In the event the fire is in a much larger void space, such as a strip mall, multiple dwelling, or any other large building, it may be possible to utilize an Inverted Trench Cut to stop the fire. This can be advantageous for a few reasons; first, it takes less effort to pull ceilings from below than it takes to open up a three-foot trench the entire depth of the structure in a multi-layered roof assembly. Secondly, accessibility is much easier from the inside than to set up companies on the roof. Also, there may be a considerable amount of time that passes before a sufficient amount of personnel arrive to trench the roof. The inverted trench cut is performed in two steps. Operating under the assumption that conditions are such that the evolution can be done safely and from the most advantageous location, the best location to perform this cut is in a common area of the building, such as a hallway or other suitable space, which may provide a bit more structural stability. Pull the ceiling area along the wall closest to the advancing fire. This will provide the best protection for firefighters if there is a partial collapse of the roof assembly.
To make an inverted trench cut, first open up a three-foot section of ceiling along the wall in the hallway (or suitable space) closest to the advancing fire. This opening should be from wall to wall as much as possible. Second, position a 2½-inch handline in the hall to darken any advancing fire in the attic/void space area. The application of water on the underside of the roof area will slow or stop the fire and the spread of convection currents. This line should only be operated if fire is evident or imminent. This cut can be used on two sides of the spreading fire in an effort to squeeze off the extension and extinguish the fire.
Should the attic space become fully involved, the operation of large-caliber streams may be the only option; however, without a route to the underside of the roof assembly, this tactic may be ineffective, and may only result in additional water damage to the rest of the structure (photo 9). If the attic gets opened up, and the stream can get a good shot into the attic void, then the operation may be successful. If not, then the roof assemblies will most likely burn off, and the attack can be from above the fire.
Fires in attics and void spaces will be difficult to handle without proper coordination between ventilation and suppression forces. Underestimating the amount of energy that can be present during operations will tax even the most seasoned firefighters. Be sure to have the right resources on scene to mount the attack to ensure the best results for your personnel. Know your buildings; picture the hidden vertical and horizontal voids that travel through the building. If the fire gets hold of the voids and the attic, plan for early collapse and keep a safe distance.
Until next time, stay focused and stay safe.
MICHAEL P. DALEY is a lieutenant and training officer with the Monroe Township, NJ, Fire District No. 3, and is an instructor with the Middlesex County Fire Academy, where he is responsible for rescue training curriculum development. Mike has an extensive background in fire service operations and holds degrees in business management and public safety administration. Mike serves as a rescue officer with the New Jersey Urban Search and Rescue Task Force 1 and is a managing member for Fire Service Performance Concepts, a consultant group that provides assistance and support to fire departments with their training programs and course development. Mike has been guest on several Firehouse.com podcasts including:Successful Rescue Operations in Today's Fire Service, Preparing for Tomorrow's RIT Deployment Today and Basement Fire Tactics Roundtable podcasts. View all of Michael's articles and podcasts here. You can reach Michael by e-mail at: FSEducator@aol.com.