As more incident commanders turn to positive-pressure ventilation as part of their firefighting attack strategy, the potential for injuries rises.
Consider the Massachusetts volunteer firefighter who died in November 2003 while fighting a basement fire in a residential structure. According to the, “the victim and another firefighter were in the basement applying water to the fire on the ceiling. A deputy chief in the basement reported to incident command that the fire was knocked down and requested ventilation.
“A positive-pressure ventilation fan was started at the front door as the basement windows were opened. Suddenly, thick black smoke filled the entire basement area as the hose line became covered by debris falling from shelving in the basement. The deputy chief called for a mayday [and] told the crew to exit the basement. He was assisted from the structure, fell unconscious and was rushed to a hospital.”
The rescue of the victim was more problematic due to heightened fire conditions. The firefighter was recovered 90 minutes later and transported to a local hospital, where he was pronounced dead.
This NIOSH report underscores the importance of completely understanding the precautions required to safely use PPV and positive-pressure attack. For example, unless PPA has been started in coordination with the initial attack, it shouldn't be initiated until all interior crews have exited the structure.
Firefighting has always been a dangerous and sometimes deadly occupation, despite our improvements in personal protective equipment, apparatus, tactics, and command and control procedures. Danger is also an element when positive-pressure attack is improperly placed into operation or used in situations where it shouldn't.
There are many PPA situations where precautions are necessary. Affording these precautions their due respect will help make PPA a safer and more advantageous tactic. Firefighters should watch out for the following situations.
When firefighters or victims are standing at windows or other potential exhaust openings. The first tactical priority of any fire operation is to rescue survivable victims — and yes, sometimes firefighters. If you arrive on scene and observe a person at a window waiting to be rescued, a fan could make matters worse. If blowers are put into operation at the ventilation point or attack entrance prior to the rescue, there's a chance that the window at which the victim is standing could become the exhaust opening. If this occurs, all of the heat and toxic products of combustion are headed toward the trapped person and may have deadly consequences. It's imperative that victims are rescued from potential exhaust openings before any PPA operations are started.
When firefighters have entered the structure prior to the blower being used. Firefighters whose positions within the structure aren't know could be in for disastrous results if the blower is started. They may have moved to an area between the fire and exhaust opening, or they may have not yet made a large-enough exhaust opening.
Pressurizing a structure moves the interior atmosphere to the area of decreased pressure. Performed appropriately, this moves high volumes of heat and products of combustion through the exhaust opening to the outside. Firefighters who are operating between the fire and the exhaust opening are directly in line with this atmosphere of extreme heat and toxic products of combustion.
Positive pressure can operate properly only if there's an adequate ventilation point and an exhaust opening. The exhaust opening must be of adequate size to accommodate the volume of heat and smoke being released from the structure. If the opening isn't large enough, the interior conditions may deteriorate as heat and smoke circulate, much like in a convection oven. If firefighters are inside the structure when this occurs, prepare for the worst.
An exhaust opening's adequacy depends on the amount of heat and products of combustion in the structure. If there's a high fire load, the exhaust should be three to four times the size of the ventilation point. If interior conditions are light to moderate in the amount of heat and products of combustion, an adequate exhaust should be two to three times the size of the ventilation point. As with all ventilation operations, the size of the exhaust opening should be dictated by interior conditions. If the heat is high and combustion byproducts are pushing through the exhaust with extreme force, the exhaust opening should be increased.
Firefighters must never precede the blower being placed into operation. They should enter the structure only after an adequate exhaust opening has been ensured and the blower has been turned on. If crews are already inside, they must exit the structure before starting the blower and then reenter.
When combustible or flammable atmospheres are present. Occupancies such as grain-processing plants and grain elevators with suspended particles in the air are combustible-rich environments. The potential for dust explosions is significant, and the use of blowers may direct this combustible atmosphere to an ignition source.
In such environments, there often is a small primary explosion followed by a massive secondary explosion. The potential for a secondary explosion may be reduced by not using blowers because blowers can increase the concentration of suspended particles by picking them up from the floor or other surfaces and directing them to the source of the primary explosion.
The same precaution should be noted for other flammable and combustible atmospheres where the use of blowers may direct the contaminated air to an ignition source, such as in an incident involving gasoline vapors. Always keep in mind that a gasoline-fueled blower is an ignition source.
