BY ANTHONY AVILLO
When I first started taking classes for my promotional exam, I needed indoctrination into how the test worked and how to succeed at it. My mentor was and still is Chief Ed Flood. He showed me how to play in the world of the New Jersey Department of Personnel and had a knack for figuring out the best way to approach not only the testing game but also the fireground. I have seen no one in this business who had such a grasp of both firematics and personnel management as Flood. In fact, I have seen very few people who come close. He is as real as it gets.
One of the rules of thumb Flood created for addressing test issues was the tactic of using the safest, most effective path of least resistance to accomplish an objective. Although this may seem simple, it many times is not—not only in the promotional world but in the real-time world as well. The key to the game is safety: Get ’em in safe, work ’em safe, get ’em out safe. This should be the mantra of all fire officers. As such, sometimes existing conditions have made the most effective path of least resistance unsafe. This is where the officer makes his bones not only by knowing the “normal” paths of least resistance but also by his ability to adjust when these paths are no longer safe. I will discuss this rule and how it applies to specific fireground issues. Let’s start with probably the most important aspect of this business: the comprehension of building construction.
BUILDING CONSTRUCTION
Knowing the building that is on fire is more important than knowing the fire that is in the building. If we know how a building was put together, we can identify the areas that will be most vulnerable to failure and can make an educated guess on how they will fall apart. The construction of the building will have a major impact on how the products of combustion spread and is the key to understanding and forecasting the most effective paths of least resistance for fire spread and fire control.
Factors such as the location of the fire in the building in relation to the location of vertical arteries will aid in determining strategy and tactics. For instance, barring any wind condition that might adversely affect fire spread, a fire in an apartment near a window is more likely to vent out that window and create an autoexposure problem, but this should allow for an attack that keeps the fire moving in its current path of least resistance, pushing the fire out the window. You can address the autoexposure issue by stretching a line to the floor above to keep the fire from entering and by using an outside stream to wash the spandrel wall between the two floors. A fire in proximity to the entry door is likely to vent out the entry door, into the hallway, and up the stairs, especially when that door is open. That is why it is imperative to keep that door closed (i.e., control the door) until a hoseline is ready to attack the fire and keep the fire from taking the path of least resistance up the stairs where occupants (and firefighters) are seeking to use them for access to upper floors and egress. A fire deep in an apartment that is not near these arteries will also look to spread upward, but it may more easily find areas such as bathrooms and kitchens where the largest pipe chases in the building will provide the most effective path of least resistance for vertical fire spread. Since you are already aware of this possibility because of your knowledge of building construction, you will place your defense against this spread into the most likely areas in a timely manner (photo 1).
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| (1) In most residential occupancies, open interior stairs are the path of choice for fire to spread upward and for occupants to escape downward. Failure to recognize this in your protection strategy can have disastrous consequences. This fire roared out of the cellar through this open door. There was no obstacle to its upward spread from the cellar, and it took the path of least resistance, trapping several firefighters on the second floor. However, they did close the apartment door when they went in to search the second floor, thus creating a barrier, and it bought them time to get out of the building. Had the door been open, the fire would have taken the path of least resistance into the apartment, and the outcome would have been much worse. (Photo by author.) |
Understanding the types of building construction and the inherent weaknesses of each will guide the fire strategist in determining the tactics regarding where to vent, attack, force entry, and conduct overhaul and salvage and also in predicting how the building is likely to fall apart. Failing to understand these issues can lead to improper tactics that can divert fire from its natural paths into areas in which the consequences will be more severe. If you are unclear on building construction and how it influences the fire, you are merely guessing (noneducated guessing) at your operations.
FIRE ATTACK
Interestingly, many of the paths of least resistance for fire spread are also the main routes of attack and egress. This is where the major focus of the firefight is often concentrated, especially in multiple dwellings. If you surrender these common areas to the fire, both your egress and your attack routes will be blocked and will need to be altered, complicating the issue. As a result, evacuations may turn into rescues, and attack may be delayed as lines are either abandoned for bigger lines that supply more water or are rerouted to alternate attack routes or to exterior attack positions. Operational modifications take time and place more lives, both firefighter and civilian, in danger. For this reason, the incident commander (IC) must be prepared to do whatever is necessary to win the battle for the paths of least resistance in the building. There is an old saying: Save the stairs, save the building; lose the stairs, lose the building. The more you deviate or are forced to deviate from the path of least resistance for attack, the more vulnerable these arteries become and the greater an advantage the fire gains (photo 2).
