A Primer On Flashover

Dave LeBlanc uses recent training and a LODD to keep flashover fresh in out minds.

It is 2:30 a.m. and you are responding to a report of smoke on the second floor of a two story apartment house. The building is approximately 30 feet wide by 75 feet deep and has several apartments on each floor. Built in the late 40’s, the building only has local fire alarms, and no fire suppression systems.

Your company arrives at the scene and you and your officer proceed into the building to investigate. On the second floor you find a light smoke condition that smells like a mattress fire. Your officer takes the can from you and orders you to go get an 1 ¾ line.

As you begin stretching the line you notice there is now heavy smoke venting from the second floor windows. As you get to the stairs the smoke is banking down, black and you can feel a lot of heat. You slip your mask on and call out to your officer. Hearing nothing you continue to stretch the line. At the top of the stairs you feel tremendous heat and you call out to your officer again. Still hearing nothing you radio for water in the line. The second due engine is now behind you on the stairs and you tell the Lieutenant that you lost contact with your Officer and you last saw him at the rear of the seconnd floor. The Lieutenant immediately calls a “Mayday” and informs Command of the situation, the conditions and that you are going to push down the hall with the line. Command acknowledges, strikes another alarm and orders the truck to vent the rear of the second floor.

As you crawl forward the heat is intense but you cannot see a glow. You open into the smoke and no water returns. You tell the Lieutenant there is a lot of heat above you. You keep pushing in. As you enter the rear apartment you see heavy fire throughout, your line is having little affect. You are barely holding your position and the Lieutenant calls Command for another line. Suddenly you see the can that you left with your Officer. As you push forward you suddenly find your Officer. His mask is off and your and the second due engine work to remove him while controlling the fire.

While the story above is fiction, it is loosely based on a fire that claimed the life of a firefighter in 1995. The scenario above is not an unrealistic situation. Reduced manpower and early detection could lead to the circumstances described above. It is important that firefighters understand fire behavior and know the indicators of flashover. It is also equally important that firefighters know what to do when they find themselves in a potential flashover situation.

“In a compartment fire there can come a stage where the total thermal radiation from the fire plume, hot gases and hot compartment boundaries causes the generation of flammable products of pyrolysis from all exposed combustible surfaces within the compartment. Given a source of ignition, this will result in the sudden and sustained transition of a growing fire to a fully developed fire…….This is called ’flashover’……”[1]

In simpler terms Flashover is defined as the rapid change to total fire involvement in a room. It happens at the end of the growth stage. The keys words from both definitions are total involvement and sustained. When flashover occurs there is no chance for a victim to survive in that area. Firefighters must not over commit to an area where flashover is likely to occur. Fire Behavior and Flashover recognition is a vital component in every firefighters training. By recognizing the warning signs of Flashover, firefighters can take action to preventing flashover from occurring or to exit the area preventing injury or death.

So what are some of the signs that a flashover may be about to occur?

– Rapid Increase in Temperature
– Flame Roll Over
– Rapid Increase in Smoke Condition (Not always dark black smoke)
– Vent Point Ignition

With the switch to bunker gear we have better protected out firefighters, while a good thing, this can also lead to firefighters being unaware of the changing conditions around them. It is critical that every member operating inside be aware of how far they are from an exit, what the fire is doing, what the smoke is doing, and how to prevent themselves from becoming a victim.

Firefighters should routinely check above them as they crawl to see if there is flame mixed within the smoke. They should be aware of sudden increase in heat. Firefighters at doorways should look for fire in the smoke that is venting. Any of these are indicators that the room or space is about to flash over. Several of these indicators together is a sign that flashover is imminent.

What can we do to prevent flashover?

– Vent
– Not vent
– Cool

Probably the simplest way to prevent a room from flashing over is to simply close the door. By closing the door, you confine the fire to the room and reduce its oxygen supply. This should prevent the room from flashing over and allow the engine to stretch to the room and extinguish the fire.

Another option is to vent the room to the outside. By releasing the heat and fire gases, this option may prevent the room from reaching the point of flashover. However the sudden influx of outside air could also cause the room to flashover sooner.

The third option is to cool the atmosphere. By cooling the fire gases you reduce the chance of flashover, by extinguishing the fire you eliminate it almost completely. Cooling can be accomplished by the engine as they push toward the seat of the fire, or with a 2 ½ gallon can used by the truck during search.

“The FDNY has never suffered a flashover resulting in serious injury from a fire room with a functioning hoseline” – Deputy Fire Chief Vincent Dunn – FDNY (ret)

It is critical that every firefighter is aware of the signs of flashover and knows what can be done to prevent a flashover or to protect members from injury. Communication of the conditions found is vitally important to all members operating inside a structure, and coordination between fire attack and ventilation is paramount.

Firefighters that are responsible for searching should know techniques like Vent Enter and Search and defensive search. Both will allow them to check spaces that are deteriorating without overly exposing themselves. These firefighters should also know when conditions are such that entry into a room or space is futile.

As with so many aspects of firefighting, there is a lot to learn. This article certainly is a complete discussion of flashover and the concerns surrounding it, it is designed to be a starting point. A piece to create discussion and perhaps encourage more learning about one the most dangerous conditions we face as firefighters.

This article is dedicated to Firefighter Victor Melendy of the Stoughton, MA Fire Department. Firefighter Melendy was killed in the line of duty on January 28th, 1995.

1. “Flashover – A Firefighters Worst Nightmare” Paul Grimwood – Fire Tactics.net

Flashover Recognition – Barnstable County Fire and Rescue Training Academy – Course Handout.

Photo courtesy JR Adkins/FITHP.net

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