World Trade Center Fire Alarm System History

After doing a bit of research, I have pieced together the following descriptions of the two fire alarm systems that were installed in the World Trade Center from the time it opened to the September 11 Terrorist Attacks.

Please not that I am posting this history to show how fire alarm coverage worked in a campus as large as the World Trade Center, and am not trying to send the message that the fire alarm system in these buildings was more important than the 1993 bombings on the 9/11 attacks, or something like that.

In addition, I’m pretty sure that some of the pictures on here have been shared on this forum and some other ones before, so please excuse the redundancy.

With all that said, here it is:

Original Fire Alarm System (Prior to 1993 Bombings)

The pre-1993 fire alarm system encompassed WTC 1, WTC 2, WTC 4, and WTC 5, as well as the concourse and sub-grade levels.

The system consisted of American Multiplex Remote Monitoring Transponders, on every third floor, connected to the Digital Computer and Console in the Operations Control Center (OCC) on the B-! Sub-Grade Level. The Transponder monitored Pyrotronics CR-7 equipment connected to type DI-2, DI-3, DI-4A, and DI-7 smoke detectors (non-addressable), Pyrotronics System 3 panels, tenant proprietary systems, waterflow stitches, tamper switches, and control contacts.

Pyrotronics XL3 smoke detector systems, with addressable detectors were installed in the mechanical equipment rooms of WTC 1, as well as WTC 2, and were connected via a CXL Communication Devices to a console in the OCC.

Manual pull stations were wired to an existing Executone system which alarmed directly to NYFD.

The pull stations used in this system were break glass stations combined with a two-way intercom in one unit. The glass rod was broken by pushing a spring-loaded pushbutton. A protective shield helped to stop the flying glass. The speaker/microphone, located inside of the pull station, allowed conversation over the fire intercom system to the Police Security Room on level B1.

The pull stations were model C3002, manufactured by Executone, Inc., located in Long Island City, New York.

Many tenants during this time had their own smoke alarm systems. Since the designs of those systems were varied, their descriptions are beyond the scope of available documentation.

There were two types of speakers used in the WTC: the horn loudspeaker and the recessed ceiling speaker. Speakers were located in the corridors stairways, and in the core area of the ventilation ducts.

(I do apologize for the couple of images that are rotated incorrectly.)

Executone C3002 Pull Station in the World Trade Center (Pre-1993 Bombings)

Executone C3002 Pull Station in the World Trade Center (Pre-1993 Bombings)

Executone C3002 Pull Station in the World Trade Center (Pre-1993 Bombings)

Fire Alarm/Public Address Control Panel in the World Trade Center (Pre-1993 Bombings)

Pyrotronics Smoke Detector in the World Trade Center (Pre-1993 Bombings)

Pyrotronics Smoke Detector in the World Trade Center (Pre-1993 Bombings)

Duct Detector in the World Trade Center (Pre-1993 Bombings)

Duct Detector

Public Address Loudspeaker in the World Trade Center (Pre-1993 Bombings)

Fire Alarm System Components in the World Trade Center (Pre-1993 Bombings)

Fire Alarm/Public Address System Control Panel in the World Trade Center (Pre-1993 Bombings)

Waterflow Control in the World Trade Center (Pre-1993 Bombings)

Waterflow/Sprlinker Control in the World Trade Center (Pre-1993 Bombings)

Post 1993 Bombings System
The fire alarm systems in WTC 1 and WTC 2 were replaced following the 1993 World Trade Center bombings.

A Cerberus Pyrotronics MXL-V fire alarm system with emergency voice/alarm capabilities was chosen for the new system. The system supported a decentralized infrastructure that consisted of six independent fire alarm systems protecting WTC 1, WTC 2, WTC 4, WTC 5, Concourse Level and the Sub-Grade Levels. These four buildings had a master monitoring and control Network Command Center located at each building’s Fire Command Station which were located in the entrance lobby of each building. Multiple redundant Network Command Centers were installed. The installation of the system was divide into these three phases:

  1. Phase one consisted of the system’s backbone, the master fire alarm panel, which was the Cerberus Pyrotronics MXL-V, Cerberus Pyrotronics MXL-VR remote transponder panels, and amplifier cabinets. This phase was completed sometime between 1995-1997.

  2. Phase two consisted of transferring monitoring and control of existing fire alarm devices to the new system. Both the existing American Multiplex system and the MXL-V were operating concurrently during this time. New core area speakers, warden phones, and pull stations were connected to the new fire alarm system as well.This phase was also completed sometime between 1995-1997.

  3. Throughout phase three, all existing fire detection devices were replaced, and the new speaker and strobe capabilities were expanded into all tenant and mechanical spaces. The existing American Multiplex system was to be disconnected and removed, but that had no occurred by the September 11 attacks. It was estimated the 25 % of the American Multiplex system was still in use at that time.

By 9/11, 85 % it was estimated that 85% of WTC 1 was completed, 80% of WTC 2 was completed, both WTC 4 and WTC 5 were 60 % completed, the concourse level was 100 % completed, the mechanical rooms were 40% completed, and the sub-grade and global fiber optic loop interconnecting all six systems were 0% completed.

