branch –

Elevator lobby sm

detectors, passenger and freight.

2. AREA Branch –

Open area smok

– phone, electric, fire alarm closesprinkler monitoring.

3. HVAC Branch –

Ventilation smok

for plenums and ducts.

4. TEN1 Branch –

Tenant 1fire alar

subsystem interface monitoring b

5. TEN2 Branch –

Tenant 2 fire alar

subsystem interface monitoring b
Notification Appliance Devices 

M X LV NCC

F C S R F C S R F C S R F C S

T O W E R 1 F C S

M X L -V R

C O N C O U R S E

X -N E T

S U B G R A D E

X -N E T

T O

W

E

R 1

A M P

T O W E R 1 T O W E R 2 C O NCO U R S E S U B G R A D E

M X LV NCC M X LV N C C M X LV N C C M X LV NCC

R F C S R F C S R F C S R F C S

O C C

W T C 4

X -N E T

W T C 5

X -N E T

W T C 4 W T C 5 T O W E R 1 T O W E R 2

M X LV NCC M X LV NCC M X LV N C C

F C S

T O W E R 2

M X LV N C C

F C S 

C O N C O U R S E

X -N E T

SUBG 

X -N 

C O NCO U R S E S U 

M X LV N C C M X L

T O

W

E

R 2

T O W E R 2 F C S

PSR

A M P

PSR

A M P

PSR

A M P

PSR

A M P

M X L -V R

A M P

M X L -V R

A M P

M X L -V R

A M P

M X L -V R

A M P

M X L -V R

A M P

M X L -V R

A M P

M X L -V R

A M P

M X L -V R

A M P

M X L -V R

A M P

P S R

A M P

P S R

A M P

P S R

A M P

P S R

A M P

TYP IC A L L O O P INCL UDE S E IG H T P S R AM P L IF IE RP A N E L S

T Y P IC A L LO O P IN C L U D ES E IG H TPSR A M P L IF IE RP A N E LS
Notification Appliance Devices 

EC

T

C

T

C EC

ME

N

S 50

B

E

C

C LA

DIE

S FA 17 A

FS

4

9

EC

T

C

T

C EC

PELV

Sp

e

a

k

er Circ

uits C & D

Counter R

otatin

g I

nterleaved

S

peaker Circuits A & B

C

ounter R

otating I

nterleaved

Cla

ss B- 7

0.7 V - 15

0 / 2

0

0

C Teflon FPLP Fr

e

e Air

4 Circuits Pro

vid

e

d

P

er Floor + A

dditio

n

al Stairw

a

y

O

nly

Circuit t

ypi

c

ally e

v

ery 4-5 Floor

s. C

oordinated with R

e

e

ntry

Points.
Notification Appliance Devices 

•

Ceiling mounted round speakers, 70 volt 

•

Wall mounted square speakers, 70 volt (

•

Wall mounted speakers, 25/70 volt (SPK

•

Wall mounted speakers, 70 volt, with 24 

strobe (SS70-15/75)

•

Wall mounted strobes, 24 volt 15/75 cd (

•

Wall mounted combination speaker, 70 v

volt 15/75 cd strobe (SS70-15/75)
Warden & Fireman Telephones 

M XLV NC C

FC S RFCS RFCS RFCS

TO W ER 1 FCS

M XL-VR

C ON CO URSE

X -N ET

S U B GR ADE

X -NET

TO

W

E

R 1

PHO NE

TOW ER 1 TOW ER 2 CO NCO URSE SU BG RADE

M XLV N CC M XLV NCC M XLV NCC M XLV NC C

R FCS R FCS R FC S R FC S

O CC

W TC 4

X -N ET

W TC 5

X -N ET

W TC 4 W TC 5 TO W ER 1 TO W ER 2

M XLV N CC M XLV N CC M XLV NCC

C O

C O 

FC S

TOW ER 2

M XLV NCC

FC S 

C ONCOURSE

X -N ET SU BGRAD

X -N ET

C O N CO URSE S U B

M XLV NC C M XLV 

TO

W

E

R 2

TO W ER 2 FCS

M XL-VR

PHO NE

M XL-VR

PHO NE

M XL-VR

PHO NE

M XL-VR

PHO NE

M XL-VR

PHO NE

M XL-VR

PHO NE

M XL-VR

PHO NE

M XL-VR

PHO NE

M XL-VR

PHO NE

P SR

P HO NE

P SR

P HO NE

P SR

P HO NE

P SR

P HO NE

PSR

P HO NE

PSR

P HO NE

PSR

P HO NE

PSR

P HO NE
Warden & Fireman Telephones 

•

Flush wall mounted floor warden telepho

(FB-300)

