In a wildfire burning embers transported downwind are what cause most structures to burn

Sheltering from the Creek Fire at the Mammoth Pool Reservoir
Sheltering from burning embers and the Creek Fire at the Mammoth Pool Reservoir Boat Launch, Sept. 5, 2020. Photo by Cameron Colombero, via Mike Ikahihifo.

Most structures that burn in a wildfire are not ignited by direct flame impingement, but by burning embers that are lofted and carried downwind ahead of the fire.  At Wildfire Today we first covered the role of embers in igniting structures in 2010, a concept brought into the public consciousness by Jack Cohen, a researcher at the Missoula Fire Science Lab. To reduce the chances of a home burning in a wildfire, the most bang for the buck is to concentrate on the Home Ignition Zone. The flammable material near the structure needs to be modified, reduced, or eliminated to the point where multiple burning embers landing in the zone will not propagate the fire and spread to the structure.

The video below produced by the New Jersey Forest Fire Service elaborates on this concept. It is queued up to 1:42 where the issue is addressed.

More information is in our articles tagged “Home Ignition Zone.”

Bill introduced to promote prescribed fire intends to reduce fire risk

It would appropriate $300M annually for the federal land management agencies’ prescribed fire programs. But are there other ways to reduce fire risk?

September 24, 2020 | 8:10 a.m. MDT

Prescribed fire at Chickasaw National Recreation Area
Prescribed fire at Chickasaw National Recreation Area in Oklahoma by M. Fidler, February, 2013.

A bill has been introduced in the U.S. Senate that would make large sums of money available to increase the number of acres treated with prescribed fire (also known as controlled burns).

It has been fashionable during the last two years to blame “forest management” for the large, devastating wildfires that have burned thousands of homes in California. According to a 2015 report by the Congressional Research Service the federal government manages 46 percent of the land in California. The California Department of Forestry and Fire Protection manages or has fire protection responsibility for about 30 percent.

Research conducted in 2019 to identify barriers to conducting prescribed fires found that in the 11 western states the primary reasons cited were lack of adequate capacity and funding, along with a need for greater leadership direction and incentives. Barriers related to policy requirements tended to be significant only in specific locations or situations, such as smoke regulations in the Pacific Northwest or protecting specific threatened and endangered species.

The National Prescribed Fire Act of 2020, Senate Bill 4625, which was introduced last week by Senator Ron Wyden of Oregon and two cosponsors, would help address the capacity issue by appropriating $300 million for both the Forest Service and the Department of the Interior (DOI) to plan, prepare, and conduct controlled burns on federal, state, and private lands. It would also provide $10 million for controlled burns on county, state and private land that are at high risk of burning in a wildfire. Additionally, the bill establishes an incentive program that would provide $100,000 to a State, county, and Federal agency for any controlled burns larger than 50,000 acres. (Summary and text of the bill)

In order to carry out the projects, the legislation would establish a workforce development program at the Forest Service and Department of the Interior to develop, train, and hire prescribed fire practitioners, and creates employment programs for Tribes, veterans, women, and those formerly incarcerated.

In an effort to address air quality control barriers,  the bill “Requires state air quality agencies to use current laws and regulations to allow larger controlled burns, and give states more flexibility in winter months to conduct controlled burns that reduce catastrophic smoke events in the summer.” The legislation will allow some prescribed fire projects larger than 1,000 acres to be exempt from air quality regulations.


Our Take

Appropriating more funds and hiring additional personnel for conducting prescribed fires could definitely result in more acres treated. If the bill passes, it would be a large step in the right direction. It is notable that the bill specifically mentions hiring those who were formerly incarcerated. Those who served time for non-violent offenses often deserve another chance, especially if they learned the firefighting trade on a state or county inmate fire crew.

There are many benefits of prescribed fires, including more control over the adverse health effects of smoke, improving forest health, and returning fire to dependent ecosystems.

