Missoula science lab assists firefighters

Above: Screenshot from the Missoula Fire Sciences Lab presentation. USFS.

The U.S. Forest Service has produced a fancy “story map” about the science being conducted at the Fire Sciences Lab in Missoula, Montana. I have toured the facility but was not aware of the breadth of the work now being conducted in the Wind Tunnel & Combustion Chamber, Soils Lab, Chemistry & Emissions Lab, Ecophysiology Lab, Tree Ring Lab, and Fuels Lab.

The presentation, which only takes a few minutes to scroll through, is mostly photos with brief descriptions of the work going on in the various departments. With science under attack in recent years, it is heart warming to know that some federal employees in Missoula have our backs.

Missoula Fire Sciences Lab
Screenshot from the Missoula Fire Sciences Lab presentation. USFS.

Can southern California wildfire conflagrations be stopped?

Thomas Fire southern California, December 9, 2017
Thomas Fire in southern California, December 9, 2017. Photo by Kari Greer for the USFS.

While the residents of southern California await the wind event that will start Tuesday night bringing winds gusting in some areas at 75 to 85 mph along with single-digit humidity, someone might wonder, can wildfire conflagrations that occur in southern California during extreme conditions be stopped?

That topic has been discussed for many decades but it can be instructive to know the thoughts of scientists who study wildland fire as a profession.

One of the pioneers in the scientific study of fire behavior was Clive M. Countryman, a U.S. Forest Service researcher who four years after the disastrous fires of 1970 addressed the issue in a 16-page paper, “Can Southern California Wildland Conflagrations Be Stopped?”. Mr. Countryman reported that he was not able to develop “a radically new concept of suppression”, deciding instead that the best prospect is to reduce fuel energy output.

Thirty years later Marty Alexander, a Canadian wildfire researcher, took a close look at Mr. Countryman’s findings, came to a similar conclusion, and summarized the issue in a 2004 paper.

Attempting to redefine the common denominators of tragedy fires

“A Classification of US Wildland Firefighter Entrapments Based on Coincident Fuels, Weather, and Topography”

Above: Figure 1 from the research paper. Distribution of 166 US wildland firefighter entrapments that occurred within CONUS (1981–2017) by time of day (local time) and month of the year.

On October 9, 2019 a document was published that summarized the work of four researchers who sought to find commonalities that led to the entrapments of firefighters on wildland fires. The paper is titled, “A Classification of US Wildland Firefighter Entrapments Based on Coincident Fuels, Weather, and Topography.” Apparently they were hoping to confirm, fine tune, revise, or update the “Common Denominators of Fire Behavior on Tragedy Fires” defined by Carl C. Wilson after the 1976 Battlement Creek Fire where three firefighters were killed near Parachute, Colorado.

Mr. Wilson developed two lists, one with four items and another with five. Here is the five-item list:

  1. Most of the incidents occurred on relatively small fires or isolated sectors of larger fires.
  2. Most of the fires were innocent in appearance prior to the “flare-ups” or “blow-ups”. In some cases, the fatalities occurred in the mop-up stage.
  3. Flare-ups occurred in deceptively light fuels.
  4. Fires ran uphill in chimneys, gullies, or on steep slopes.
  5. Suppression tools, such as helicopters or air tankers, can adversely modify fire behavior. (Helicopter and air tanker vortices have been known to cause flare-ups.)”

The four more recent researchers conducted an analysis of the environmental conditions at the times and locations of 166 firefighter entrapments involving 1,202 people and 117 fatalities that occurred between 1981 and 2017 in the conterminous United States. They identified one characteristic that was common for 91 percent of the entrapments — high fire danger — specifically, when the Energy Release Component and Burning Index are both above their historical 80th percentile.

They also generated an update of the time of day the entrapments occurred as seen in the figure at the top of this article. This has been done before, but it’s worthwhile to get an update. And, this version includes the month.

You can read the entire open access article here. If you’re thinking of quickly skimming it, the 7,000 words and the dozens of abbreviations and acronyms make that a challenge. There is no appendix which lists and defines the abbreviations and acronyms.

The authors of the paper are Wesley G. Page, Patrick H. Freeborn, Bret W. Butler, and W. Matt Jolly.

