Embers and small flames are the main way that the majority of homes ignite in wildfires. Embers are burning pieces of airborne wood and/or vegetation that can be carried more than a mile through the wind. They can cause spot fires and ignite homes, debris and other objects.
There are methods for homeowners to minimize the likelihood of flames or surface fire touching the home.
What is the Home Ignition Zone?
Homes ignite due to the condition of the home and everything around it, up to 200’ from the foundation. This is called the Home Ignition Zone (HIZ).
The concept of the home ignition zone (HIZ) was developed by retired USDA Forest Service fire scientist Jack Cohen in the late 1990s, following some breakthrough experimental research into how homes ignite due to the effects of radiant heat.
The HIZ is divided into three zones:
Immediate zone
The home and the area 0-5 feet from the furthest attached exterior point of the home; defined as a non-combustible area.
Science tells us this is the most important zone to take immediate action on as it is the most vulnerable to embers. START WITH THE HOUSE ITSELF then move into the landscaping section of the Immediate Zone.
- Clean roofs and gutters of dead leaves, debris and pine needles that could catch embers.
- Replace or repair any loose or missing shingles or roof tiles to prevent ember penetration.
- Reduce embers that could pass through vents in the eaves by installing 1/8 inch metal mesh screening.
- Clean debris from exterior attic vents and install 1/8 inch metal mesh screening to reduce embers.
- Repair or replace damaged or loose window screens and any broken windows Screen or box-in areas below patios and decks with wire mesh to prevent debris and combustible materials from accumulating.
- Move any flammable material away from wall exteriors – mulch, flammable plants, leaves and needles, firewood piles – anything that can burn. Remove anything stored underneath decks or porches.
Intermediate zone
5-30 feet from the furthest exterior point of the home.
Landscaping/hardscaping- employing careful landscaping or creating breaks that can help influence and decrease fire behavior.
- Clear vegetation from under large stationary propane tanks.
- Create fuel breaks with driveways, walkways/paths, patios, and decks.
- Keep lawns and native grasses mowed to a height of four inches.
- Remove ladder fuels (vegetation under trees) so a surface fire cannot reach the crowns. Prune trees up to six to ten feet from the ground; for shorter trees do not exceed 1/3 of the overall tree height.
- Space trees to have a minimum of eighteen feet between crowns with the distance increasing with the percentage of slope.
- Tree placement should be planned to ensure the mature canopy is no closer than ten feet to the edge of the structure.
- Tree and shrubs in this zone should be limited to small clusters of a few each to break up the continuity of the vegetation across the landscape.
Extended zone
30-100 feet, out to 200 feet.
Landscaping – the goal here is not to eliminate fire but to interrupt fire’s path and keep flames smaller and on the ground.
- Dispose of heavy accumulations of ground litter/debris.
- Remove dead plant and tree material.
- Remove small conifers growing between mature trees.
- Remove vegetation adjacent to storage sheds or other outbuildings within this area.
- Trees 30 to 60 feet from the home should have at least 12 feet between canopy tops.
- Trees 60 to 100 feet from the home should have at least 6 feet between the canopy tops.
Before a wildfire threatens your area…
In and around your home
- Clear leaves and other debris from gutters, eaves, porches and decks. This prevents embers from igniting your home.
- Remove dead vegetation and other items from under your deck or porch, and within 10 feet of the house.
- Screen or box-in areas below patios and decks with wire mesh to prevent debris and combustible materials from accumulating.
- Remove flammable materials (firewood stacks, propane tanks) within 30 feet of your home’s foundation and outbuildings, including garages and sheds. If it can catch fire, don’t let it touch your house, deck or porch.
- Wildfire can spread to tree tops. Prune trees so the lowest branches are 6 to 10 feet from the ground.
- Keep your lawn hydrated and maintained. If it is brown, cut it down to reduce fire intensity. Dry grass and shrubs are fuel for wildfire.
- Don’t let debris and lawn cuttings linger. Dispose of these items quickly to reduce fuel for fire.
- Inspect shingles or roof tiles. Replace or repair those that are loose or missing to prevent ember penetration.
- Cover exterior attic vents with metal wire mesh no larger than 1/8 inch to prevent sparks from entering the home.
- Enclose under-eave and soffit vents or screens with metal mesh to prevent ember entry.
Creating an emergency plan
- Assemble an emergency supply kit and place it in a safe spot. Remember to include important documents, medications and personal identification.
- Develop an emergency evacuation plan and practice it with everyone in your home.
- Plan two ways out of your neighborhood and designate a meeting place.
- Learn more about emergency preparedness planning (Everbridge link here).
During the time a wildfire is in your area…
- Stay aware of the latest news and updates from your local media and fire department. Get your family, home and pets prepared to evacuate.
- Place your emergency supply kit and other valuables in your vehicle.
- Move patio or deck furniture, cushions, door mats and potted plants in wooden containers either indoors or as far away from the home, shed and garage as possible.
- Close and protect your home’s openings, including attic and basement doors and vents, windows, garage doors and pet doors to prevent embers from penetrating your home.
- Connect garden hoses and fill any pools, hot tubs, garbage cans, tubs, or other large containers with water. Firefighters have been known to use the hoses to put out fires on rooftops.
- Leave as early as possible, before you’re told to evacuate. Do not linger once evacuation orders have been given. Promptly leaving your home and neighborhood clear roads for firefighters to get equipment in place to fight the fire, and helps ensure residents’ safety.
Please see other articles on this site for more information or visit the Nation Fire Protection Agency website.