But it gets complicated when prescribed fire is expected to “…help prevent the blistering and destructive infernos destroying homes, businesses and livelihoods”, as cited in a release issued last week by the Senate Committee on Energy and Natural Resources.

One provision of the bill is poorly worded and is confusing. In Section 102 it is either saying that no later than September 30, 2022 every unit of the USFS, FWS, NPS, and BIA must conduct a prescribed fire larger than 100 acres, possibly only applying to units west of the 100th meridian. Or, it might be interpreted as meaning each unit larger than 100 acres must conduct at least one prescribed fire. But either way it is ridiculous and arbitrary. Some 100-acre units might never be suitable for prescribed fire. Planning to use fire as a tool is based on science and the determination that treating an area with fire is PRESCRIBED in order to accomplish a number of specific objectives, not well-meaning but possibly detrimental legislation.

Scenario #1, Moderate fire conditions

There is no doubt that if a wildfire is spreading under moderate conditions of fuels and weather (especially wind), when the blaze moves into an area previously visited by any kind of fire the rate of spread, intensity, and resistance to control will decrease. Firefighters will have a better chance of stopping it at that location. The size of that earlier fire footprint will be a factor in the effectiveness of stopping the entire fire, since the wildfire may burn through, around, or over it by spotting. The availability of firefighting resources to quickly take advantage of what may be a temporary reduction in intensity is also critical. Unless the prescribed fire occurred within the last year or so there is usually adequate fuel to carry a fire (such as grass, leaves, or dead and down woody fuel) depending on the vegetation type and time of year. It is much like using fire retardant dropped by air tankers. Under ideal conditions, the viscous liquid will slow the spread long enough for firefighters on the ground to move in and put out the fire in that area. If those resources are not available, the blaze may eventually burn through or around the retardant.

Scenario #2, Extreme fire conditions

The wildfires that burn hundreds or thousands of homes usually occur during extreme conditions. What the most disastrous fires have in common is drought, low fuel moisture, low relative humidity, and most importantly, strong wind. In the last few weeks in California and Oregon we have seen blazes under those conditions spread for dozens of miles in 24 hours.

Rich McCrea, the Fire Behavior Analyst on the recent North Complex near Quincy, CA, said the wind on September 8 pushed the fire right through areas in forests that had been clear cut, running 30 miles in about 18 hours.

We can’t log our way out of the fire problem.

Sheltering from the Creek Fire at the Mammoth Pool Reservoir
Burning embers lofted by the Creek Fire are seen as people are sheltering at the Mammoth Pool Reservoir Boat Launch, Sept. 5, 2020 in Northern California. Photo by Cameron Colombero, via Mike Ikahihifo.

On September 8, 2020 the Almeda Drive Fire burned 3,200 acres in Southern Oregon — it was not a huge fire, but there were huge losses. The 40 to 45 mph wind aligned with the Interstate 5 corridor as it burned like a blowtorch for 8 miles, starting north of Ashland and tearing through the cities of Talent and Phoenix. Approximately 2,357 structures were destroyed — but not all by a massive flaming front. Burning embers carried up to thousands of feet by the fire landed in receptive fuels near or on some structures, setting them alight.

structures burned Almeda Drive Fire Phoenix Talent Oregon
A portion of the Almeda Drive Fire in the area of Phoenix and Talent in southern Oregon. Screenshot from video shot by Jackson County on September 8, 2020.

What can be done to reduce fire losses?

Jack Cohen is a retired U.S. Forest Service Research fire scientist who has spent years determining how structures ignite during extreme wildfires. In a September 21, 2020 article he wrote for Wildfire Today with Dave Strohmaier, they addressed how homes ignite during extreme wildfires.

“Surprisingly, research has shown that home ignitions during extreme wildfires result from conditions local to a home. A home’s ignition vulnerabilities in relation to nearby burning materials within 100 feet principally determine home ignitions. This area of a home and its immediate surroundings is called the home ignition zone (HIZ). Typically, lofted burning embers initiate ignitions within the HIZ – to homes directly and nearby flammables leading to homes. Although an intense wildfire can loft firebrands more than one-half mile to start fires, the minuscule local conditions where the burning embers land and accumulate determine ignitions. Importantly, most home destruction during extreme wildfires occurs hours after the wildfire has ceased intense burning near the community; the residential fuels – homes, other structures, and vegetation – continue fire spread within the community.