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| (2) Firefighters stretch an attack line through the front door, the safest and most effective path of least resistance to fight this fire. Using this tactic, they can accomplish the following objectives: protect the stairs, attack from the unburned side, protect the search, and confine and extinguish the fire. Placing this line anywhere else would not allow them to meet all these objectives. I would also quickly stretch a second line for backup and to cover the floor above, stretch an exposure line into the alley on the D side, and place a line inside the D exposure as well. (Photo by Bob Scollan.) |
FORCIBLE ENTRY
Forcible entry is an operation in which the more common paths of least resistance may be unavailable for one reason or another either because of barriers or safety concerns. Often, the entry team will have to improvise. Using the mantra of the safest, most effective path of least resistance can often lead to the best (and safest) decision on how to enter a building. For instance, the front door is usually the path of least resistance both into and out of the building. If that door is heavily fortified and the situation is minor, it may be easier and less damaging to enter through a window than to try to defeat the door. Reconnaissance may even reveal a less heavily fortified door at the rear or sides. Although this may not be the closest door to the street, it may still be the most effective path of least resistance. It is easier and quicker to force a wood side or rear door than to waste time and personnel trying to force an impenetrable front door. By the time the door is forced, it may be the only thing left standing. In the hallways of fire-resistive buildings, the door may be steel set in a steel frame, but the wall may be gypsum board or even concrete block. In many cases, especially if a hydraulic forcible entry (rabbit) tool is not available, it is easier and less time consuming to breach the wall and reach in and unlock the door. Be flexible in your decision making. At a residential high-rise fire in North Bergen, New Jersey, oxygen cylinders used for medical purposes were exposed to a fire that originated on a couch. When a cylinder exploded, it blew out the gypsum board hallway wall and the glass balcony doors. The steel apartment door was left intact. The explosion took the paths of least resistance (photo 3).
![(3) An oxygen cylinder that ruptured under fire attack blew a hole in this wall, taking the path of least resistance through the gypsum board wall. The steel entry door was damaged but left intact. The pike poles seen in the center are actually leaning up against the wall on the other side of the hallway. Note also the spalled concrete and the sagging rebar, indicating the point of origin of this fire. [Photo courtesy of the North Bergen (NJ) Fire Department.]](/content/dam/etc/medialib/new-lib/fireengineering/print-articles/2012/aug/avilo3-1205fe.jpg) |
| (3) An oxygen cylinder that ruptured under fire attack blew a hole in this wall, taking the path of least resistance through the gypsum board wall. The steel entry door was damaged but left intact. The pike poles seen in the center are actually leaning up against the wall on the other side of the hallway. Note also the spalled concrete and the sagging rebar, indicating the point of origin of this fire. [Photo courtesy of the North Bergen (NJ) Fire Department.] |
VENTILATION
Almost nowhere on the fireground is the understanding of paths of least resistance more critical than during ventilation operations. Just as proper and timely ventilation can effectively channel fire away from both victims and exposures, so, too, can misplaced, uncoordinated ventilation create havoc on a building and those still inside, including firefighters.
Inadequate ventilation often destroys contiguous structures with common cocklofts because of a failure to take advantage of the most effective path of least resistance. This failure can often be identified by the one completely destroyed structure in the center of the row and the destroyed roof and top floors of all the adjacent buildings to the leeward (and if you really screw up, to the windward) side. The key to success is to vent early over the natural vertical arteries such as scuttles, bulkheads, and skylights. On a lower-floor fire, this should be sufficient in regard to vertical ventilation. Opening and examining these natural arteries will take advantage of the most effective path of least resistance and channel the products of combustion upward. If the fire is on the top floor or in the cockloft, in addition to the aforementioned natural openings, cutting the roof as close to directly over the seat of the fire as is safe will also pull the fire up and out of the building. This will slow the horizontal fire spread under the roof. If the fire is not given an opportunity to travel upward (where it wants to go), it will follow the other path of least resistance, horizontally throughout the cockloft (photo 4).
