Fighting Interface Fires: A Review

SUDDENLY, IT’S ALL AROUND YOU, UNDER YOU, above you! You’ve trained, you’ve drilled, and you’re ready for whatever this monster throws at you. The “monster” is the fire in the wildland/urban interface (WUI) or the I-Zone. If you live or work where manmade improvements are in proximity to forested, brush-covered, or grass lands, it’s probably a good idea to read on, even if only to refresh your already perfect competence.

If you have been cultivating cobwebs in the I-Zone section of your brain, this may help clean out some of them. We’ll look at the aspects of safety, actions, and considerations en route to and at the incident, resources, attack modes, and the generally accepted criteria for throwing in the towel on a structure you’ve chosen to defend.

One pet peeve of mine is to have the concept of “safety first” buried somewhere in the back pages, or approached as an afterthought. Here, we will begin with safety, first, (a novel idea) with the acknowledgement that you need to be thinking safety before, during, and after an incident-including one in the I-Zone. It is also assumed that you trained to be safe as well as to recognize behaviors that are not safe.


Not too many years ago, we trained, drilled, and frequently tested on the Ten Standard Fire Orders (10s), 18 Watch Out Situations (18s), six Common Denominators of Tragedy Fires, seven Downhill and Indirect Firefighting Guidelines, and a litany of other rules of engagement. The situations stressed in the 10s and 18s have been effectively considered and consolidated into LCES: Lookouts, Communications, Escape Routes, and Safety Zones. All personnel must commit LCES to memory.

  • Post lookouts whenever there is known or potential danger. Lookouts must be experienced and knowledgeable and be able to communicate with those they are looking out for. Lookouts need to be in a position to see the hazards and the firefighters and warn firefighters of hazards that become dangers. Multiple lookouts may be needed because of incident size, terrain, fuels, or fire behavior.
  • Communications are critical to incident safety. Prior to deployment, a briefing should be conducted to communicate safety issues, incident objectives, strategy and tactics, command and tactical frequencies, resource assignments, and other important factors. Personnel must be able to warn others of approaching danger, changes in tactics, and other situation status information.
  • Preplan escape routes, preferably at least two, in case conditions worsen and your primary route of escape is compromised. Identify, flag if necessary, and communicate escape routes to all personnel. This component of LCES can be quite dynamic; it must be constantly reevaluated. Escape routes must lead to a safety zone.
  • A safety zone is an area of refuge of sufficient size and favorable topography to protect firefighters without their having to deploy fire shelters. Consider proximity fuels, slope, wind, and fire intensity and behavior when establishing safety zones.

If you are unable to put any portion of LCES into action (insufficient resources, inadequate communications capabilities, or fuels or topography or fire behavior that precludes establishing patent escape routes or safety zones), you need to pull back and reassess your options and your risk analysis. Remember, no stand of grass, brush, or timber is worth losing a life over.

Other safety considerations include the following:

  • Taking refuge in a structure, vehicle, or fire shelter. Train and drill on each of these topics regularly.
  • Completing briefings. Ensure that you have given all the necessary information to your subordinate and adjacent forces and that you have received answers to all of your questions regarding the assignment and the incident.
  • Not underestimating the effects of radiant heat, dehydration, and exhaustion on your firefighters.
  • Driving safely. Too many vehicle-related incidents occur, distracting from the original emergency. They include accidents caused by excessive speed, poor visibility, inadequate roadway widths, heights, surfacing, and bridge load limitations.


Most of these considerations are related to the environment and are components of the bigger picture to be assessed while you are en route.


  • What is the temperature?
  • Relative humidity?
  • Wind speed and direction?


  • Type and size (i.e., six-inch-tall grass vs. 20-foot-tall brush)?
  • Arrangement-are fuels continuous or sparse?
  • Fuel moisture-is the fuel dead or alive?


  • Aspect (North, South, East, West)?
  • Slope?
  • Chimneys and saddles?
  • Natural or manmade barriers (roads, streams, rock outcroppings, for example)?


  • Location?
  • Travel time (and turnaround time for water supply if applicable)?
  • Limitations (topography, bridges, fences, cul-de-sac streets)?
  • Hazards (crime scenes, hazmats, power lines down, bee colonies, big dogs, booby-trapped marijuana gardens)?

Smoke column:

  • Is the smoke rising straight up, signaling unstable atmospheric conditions, and how might that affect fire behavior?
  • Is wind holding the column to the ground?
  • Is the size of the column changing, indicating rapid growth or multiple heads?
  • What is the color of the smoke? Lighter (white, light gray) colors indicate vegetation burning; a sudden change to brown or black indicates a change in the type of fuel being consumed, such as a structure, a vehicle, or a pile of tires.


