New Orleans, LA, firefighters from first-due Engine 39 made a quick interior attack from the front of a vacant, one-story dwelling, but retreated before the rear of the Lower Ninth Ward structure collapsed. Three sudden, unpredictable events are killing firefighters operating inside burning buildings: flashovers, collapses and explosions.
Photo credit: Photo by Chris E. Mickal/www.firelinephotos.com
Two San Francisco, CA, firefighters are killed in a flashover; four Houston, TX, firefighters die when a motel roof collapsed; 10 West, TX, firefighters are killed in an ammonium nitrate explosion.
Three sudden, unpredictable events are killing firefighters operating inside burning buildings: flashovers, collapses and explosions. If any of these three devastating events does not immediately kill firefighters, it causes them to be trapped and prevents their escape; fire and smoke will kill them later.
After being ensnared, stunned, buried or injured by one of these deadly surprises, firefighters are killed by spreading flame, heat, smoke or deadly fire gases. “Caught and trapped” is the category the National Institute for Occupational Safety and Health (NIOSH) Firefighter Fatality Investigation and Prevention Program uses to describe this type of death in its investigations of firefighter line-of-duty deaths (see http://www.cdc.gov/niosh/fire/). The NIOSH studies comprise one of the largest documented and detailed sources of reliable information about firefighter fatalities. They are a major resource for research on how firefighters die fighting fires. The agency has documented and published analyses of 550 firefighter fatalities since 1985.
From 2003 to 2012, NIOSH investigated 358 firefighter deaths. During structure firefighting, the number-one category of firefighter deaths was being “caught and trapped.” Fifty firefighters were caught and trapped while searching and operating hoselines in building fires. (During that period, 175 firefighters died of heart attacks, 43 died in vehicle accidents, 30 died in structure collapses, 20 were killed during training,12 died in explosions, 11 were killed by falls, seven died at wildfires, five were electrocuted and five were killed in mechanical accidents.)
Flashovers, collapses and explosions occur when firefighters are preoccupied with other life-and-death decisions during structure fires, such as searching for victims or advancing hoselines.
Flashovers are the most common deadly surprises killing and injuring firefighters searching at structure fires. While searching in smoke, being suddenly engulfed in flame and heat at 1,000 degrees Fahrenheit changes everything. If that situation does not kill firefighters immediately, it can cause them to make bad decisions, such as heading for an exit in the wrong direction, or it can block an escape exit with flame. NIOSH fatality reports reveal that firefighters who are caught and trapped by flashover are most often firefighters who search a fire area without a protective hoseline. Firefighters assigned to ladder companies and rescue companies most often suffer this fate. This is one reason safety officials want firefighters to have a hoseline with them when they conduct initial searches. A hose stream prevents firefighters being trapped by flashover by stopping the buildup of heat and the radiation feedback of heat from ceilings and upper walls in a fire area. Firefighters operating hoselines are not killed by flashover. They may be killed by a sudden collapse or explosion, but not by a flashover. Firefighters moving forward in a fire area and throwing three-quarters of a ton of water ahead of them do not have to worry about a flashover.
Searching with a hoseline, however, may not always be possible, so when it is necessary to take a high-rise assignment to save a victim, firefighters must size-up the fire. Flashover warning signs are hot smoke and rollover. If you see flashover warning signs, limit the distance of entry and search.
When heat builds up
Superheated smoke in a fire area that makes a firefighter crouch down to get beneath the heat level is a warning sign flashover could occur suddenly. Hot smoke indicates heat building up at ceiling level and the start of its transfer of heat down into the room from the ceiling and upper walls. This heat buildup brings gases to auto-ignition temperature and then flashover. It is this re-radiation of heat from ceiling and upper wall that triggers a flashover. This warning sign of flashover cannot be seen, it can only be sensed on skin.
The second warning sign of flashover is rollover, a term used by firefighters that can be described as flashes of flame mixed with smoke pushing out of the top of a door or window opening. Rollover is a sporadic flaming mixed with smoke. Scientific testing shows us this rollover phenomenon can precede the more deadly event, flashover.
A major cause of firefighter entrapment by flashover is fire venting. Venting can be caused by a pane of glass cracking and falling out of a window frame or uncoordinated, premature venting of a fire area. Venting before a hoseline is operating, either by the searching firefighter or an outside vent firefighter, can trigger a flashover and trap firefighters searching inside. Venting and searching should be coordinated with the advance of a hoseline. Uncontrolled, unplanned and sometimes unauthorized venting of windows and doors, from inside or outside, can let fresh air feed a fire, creating sudden, rapid and increased fire growth and flashover.
