Plan of attack
Changing from an offensive to a defensive attack
NFPA Journal®, January/February 2008
An offensive attack on a fire is one of the most efficient ways to save lives and property and as such is preferable whenever it can be safely conducted. On arrival, a fire department may encounter conditions that require a defensive attack. However, there are instances when fire fighters must take part in both—when an attack that begins in an offensive mode is changed to a defensive attack due to deteriorating conditions.
Experienced Incident Commanders (ICs) recognize conditions indicating when the initial attack should be defensive or when changing conditions dictate a change in strategy. Defensive attacks are usually conducted when the building's structural integrity is questionable, fire conditions or other hazards prevent entry, or the risk to fire fighters is too great in terms of what can be saved.
It's essential that company and chief officers are proficient in applying risk-versus-benefit principles when making the offensive/defensive decision. When the fire is not immediately extinguished, building conditions often deteriorate to a point where occupant survival is improbable and structural collapse becomes more likely. When occupant survival is unlikely or when all building occupants have been safely evacuated, the life-safety benefit is no longer a factor. At this point the IC should reevaluate the risk-versus-benefit analysis. If a decision is made to continue an offensive attack when the occupants' lives are no longer in danger, the IC must closely monitor the extinguishment progress. If the fire continues to grow, a decision may be made to switch to a defensive strategy.
During an offensive attack the safety officer and IC may make a joint decision to "start the clock," meaning that, after a specified period of time, they will reevaluate the operation. If they determined that the fire is not being brought under control, the IC will call off the offensive attack and reposition fire fighters into a defensive mode. For example, the clock could be set at 10 minutes for a fire that is self-venting through the roof. During the 10-minute period the IC and safety officer closely monitor the situation, and if conditions warrant, could decide to change to a defensive attack at anytime. If units are successful in containing the fire within 10 minutes, the operation will probably continue in the offensive mode. However, if the total volume of fire is not significantly reduced after 10 minutes, a change in strategy to a defensive attack will be initiated.
Changing from an offensive to a defensive strategy is often a test of the IC's management skills. Whenever possible a managed retreat is preferred over a "drop everything and run" emergency retreat. During a managed retreat, units assigned to search and rescue, as well as other crews working above the fire, retreat to the outside or at least evacuate to a position below the fire, before hose streams are backed out of the building. However, there are times when an emergency retreat is necessary, such as when a building collapse is imminent.
When "starting the clock," the IC should assign someone to the planning section to develop a plan to redeploy companies, apparatus, and equipment. If conditions indicate the possibility of a catastrophic building collapse, all personnel and apparatus should be placed beyond the collapse zone, which is usually 1.5 times the height of the building. In a multistory building the calculated collapse zone could be a considerable distance, sometimes exceeding the width of the street and beyond the effective reach of master streams. Therefore, at times safely and effectively applying water to the building of origin may not be possible. This may lead to a nonattack decision, in which the building of origin is written off as a total loss in favor of protecting exposures.
A defensive attack generally requires fewer personnel than an offensive attack. Therefore, fire fighters may not be assigned to a specific task once defensive streams are in position. When this is the case, unassigned fire fighters have a tendency to take action and freelance. Often this freelancing involves redeploying handheld hose lines that were used during the offensive attack. Many of the fires we studied show fire fighters standing near a structure that is in danger of collapse using a totally ineffective small diameter hose line.
Offensive and defensive strategies should never be conducted in the same building at the same time. However, there are times when a change in strategy is necessary due to worsening conditions. When changing strategies from offensive to defensive, it is imperative that the IC maintains control and creates a plan for a smooth and safe transition.
This column is adapted from the book Structural Fire Fighting and Tactics, Second Edition, available at www.nfpa.org or (800) 344-3555.