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| (4) Sometimes the fire will do what we wanted to do. The roof of this lightweight-constructed Class V (wood-frame) townhome vented on its own and localized this fire. Almost instantaneously with this “fire through the roof” action, the adjacent areas became more tenable and more easily defended. The vertical draft of heat by the path of least resistance reduced the potential for horizontal spread. Note one thing in addition: No ladder pipes are being applied to this area—yet. That would only negate the path of least resistance. (Photo by Bob Scollan.) |
Lack of ventilation can also cause firefighters to be chased out of the building at best and burned at worst. Suppose an attack team is positioned at the door to a burning apartment. To properly coordinate the attack, a vent team should be ready on the building’s exterior, somewhere opposite the nozzle, to remove windows to allow the smoke and heat to exhaust to the exterior, away from the attack team. This is how it is supposed to happen. This coordination of attack is critical. If this attack support is not in place, the products of combustion and steam have no way out of the structure and will be forced to take the path of least resistance out of the structure, which will now be through the entry point of the attack team. Because of this lack of coordination and support, many firefighters and evacuating civilians have suffered burn injuries, and many buildings have been needlessly destroyed.
The wind can also play a major part in influencing the path of least resistance. Wind can make the products of combustion take unusual paths of least resistance in a building that the attack team may not be ready for. Take, for example, a fire in a building where the wind is gusting right into the fire apartment. Suppose also that the apartment door has been left open. Instead of allowing the fire to vent out the window, the wind has now changed the path of least resistance. When the attack team gets onto the fire floor and tries to advance down the hall or into the apartment, the fire and heat being blown at them may overwhelm the team. In this case, the team may have to retreat to the safety of a stairwell while a master stream is deployed from the outside to knock down the fire, taking advantage of the wind-created path of least resistance. Often, on the higher floors out of reach of aerial streams, sometimes the best thing to do is to close the doors and let the fire consume the contents—in essence, a controlled burn. This should only be attempted in a fire-resistive building. Uncoordinated exterior lines can have the same effect. This is why opposing streams and opposing interior and exterior attacks are so dangerous. Since exterior lines are usually larger, they will always overpower smaller interior lines, pushing fire and heat into paths of least resistance, wreaking havoc on people and property.
SEARCH AND RESCUE
Most fire victims will attempt to escape the building using the most effective path of least resistance, the stairs and front door. Other paths include, but are not limited to, remote doorways; windows; fire escapes; and, as a last resort, jumping (an absolute path of least resistance and the most dangerous). Many victims are found near doors or windows, overcome by the products of combustion that are also looking to follow these same paths. Removing occupants by alternate paths of egress does not take advantage of the paths of least resistance; as a result, it takes more time to get out and is far more dangerous to the victim and the firefighter. It is much easier and safer to take a victim down the interior stairs than a fire escape; an aerial; or, tougher yet, a ground ladder. The rope rescue is at the extreme, eating up personnel and exposing rescuers and victims to deadly risk. The bottom line that we must understand is this: Regarding victim removal, the more we deviate from the path of least resistance, the more time it takes, the more personnel it requires, and the more danger is involved (photo 5).
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| (5) This is not only a civilian nightmare but a rescuer’s nightmare, too. This operation is extremely difficult and dangerous, requires more personnel to accomplish, and is time-consuming. In fact, the ripple effect resulting from the need for this action usually means other tactics such as forcible entry, interior search, and usually ventilation are affected or delayed. This leads to a loss of coordination on the fireground and increases the danger to all involved. (Photo by Ron Jeffers.) |
In regard to primary search, some of the tools we can use to assist in maintaining the paths of least resistance out of a building are lifelines and thermal imaging cameras. This is especially true in large-area buildings, where these tools are an absolute must. Knowing in advance where paths of least resistance are will save valuable time and will allow rescue teams to focus on critical areas early in the operation. This is also why it is critical to use a lifeline during rapid intervention company operations, where seconds count, because once we find a down firefighter, additional rescuers can use the lifeline to follow the most effective path of least resistance to access the firefighter. Rescuers also follow this lifeline as they remove the down firefighter because it also provides the path of least resistance out of the building.