The “point of no return”
In a rare instance when a search must be conducted without a hoseline because a trapped victim is seen, heard or reported by a credible witness, and entry must be made, searching firefighters must understand there is a “point of no return.” This is the point beyond which you will not return if flashover occurs. A firefighter who searches too far inside a smoke-filled superheated room that has warning signs of flashover will not escape if caught in a sudden flashover.
Firefighters must be aware of the point of no return. If you decide to search beyond the point of no return and the room flashes over, chances are you will not survive. The point of no return is five feet inside the room. You may ask how this information originated. Years ago, five feet was the distance a firefighter without protective equipment could search inside a hall or room at a serious fire. At one such fire a firefighter wearing half boots, a canvas coat and no mask or hood could go only five feet into a room because of heat, hot, dripping paint, blinding smoke and choking gases. The firefighter could make a sweep of the floor with a tool, look for a victim lying on the floor below the flame and heat, check behind the door, and then back out and close the door. To advance farther, the firefighter had to wait for a hose team, then together they would advance while throwing three-quarters of a ton of water for protection and search the fire area.
Verified by scientific tests
In addition to fireground experience, scientific tests verify the logic of this point-of-no-return distance. Testing with humans has determined severe pain is caused by heat of 320° F on unprotected skin and the normal walking rate is 2½ feet per second (walking upright, not crawling, without many pounds of gear and tools). If you walk five feet inside a room and it flashes over, studies say, you have two seconds to get out – count “a one and a two.” If you go 10 feet inside the room and engulfed with 1,000° F heat, it will take you four seconds to escape. If a smoke-filled room suddenly flashes over and you are 15 feet inside, and if you are not caught, trapped and killed by the flashover, but lucky enough get back to a window or door, chances are you will be sent to a burn center.
Think about it. Beyond five feet in a room that flashes over is the point of no return.
NIOSH investigations reveal that collapses are the second-leading cause of firefighter deaths during interior structure firefighting. A study conducted by the National Fire Protection Association (NFPA) on firefighter deaths from collapse shows that 56 firefighters died in structure collapses from 1991 to 2000 (http://www.nfpa.org/assets/files/pdf/os.ffanalysis.pdf). The NFPA study broke down what part of a structure kills most firefighters. During that 10-year period, the largest number of firefighters (21) were killed in floor collapses. Nineteen firefighters were killed when roofs collapsed, 14 were killed by wall collapses and two died when ceilings collapsed. Now we know that when you enter a burning building, the floors and roof are the biggest collapse dangers.
One interesting fact brought out in the NFPA study is about roof collapse. Of the 19 firefighters killed when roofs collapsed, 15 were under the roofs when they caved in and four were on top of roofs. Firefighters operating below are in more danger when a roof collapses. We see many training videos of firefighters falling through roofs, but there are no videos from inside a burning building capturing the roof coming down on firefighters. Our view of roof collapse dangers is distorted. The collapse danger of operating under the roof is three times more deadly. The first step of risk management is identifying risks accurately, then managing the risk to reduce deaths and injuries.
Reducing collapse danger
How can an incident commander reduce collapse danger during a fire? If the structure, fire conditions and staffing allow, an incident commander or safety officer may be able to make a 360-degree collapse size-up of an unattached fire building. In many urban or suburban locations, however, this rarely can be accomplished, so the facade of the burning building should be examined. Parapet walls, canopies, marquees and cornices are collapse dangers. Truthfully, the incident commander has limited ability to check the stability of a building during the initial stages of a fire. The incident commander cannot see the interior, roof conditions or rear wall. Command responsibilities of fire size-up, hose placement, rescue, venting and ladder placement consume the incident commander’s attention.
The most important collapse size-up comes from firefighters and fire officer inside the fire building. They are the eyes and ears of the incident commander and must report any structural defect discovered during the interior firefighting operation. It is a myth that an incident commander at a command post will identify a collapse danger and warn firefighters inside the burning building. The fact is that firefighters discover collapse danger signs and notify the incident commander, who then notifies firefighters of safety actions. The incident commander is responsible to notify sector, division, group, company officers and firefighters down the chain of command of actions to take to protect against the reported danger.
One collapse warning sign that must always be reported to the incident commander is the presence of truss construction. Even if there is no collapse warning, just the presence of truss construction must be reported. The danger of truss construction is that collapses occur suddenly, without warning.
Three indicators of truss construction can be identified by firefighters operating inside, around and on the roof of a burning building: rounded roof surfaces; large open areas without supporting columns; and large public occupancies such as theaters, restaurants, bowling alleys, places of worship and supermarkets.
The best collapse warning comes before a fire. It comes from identifying occupancies with collapse dangers during inspections and establishing firefighting pre-plans. The pre-plan strategy is then programmed into the dispatch computer system. If a fire occurs, this information is relayed to the incident commander at a fire. This is the best way to protect firefighters from truss collapse danger during a fire.