Throughout the 12,000,000 ft2 WTC complexes, it was estimated that over 10,000 iniating devices (including smoke detectors, pull stations, water flow indicators, etc.), 30,000 notification appliances (speaker/strobes), and over 700,000 ft of conduit and 5 million feet of wire were installed.

During this time, speakers were located in all floor areas, and were spaced to insure intelligibility and audibility. In addition, strobes were located in all common areas that were area spaced and rated to ensure adequate illumination for notification of the hearing impaired. The speaker strobes were supposedly Cerberus Pyrotronics SS70-15/75, or a similar product (as speculated by a member of The Schumin Web Community several years ago).

“This is a photgraph of the One World Trade Center Fire Command Station (310A). Seated is Lloyd Thompson, Fire Safety Director and Standing John Drucker Jr., Siemens Fire Safety Project Manager. The equipment shown is the WTC Fire Alarm and Evacuation System. I spent 8 1/2 years at the WTC working with the Port Authority of NY & NJ to restore, engineer and upgrade the Base Building Fire Alarm and Evacuation System at the World Trade Center. God Bless those who perished that fateful day especially my dear friend James Barbella. Sincerely, John Drucker jr.”

Cerberus Pyrotronics MXL System

A representation of the Cerberus Pyrotronics pull stations in the WTC fire alarm system.


That is very nice. I’ve been wondering this for some time now, but hadn’t really looked into it.

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Really cool find! I’m always interested in what alarm systems are in massive skyscrapers like that! I wonder what the new World Trade Center complex has as far as fire alarm/mass notification systems. I know I saw a documentary on the rebuilding of the tower and how they added wider, pressurized stairwells, and upgraded the materials in the building to make it a lot stronger, especially in the core of the building.

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I wonder what alarms they will have in the new buildings. Will it be a Simplex system? It seems like Simplex would fit nice in there.

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If I remember correctly, a tech familiar with the matter said that some little New York based company that we wouldn’t know about was doing it. If not, I wouldn’t be surprised if it was another Cerberus Pyrotronics/Siemens system since the Port Authority did have contracts with them before.

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I just can’t see it being Fire-Lite or Silent Knight. I don’t think the largest Fire-Lite panel being able to handle that many devices. They would probably have to link a couple panels together or something.

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Fire lite or SK – Don’t even count on it . Those panels and systems were meant for small installations.

The only things that would be able to do the job is the largest systems offered by Simplex, Notifier, or Siemens.

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I’m trying to find out more details about this and weather or not this claim is accurate (it is a couple of years old), but according to a tech on DFA:

[quote] In talking to the architect and engineers for the buildings, I know what manufacture is going in these buildings and its not from one of the big 4 (Honeywell Life Safety (Gamewell-FCI, Notifier), Edwards, Simplex, Siemens) but a little known New York City manufacture. Cannot disclose till the official deal is complete since I know the functional requirements may not be met using this manufacture. [/quote]
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I wouldn’t call fire lite small!

I don’t think he’s calling the company small, if that’s what you were thinking, but instead, he is saying that their product line is aimed mostly at small to mid sized systems, and their equipment wouldn’t be well suited for a job as large as the WTC.

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Judging by this claim, the new system is most likely made by Firecom (LSN2000 system). They’re based in NYC and specialise in highly customizable high-rise fire systems, one of which I’ve actually seen across the street from the WTC at the World Financial Centre.

So EST/Edwards wouldn’t work? I don’t know much about their products.

EST has networking panel capabilities as far as I know. So it could probably work. It’s really tough to judge what could get the job done in such a large building like the World Trade Centers. My brain would fry just thinking about working on such a project. :?

I have confirmed with a tech familiar with the matter that the system will indeed be made by FireCom, which, once again, is a New York based company.

According to him, all of the major Honeywell brands were trying very hard to get this project, due to its size and scope. However, FireCom agreed to sell the equipment to them for very cheap since they were after the service contract for the building.

Looks like the initiating devices are most likely to be rebranded Sigcom T-Bars, and rebranded Apollo smokes. My guess is that they’ll use Wheelock Notification Appliances since that is what FireCom has used in other setups (such as in the new WTC 7 building).

I have videos from 9/11 which demonstrate the fire alarms- however, due to the very touchy nature of the subject I wanted to know your guys’s opinion before I link them.

As I said in my first post, this topic exists to show the workings of fire alarm systems in large buildings, and is not trying to say that they were the most important part of 9/11 or something like that. As long as everybody remebers that, I think your videos will be fine.

Beat ya to it, Prog! :mrgreen:

Well, this was footage from 9/11 in which the fire alarm was in the background which is why it could be touchy.

Was this video to which you were referring?

The whoop tone that they have on the system is kind of creepy, especially in the environment that it was sounding in.

Well, yes, that was one of them.
And yes, that’s very eerie.
I’ll get around to posting the others soon; I’ll have way more time once finals start on Friday.