•

Surface wall mounted floor warden telep

(FB-301S)

•

Remote firefighters telephone station wit

cable (FT-301CL)

•

Surface box for fireman standpipe or ma

(PUR17)

•

Firefighters telephone jack (FJ-303)

•

Portable firefighters telephone (PT-304)
Task 3 – WTC1 & 2 Fire 

Modifications Post 1993 B

• Document pre-1993 fire alarm • Provide comparison of the per

and functions between the old 1993 fire alarm system.
Pre-1993 Fire Alarm S

•

Operations Control Center

•

Base Building Fire Alarm Equi

Circuits

•

Detection, Monitoring, Control 

Circuits

•

Notification Appliance Devices 

•

Warden & Fireman Telephone

Circuits
Operations Control C

•

Fire Alarm Zone Annunciator w

Recorder

•

Public Address Console

• 10 Zone Intercom & NYCFD F

Signal Transmission Panels.

• Intercom Tape Recorder
Operations Control C
Operations Control C
Warden & Fireman Telep

Circuits (pre-1993

•

Break Glass Stations provided auto

alarm notification to NYFD & two-wcommunication.

•

PA console operator has 20 secon

respond or fire alarm signal autombroadcast to fire zone.

•

Adjustable delay in sending alarm 

•

Fire Line Communications System

separate Standpipe Fireline

Comm

phone system.
Warden & Fireman Telepho

Circuits
Comparison of Performance 

Pre & Post 1993 Fire Alarm 

•

Similar Functions

–

Return air smoke detection

–

Elevator lobby smoke detection and r

–

Mechanical room air handling unit sm

and shutdown

–

Sprinkler water flow and tamper moni

–

Tenant systems monitored

–

Voice broadcast capability for each flo

–

Occupant and fireman two-way comm

each floor

–

Notification of NYFD upon alarm
Comparison of Performance 

Pre & Post 1993 Fire Alarm 

•

Post 1993 Enhanced Features

–

All equipment functions and circuits were made or 

recognized performance standards (Class A).

–

System had distributed intelligence and control fea

–

Consolidated all the fire detection, monitoring, con

communication systems for the common use area

–

Smoke detection was also provided in electrical, te

alarm closets.

–

Manual stations were provided by each stairway d

–

Floor return air detectors would shutdown associa

upon activation.

–

Mechanical Equipment Room air handling units pr

deluge sprinkler activation capability.

–

Speakers and strobes were spaced and installed b

intelligibility, audibility, and visual performance sta

–

Common two-way telephones provided for floor w

firefighters.
Task 4 – Probable Performan

Alarm Systems on 9/11

• Fire alarm print-outs lost on 9/• Analysis based on limited vide

witness accounts.

• Fire alarm visual indications pr

inconclusive evidence without alpha/numeric display or print-
Task 4 – Probable Performan

Alarm Systems on 9/11

• Fire Command Station

– All equipment viewed on Nudet 

to be functioning.

– All panels have an illuminated a

trouble indication.

– WTC2, Concourse, and Sub-Gra

have an illuminated audible silenindication at 9:58 AM, seconds bWTC2 collapse.
Task 4 – Probable Performan

Alarm Systems on 9/11

• WTC2 telephone zone illumina

indicate warden telephones on 71, 73, 93, and 94 are active. 

• The WTC1 Fire Safety Directo

an audio alarm signal to floors 84 at 8:59 AM. Speaker zone not illuminate above floor 84 foreasons.
Task 4 – Probable Performan

Alarm Systems on 9/11
Task 4 – Probable Performan

Alarm Systems on 9/11

• Speaker panel and telephone 

indicate circuits on floors 76-84 malfunctioning. (Based on Druckers 

recollection). Cause likely is loss 

circuits. Evidence is inconclus