Five common denominators on tragedy fires

And updated data

Entrapment Time of day wildland firefighters
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.

A reminder:

Five common denominators of fire behavior on fatal and near-fatal fires have been identified through studies of tragedy fires. It is important for firefighters to readily recognize them to prevent future disasters.

Such fires often occur:

  1. On relatively small fires or deceptively quiet areas of large fires.
  2. In relatively light fuels, such as grass, herbs, and light brush.
  3. When there is an unexpected shift in wind direction or in wind speed.
  4. When fire responds to topographic conditions and runs uphill.
  5. Critical burn period between 1400 and 1700.

Alignment of topography and wind during the critical burning period should be considered a trigger point to reevaluate tactics.

Blowup to burnover conditions generally occur in less than 60 minutes and can be as little as 5 minutes.


Updated research

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.

The 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 factor 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 (Energy Release Component and Burning Index) are both above their historical 80th percentile.

More information about this research.


Recent burnovers in the United States that resulted in fatalities; with time and date:

Looking forward

One thing that will be interesting to watch is if the historical three-hour window from 1 to 4 p.m. when many of the fatalities have occurred is going to be stretched as the earth warms and extreme fire behavior becomes more frequent.

Hey! Let’s be careful out there.

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.

[…]

Conclusions

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.

Update on the condition of the firefighters who deployed fire shelters on the Cedar Fire

(UPDATED at 12:52 p.m. MDT June 30, 2016)

Today the BIA released a “24 Hour Report” about the fire shelter deployment on the Cedar Fire. It provided a few facts that were not previously disclosed by the agency.

The six firefighters deployed their shelters in an area that had already burned, and they were evaluated in the hospital for “smoke inhalation”.

The Serious Accident Investigation Team will be led by Jon Rollins, Chief Investigator for the National Park Service.

****

(Originally published at 9:52 p.m. MDT, June 29, 2016)

The Bureau of Indian Affairs provided more information today about the six firefighters on the Cedar Fire south of Show Low, Arizona who on June 28 found themselves in a situation where they had to deploy fire shelters. The firefighters, all from the Navajo Interagency Hotshot Crew, walked away from the site and were transported to Summit Healthcare in Show Low where they were treated and released that evening.

A Serious Accident Investigation Team has been formed and will investigate the circumstances surrounding the deployment.

We don’t know why or how the incident occurred, but if recent history holds true, we may never know, thanks to the unintended consequences of Senator Maria Cantwell’s and Representative Doc Hastings’ hastily conceived Public Law 107-203 signed into law in 2002.

But putting aside the unknown details of fire behavior, decisions made on the fireline, and the strategy and tactics being used on the Cedar Fire yesterday, there a few things that we do know.

  • The Type 1 Incident Management Team issued an update titled “Final Cedar Fire Update” on Monday, June 27. It said in part, “While 554 firefighters are working on the fire [Monday] morning, only the Team itself will remain by Tuesday afternoon. The Bureau of Indian Affairs (BIA) will assume command of the fire at 6 A.M. Tuesday.” That Monday update said the fire received rainfall on Sunday and more rain was expected on Monday.
  • The Type 1 Team turned the fire over to the Fort Apache Agency at 6 a.m. on Tuesday, June 28. There was no mention of a Type 2 or Type 3 Incident Management Team.
  • The Fort Apache Agency posted a fire update on Facebook at 1:05 p.m. on Tuesday, June 28 saying the resources on the fire that day were, “Navajo Hotshots, 3 Type 6 Engines, Fort Apache Fuels Type 2 IA Crew.” And, “Fire Personnel will continue to hold and mop up the fire.” These two crews and three engines probably amounted to a maximum of 50 people, plus miscellaneous overhead. This was down from 554 the previous day, a 91 percent reduction in personnel overnight.
  • Candy Lupe, a Public Information Officer with the Bureau of Indian Affairs’ Fort Apache Agency, told Wildfire Today that she was not sure exactly when the incident occurred but estimated it happened around 3 p.m. Arizona time on Tuesday, June 28.
  • The infrared scan of the fire conducted very early Monday morning, June 27, showed “scattered” and “isolated” heat over much of the fire. There was no record of an infrared scan prior to the day shift on Tuesday June 28, but they had been completed every day from June 17 through June 27.

We’re not pointing fingers or attempting to lay blame on anyone. Hopefully the investigation will bring to light some lessons that can be learned.

Carl WilsonThe incident brings to mind the Common Denominators of Fatal and Near-Fatal Fires, developed by Carl Wilson in 1976. Mr. Wilson put two lists together, a four-item list based on his studies of 61 fatal fires, and a five-item list that included an additional 31 near-fatal fires. More information about these lists is in our February 1, 2016 article, Are there 4 or 5 common denominators of fire behavior on fatal fires? Almost all recent wildland fire publications, if they publish the list, only have the four-item list.

These lists are not intended as a quick and easy checklist for investigators, nor are they rules or guidelines that must be followed. They are simply interesting commonalities seen on many fatal and near-fatal fires. Things to think about, not rules that must be adhered to.

Here is the five-item list that includes data from fatal and near-fatal fires:

  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.)”

Are there 4 or 5 common denominators of fire behavior on fatal fires?