“Uncontrollable extreme wildfires are inevitable, however, by reducing home ignition potential within the HIZ we can create ignition resistant homes and communities. Thus, community wildfire risk should be defined as a home ignition problem, not a wildfire control problem.”

"Community wildfire risk should be defined as a home ignition problem, not a wildfire control problem." Jack Cohen and Dave Strohmaier.

Again, prescribed fire has many benefits to forests and ecosystems, and Congress would be doing the right thing to substantially increase its funding.

But in order to “…help prevent the blistering and destructive infernos destroying homes, businesses and livelihoods”, we need to think outside the box — look at where the actual problem presents itself. The HIZ.

I asked Mr. Cohen for his reaction to the proposed legislation that he and I were not aware of when the September 21 article was published.

“Ignition resistant homes, and collectively communities, can be readily created by eliminating and reducing ignition vulnerabilities within the HIZ,” Mr. Cohen wrote in an email. “This enables the prevention of wildland-urban fire disasters without necessarily controlling extreme wildfires. Ironically, ignition resistant homes and communities can facilitate appropriate ecological fire management using prescribed burning. The potential destruction of homes from escaped prescribed burns is arguably a principal obstacle for restoring fire as an appropriate ecological factor. Therefore, it is unlikely that ecologically significant prescribed burning at landscape scales will occur without ignition resistant homes and communities.”

Here are some suggestions that could be considered for funding along with an enhanced prescribed fire program.

  • Provide grants to homeowners that are in areas with high risk from wildland fires. Pay a portion of the costs of improvements or retrofits to structures and the nearby vegetation to make the property more fire resistant. This could include the cost of removing some of the trees in order to have the crowns at least 18 feet apart if they are within 30 feet of the structures — many homeowners can’t afford the cost of complete tree removal.
  • Cities and counties could establish systems and procedures for property owners to easily dispose of the vegetation and debris they remove.
  • Hire crews that can physically help property owners reduce the fuels near their homes when it would be difficult for them to do it themselves.
  • Provide grants to cities and counties to improve evacuation capability and planning, to create community safety zones for sheltering as a fire approaches, and to build or improve emergency water supplies to be used by firefighters.

Our article “Six things that need to be done to protect fire-prone communities” has even more ideas.

Community destruction during extreme wildfires is a home ignition problem

burned homes
US Forest Service photo

By Jack Cohen and Dave Strohmaier

We must abandon our expectation that we can suppress 100% of wildfires and reject the false narrative that community protection requires wildfire control. Community wildfire disasters have only occurred during extreme conditions when high wind speed, low relative humidity, and flammable vegetation result in high fire intensities, rapid fire growth rates, and showers of burning embers (firebrands) starting new fires. Fire agencies primarily use wildfire suppression tactics for protecting communities from wildfires. But as we see from current extreme wildfire conditions in California, Oregon, and Washington, fire suppression can quickly become overwhelmed and ineffective.

Wildfires, and thus extreme wildfires, are inevitable. Does that mean wildland-urban (WU) fire disasters are inevitable as well? Absolutely not! WU fire research has shown that homeowners can create ignition resistant homes to prevent community wildfire disasters. How can that be possible?

aerial photo Paradise Camp Fire
Paradise, California, off Herb Lane near Skyway in Paradise. From Butte County drone mapping project. November, 2018.