Among the most dangerous operations conducted on the fireground are vent-enter-search (VES) operations in which firefighters use ladders, fire escapes, and porch roofs to enter a building’s upper floors to search for and remove victims. In these cases, windows become the most effective path of least resistance for entry. However, this firefighter-created path also creates a potentially deadly situation because it can also be the path of least resistance for products of combustion. For this reason, it is critical that the first action firefighters take on VES missions is to create a barrier between themselves and the fire (and the attack team) by closing the door to the room they enter. If this is not done, hose streams may drive fire and the products of combustion toward the open entry window, possibly incinerating the firefighter. In fact, you should base your decision on whether to enter the room on this factor: Can I get to the door to this room and close it before the fire gets there? If the answer is no, this might be nothing more than a vent and sweep instead of a VES. It is a race and a gamble, and understanding the paths of least resistance for fire spread can help you make a correct and safe decision.
Closing doors between you and the fire operation is critical to buying time for a search, especially on the upper floor. The question to ask is, “How can the fire get to me?” Closing doors and being aware of secondary means of egress are equally critical.
A firefighter was badly burned and suffered traumatic injuries when going to search the upper floors of a burning building. The fire was in the cellar, and a rear door leading from the cellar to the upper floors was open. This was the path the search team took to get to the upper floor. The fire extended to the first floor and when the line protecting the first floor began to attack that fire, they pushed it at the rear stairwell. As a result, the products of combustion were pushed into the paths of least resistance, the rear stairs leading to the upper floors. The ensuing fireball chased the firefighter up to the third floor, where he was forced to jump out a window. He fell through an awning and narrowly missed an upside-down wood picnic table. He suffered severe burn injuries, multiple fractures, and internal trauma.
For this same reason, firefighters should never attempt to enter a fire building through the bulkhead door and stairway from the roof or use this artery to get to the roof from the interior. The bad stuff will always seek the most effective path of least resistance, regardless of who is standing in it.
OVERHAUL
Overhaul can be divided into precontrol overhaul and postcontrol overhaul. Knowledge of building construction is critical to both operations to take advantage of the paths of least resistance. Knowing where to open the building ahead of a spreading fire is the first and most important aspect of precontrol overhaul. For instance, knowing where a basement fire in a balloon-frame dwelling is likely to spread, you will position lines in the attic early in the firefight, a strategy not usually pursued in buildings of other types of construction. Likewise, in ordinary construction, the building may be a maze of honeycomb-like voids, inviting many different ways for fire to spread in many directions at once. Sometimes, fires will not spread as easily vertically and have to move relatively great distances horizontally before finding a vertical channel. One fire that started in a ceiling light fixture spread through the space above the ceiling, passing over room partitions to the other side of the apartment, where it found a vertical void adjacent to the chimney. It then spread to the upper floors and the cockloft. While it is usually best to check around suspected and known vertical openings (paths of least resistance), don’t be lulled into neglecting horizontal paths of least resistance. Check above drop and tin ceilings; check inside soffits, cornices, and facades; and pull ceilings in exposures to check for horizontal fire spread based on building construction characteristics and potential paths of least resistance.
In postcontrol overhaul tactics, take advantage of the same building openings as in precontrol overhaul. In addition, manmade openings such as light fixtures, plumbing and wiring areas, ductwork, and outlets are all paths of least resistance and must be checked. In addition, the area directly over the fire may allow fire to spread into ceiling voids or to upper floors even where no manmade openings exist. Conduction, convection, and radiation will be the culprits here. The objective of postcontrol overhaul is to make sure the fire is out. Keep in mind that the most effective paths of least resistance for fire travel will assist in ensuring you meet this objective.
SALVAGE
Primary damage results from fire itself; secondary damage is a result of the firefighting operations, including structural and contents damage that occurs as part of fire control and the water damage suffered as a direct result of suppression agent application. Forecasting the most effective paths of least resistance for fire travel and then removing combustibles from those areas before they become involved not only reduces the available fire load but also saves property. For example, take a building that is exposed to a fire occurring in an adjacent building through the shaft that is between them. The exposed building is of ordinary construction. If it is a warm day, many windows may be open. The most effective path of least resistance for exposure ignition from radiated and convected heat will be through the open windows. Closing the windows, removing combustibles, and venting windows opposite the fire to dissipate heat are passive ways to lessen the heat’s impact on the building. Coating the building with water and stretching lines through the interior to the window areas of the exposed rooms are more dynamic. Why do we do this? Because the window represents the most effective path of least resistance for fire travel into the building. Therefore, in this case, it must be the first area you protect in the exposure.
