Wednesday, May 11, 2011

Safest, most effective Path of Least Resistance Pt. 4: Search & 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 (absolute path of least resistance and the most dangerous). Many victims are found near doors or windows, having been overcome by the products of combustion that are also looking to follow these same paths. Alternate paths of egress do not take advantage of the paths of least resistance, and as a result, take more time to get out and are far more dangerous, both to the victim and the firefighter. They also take more time. It is much easier and safer to take a victim down the interior stairs than it is to get them down 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.

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 where paths of least resistance are in advance will save valuable time and will allow rescue teams to focus in on critical areas early in the operation.

One of the most dangerous operations conducted on the fireground are vent, enter, search (V.E.S) operations whereby firefighters utilize 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. This firefighter created path also creates a potentially deadly situation due to the fact that a path of least resistance for products of combustion opposite the attack line has also been created by the open entry window. For this reason, it is critical that the first action taken by firefighters on V.E.S. missions is to create a barrier between themselves and the fire and the attack team by closing the door to the room that they have entered. If this is not done, fire and the products of combustion can be driven by hose streams toward the open entry window, possibly incinerating the firefighter.

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 there was a rear door leading from the cellar to the main living areas which was open. This was the path the search team took. 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, that being 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 as well as multiple fractures and internal trauma.

It is for this same reason that firefighters should never attempt to enter a fire building via the bulkhead door and stairway from the roof or utilize 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.

Safest Most Effective Path of Least Resistance pt 3: 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.

Contiguous structures with common cocklofts are often destroyed by inadequate ventilation, caused by a failure to take advantage of the most effective path of least resistance. This failure can be often 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 for 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 as 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.

Lack of ventilation can also cause fire forces to be chased out 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, leaving the products of combustion (and steam) no way out of the structure, the products of combustion will be forced to take the path of least resistance out of the structure, which will now be via the entry point of the attack team. Many firefighters have suffered burn injuries and many buildings have been needlessly destroyed due to this lack of coordination and support.

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, it may be overwhelmed by fire and heat being blown at them. In this case, the team may have to retreat to the safety of a stairwell while a master stream is used from the outside to knock down the fire, taking advantage of the wind-created path of least resistance. Uncoordinated exterior lines can have the same effect. This is why opposing streams and interior/exterior attacks are so dangerous. Exterior lines, which are usually larger, will always overpower smaller interior lines.