Catastrophic hidden hazard


Well, it’s not really hidden, but it might as well be unless all your firefighters can recognize the hazard immediately and operate defensively.

The photo at right shows a posttensioned concrete building. There can be one or more floors that are hard, dry, and may be walked on but that are not connected to the columns! If a fire damages the gravity resistance system (GRS), the floor (which is a mass of concrete) will collapse on the floor below. No concrete floor is designed to sustain such an impact load, and the floors below will successively pancake.

The first safety measure is to update the status of all concrete buildings under construction every day. Failing that, all personnel (down to the rookie) should be trained to recognize this hazard.

The left arrow in the photo indicates a cable sticking out of the concrete. This cable is one of the tendons that provide the concrete’s required tensile strength. This floor has been tensioned-i.e., it is now attached to the columns. The exposed tendons, however, have not yet been cut off and “dry packed” (i.e., the space through which the cable runs filled in with a rich concrete mix) and can conduct heat to the working (attached) section of the cable, which will fail at 800°F.

Photo by author

The right arrow in the photo indicates the wooden falsework supporting the concrete that has not yet been tensioned. This is the first time I have seen fire-flimsy wooden I-beams used for this purpose. Do not be fooled if the formwork/falsework is constructed of aluminum supporting fiberglass forms. Many believe that fiberglass is noncombustible. Fiberglass is glass fiber-reinforced polyester resin plastic, which burns readily.

If you have concrete construction in progress but are not concerned about how it is being built, I suggest you be sure your dispatcher knows how to get an Urban Search and “Recovery” (not “Rescue”) unit to respond. [See Building Construction for the Fire Service (BCFS3), pp. 338-340, 347, 354-357.]


The Fire Department of New York (FDNY) deploys one or more firefighter assist and search teams (FAST) at all significant fires, and many fire departments have similar operations under different names. An article in WNYF1 (the official training publication of FDNY) by Captain John Jonas of Ladder 6 describes a successful Mayday response that included a rope rescue of a trapped lieutenant and provides significant information.

I have heard of units assigned to FAST standing around, grousing that they were missing out on the action. The following quote from the article is pertinent and worth adopting in the instructions of any fire department that does not have FAST or something similar.

“You should adopt the attitude that you will be utilized to rescue a trapped firefighter. This means having your members completely geared up at all times, including hoods and self-contained breathing apparatus (SCBA) in standby mode. Anything less could result in critical time loss if a ‘Mayday’ is transmitted. Be ready to go to work immediately!”

The following points summarize the remainder of the article.

  • FDNY requires that units supplement the standard ladder company tools with search ropes and lifesaving rope equipment. The officer should size up the situation and have additional equipment on hand, possibly ground ladders, with halyards untied. Every second counts. It might not be wise to move a ladder already in place. It might be the emergency exit for other firefighters.
  • The FAST officer should monitor the fireground radio, noting particularly units entering a potentially dangerous situation.2
  • The officer should consider alternate access points to various areas of the building. The FAST team should not be the last in a line of people who could not reach the trapped firefighter. The FAST unit officer should practice the following with the unit: “If firefighters are trapped here, and the fire is here, I will order this.”
  • Units should be fully familiar with the ropes used in rescue. A drill in darkness would be advisable. There must be no fumbling when the time comes to do the job.

Additionally, I recommend that the unit carry wire cutters and a small bolt cutter or similar tool that can cut the metal frames of a suspended ceiling. A firefighter fatality at the Houston, Texas, McDonald’s tragedy was found entangled in the wires and framework of the very common metal frame and lay-in tile ceiling.


Be sure to clip and save “Lone Star Steakhouse Fire, Downers Grove, Illinois” by Bob Tutko and David R. Burns (Fire Engineering, May 2001), which describes a very close call in a large restaurant. There are many buildings of similar construction throughout the country. Do not let your first experience with this type of building be your last. Memorize this story, and use it when you need it. Make this story your own experience.

The article makes reference to BCFS3, where I note that doubling up trusses under heavy loads does not help us. I first photographed this practice in a drugstore under construction early in my concentration on building construction. I had no experience to cite, but I recognized the hazard. The folks at Downers Grove stored away my analysis and used it when confronted with a similar situation. I have been told from time to time, “I studied your book for the promotion exam.” That’s well enough, but it wasn’t written to help you pass promotion exams; it was written to save your life in the real examination that takes place on the fireground.

I was pleased to note that a company abandoned its line and evacuated. All fire departments should have a policy that states: “Take nothing out unless it helps you to escape.” Don’t leave any doubt by thinking that common sense would tell them that. Common sense is guesswork!

The Snowmass Village (CO) Fire Department calls them “exit tools”-the tools you take with you when evacuating. The United States Navy drills regularly on “Abandon Ship.” Do you drill on evacuations? Stress looking forward so you can see tripping hazards. Looking back is a useless waste of vital seconds.

The “Firefighter’s Radar” [thermal imaging camera (TIC)] would have shown the heavy fire overhead and probably would have resulted in an earlier evacuation. In the Astoria, New York, hardware store disaster, Lieutenant Brendan Manning, using a thermal imaging camera, had detected fire in the ceiling and was reporting it to command when the cellar blew.


Fires generate visible particles (smoke) and gases, which are usually invisible. In the immediate vicinity of the fire, they usually move together. As the mixture gets farther and farther from the fire, the smoke particles may deposit on surfaces, while the gases are free to move according to the laws of fluid movement. Without the visible particles, no hazard is evident.

