Fire Shelter History

Fire Shelter Development

Modern fire shelter development began in Australia in 1958 with work on a bell-shaped shelter made of a laminate of aluminum foil and glass cloth (see Figure 1).

In 1959, the Australians abandoned the bell-shape in favor of an A-frame design. That same year, the Forest Service’s Missoula Equipment Development Center (MEDC) began developing a fire shelter. Over the next few years, MEDC, and the Australians shared ideas and shelters (see Figures 2 and 3).

Figure 1 Early prototype shelter design.

Figure 2 Testing suits made of shelter material.

Figure 3 Testing radiant heat shields.

In 1967, the Forest Service made its first large purchase of 6,000 fire shelters through the General Services Administration (GSA). These shelters were made of an aluminum foil and glass cloth laminate with a kraft paper barrier inner liner. The shelter had an A-frame shape, weighed 4.3 pounds, and was accordion folded into a 14- x 6- x 3-inch package. It had an orange case and attached belt for carrying. The kraft paper liner was eliminated in 1974.

The Forest Service made carrying the fire shelter mandatory in 1977 after three firefighters without shelters were killed on the Battlement Creek Fire in Colorado in 1976.

In 1981, toxicity testing was added to the fire shelter specification. Additionally, the shelter was modified to include hold down flaps, the folding method was updated resulting in a package measuring 9 x 5 ¾ x 3 inches, and the case was changed from orange canvas to yellow nylon (see Figure 4).  In 1989, a hard plastic case liner was added to improve the shelter’s durability.

The old-style shelter was designed to reflect radiant heat and to trap breathable air, not to withstand flame contact, which rapidly damaged the shelter (see Figure 5).

The aluminum foil layer reflected radiant heat away from the shelter while the fiberglass backing provided strength and stiffness to the aluminum foil. The adhesive was selected to withstand high temperatures without being toxic.

Figure 4 Old-style shelter used until 2010.

Figure 5 Early graphic of how a shelter worked.

Old-style shelter

M-2002 shelter

Development of the M-2002 Fire Shelter

Figure 6 Old-style shelter showing the adhesive igniting inside the shelter during testing.

MTDC tested fire shelter prototypes and the old-style shelter during the late 1990s. Data was collected and compared for both temperature and heat flux (heat flux is a measure of the rate of energy transfer, usually measured in kilowatts per meter squared (kW/m^2­­)). During testing, insulated cameras were placed inside and outside the shelters to better understand and visualize the conditions inside the fire shelter. In 1999, video from inside one of the old-style shelters, viewed in slow motion, showed an ignition inside the fire shelter (see Figure 6).

The Forest Service contracted with the Department of Mechanical Engineering at the University of Alberta (UA) to determine the cause of the ignition. The tests at UA showed that when the shelter cloth was heated to a temperature of 450 to 500 degrees Fahrenheit, the adhesive used to bond the laminate would begin to turn into gas. This gas could pass easily through the fiberglass cloth and collect inside the shelter. If the gas reached a concentration that was high enough and was then heated to ignition temperature, the gasses inside the shelter could ignite. This sequence was most likely to occur if the shelter was exposed to direct flame. The flames inside the shelter raised concerns that they might injure a firefighter, cause a firefighter to panic and abandon their shelter, or lead to more rapid failure of the fire shelter.

In January of 2000, MTDC was directed by Forest Service Fire and Aviation Management (FAM) leadership to pursue the development of a new fire shelter.

The goals of the shelter development project were to:

• Maintain the same level of protection in radiant heat offered by the old-style shelter
• Improve protection from direct-flame contact
• Maintain the requirement that the occupant not be exposed to dangerous toxic compounds from the shelter
• Provide an acceptably strong and durable shelter
• Prevent flammable gases from collecting inside the shelter
• Consider weight, bulk, and cost

The process used to develop the shelter included:

• Develop lab-based tests
• Find and/or develop new materials and designs for testing
• Test the new materials and designs
• Test the old-style shelter for baseline comparisons
• Compare the results for the new materials and designs to those for the old-style shelter
• Offer options to decision-makers for final design selection

Figure 7 Full-scale fire shelter testing.

In 2001, testing methods were developed and implemented to evaluate toxicity and thermal performance of shelter prototype materials.  This allowed MTDC to evaluate and compare potential fire shelter materials under repeatable and reliable testing parameters. Later that year, new materials, and material combinations were developed and tested using the new methods.

In February of 2002, ten prototypes of varying weight, bulk, and performance levels, were presented to Interagency Fire Directors. The Fire Directors selected four shelter prototypes for evaluation in the next phase of testing.