Our article about adding to the list of common denominators of fatal fires led someone to ask in a comment, “When and why was Wilson`s 5th Common Denominator dropped ?”

In 1976 four firefighters were entrapped on the Battlement Creek Fire, killing three near what is now Parachute, Colorado. Following the tragedy, Carl C. Wilson, who at one time was the Chief of Forest Fire Research at the U.S. Forest Service’s Pacific Southwest Forest and Range Experiment Station, published a paper titled Fatal and Near-Fatal Forest Fires: The Common Denominators.

Carl WilsonIn developing his paper, Mr. Wilson studied 67 fires that occurred during the 61-year period from 1926 to 1976 on which a total of 222 firefighters were killed from “fire-induced injuries”. He also evaluated 31 other “near-fatal” fires, searching for common themes or causes of the deaths in all of the fires. His results were considered ground-breaking. Since then his lists of Common Denominators have been republished, quoted in fatality reports, and included in many standard publications that are very familiar to firefighters.

When we listed his Common Denominators in the January 29 article we used the four that are seen in all of the recent and semi-recent publications that we looked at, including the last paper version of the Fireline Handbook (2004), the 2014 Incident Response Pocket Guide, and the report authored by Dick Mangan, Wildland Firefighter Fatalities in the United States: 1990-2006. The only revision of the Fireline Handbook since 2004 was completed in 2013 and was renamed Wildland Fire Incident Management Field Guide (PMS 210). It does not include the Common Denominators. The 2004 and 2006 editions of the Incident Response Pocket Guide also include the four-item list.

After a great deal of searching we found that there is another list of Common Denominators attributed to Mr. Wilson that has similar but different wording, and has five instead of four. The five-item list was in a 2011 paper by by Martin E. Alexander and Miguel G. Cruz and also in the 1998 version of the Fireline Handbook.

Finally we found a copy of Mr. Wilson’s paper, Fatal and Near-Fatal Forest Fires: The Common Denominatorsthat was published in 1977 in The International Fire Chief. It has two different lists.

The first, the five-item list, is printed on the first page just below the heading “Common Denominators of Fatal Fires”.  Here is the text just below that heading:

“Based on personal knowledge and information obtained from reports and reviewers, the following generalizations can be made about the fatal fires in Tables 1 and 2 [tables 1 &b 2 are fatal fires]:

  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.)”

A key to that list is that it only applies to the 67 fatal fires he studied, and not the 31 that were near-fatal.

Toward the end of the paper in the “Conclusions” section, Mr. Wilson wrote:

“There are four major common denominators of fire behavior on fatal and near-fatal fires. Such fires often occur:

  1. On relatively small fires or deceptively quiet sectors of large fires.
  2. In relatively light fuels, such as grass, herbs, and light brush.
  3. When there is an unexpected shift in wind direction or in wind speed.
  4. When fire responds to topographic conditions and runs uphill.” 

We’re not sure why Mr. Wilson broke down the common denominators into fatal and near-fatal fires. I don’t know that it adds value, but can, and has, produced a little confusion when two different versions of the lists are floating around.

Adding to the list of common denominators of tragedy fires

More common denominators of tragedy fires.

(Photo: Happy Camp Complex, 2014, by Kari Greer.)

About forty years ago Carl Wilson, one of the early wildland fire researchers, developed his list of four “Common Denominators of Fire Behavior on Tragedy Fires”, that is, fatal and near-fatal fires.Carl Wilson

  1. Relatively small fires or deceptively quiet areas of large fires.
  2. In relatively light fuels, such as grass, herbs, and light brush.
  3. When there is an unexpected shift in wind direction or wind speed.
  4. When fire responds to topographic conditions and runs uphill. Alignment of topography and wind during the burning period should always be considered a trigger point to re-evaluate strategy and tactics.

Our study of the 440 fatalities from 1990 through 2014 shows that entrapments are the fourth leading cause of deaths on wildland fires. The top four categories which account for 88 percent are, in descending order, medical issues, aircraft accidents, vehicle accidents, and entrapments. The numbers for those four are remarkably similar, ranging from 23 to 21 percent of the total. Entrapments were at 21 percent.

But as Matt Holmstrom, Superintendent of the Lewis and Clark Interagency Hotshot Crew recently wrote for an article in Wildfire Magazine, Mr. Wilson’s common denominators only address fire behavior.

Mr. Holmstrom explored eight human factors that he believes merit consideration. I’m generously paraphrasing, but here are the areas he mentioned:

  1. Number of years of experience.
  2. Time of day (especially between 2:48 p.m. and 4:42 p.m.)
  3. Poorly defined leadership or organization.
  4. Transition from Initial Attack to Extended Attack.
  5. Earlier close calls or near misses on the same fire.
  6. Personality conflicts.
  7. Using an escape route that is inadequate.
  8. Communication failures.

He goes into much detail for each item and cites numerous fires which he said were examples. It is a thought-provoking article. Check it out.

UPDATE January 29, 2016. Larry Sutton authored an article in a 2011 issue of Fire Management Today (pages 13-17) that also explored the Common Denominators of Human Behavior on Tragedy Fires. At the time Mr. Sutton was the fire operations risk management officer for the U.S. Forest Service at the National Interagency Fire Center in Boise, Idaho.