Standard operating guidelines (SOGs) for structure fires with any type of truss construction must also be determined. A recognized standard operating procedure (SOP) used by some fire departments is as follows: If the fire involves only contents like furniture, a standard operating hoseline attack can be considered. However, if the fire has spread to the beams, floors or roof or is spreading inside concealed spaces, the incident commander should order the evacuation of all occupants and firefighters to the exterior and conduct a defensive attack.
Explosions are a part of a firefighter’s deadly, uncontrolled work environment. Firefighters are exposed to many types of explosions. Sources include terrorist bombs, gas mains, flammable liquid vapors, gas cylinders, oil burners, vehicle gasoline tanks, manholes, fertilizers, chemical plants and backdrafts/smoke explosions. An explosion can result in a collapse, fire and multiple trapped victims. Explosions produce, shock waves blowing firefighters back into a street, a fireball engulfing firefighters and flying missiles of shrapnel that injure and kill. Firefighters nearby will be rendered unconscious, badly burned, buried in collapse rubble and disoriented. After an explosion, autopsies report causes of death as thermal burns, smoke inhalation and blunt-force trauma.
In a structure fire, explosions often occur when flames reach a pocket of leaking natural gas, heat illegally stored explosive contents or when flame and air mix with flammable vapors from arsonist’s accelerant. Sometimes, gases flow through conduits from street manholes into nearby cellars and explode.
Any indication of explosion danger must be reported to command and the incident commander must order firefighters to evacuate the area. A sudden explosion is one of the deadly hazards of structure firefighting. Protective equipment and defensive fire strategy are the number-one and number-two priorities.
The best strategy is to inspect all buildings in a community and identify explosion hazards. Explosion hazards are found most often in commercial occupancies, not public or residential. A pre-plan should be produced recommending defensive firefighting when any explosive danger is discovering during inspection. Only when there is no known danger of explosive content should an interior firefighting attack be the strategy.
It could be argued that if fire departments did not conduct interior firefighting operations, but instead fought all fires from the exterior, there would be more explosions during fires. In addition to saving lives of trapped victims, interior firefighting extinguishes fire before it reaches unknown or illegally stored explosive contents. However, it must be restated that any time there is a warning sign of explosion, the incident commander must stop fire operations, order bystanders and firefighters to withdraw to safety and not fight the fire. When the danger involves ammonium nitrate, dynamite, blasting agents or similar materials, firefighters must be withdrawn 2,000 feet away.
Unfortunately, at most structure fires where explosions occur, there are no warnings signs, no pre-planned defensive strategy and no time to act defensively. The last defense when there is a sudden explosion during firefighting is protective equipment: helmets, eye shields, hoods, gloves, boots, bunker pants, coat and facemasks.
To guard against explosions
There are several tactics incident commanders can incorporate in firefighting procedures to reduce the effects of explosions. These tactics are the same as those that fire protection engineers use to provide explosive protection in industrial plants: confinement, venting, quenching and isolating
• Confinement. Firefighters can confine the area by temporarily closing a door until the hose attack team has water in the hoseline, is ready to move and has all protective gear in place.
• Quenching. A hose team discharging water on a fire may quench an explosive atmosphere. How many times have firefighters discovered an illegally stored explosive device or pressure container during overhauling and quenching stopped an explosion?
• Venting. Coordinated venting with hoseline advance is an important explosion-mitigation tactic. When the hose team is advancing, every portal to the fire area should be vented: skylights, scuttle covers, front, side and rear doors and all the windows. Now, if a sudden explosion occurs, the blast will be diverted out of the fire area. Venting must be coordinated and not done before the hoseline is extinguishing the fire.
• Isolation. A strategy to prevent explosion death and injury is by having firefighters flank a doorway opening with hoselines. Directing a hose stream into a doorway at angles and standing away from the opening is called a flanking tactic. This tactic will isolate shockwaves and flying shrapnel. Firefighters will be away from the path of destruction.Conclusion
NIOSH line-of-duty death investigations indicate that from 1985 to 2012, the number of firefighters killed and caught and trapped by flashover, collapse and explosion increased. There could be several reasons. One may be that our excellent modern fire gear lets firefighters enter and search in superheated fires. Another reason may be the increase of firefighters performing high-risk search tactics such as entering a fire area before a hoseline is in operation. Another cause may be uncoordinated, premature and sometimes unauthorized venting, which can trigger heat buildup and flashover, or wind-driven fire or sudden rapid fire growth, all of which can trap firefighters. n
National Institute for Occupational Safety and Health (NIOSH). http://www.cdc.gov/niosh/fire/.
National Fire Protection Association (NFPA). Selected Special Analyses of Firefighter Fatalities http://www.nfpa.org/assets/files/pdf/os.ffanalysis.pdf, page 12.