The four shelters were subjected to an intensive round of small- and full-scale testing (see Figure 7) and toxicity testing. The results were peer-reviewed and then presented to the Fire Directors on June 2, 2002. The group unanimously selected the M-2002 fire shelter because of its bulk, weight, and level of protection.

2014 Fire Shelter Project Review

The M-2002 shelter underwent a project review beginning in 2014 and concluding in early 2019.

NTDP executed an exhaustive search of materials and designs, working with 23 different entities, from which hundreds of different materials and material combinations were produced.

The fire shelter material search was divided into three categories:

• Lighter weight and less bulk with similar performance to the current shelter.
• Similar weight and bulk with improved performance.
• Heavier weight and bulk with pronounced improved performance.

The U.S. Forest Service entered into a collaborative agreement with the National Aeronautics and Space Administration (NASA) Langley Research Center, located in Hampton, Virginia, to examine potential improvements to fire shelter performance. A team of engineers from NASA was developing flexible heat shields to protect spacecraft from the high temperatures of atmospheric entry under NASA’s Hypersonic Inflatable Aerodynamic Decelerator (HIAD) project. NASA and the U.S. Forest Service found common performance requirements between fire shelters and flexible heat shields that could benefit both organizations. North Carolina State University Wilson College of Textiles received a grant under the Assistance to Firefighters Program of Federal Emergency Management Agency (FEMA) and submitted fire shelter prototypes that were considered by the National Wildfire Coordinating Group (NWCG) Fire Shelter Subcommittee (FSSC). North Carolina State’s shelter submissions closely mirrored the NASA prototypes.

The materials and shelter designs were evaluated on weight, bulk, durability, and toxicity – critical factors for suitability for use in fire shelters. Material samples were tested based on three tiers.

• Tier 1 tests for small-scale thermal and radiant heat exposure.
• Tier 2 has material toxicity screening and strength testing.
• Tier 3 performs full-scale shelter tests: convective and radiant exposure, durability, seam strength, elevated seam strength, and peel strength.

Suitable materials were tested in a small-scale flame test to determine material strength, durability, flammability, thermal performance, and off-gassing toxicity (Tier 1 and 2). Materials that showed promise in the small-scale test were then constructed into fire shelters and tested in full-scale, direct-flame tests to measure the performance of the overall fire shelter design (Tier 3). Shelters were subjected to crown fire testing in the Northwest Territories of Canada, as well as lab testing at UA from 2015 through 2017.

After hundreds of full-scale lab tests, four prototype designs were selected for wear testing by firefighters during the 2018 fire season. A total of 60 prototype shelters were produced for wear testing to expose any unforeseen issues with production, packaging, material/component wear, and durability.

A smaller, lighter prototype performed better than the current shelter, but did not satisfactorily endure production rigors and was eliminated from consideration. A second prototype for line-going firefighters was carried by 20 Interagency Hotshot Crew members for wear testing. Finally, two larger, bulkier shelters were carried by engine and equipment operators only. Two of the shelters tested were designed by NASA as part of the NASA and United States Forest Service (USFS) cooperative agreement for this project.

The prototype designed for line-going firefighters showed a 37-second direct-flame test performance improvement, however, it is nearly one pound heavier and has 1.7 times more volume than the current shelter (see Figure 8). The prototype designed for equipment operators showed a 52-second direct-flame test performance increase, however, it was more than four times the volume, and nearly 1½ pounds heavier (see Figure 9).

Figure 8 Left image is of the prototype carried by firefighters during the 2019 wear trial. The right is the current shelter.

Figure 9 Fire shelters carried during the 2019 field wear trial. The left shelter was for equipment and engine operators and the right shelter was carried by firefighters. The current shelter (middle) shows the difference in size of the prototypes.

The FSSC weighed many facets of the fire shelter but emphasized the following:

• Physiological stress from additional weight.
• Limited storage space in firefighters’ packs.
• Limited incremental increase in protection.
• Firefighter survey responses indicating a desire for a lighter weight/less bulky shelter, and.
• Decreasing trend in annual fire shelter deployments.

The five-year study concluded that the current fire shelter model continues to provide the most practical amount of protection given tradeoffs of weight, volume (bulk), durability, and material toxicity. The study resulted in modifications to the shelter including:

1) An updated pattern design to use material more efficiently.

2) A new adhesive formula that withstands higher temperatures before degradation occurs and is less soluble in water.

3) Changes to the fire shelter’s polyvinyl chloride (PVC) bag to ensure a more reliable opening.