As stated earlier, water will always seek the paths of least resistance but in a downward and opposite manner when compared with heat. When planning a property conservation strategy, the officer in charge of the salvage group must think like water. That officer must consider all the paths of least resistance to divert the water or place equipment aimed at limiting or eliminating water damage before the water arrives. In other words, identifying the most effective paths of least resistance for water runoff before the water actually gets there is a proactive method of reducing secondary damage.
COLLAPSE
All collapses are gravity-dependent. Once the pull of gravity is stronger than the integrity of the building’s connections, collapse will occur. Buildings will always fall in the path of least resistance. For instance, a building connected on one side but not the other will likely fall into the area where there is no resistance. Lean-over collapses are a perfect example of this principle. The building is likely to lean and collapse into the path of least resistance, which is the adjacent lot or street. Although no one can predict exactly how and when a building will fail, determining the likely paths of least resistance can help establish both collapse zones and safety perimeters (photo 6).
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| (6) This braced frame building collapsed into the path of least resistance, the adjacent lot. Although we can never predict exactly how or when a building will collapse, forecasting paths of least resistance for building failure can help establish and maintain collapse zones. (Photo by author.) |
Collapse rescue is another area where an awareness of the paths of least resistance may pay dividends when developing a rescue plan. Chief officers developing strategies to rescue collapse victims must, however, very seriously consider that the most effective paths of least resistance are often not the safest paths. Secondary collapse, fire involvement, and utility hazards are just a few of the concerns that can complicate a rescue operation and make the most effective path of least resistance unacceptable as a rescue route. Remember that when life is involved, the rule of thumb must be to use the safest, most effective path of least resistance to achieve the objective. If the seemingly most effective path of least resistance is unsafe, it no longer satisfies the rule of thumb.
The IC or rescue group supervisor must weigh the risk of rescuing by unsafe, albeit most effective, paths of least resistance vs. the time it might take to access victims by a safer but more time-consuming access route. This is a difficult decision. Rescuers who become victims are no longer rescuers; they are now part of the problem. Apply this mentality also to confined space, high-angle, trench rescue, and other technical rescue incidents. Under no circumstances should command ever let the risks outweigh the potential gains.
UNINTENDED CONSEQUENCES
It is interesting (and not surprising) to note that in direct contrast to proper tactics and their relation to the paths of least resistance, improper tactics will also take advantage of paths of least resistance and may lead to unintended consequences. For example, misunderstanding of building construction and the associated dangers of compromised structural components have led to death and injury when failing building components unexpectedly fall. Hoselines improperly placed because of improper tactics, a lack of training, or a lack of information regarding the location of the fire can push fire into uninvolved areas. Improperly located ventilation operations will also pull fire into uninvolved areas, possibly jeopardizing rescue and attack operations. In addition, improper and uncoordinated positive-pressure ventilation will push fire into paths of least resistance, often burning down the building. There are many examples of misuse of the most effective paths of least resistance that have resulted in outcomes quite different from those intended. You must learn from them.
Using the safest, most effective path of least resistance to accomplish objectives is a tried and true method of addressing fireground concerns. Many effective strategists probably do not even think of it when they are using it. It comes automatically with proper training, critiques and self-analysis, and experience. When faced with a difficult fireground decision, applying this rule of thumb to the potential solutions will assist in arriving at the safest and most proper decision.
ANTHONY AVILLO, a 27-year veteran of the fire service, is a deputy chief in North Hudson (NJ) Regional Fire & Rescue, assigned as 1st Platoon regional tour commander. He has a BS degree in fire science from New Jersey City University. He is an instructor at the Bergen County (NJ) and Monmouth County (NJ) Fire Academies. He is an FDIC instructor and a member of the FDIC advisory board and the editorial advisory board of Fire Engineering. He is the author of Fireground Strategies, 2nd edition (Fire Engineering, 2008) and Fireground Strategies Workbook Volumes I & II (Fire Engineering, 2002, 2010). He was a contributing author to Fire Engineering’s Handbook for Firefighter I and II (Fire Engineering, 2009) and is co-author of its Study Guide (Fire Engineering, 2010). Avillo was a collaborator in the Tactical Perspectives DVD series (Fire Engineering, 2011). With Chief Jim Duffy of the Wallingford (CT) Fire Department, he cohosts “Fireground Strategies and Other Stuff from the Street” on fireengineeringradio.com. Avillo received the 2012 Fire Engineering/ISFSI George D. Post Instructor of the Year Award.
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