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December 2003: Wildfires

Wildfires have always been a concern in the United States. There have been recent wildfires in California, Arizona, New Mexico and Florida.

Wildfires can cause ignition to a building by: flying embers landing and igniting exposed combustible portions of the building, fire spreading right up to the walls of the building, and heat radiating from the fire that ignites exposed combustibles (construction or occupancy).

Wildfire exposure can be lessened by looking at several factors:

Terrain and Landscaping

Create an open area around the buildings, outdoor structures, and yard storage by reducing the numbers of trees and shrubs so that there is not a continuous line of vegetation to the buildings. It is not necessary to remove all trees within the area, but the trees should not overhang the buildings or other important structures. The size of the area should increase with the steepness of the slope around the building.

Plants with high water or salt content or low amounts of volatile oils generally have low flammability. Do not plant shrubs under trees or against buildings. Select smooth bark, rather than fibrous or rough bark trees, as these will not hold wind-blown sparks.

Before and during the fire danger season, pay particular attention to maintaining a zone of fuel reduced vegetation. Remove dead tree parts debris in and around the trees; remove trees or prune limbs that overhang buildings; and prune lower branches of trees and shrubs and remove vegetation beneath to provide a vertical firebreak.

Prior to any changes in landscaping, the various jurisdictional authorities should be contacted for potential environmental impacts.

Construction

Steel sheeting on exterior walls should be insulated with mineral wool to reduce the heat transfer. If timber is used, it should be made fire retardant, and have smooth fire-retardant painted surfaces to minimize areas where sparks may lodge.

Combustible walls can be protected with outside sprinkler protection as an alternative to replacing the combustibles or covering with noncombustible sheeting. They should be arranged to operate automatically unless the location is constantly attended and the Emergency Organization (EO) can open the valve.

Make roofs of continuous sheet materials that fit tightly with no gaps, or gaps filled with fire resistant materials. Seal the rib opening of metal roof decks at the eave and ridge with fire resistant materials.

Replace existing roofs having wood shingle covers. Make existing terracotta and concrete tiles covers tolerable by filling all gaps with sand/cement mortar.

If timber framing is used and the beams extend outside the walls to form canopies or eaves, the beams should be encased with a noncombustible sheet material.

Provide openings to underfloor void spaces, vents in the walls or roofs, weep holes in brickwork walls, and chimneys openings with screens.

Exterior doors should automatically close. The doors and frames should have a minimum one-hour fire rating. Gaps around the door should be sealed. Glazed doors should use wire glass.

Protect windows and frames with one-hour fire rated shutters. The shutters should be strong enough to withstand the impact of flying debris, high radiant heat, and short-term flame contact. Outside sprinklers are not an alternative to fitting shutters to windows.

Skylights should be made of wire glass and be provided with noncombustible covers. Steel covers should be insulated with fire resistant materials. Replace existing plastic skylights.

Occupancy

Avoid combustible yard storage, which will be ignited by a wildfire and expose the building. If yard storage is unavoidable then keep it to the minimum levels possible, maintain space separation between the yard storage and any building regardless of construction, and separate the storage into small blocks with space separation. Do not store under awnings or platforms.

Human Element

Train and equip the EO to deal with a wildfire emergency. Additional fire fighting team members are needed as compared to a ''normal'' industrial EO as the public fire service may not be able to assist due to the large number of properties that may be exposed by the wildfire.

Access restriction by authorities or EO members responding to their exposures at their residences may not allow the members to respond to wildfires exposing the building.

If you would like further information regarding wildfires, please contact Risk Logic Inc.