Some year ago, there was a smoky fire in the basement of what was then The New York Times building (in Times Square, New York City, where the New Year’s Eve ball drops). Two members of Ladder 24 went to the upper floors by elevator, leaving their SCBA in the lobby, since no smoke was evident. They were found dead of carbon monoxide (CO) poisoning on an upper floor. The elevator operator was found dead in the elevator.

Before SCBA became readily available, many fire departments used masks that filtered out the protective irritating smoke but allowed all but a small percentage of CO through to the unwary firefighter [a small percentage was trapped by a substance that converted CO to carbon dioxide (CO2)]. No device was provided to determine whether the CO in the environment was beyond the mask’s filtering ability. We removed 50 of the masks from the apparatus at the Norfolk (VA) U.S. naval base. One Maryland firefighter died in a drill fire in a donated building while wearing a filter mask.

In “The Dangers of Carbon Monoxide at the ‘Routine Fire’ ” (Fire Engineering, February 2001), Miami-Dade (FL) Captain David Wood describes two fires at which he was affected by CO. It is a must-read and training clip. In the accompanying sidebar, “Carbon Monoxide: A Silent, Dangerous Enemy,” a great veteran, retired FDNY Deputy Chief Jim Murtaugh, recommends that one member of each team wear a CO detector. Don’t have one? Requisition a canary in a cage. This might rattle a cage and get you the equipment. Although almost nothing feels better than taking off the SCBA facepiece, it can be fatal!


Have any of you experienced summer stack effect in a high-rise fire? This condition results from the building’s interior being colder than the exterior. In the stack effect, the smoke and gases ride downward. I heard of an incident in which the five floors below the fire floor became untenable because of the smoke. If you did have such an experience, please contact me.


An illustration of “The Detroit Bundle System” by John A. Reardon and James Yuill (Fire Engineering, March 2001) raises a question. It appears that the open outlet of the wye gate valve does not have a cap on it. A California fire captain was badly injured when, as can easily happen, the valve handle was open. When the line was charged, the backlash caused the wye gate to hit him. Such outlets should be capped for safety. In addition, the cap will prevent damage to the threads, which could make the outlet useless when it is most needed.


The French company LaFarge Corporation has developed a product called “DuctalT lightweight flexible concrete.” Lightweight beams can be smaller and lighter than steel I-beams. Nothing is said of fire resistance properties. Concrete (often regarded as “fireproof”) is inherently noncombustible.3

When I wrote the first edition of BCFS, I sent each chapter to authorities for review. The Concrete Institute stressed that so-called reinforced concrete4 maintains its strength only when the steel and concrete remain in contact as designed and built. When this bond fails, the structure fails.

Concrete is made to meet fire resistance standards only when so specified for fire resistive structures. Even then, the proof is in the fire. When we were building the Navy firefighting school in Panama, no steel was available for the 15-foot oil fire tank. A New York concrete man who had built fire-resistive structures formulated concrete that resisted hundreds of fires. Another worker supposedly following the same recipe built a foam firefighting pit that violently spalled when it was used.

I would be very wary of a heavily involved structure that features lightweight concrete I-beams. If you have seen this type of construction, contact me at; include pictures.5


This section of my column will generally present a danger that is not evident on size-up and may not even be noticeable on a prefire survey. Some can be discovered by mentally undressing the building and applying what you have learned about buildings of various types.

The following item is particularly directed at training, especially to those who teach firefighting in “designed to be safe” training structures using trifling fires or controlled gas burner fires. I strongly believe that you are cheating your students if you let them conclude that the training received resembles real life. Lectures should bring out the hidden hazards that too often have killed firefighters. The training building is designed not to collapse, so collapse is not on the radar of the instructor or the firefighters. Discuss the gravity resistance system and how fire can damage it and cause gravity, which wants to pull the building down, to act. Massive collapse is not the only hazard. Local collapse, such as the failure of a floor attacked by fire from underneath, as in a cellar fire, has killed many firefighters.

Warn the students never to get into an alleyway between a burning building and an exposure.

Discuss trusses (both wood and steel) that have caused multiple casualties. Point out that all loads must be delivered to the ground. This is accomplished by a series of connections. The failure of any one of the connections may start the collapse.

Just when one of the gusset plates secured to the wood of a lightweight truss by 3/8-inch prongs will fall out and cause the truss to collapse cannot be known. No firefighters should be on or under burning trusses.


Recent events have raised concerns among fire departments regarding possible attacks on personnel by firefighters and others who are mentally unbalanced. But what about the possible problem of a senior commander whose abilities have deteriorated sufficiently to be hazardous to those on the fireground? The story concerning the loss of two lives and injuries to many other firefighters at a 1946 fire in New York City is available by e-mail at Request “The Broadway Disaster.”


I love writing this column, but why should I have all the fun? Please send me your hidden hazards. Together, we will assemble a teaching tool to counteract any false impressions gained in live fire training.



  1. “The FAST Unit-What You Should Consider,” WNYF, 2nd, 1999, p. 13.
  2. This is not the place or the time for a social visit with other units.
  3. An exception is some concrete made with cinders. In some cases, the cinders were not completely burned, and gas pockets in the cinders will burn.
  4. The steel does not reinforce the concrete; it provides tensile strength (which concrete lacks) where needed, thus creating a composite material the Europeans call “FerroCemente,” a better name).
  5. Based on an article “Performance Concrete” by Michael Morris, Popular Science, Jan. 2001.

FRANCIS L. BRANNIGAN, SFPE (Fellow), the recipient of Fire Engineering’s first Lifetime Achievement Award, has devoted more than half of his 59-year career to the safety of firefighters in building fires. He is well known as the author of Building Construction for the Fire Service, Third Edition (National Fire Protection Association, 1992) and for his lectures and videotapes. Brannigan is an editorial advisory board member of Fire Engineering.

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