Below are excerpts from their research:

…Given the findings of this study and previously published firefighter safety guidelines, we have identified a few key practical implications for wildland firefighters:

  1. The fire environment conditions or subsequent fire behavior, particularly rate of spread, at the time of the entrapment does not need to be extreme or unusual for an entrapment to occur; it only needs to be unexpected in the sense that the firefighters involved did not anticipate or could not adapt to the observed fire behavior in enough time to reach an adequate safety zone;
  2. The site and regional-specific environmental conditions at the time and location of the entrapment are important; in other words, the set of environmental conditions common to firefighter entrapments in one region do not necessarily translate to other locations;
  3. As noted by several authors, human factors or human behavior are a critical component of firefighter entrapments, so much so that while an analysis of the common environmental conditions associated with entrapments will yield a better understanding of the conditions that increase the likelihood of an entrapment, it will not produce models or define characteristics that predict where and when entrapments are likely to occur.


The one characteristic that was common for the majority of entrapments (~91%) was high fire danger. As a general guideline, regardless of location, the data suggest that entrapment potential is highest when the fire danger indices (ERC’ and BI’) are both above their historical 80th percentile. Until recently, spatially-explicit information on fire danger has not been widely available as most firefighters have relied on fire danger information available at specific weather stations, which are often summarized into Pocket Cards [83]. Fortunately, fire danger forecasts across CONUS are now available in a mobile-friendly format (see https://m.wfas.net) that can be displayed spatially for each of the fire danger indices separately or combined into a Severe Fire Danger Index.



The times and locations where wildland firefighter entrapments occur in the US cover a wide range of conditions. Current firefighter safety guidelines seem to emphasize only a subset of the possible conditions due to a focus on the factors that maximize the potential for extreme fire behavior. While many of these safety guidelines are still intuitively valid, caution should be exercised during relevant firefighter training so as to not ignore or undermine the fact that entrapments and fatalities are possible under a much wider range of conditions.

Despite the wide range of environmental conditions associated with entrapments, we have shown that it is possible to identify unique combinations of environmental variables to define similarities among groups of entrapments, but these will necessarily be context and site specific. For most entrapments, the only common environmental condition was high fire danger, as represented by fire danger indices that have been normalized to represent the historical percentile at a particular location. As such, at large spatial scales, fire danger and its association with fire weather should continue to be monitored and reported to firefighters using both traditional methods (i.e., morning fire weather forecasts) and also newer methods that take advantage of advancements in mobile technology.

New fire retardant gel developed that can remain effective for months

It could be used to pretreat areas at high risk of fire ignitions to make them fire resistant

long term gel fire resistant
Overhead time-course images of 3 m × 3 m unmowed (standing) grass plots that were untreated or treated with different coverage levels, dried, weathered, and allowed to dry again over time in the environment prior to burning. The normalized area burned over time demonstrates that CL2 (coverage level 2, or 2 gallons per 100 square feet) is sufficient to preclude spreading of the fire. Air tankers use the same unit of measurement, coverage level, to specify how much retardant will be dropped. Figure from the research.

A group of scientists and engineers have developed a new fire retarding chemical, actually a gel in this case, that they say can be effective for months after being applied to vegetation.

The millions of gallons of red fire retardant that air tankers drop every year is usually made from ammonium phosphate or its derivatives. It has  been called “long term fire retardant” because even after it dries, the chemical can interfere with the combustion process and may still retard the spread of  a vegetation fire to a limited degree. However research and experience in the field has shown some formulations can be toxic to fish.

Gels have been used by firefighters for several decades on structure fires occasionally on vegetation fires. The products can be more effective than plain water due to their ability to stick to a vertical surface or vegetation. Water can remain in the gel for an hour or more depending on the ambient temperature, wind, and humidity. GelTech Solutions recently received a contract from the Oregon Department of Forestry to supply a blue-colored version of FireIce HVB-Fx gel to be used in air tankers. The company says the product passed the U.S. Forest Service’s newly revised, more challenging requirements for wildland fire chemicals. But the safety data sheet for the product says, “Titanium dioxide [a component of the product] has been classified by IARC as a possible carcinogen to humans (Group 2B) through inhalation of particulate dust.”  The safety data sheet goes on to say, “This classification is based on inadequate evidence for carcinogenicity in humans, but sufficient evidence of carcinogenicity in animals (rats). It should be noted that recent studies have demonstrated that the rat may be particularly sensitive to high levels of toxicity dusts such as titanium dioxide. Epidemiology studies do not suggest an increased risk of cancer in humans from occupational exposure to titanium dioxide. The conclusions of several epidemiology studies on more than 20,000 TiO2 industry workers in Europe and the USA did not suggest a carcinogenic effect of TiO2 dust on the human lung.”

