How do firefighters decide how to attack a building fire?

The incident commander, usually the first officer on scene, sizes up the fire and chooses a strategy: offensive, defensive, or a transition between the two. The choice rests on whether anyone may still be alive inside, how big the fire is, the state of the structure, and the water and personnel available. The decision is not made once. It is checked repeatedly as conditions change. [1] [2]

A Phoenix fire department document says size-up, risk management and the rescue profile drive strategy. It lists the factors command considers: the rescue profile of occupants, fire and smoke volume, fire extent, structural conditions, ingress and egress, smoke conditions and ventilation, and available resources. In this framework an offensive strategy puts crews inside the hazard zone, while a defensive strategy attacks from outside it and works to stop spread to neighboring buildings. [1]

A Carroll County, Maryland procedure names three main factors. Water supply matters because a lack of a reliable source limits an offensive attack. Personnel matter because crews are needed for backup tasks such as a two-out team, backup hoselines, ladders and ventilation. Structural condition matters too, including construction type, occupancy, level of involvement and the building's prior condition. [2]

The first-arriving officer also has to gather information such as construction, contents, fire load, access, emergency exits and the estimated time since ignition, and judge which way the fire is likely to spread. [3]

Firehouse lists conditions that call for an exterior, defensive operation: a fire beyond the control of handheld hoselines, heavy fire with no civilians in the building or no one who could still be alive, too few resources, an inadequate water supply, lightweight structural components, or risk to firefighters that outweighs the gain. The article adds that commanders must be ready to write off parts of a building, or all of it, if it is beyond saving. Concentrating on a lost building leads to chasing the fire, while realistic goals about what can be saved reduce losses. [4]

Transitional modes combine the two approaches. Firehouse gives the example of a heavily involved house where a report of trapped people still allows an interior attack, with hoselines protecting the search crews, while the commander expects to go defensive once rescues are done. A switch from offensive to defensive can also be forced by worsening fire, structural failure, collapse indicators or reports of no progress. [4]

FireRescue1 describes this as an observe, orient, decide, act loop. After acting, the commander looks for benchmarks such as smoke changing from black to gray to white with less heat and push, and for warning signs such as new smoke at the roofline or heat in void spaces. Commanders often prepare backup plans in advance, so a change of strategy, repositioning of crews or a call for more resources can be made quickly. [3]

The Phoenix document likewise says command must declare the strategy initially and keep confirming it against benchmarks and elapsed-time notifications. [1]