Truss Roofs: Do You Know Where the Firefighter Killer Hides?
Lack of recognition of key aspects related to building construction is one of the top five common threads when analyzing firefighter fatality case studies. A good number of times, this lack of recognition can be attributed to a hidden danger that is not readily observable. Buildings that contain any type of truss construction are susceptible to collapse from fire exposure in a very short amount of time. One of the most easily identifiable (when able to be visualized) roof trusses is the bowstring truss. Unfortunately, it has also been the culprit in numerous firefighter fatalities over the years due to the dangers that are presented.
Some of the most notable fires that have affected the fire service have involved bowstring truss construction. On August 2, 1978, six New York City firefighters were killed and 34 were injured fighting a fire in a supermarket when the roof collapsed. On July 1, 1988, five Hackensack, NJ, firefighters were killed while operating under a bowstring truss roof fighting a fire in an auto dealership. On February 11, 1998 two Chicago firefighters were killed and three were injured while fighting a fire in a automotive tire service center. Twenty years of time passed between these three incidents listed, yet we as a fire service even until today in 2007, some 29 years later, are still making some of the same mistakes that are putting our personnel in danger.
The first step in dealing with any type of truss construction is recognizing its presence. The bowstring truss as stated is one of the most easily identifiable when it is able to be seen. Prior to 1960, it was one of the most common designs for large commercial and industrial occupancies. It is most easily recognized by the characteristic round "half-circle" or arched shape that it gives the roof of a structure.
The principles of truss construction are the same with a bowstring as other truss construction - web members form triangles which transfer tension from the bottom chord and compression from the top chord of the truss onto load bearing walls. One big difference however is that due to the arch shape, compression is also forcing the load bearing walls outward as well as downward. From the interior, a bowstring truss building can be recognized by large open areas with few columns present for support. Occupancies that it is most commonly found in include: industrial complexes, automobile repair centers and dealerships, bowling alleys, supermarkets and banquet facilities.
Often times, the characteristic arched roof of the bowstring truss building cannot be readily visualized by responding fire companies. Buildings spaced very close together or parapet walls designed for aesthetics to hide the unsightliness of the roof area on the businesses often impede the view of the roof area. This is yet another reason to ensure that a view of all sides of the structure as well as a view from above are taken in one way or another when an incident commander is performing a risk versus benefit analysis on the fireground. As an officer, if you can not access the rear of the building, assign a company to come in from another direction to get there. The same goes for the roof, if you can't see it, get someone in a safe position to let you know the information that you need.
Some jurisdictions such as the State of New Jersey, have passed ordinances or laws requiring buildings containing truss construction to have warning placards placed on them to alert firefighters. The placards (a white triangle with red lettering) are meant to function as a reminder to firefighters and incident commanders to constantly reevaluate the conditions as well as progress when operating in these types of buildings.
Another reminder may be to have a critical information dispatch system in place where information such as this is stored in a computer file until a call at the address takes place. Fire department dispatchers can relay this information to fire companies as they respond.
The best remedy however is to know the buildings within your response district. As previously stated in some of the prior articles in this series; company inspections or preplanning offer great opportunities for us in this regard but are not necessary to accomplish this goal. Taking a few moments to look at things after a false alarm activation or medical run prove to be invaluable at 3 a.m. when smoked is banked down to the floor level in that same building.
Knowledge of construction features as well as what "secrets" are contained within the buildings in our response areas remains paramount for us to have the ability to take the proper actions on the fireground. Many times, renovations take place without proper permits or inspections and can prove fatal even when carried out to the standards set forth in building codes.
An important point to remember is that any type of alteration to a truss system will more than likely present additional danger when placed under fire conditions. The fire mentioned in New York had office spaces located between the trusses, it is in this area the fire supposedly originated. The truss space in the Hackensack, NJ, fire was covered by heavy lathe and plaster and was used for additional storage. The incident that took place in Chicago had unprotected polystyrene insulation glued to the bottom chord of the trusses which contributed to rapid fire spread. All of these listed were alterations to a system that is already a hazard to our profession.
The void space created by a bowstring truss can allow heat, smoke and fire conditions to go undetected causing a false sense of security for firefighters operating beneath it. Because more surface area is exposed to flames than with standard construction, collapse can take place in a much shorter time frame. At many incidents involving trusses, crews inside the building reported that they have little or no signs of smoke when heavy smoke may be visible from the roof on the exterior. Communications and updates between interior and exterior personnel must be continual when dealing with any type of truss construction.
Any building on fire that is suspected to be truss construction must have ceilings opened quickly to expose the truss area for inspection. If trusses are exposed to fire on inspection, it is highly recommended that crews be withdrawn and defensive measures be utilized. There is no way of knowing exactly how long the fire in the truss space may have been burning and what damage may already be done. It is important to note however, that firefighters must exercise caution when opening up ceilings in truss construction to eliminate backdraft or flashover potential once air is fed into the void space.
It is imperative that we take the steps necessary to change our tactics and the way that we act on the fireground, especially when it comes to risk versus benefit analysis. Take the time needed to "read the structure" and get your crew out to look at buildings inside your first due area. Our job will always contain danger no matter how hard we try to control it but why should we continue to ignore the factors that we can control and not learn from our own mistakes?
Are you prepared to meet the challenge if it comes during your shift?
Jeffrey Pindelski is a 16 year plus student of the fire service and currently a battalion chief with the Downers Grove Fire Department in Illinois. He previously served for 12 years as a firefighter and lieutenant on the truck and heavy rescue companies. Jeff is a staff instructor at the College of Du Page and also instructs courses at the Downers Grove Fire Academy. He has been involved with the design of several training programs dedicated to firefighter safety and survival and is the coauthor of the text R.I.C.O., Rapid Intervention Company Operations.