This is not the first time blue gel has been used in air tankers. The photo below was taken in the Black Hills of South Dakota August 15, 2006.

blue gel air tanker fire retardant
A single engine air tanker drops blue gel on a fire near Shep’s Canyon in the Black Hills of South Dakota August 15, 2006. Photo by Bill Gabbert.

The scientists who developed the new fire retarding gel that they claim has “persistent retention”qualities said their formulation is environmentally benign, nontoxic, and will “biodegrade at desired timescales.” After application, it will retain its ability to prevent fires throughout the peak fire season, even after weathering that would sweep away conventional fire retardants. The cellulose-based gel-like fluid stays on target vegetation through wind, rain and other environmental exposure, they said.

“This has the potential to make wildland firefighting much more proactive, rather than reactive,” said Eric Appel, the study’s senior author and an assistant professor of materials science and engineering.

Treating wildfire prone areas prophylactically could provide a highly targeted approach to wildfire prevention, but, until now, long-lasting materials have not been available.

The researchers have worked with the California Department of Forestry and Fire Protection (CAL FIRE) to test the retardant materials on grass and chamise — two vegetation types where fire frequently starts. They found the treatment provides complete fire protection even after half an inch of rainfall. Under the same conditions, a typical commercial retardant formulation provides little or no fire protection. The researchers are now working with the California Department of Transportation and CAL FIRE to test the material on high-risk roadside areas that are the origin of dozens of wildfires every year.

“We don’t have a tool that’s comparable to this,” said Alan Peters, a CAL FIRE division chief in San Luis Obispo who monitored some of the test burns. “It has the potential to definitely reduce the number of fires.”

The Stanford-developed treatment contains only nontoxic materials widely used in food, drug, cosmetic and agricultural products, according to the developers. The unique properties of these gel-like retardant fluids allow them to be applied using standard agricultural spraying equipment or from aircraft. It washes away slowly, providing the ability to protect treated areas against fire for months as the materials slowly degrade.

Link to the research paper, “Wildfire prevention through prophylactic treatment of high-risk landscapes using viscoelastic retardant fluids”.

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

Researchers analyze wildfire ignition with almost 100 tests of exploding targets

Exploding targets have ignited numerous wildfires and are banned in many areas

Above: Figure from “Experiments on Wildfire Ignition by Exploding Targets”, by Mark A. Finney, C. Todd Smith, and Trevor B. Maynard. September 2019.

Researchers with the U.S. Forest Service and the Bureau of Alcohol, Tobacco, Firearms and Explosives detonated almost 100 exploding targets to gather information about how likely they are to ignite a wildfire.

Exploding targets consist of two ingredients that when mixed by the end user explode when shot by a gun. They have caused many fires since they became more popular in recent years, have been banned in some areas, and caused the death of at least one person. In 2017 an exploding target started what became the 46,000-acre Sawmill Fire southeast of Tucson, AZ. After the ingredients are combined, the compound is illegal to transport and is classified as an explosive by the Bureau of Alcohol, Tobacco, Firearms, and Explosives.

The tests were carried out in 2015 and 2018 by shooting a high powered rifle at the targets — 46 tests in 2015 and 51 in 2018. The results could not have been more different in the two batches of tests. There were no ignitions of the nearby straw bales from the exploding targets in 2015 (zero percent), but there were 22 in 2018 (43 percent). The weather conditions made the difference. In 2015 the temperature was 31 to 46 and the relative humidity was 64 to 99 percent. During the 2018 experiments the temperature was 71 to 82 and the relative humidity ranged from 14 to 23 percent, conditions much more conducive to ignition of vegetation.

