BY ALAN M. PETRILLO
Sixty wildland firefighters are carrying one of four new fire shelter prototypes for “wear testing” as part of the continuing Fire Shelter Project Review, administered by the United States Department of Agriculture’s United States Forest Service (USFS) National Technology and Development Program and initiated in 2014 to identify possible improvements to the fire shelter system.
The National Wildfire Coordinating Group (NWCG) Fire Shelter Subcommittee, which comprises federal, state, and local wildland firefighters; wildfire safety specialists; fire management officers; and other fire shelter users, selected the four new fire shelter prototypes for wear testing. Sixty prototypes of four different new fire shelter designs that have shown improved performance in lab tests were issued to wildland firefighters to evaluate the durability of the shelters. The wildfire environment is very rugged, and fire shelters must be carried by wildland firefighters for years yet still be functional when needed.
Two of the new fire shelter prototypes are designed for ground firefighters, and 20 of each of these prototypes were issued to Interagency Hotshot Crew members for wear testing. The other two new fire shelter prototypes, which were determined to be too bulky for ground firefighters, are being tested by engine and equipment operators. Ten of each of the two bulkier prototypes were issued. The National Aeronautics and Space Administration (NASA) and the USFS have a cooperative work agreement for this project, and two of the prototype fire shelters are NASA designs.
“The biggest job that a fire shelter has to do is be carried around by a wildland firefighter all day, every day, all season long,” says Tony Petrilli, Fire Shelter Review leader with the USFS National Technology and Development Program. “That doesn’t lend itself to the use of a lot of materials that can withstand high temperatures because of weight, bulk, durability, and toxicity.”
The fire shelter is an aluminized cloth tent that offers protection in a wildland fire entrapment situation by reflecting radiant heat and providing a volume of breathable air. The current version, Model 2002, is shaped like a half cylinder with rounded ends. The previous version of the fire shelter was triangular prism-shaped, similar to a small one-person tent. Fire shelters have been required as personal protective equipment since 1977.
The Model 2002 fire shelter comprises two layers, with an outer layer of woven silica laminated to aluminum foil. The foil reflects radiant heat, and the silica cloth slows the transfer of heat to the inside of the shelter. The inner layer is fiberglass laminated to aluminum foil. The inner layer of foil prevents heat from being reradiated inside the shelter, and it prevents gases from entering the shelter. When the two layers of materials are sewn together, the air gap between them provides additional insulation.
The USFS National Technology and Development Program notes that wildland fires are typically 1,600°F and in some instances can reach 2,000°F. It says the most extreme temperature of a wildland fire was measured at 2,400°F. It points out that a tenable condition for an extended period for humans is about 250°F, although humans can survive up to 300°F for a short period of time.
The Model 2002 fire shelter currently in deployment has been tested and shown survivable temperatures in typical exposures of 1,700°F with some flame contact. It has been in use nationwide by all wildland firefighters since 2010 and offers 54 seconds of survivability in lab tests. The current and previous versions of fire shelters have saved the lives of hundreds of wildland firefighters since the 1960s, according to USFS National Technology and Development Program data.
While the four new fire shelter prototypes that were being wear tested this summer offer increased protection, two of the four are also bulkier and heavier. Wildland firefighters carry a backpack that weighs an average of 45 pounds. But, adding weight and bulk to the fire shelter can increase the daily physiological stress on wildland firefighters, the USFS Forest Service National Technology and Development Program notes. It says that a 2014 survey of more than 3,800 wildland firefighters indicated wildland firefighters prefer a lighter fire shelter that matches the performance of the current fire shelter over a more protective fire shelter with additional weight and bulk.
Over the past four years, the USFS National Technology and Development Program evaluated and tested hundreds of potential fire shelter materials and designs submitted by 23 different organizations from all over the world. The materials and designs were evaluated on weight, bulk, durability, and toxicity, which are critical to determine suitability for use in fire shelters. Suitable materials were tested in a small-scale flame test to determine material strength, durability, flammability, and thermal performance. Materials that showed promise in the small-scale test were then constructed into fire shelters and tested in a full-scale, direct-flame test to measure the performance of the overall fire shelter design.
Some of the shelters were tested in crown fire testing in the Northwest Territories of Canada, as well as in lab testing at the University of Alberta, Canada, during the summer and fall of 2015 and 2016. The latest full-scale testing was conducted in October 2017.
After completion of the wear tests, the USDA Forest Service National Technology and Development Program will evaluate the results and conduct a final round of full-scale direct flame testing to ensure the four new fire shelter prototypes are still able to perform after being carried by ground firefighters and equipment operators over the summer. The final results will be presented to the NWCG Fire Shelter Subcommittee, which will make a recommendation on whether to adopt one or more of the new fire shelter prototypes or to continue to use the existing fire shelter.
Wildland firefighters are trained to consider fire shelters as a last resort and to avoid situations that can lead to entrapment, according to the USDA Forest Service National Technology and Development Program. It notes that, as with the current fire shelter, it is likely that none of the four new fire shelter prototypes can ensure survival in all wildfire conditions. Nationwide, in 2017, wildland firefighters deployed fire shelters on two separate incidents when they were caught in fire entrapment situations, and all three wildland firefighters survived.
ALAN M. PETRILLO is a Tucson, Arizona-based journalist, the author of three novels and five nonfiction books, and a member of the Fire Apparatus & Emergency Equipment Editorial Advisory Board. He served 22 years with the Verdoy (NY) Fire Department, including in the position of chief.