Recall the destruction in Paradise, CA, during the extreme 2018 Camp Fire. Most of the totally destroyed homes in Paradise were surrounded by unconsumed tree canopies. Although many journalists and public officials believe this outcome was unusual, the pattern of unconsumed vegetation adjacent to and surrounding total home destruction is typical of WU fire disasters. In 2020 we see the same patterns of home destruction and adjacent unconsumed vegetation in photos from Malden, WA, and Phoenix, Talent, Blue River, and Mill City OR. Home destruction with adjacent unconsumed shrub and tree vegetation indicates the following:

burned home
U.S. Forest Service photo.
  • High intensity wildfire does not continuously spread through a residential area as a tsunami or flood of flame.
  • Unconsumed shrub and tree canopies adjacent to homes do not produce high intensity flames that ignite the homes; ignitions can be only from burning embers and low intensity surface fires.
  • The “big flames” of high intensity wildfires are not causing total home destruction.
structures burned Almeda Fire Phoenix Talent Oregon
The Almeda Drive Fire in the area of Phoenix and Talent in southern Oregon. Image by Jackson County, September 8, 2020.

Surprisingly, research has shown that home ignitions during extreme wildfires result from conditions local to a home. A home’s ignition vulnerabilities in relation to nearby burning materials within 100 feet principally determine home ignitions. This area of a home and its immediate surroundings is called the home ignition zone (HIZ). Typically, lofted burning embers initiate ignitions within the HIZ – to homes directly and nearby flammables leading to homes. Although an intense wildfire can loft firebrands more than one-half mile to start fires, the minuscule local conditions where the burning embers land and accumulate determine ignitions. Importantly, most home destruction during extreme wildfires occurs hours after the wildfire has ceased intense burning near the community; the residential fuels – homes, other structures, and vegetation – continue fire spread within the community.

Uncontrollable extreme wildfires are inevitable; however, by reducing home ignition potential within the HIZ we can create ignition resistant homes and communities. Thus, community wildfire risk should be defined as a home ignition problem, not a wildfire control problem. Unfortunately, protecting communities from wildfire by reducing home ignition potential runs counter to established orthodoxy.

There are good reasons to do “fuel treatments” for ecological and commercial objectives. But the greatest fuel treatment effect on wildfire behavior is within the fuel treatment area; fuel treatments do not stop extreme wildfires. So let’s call a spade a spade and not pretend that many, or even most fuel treatment projects actually reduce home ignition potential during extreme wildfires. Because local conditions determine home ignitions, the most effective “fuel treatment” addressing community wildfire risk reduces home ignition potential within HIZs and the community. Wildfires, exacerbated by climate change, will occur. Community destruction during extreme wildfires will continue as long as wildfire suppression remains the primary approach for community protection. Conducting the same ineffective strategy and tactics expecting different results will continue to be a recipe for disaster when it comes to protecting homes from extreme wildfire.

To make this shift, land managers, elected officials, and members of the public must question some of our most deeply ingrained assumptions regarding fire. For the sake of fiscal responsibility, scientific integrity, and effective outcomes, it’s high time we abandon the tired and disingenuous policies of our century-old all-out war on wildfire and fuel treatments conducted under the guise of protecting communities. Instead, let’s focus on mitigating WU fire risk where ignitions are determined – within the home ignition zone.

For further information:


Jack Cohen, PhD, retired US Forest Service Research fire scientist determined how structures ignite during extreme wildfires, created the home ignition zone concept, and co-developed NFPA Firewise USA.

Dave Strohmaier is Missoula County Commissioner. He previously worked for both the Bureau of Land Management and US Forest Service in fire management, and has published two books on the subject of wildfire in the West.

How to prevent your house from burning during a wildfire

We can benefit from Dr. Jack Cohen’s research

Above: Screenshot from the NFPA video below.

In light of the article posted earlier today reporting on Secretary Ryan Zinke’s order for the Department of the Interior to be more aggressive about conducting fuel treatment activities to better protect facilities from burning in a wildfire, this video is very appropriate.

Nobody knows more than Dr. Jack Cohen about why and how structures burn. He also knows what homeowners can do to make their homes fire resistant.

Before recently retiring, Dr. Cohen was a Fire Science Researcher with the U.S. Forest Service.

Is a little pre-fire mitigation around structures better than none?

