Fire, Explosion & Collapse: Firefighters Trapped!

Flashover, backdraft and smoke explosions. All hazards to firefighters — sometimes predictable, sometimes not, but we have to know what some "warning signs" may be. This month's Close Call will help us learn by taking us to a related event and reading...


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Our unit, Quint 5-6, was assigned to the C Division at the rear of the taxpayers. As we arrived, there was a medium smoke condition at the rear of a sporting goods store. The rear of the store was single story and directly abutted a two-story brick building containing college classrooms and state offices (B exposure). A small alley separated that building from the rear of a pizzeria (D exposure), which also was one story. The alley between the two single-story sections of the buildings led to a rear door to the sporting goods store and stairs leading to apartments on the second floor. It was clear that the body of fire was in an area toward the front of the store at the top of the stairs.

Engine 14 (Mannington) was assigned to supply water to us. As this was being set up, two firefighters went up the stairs to check on the apartments. They reported that the stairs, which were not yet involved in fire, were very weak and rickety. I was leery of sending two fully equipped firefighters with hoselines up the wooden stairs because of their condition. In addition, the smoke coming out of the single-story rear section of the sporting goods store was now thick, black, and pushing. I knew a problem was most likely imminent. I did not want firefighters in the alley between the buildings with their only avenue of escape taking them past a potential problem of either a smoke explosion or flashover.

A ground ladder was placed on the C side of the sporting goods store with the intent of cutting a hole in the roof. On the D side of the sporting goods store, there were four 250-gallon fuel oil tanks. There were no doors to access the single-story rear section of the sporting goods store. There were boarded-up windows on the D side above the fuel oil tanks. Due to the heavy black smoke pushing out from the boarded-up windows and eaves, I ordered the firefighters to open up the windows and to place a handline in service. This provided quicker ventilation than opening up the roof to a building with no doors for access (the door next to the stairs was at the opposite end of the alley). At the same time, the main ladder was placed to the roof of the B exposure and access was made to assess conditions. At this point, fire was not involving the attached two-story B exposure and all occupants were out.

While the handline with three firefighters flowed water into the windows, and me only a few feet away, it happened — a sudden loud rush of air. It had a constantly changing pitch and it was louder than releasing air directly out of a compressed-air bottle. Heavy black smoke starting pushing out of the windows so hard that the alley between the buildings became completely filled with smoke, obscuring the firefighters.

A split second later, a loud explosion entirely blew out the D-side wall of the sporting goods store, where we were operating and where the fuel oil tanks were located. Two firefighters were knocked down and one lost his helmet. Electrical wires that were connected to the building fell to the ground around us and three of the four fuel oil tanks were knocked over. The double brick wall on the D side of the store had blown out about 10 feet and there was a lean-to roof collapse.

Immediately, I knew we had a backdraft/smoke explosion. As the firefighters ran in my direction, I saw the collapsed wall and performed accountability. No injuries were reported, and all firefighters were accounted for. I radioed to command what happened and that we were going into defensive operations. Initially, I had no idea that anything happened in front of the store and thought the explosion had occurred only in the rear. I heard command order an emergency evacuation and give a report on conditions at the front of the row of buildings. Then I knew the explosion was much larger than I originally thought.

After the explosion, there was very little fire in the collapsed single-story section of the sporting goods store in the rear. In fact, a plastic oscillating fan sat on a desk, undisturbed, under the collapsed roof and it wasn't even melted. However, heavy fire was visible venting from the center of the building toward the front. The firefighter on the roof of the B exposure reported feeling that entire building shake.

Several of our firefighters had taken a reading-smoke class a few months before this fire. Without being told to, they had already started to retreat prior to the explosion based on the smoke conditions. They were standing next to the fourth fuel oil tank, the only one still standing, when the explosion occurred. The backdraft/explosion occurred faster than anyone could react. I am convinced my decision not to send firefighters up the wooden stairs or on the roof of the sporting goods store and the firefighters' own decision to back out based on conditions prevented serious injuries or even a fatality. Conditions for this explosion were very similar to conditions prior to a flashover. One difference was the very loud sound of rushing air a split second before the explosion.