When backdraft conditions are observed. Backdraft conditions exist when combustibles have reached their ignition temperatures, but because of inadequate oxygen combustion can't continue. The likelihood of victim survivability and salvage of the contents or the building is poor. Firefighters should therefore carefully plan their attack knowing that the risk is high and the possibility of any life saving is probably low. The textbook way of dealing with this explosive situation is to safely ventilate high. Because positive pressure relies on the use of easily accessible means of ventilation such as doors and windows, it isn't recommended for incidents that are displaying backdraft conditions.
Exhaust openings, the possibility of rekindles and blower noise have the potential to catch firefighters off-guard.
Positive pressure operates on the principle of high pressure moving to an area of lower pressure, typically to the outside through a window or door. Although the structure's interior is cleared of heat and toxic products of combustion quickly and rather calmly in terms of air movement, the same isn't true of conditions immediately outside the exhaust opening.
Heat and smoke exit the structure forcefully, and firefighters must be prepared. They shouldn't be in an area where they may become trapped between the exiting heat and smoke with no escape route. We learned this early during our PPV experiments when we had an exhaust opening on a porch that was spewing flames and the only protection was to become one with a side wall of the porch.
Plan to not be near the exhaust opening, and have a way to escape after making the exhaust opening. Exposures, such as overhangs, soffits and nearby structures, also should be noted and protected with appropriate hand lines if necessary.
The universal bane of firefighters is being called back to the scene of a previous fire due to a rekindle. The speed and efficacy at which blowers rid a building of smoke and heat is impressive. However, that same efficiency during overhaul may lull firefighters into believing that they have completely extinguished the fire even though burning still may be occurring inside unopened voids.
Rekindles don't happen in areas that have been adequately opened and inspected. Before leaving the scene, blowers should be turned off for a minimum of 10 minutes. Firefighters should then carefully re-inspect the area for any signs of hidden fire, such as drift smoke or heat. Remember to open early and open often to prevent rekindles. The use of wetting agents throughout the fire area is also a tried-and-true practice for reducing rekindles.
Mark Twain wrote, “Noise proves nothing. Often a hen who has merely laid an egg cackles as if she had laid an asteroid.” With all due to respect to Mr. Twain, blowers and noise are another matter entirely. Blower noise can be a distraction at the fire scene, especially for incident commanders who are too close to the blowers to communicate effectively. The solution is easy: Locate the IC position away from the action-intensive area surrounding a blower.
On the other hand, blower noise has its upside. It reassures interior crews that ventilation is operating and that interior conditions will continue to improve. That reassuring noise also may provide the necessary auditory clue for lost or disoriented firefighters to find their way out of the structure. This was the case with one of our firefighters during an emergency evacuation of a structure where the roof was collapsing.
There's nothing more important in the use of positive-pressure attack than training. It's surprising and dismaying that departments will spend hard-earned budget dollars on blowers with the belief that crews are capable of using them safely simply because they have been placed on the apparatus. The precautions presented here must be shared with firefighters, who also need to understand the theory and operational components of positive-pressure attack. Firefighters also must constantly practice and drill using the blower so that a systematic approach to ventilation is achieved.
The blower is a relatively simple piece of machinery, and the idea that you have to place it in front of door and then break out a window is also simple. Of course, it's more complicated than that. But if training and education take place, PPA can be a way for departments to achieve the elusive and safe coordinated fire attack. However, if no one teaches and trains on this powerful tool, it probably won't be used. Or worse, it will be used improperly, resulting in a victim not being rescued or a firefighter being injured.
We recently arrived at a basement fire where crews used their system to simultaneously deploy hose lines and blowers: ventilation coordinated with fire attack. A fully involved basement fire that had burned to the point of floor failure was reduced to a safe fire incident that was completely finished within 15 minutes. With education, training and an awareness of situations that require precautions, that success can be available to any department.
Kriss Garcia is a battalion chief for Salt Lake City Fire Department. He is an instructor for the National Fire Academy as well as the Utah Fire and Rescue Academy. He has an associate degree in pre-hospital care as well as bachelor degrees in public administration and education.
Reinhard Kauffmann is a battalion chief for Salt Lake City Fire Department, where he has worked for 28 years. Currently he is assigned as the fire chief for the Salt Lake City International Airport Authority. Kauffmann is an instructor for the Utah Fire and Rescue Academy. He is a graduate of the University of Utah with a bachelor's degree in science.