According to experience from Colorado’s Fourmile Canyon Fire, sometimes the answer is “No”.

When Dave Lasky was leading the effort in the Four Mile Fire Protection District not far from Boulder, Colorado conducting pre-fire mitigation near structures, he and others assumed that doing SOMETHING, cutting trees and building slash piles, would be better than doing nothing. They realized it would not be the total solution in the wildland-urban interface (WUI), but when the Fourmile Canyon Fire started on September 2, 2010 the Fire Protection District found out how wrong they were.

Fourmile fire_map_MODIS_0418_9-8-2010
Map of the Fourmile fire near Boulder, showing heat detected by the MODIS satellite at 4:18 a.m. Sept. 8, 2010. Map by Wildfire Today and NASA.

After the ashes cooled, Dr. Jack Cohen, a U.S. Forest Service fire researcher who has investigated the effects on structures at numerous WUI fires, found what he has seen many times before (more details here). Most of the damaged homes, 83 percent in this case, ignited from airborne fire embers or surface fire spreading to contact the structure; not from high intensity crown fire or direct flame impingement.

The fuel reduction along travel corridors may have helped residents to evacuate, but the unburned slash piles, Mr. Lasky said, could have been a problem:

 In several areas, our crew’s piles were associated with complete stand mortality. We created ladders into the canopy. At best, these unburned piles represented a sad waste of money, and at worst, it is possible that if we hadn’t treated them, these stands might not have carried fire.

Below are excerpts from an article written by Mr. Lasky about what he learned. It first appeared at the website for Fire Adapted Communities Learning Network.


“Doing something is not better than doing nothing.
When the mitigation crew approached residents in the past, they often said, “I didn’t move up here to see my neighbors. I don’t want to cut trees.” In an effort to build momentum, we often performed work that we knew was not reflective of the best science, cutting fewer trees than we should have. This practice was in regard to both defensible space as well as shaded fuel-break projects. The hope was that as communities adjusted to the cosmetic changes, we’d be able to reenter and accomplish more.

“I still hear many colleagues say “let’s just get something done.” I believe this is wrong. We need to do it right or not do it at all. Half measures are proven to fail and engaging in them has great reputational costs. In the current climate of high-profile, catastrophic fires, I am not interested in fear mongering. But I am interested in applying our limited resources to only those communities that are fully committed.

“It’s not just about cutting trees in the wildland-urban interface.
Fuels crews are run by firefighters. Perhaps they should be run by architects. In retrospect, we spent far too much money on fuels reduction and not enough on assisting residents with the installation of fire-resistant building materials and landscaping. Few of the homes lost were directly impacted by crown fire; rather, embers undoubtedly ignited the fine fuels around them, which eventually led to the loss of entire structures. In many instances, residents would have been better served by our crew putting a decorative stone perimeter around the structure. Many residents are capable of cleaning gutters, but less can move tons of gravel. We had chainsaws, and we knew how to use them. We should have picked up our shovels instead.”

First National Legacy Award presented to Forest Service retiree

Above: Dr. Jack Cohen makes a presentation at the 2011 Fire Litigation Conference in San Diego. Photo by Bill Gabbert.

Dr. Jack Cohen received the first National Legacy Award given by the U.S. Forest Service, National Association of State Foresters, National Fire Protection Association, and International Association of Fire Chiefs in recognition of outstanding career-long contributions to wildfire mitigation as an alternative to suppression. Dr. Cohen helped develop the U.S. National Fire Danger Rating System and developed calculations for wildland firefighters’ safe zones; created defensible space principles, which resulted in the Firewise program; the Home Ignition Zone; and conducted research on ember ignitions and structure ignitability.

His research laid the groundwork for nearly all of today’s work on wildland urban interface risk reduction. Until his 2016 retirement, he was a research scientist at Missoula Technology and Development Center. The award was presented at the IAFC WUI Conference in Reno, Nevada.

Thanks and a tip of the hat go out to Robert.
Typos or errors, report them HERE.