Wildland fires are often described as being driven by supernatural forces when in fact they move in a predictable manner. Fires spread in the presence of three requirements for combustion: fuel, heat, and oxygen. In the wildland urban interface where wild and developed areas meet, the home is considered the fuel and the heat comes from the materials surrounding the home or from firebrands that land on the home. In addition to wildland fuels, the potential heat sources near the home include landscape vegetation, lawn furniture, decking, woodpiles, and even your neighbors home. We have the ability to alter the requirements for combustion near the home by removing the fuel (reducing the flammability of the home) and reducing the heat (managing the vegetation around our home). By eliminating one or more of the requirements for combustion near our home, we can effectively stop fires from spreading from the wildlands to our homes.

Homes ignite from three potential sources during a wildland fire: indirectly from the radiant heat of the fire, directly from the flames of the fire, or from firebrands that land on the home. While it is important to ensure flames do not come in direct contact with the home, research indicates that most homes do not ignite from radiant heat or directly from the main flaming front. Even during the most extreme fire events, it is low intensity surface fires that ignite the base of the structure or firebrands that land on the structure that cause a majority of the home losses. Therefore, it is important to reduce the ignitibility of the home from all potential heat sources, even those that may appear insignificant, if we want the home to survive during a wildland urban interface fire.

The ignition potential of a home depends upon the home's fuel characteristics (construction) and the heat sources immediately surrounding the home. This area is called the Home Ignition Zone (HIZ) and extends from 100-200 feet in all directions from the home. It is important to recognize that the entire HIZ does not have to be treated, but instead it represents an area that must be considered when evaluating home ignitibility. It is the relationship between the home and the material surrounding the home that is important and this relationship ultimately determines what treatments are required. The HIZ includes heat sources surrounding the home in all directions and, for most of us, this includes neighboring homes and property. All heat sources within the HIZ must be considered since many home losses during wildland urban interface fires are caused by home to home ignition. Working with your neighbors is critical when mitigating home ignitibility. Cooperation, compromise, and respect for property rights is required when attempting to mitigate heat sources outside our property boundaries.

The standard Firewise recommendations will produce an acceptable home ignition zone, but it is important to consider the process of ignition when deciding what treatments to implement. The initial and primary focus should be to the structure itself. Fire resistant roofs and sidings should be used and all external openings should be eliminated to reduce the potential for firebrands to enter the home or attic. Tempered glass, double pane windows, and metal screens are recommended and all vents or other openings should be covered by with 1/8 inch or smaller metal screen. The roof, windows, and walls should be kept in good repair and the roof and gutters should be kept free of debris.

Anything attached to the home should be considered a part of the home and often decks and fences increase the vulnerability of a home. Large timbers or fire resistant alternatives should be used when constructing decks. Debris commonly accumulates where the deck meets the house or under the deck and these areas should be enclosed or cleaned regularly. Wood fences can provide a fuel bridge from wildland vegetation to the home and should be replaced with non-flammable materials or the continuity of the fence can broken by adding masonry pillars or steel gates. A small lawn should be irrigated around the home or hardscaping installed to limit the potential for a surface fire on the lawn to ignite the home. Wood siding or decking should not directly contact ground vegetation. Non-flammable plants should be selected for landscaping and placed so that contact with the home is limited and lawn furniture should be evaluated for its flammability. Many of these options are expensive, and some are difficult to implement, but regular maintenance is one of the most critical components of reducing home ignitibility and costs very little.

Although the wildland urban interface is typically described as a location, it is more accurately characterized as a condition based on a home's ignitibility and can occur in areas with very little wildland vegetation. The goal within the wildland urban interface is not to stop fires but to stop the transition of fires from wildland vegetation to the urban environment. If this transition is stopped the wildland fires can be more effectively managed by fire management agencies without negative effects to the communities. It is the small things that determine the home ignitibility and the homeowner can effectively improve the ability of their home to survive in a wildland urban interface fire.