Experiments on Wildfire Ignition by Exploding Targets
Data about exploding target tests in 2015 and 2016. From “Experiments on Wildfire Ignition by Exploding Targets”, by Mark A. Finney, C. Todd Smith, and Trevor B. Maynard. September 2019.

The experiments in 2018 were carried out with 5.56×45 mm ammunition, which is used in some AR-15 rifles.

The researchers’ findings can be found in “Experiments on Wildfire Ignition by Exploding Targets”, by Mark A. Finney, C. Todd Smith, and Trevor B. Maynard. September 2019. (7.3 MB file)

The most common ingredients of exploding targets are the oxidizer ammonium nitrate (AN) and for fuel, aluminum powder (AL). Commercially available exploding targets have various concentrations of aluminum which is what actually burns during the explosion, which generates temperatures of about 6,700 °F.

The testing showed a direct relation between the aluminum content of the products and the prevalence of ignition and visible burning aluminum in the explosion.

The AL content of the target mixture had an effect on ignition of the straw bales:

The popularity of these products has led to a wide range of formulations to include more rimfire products that rely on increased metallic fuel content for sensitivity. The testing did show a direct relation between the aluminum content of the products and the prevalence of ignition and visible burning aluminum in the explosion. Wildland fire investigators considering an exploding target hypothesis for a fire start should be aware of the range of products available and how aluminum content, mixing, and other variables might impact the performance of the product and the likelihood of ignition. Tannerite is one of the most common commercial brands of exploding target, but with only approximately 1.6 percent AL, it is among the least likely to cause ignitions compared to brands or formulations with higher AL concentration.

During the tests in 2018 researchers used mixes with AL ranging from 1 to 10 percent.

Some of the first exploding targets had to be shot by a high-velocity projectile fired from certain center-fire rifles. Variants are now available that can be shot by rimfire cartridges (e.g., .22 Long Rifle) or pistols. These targets rely on a greater percentage of AL or other ingredients to increase sensitivity to initiation. Rimfire targets have been found with up to 25 percent AL.

The researchers had some tips for fire cause and origin investigators:

Informal observations during this research suggested that the use of exploding targets may leave evidence in and around the blast seat. The research team observed some shattered pieces of the plastic containers in and around the blast seat following testing. This plastic, which exhibited exposure to high temperatures, appeared to have embedded AN on one side of the plastic. The team also observed unconsumed AN prills on the ground around the blast seat during testing. While this in no way means such evidence is present after all exploding target explosions, fire investigators should be cognizant that potential forensic evidence may be located around the blast seat that should be collected and documented.

In addition to documenting physical evidence that can aid investigators, another thing this research accomplishes is it makes it easier to prosecute cases where a defendant is accused of starting a fire by shooting at an exploding target. It proves that the devices CAN start a fire. Prior to this, an attorney might argue, exploding targets do not ignite fires.

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

Testing a new fire model during a crowning prescribed fire

Above: Screenshot from the NASA video below about fire spread model research during a prescribed fire in Utah, June, 2019.

U.S. Forest Service scientists and others with the interagency Fire and Smoke Model Evaluation Experiment, or FASMEE, teamed up with the Fishlake National Forest to study a  prescribed fire from start to finish.

After months of planning and preparation, fire crews ignited more than 2,000 acres of Utah forest in an effort to consume living upper canopy vegetation and initiate growth of new vegetation. This June 2019 prescribed fire was designed to restore aspen ecosystems by removing conifer trees and stimulating the regrowth of aspen.

Researchers at the Pacific Northwest Research Station and Rocky Mountain Research Station, as well as other FASMEE participants, saw the fire as a unique opportunity for study.

During the event a fire model used for forecasting where and how a fire will move was put to the test. Adam Kochanski of the University of Utah used the opportunity to test the fire model known WRF-SFIRE.

WRF-SFIRE is a collaborative effort of NASA-funded teams from CU Denver, University of Utah, and Colorado State University. The project is led by Jan Mandel, Adam Kochanski and Kyle Hilburn.

The video below provides more details about the project and the test of the new fire model.

research fire model wildfire
Screenshot from the NASA video.