Warning Signs of Structural Collapse

As budgets continue to decline and layoffs, attrition, "brown-outs" and other "solutions" prevail, one thing is for certain — fewer firefighters are available and this trend does not appear as if it will improve soon. While there may not be much you can do about funding levels, you can re-double your efforts directed at firefighter safety. If there are going to be fewer of us, we simply must work harder to protect one another. This means leveraging every advantage so we can get over those things that tend to surprise us or place us in jeopardy without warning.

Structural collapse is one of those issues. Structural collapses, whether partial or complete, are responsible for numerous firefighter deaths and even more close calls. While you can never definitively predict collapses, there are often warning signs and the first step to recognizing these signs is to understand the construction type you are dealing with.

Before Entry

Even before entering a structure, you can accomplish a great deal from the exterior with the thermal imager. Factors that can be assessed from outside include locating the seat of the fire, observing changing or spreading conditions, identifying critical building construction features and identifying conditions that could threaten structural integrity.

  • Finding the seat of the fire — In some instances, fire conditions are readily evident from the exterior of a structure, especially if the building is of lightweight construction, and a thermal imager can give clues to the location or seat of the fire. In other instances, because of the size, design or construction type of the structure, the seat of the fire may not be as readily identified. In buildings of heavier construction, heat and fire conditions may only be evident in areas where construction is lighter or insulation is thinner, such as around door or window assemblies or through roof assemblies.
  • Identifying fire progress and spread — With a thermal imager, a firefighter can often assess building construction, predict the path of the fire and see where the fire has spread. Some construction features tend to conceal these conditions. These include balloon-frame construction, pipe chases and false ceilings. Voids in floor assemblies, walls and roof assemblies can hide fire spread and also should be checked.
  • Identify critical features — A thermal imager can be used to identify the type of construction and the location of critical building features. The primary area of concern in most instances will be the roof assemblies, but can also include floor assemblies, facades, overhangs and overhead electrical lines. Viewing the roof with the thermal imager from different angles may reveal telling features related to the type of roof construction. For example, the thermal imager operator may be able to identify a facade or parapet wall, letting you prepare for the dropoff and the increased potential for collapse. A thermal imager may also reveal details as to the extent of the heat buildup beneath the roof as well as the effectiveness of ventilation operations.

    • The absence of an apparent heat condition in the structure during exterior evaluation does not guarantee the absence of heavy fire inside. The location of the fire or the type of construction may be masking or hiding the fire.
    • Likewise, if the thermal imager indicates an apparent heat condition in the structure, there is no guarantee that firefighters will find such conditions inside the building. Direct sunlight on a roof can generate enough heat to make it appear as if there is fire directly below the roof.
    • Newer, more energy-efficient buildings tend to mask fire conditions and building construction features more readily than older buildings of simpler construction.

Once Inside

After a crew enters a structure, there are several ways in which they can use thermal imaging to better understand the building and fire conditions. Thermal imagers can be used to monitor fire conditions, gather information about construction features and recognize conditions that may threaten structural integrity.

  • Evaluate structural integrity — Firefighters must remember to continuously evaluate all parts of the structure as they move through with a thermal imager. Continually check the ceiling for sagging, partial collapse, heat or fire conditions. Pay equal attention to the floors. A thermal imager does not relieve you of the responsibility of sounding the floor and other basic skills, but it can help confirm what the basic skills implied.
  • Identify additional features — Firefighters equipped with thermal imagers can identify additional building construction features. These features may be hazardous, they may serve to conceal or spread a fire condition, or they may be helpful in terms of locating things like skylights (potential vent points) and windows (potential means of secondary egress).
  • Identify potential structural failures — While every effort should be made to identify and monitor critical structural components from the exterior, interior crews must do their best to monitor them as well. Sagging or other deformation of a roof support is never a good thing and your thermal imager can reveal these.

    • Never forget about the basics. When possible, verify the information being provided by the thermal imager. Thermal imaging should support the basics, not replace them.
    • Whether through pre-plan information or visual observations, make every effort to learn as much about the building construction as possible. Using this as a baseline, check to see whether the information provided by the thermal imager is consistent.


The fireground is no place to practice. The assessment of building construction is a critical skill that must be developed through knowledge and practice on the training ground. The good part about this particular skill is that it can be practiced every day.

You can use your thermal imager to assess building construction during pre-plan or inspection activities. You can even use it to look at buildings as you drive past them, keeping in mind you will need to roll your window down first (if you have to ask why the window must be rolled down, you need to read this column more often). If you see a feature of a building that you cannot explain, stop the vehicle and try to understand it. You can start at your fire station right now.

As manpower shortages become an increasing concern in the fire service, it becomes even more critical that we take the extra steps necessary to function as safely as possible. The identification of building construction type and features can be critical to understanding exactly what you are dealing with and can provide crucial decision-making information.

Dozens of firefighters are alive today because of a pending roof collapse identified with a thermal imager. If it saves even one more life, your efforts will be worth it.

BRAD HARVEY is the Thermal Imaging Product Manager at Bullard. He is a veteran of public safety as a firefighter, police officer and paramedic and is certified through the Law Enforcement Thermographers' Association (LETA) as a thermal imaging instructor. Harvey has worked as a high-angle rescue instructor and is a certified rescue technician and fire instructor. If you have questions about thermal imaging, you may e-mail him at brad_harvey@bullard.com.