Properly analyzing the incident will often be your biggest challenge, especially if you can’t see the entire fire and don’t know what is in its path. Street maps, global positioning systems, topographic maps, preplans, aerial maps, and local knowledge can be indispensable. If a local wants to tell you about the last time a fire came through, listen. Knowledge of fire behavior history at a particular location can be like déjà vu.

Size-up. Gathering information is required to formulate the plan.

  • How far has the fire traveled in a given period of time (say, from dispatch time to arrival time)? This in itself is considered fire history and can be used to estimate the fire’s forward progression or rate of spread (ROS) (Table 1).
  • Fire intensity (flame lengths), fuels burning, spot fire propagation-this information will help you decide the strategy, tactics, and resource needs.
  • Smoke conditions on the ground and in the column, up close and personal.
  • Conduct structure triage.
  • Revisit the threat estimate:
    -How many structures?
    -How much prep time do you have?
    -How hard will the fire hit? From where? How long will it last?
  • Identify key information for incoming resources.

Structure triage. The need to triage is usually the result of having many more structures threatened than you have firefighting resources to protect them. Consider the following:

  • Distribution/arrangement of structures;
  • Construction type, roof flammability, siding, openings, appurtenances;
  • Vegetation clearance/defensible space;
  • Presence of residents
    -threat of panic
    -traffic control issues
    -safe refuge area;
  • Threat estimate (see above); and
  • Prioritization: eliminate the indefensible, ignore those not immediately threatened, and deal with the rest.


For I-Zone deployment, you will need primarily fire engines, time, and water.


  • For isolated residences, you will need one engine per residence.
  • For homes with common access (less than 50 feet apart), you can usually manage with one engine per two residences.
  • For multifamily dwellings, plan on two to three engines per structure, depending on size, construction, and complexity.
  • Consider keeping one engine unassigned for use as a “floater.”


  • Average time committed per site is 20 to 40 minutes.
  • Additional time may be needed for heavy fuels or firebrand threats.
  • Time may also be required for the fire to clear your exit.


  • Approximately 200 gallons per residence, more for heavy fuels. Reserve 100 gallons in your tank, if possible.
  • The math works out so that your average water consumption will be about 400 to 800 gallons per hour/per engine.
  • Consider assigning a water tender to each engine strike team.

Other resources you should take into account include the following:

  • Bulldozers for line construction, improving access, and constructing safety zones.
  • Hand crews for line construction, defensible space clearance, and firing operations.
  • Law enforcement for traffic, crowd control, and evacuations.
  • Aircraft: Know the capabilities of fixed- and rotor-winged resources. Remember to place a “no divert” on the aircraft for a bona fide life threat.
  • Other: Office of Emergency Services, disaster relief organizations, utility companies, animal control, for example.


There are three basic attack modes to help you define your strategy and put your plan together.

  • Offensive. Also known as putting out the fire Here, you don’t have any control of the main fire (such as in extreme wind events), so you focus on saving structures.
  • Combination. This can be described as having a part of the main fire controlled and/or when your defensive actions will create a control line.

If one of these three attack modes won’t work for your situation, perhaps NO ACTION is your attack mode of choice and, given the circumstances of the incident, may well be your best option. Please be clear on this here: NO ACTION is a conscious decision based on good information, not the failure to make a decision.


The following circumstances and situations may cause you to designate a structure as “indefensible” (the politically incorrect term is “loser”).

  • If the fire is making sustained runs in live fuels and you have poor defensible space.
  • If there are more spot fires appearing than you can easily control.
  • If the water supply will not sustain as long as the threat will.
  • If the fire environment is untenable and escape routes are cut off or unusable.
  • If more than one-half of the roof is involved and there are high winds.
  • If there is an interior structure fire, windows are broken, and there are high winds.
  • If property owners or residents have not provided defensible/survivable space around structures for firefighters.


Chances are that there are more structures threatened than you have resources available. Wildfire, whether in the WUI or the outback, gives limited discretionary time to plan or organize. The fire drives all other activities, and nonwildfire problems and issues develop incidental to the fire. If you are a good multitasker, you’ll find yourself with a dynamic challenge. If multitasking is not your strong suit, these challenges may well feel like uncontrolled stressors. Good training coupled with good incident intelligence will assist you in making and implementing sound decisions.

SUZANNE TODD, a 30-year veteran of the fire service, is a battalion chief for CALFIRE. She is a graduate of the National Fire Academy’s Executive Fire Officer Program. She has taught and lectured extensively on fire suppression, hazmat, and EMS and was an instructor in the I-Zone programs at FDIC.

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