Sound The Floor, Too.

More on lightweight-construction from FossilMedic:  

FIRST ARRIVING FIRE COMPANY LIFE-THREATENING HAZARDS

There is a significant change in how firefighters die within burning buildings. Firefighters operating within a burning structure in the 1990s died mostly from smoke inhalation. They were lost or trapped and ran out of air. Firefighters who have died in structure fires in the 2000s were killed by a flashover or structural collapse. They would fall through the floor or quickly be overwhelmed by a flashover.

Most of these events occurred in Type V lightweight wood component structures. Type V lightweight wood component buildings represent most of the structures built since 1985. Even in the cities with century-old buildings, renovations and expansions of existing structures are often made using lightweight wood components. These components may be obscured by an outside veneer in order to make the new part of the structure look like the original building.

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CHICAGO REQUIRES EARLY IDENTIFICATION OF TRUSS COMPONENT BUILDINGS

Renovated buildings with lightweight wooden truss components means that the Chicago Fire Department requires the first arriving engine company officer to identify if the fire building contains trusses. Not only is this identification an important part of the fire incident size-up, in Chicago it means that a battalion chief will require more companies to remain on the scene during overhaul. This is to reduce the chance of firefighters falling through weakened floors. Even without direct fire damage, a truss floor may be unable to support a waterlogged carpet and a company of firefighters standing on the floor while hooking ceilings.

David Fornell, a former suburban Chicago firefighter who writes and presents on fire suppression practices, notes that many big city fire officers were concerned at the rapid fire development within lightweight truss component buildings that were well insulated. The concealed spaces were developing blowtorches that would exceed the firefighting power of a 1.75″ fog nozzle fire attack line. Fornell took an immersion approach while working on Fire Stream Management Handbook, published in 1991 by Fire Engineering. He rode with the busiest engines in dozens of large cities.

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SPECIAL RISKS TO THE FIRST-IN FIRE COMPANY

Many of the LODD deaths this decade were suffered by members of the first-in fire company. They were falling through fire-weakened truss component floors into the heart of the fire. They were overwhelmed by a flashover while performing a primary search.

In reading the details of these line-of-duty deaths it is clear that many of these fatalities are occurring while the rest of the first alarm companies are still responding to the event. A primary is started because there is an assumption that occupants need to be removed from the structure, or that the fire can quickly be controlled by the first fire attack line. The fire company that will be assigned as the rapid entry team is still enroute to the incident.

In almost as many situations, the first-in fire company is surprised by a sudden change in their situation. A high wind pushes the fire into the hallway, there is a failure of a window or partial collapse of a truss component. A clear condition with light smoke suddenly becomes an overwhelming wave of blinding and hot smoke. Or worse: the flame front of a flashover, the opening of a floor into a basement full of fire or the burying of the crew under hundreds of pounds of burning lightweight truss components.

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John Mittendorf, a retired Los Angeles Fire Department battalion chief, describes the practice of “sounding” a flat roof before a truck company steps on the roof. Using a roof rake, a tool similar to a pike pole, a firefighter will forcibly strike the roof to assess its integrity. You can read more in his 1998 Truck Company Operations book published by Pennwell. Maybe we need to sound the truss floors before making an entry.