Fire Shelter Used in the Wildland
Kurt Kamm
July 26, 2008
What Is a Wildland Fire Shelter
Wildland firefighters are often faced with deadly fire behavior which may result from a change of wind direction which puts them in the path of a fast moving fire, or preheating, in which a whole area may simultaneously burst into flame. Given the nature of wildland firefighting, the men are often on terrain where it is difficult to flee. All wildland firefighters identify a safe (escape) zone before starting their work, but it isn´t always accessible. A fire shelter is a mandatory item of PPE (personal protective equipment) for all wildland firefighters, and is the last line of defense in saving one´s life.
The fire shelter is carried in a package at the firefighter´s hip. The general rule is that when needed, the shelter must be deployed in 30 – 60 seconds. That´s how fast an oncoming fire moves. The shelter is approximately 80 x 120 inches and when deployed, is in the shape of a tunnel closed at both ends.
The individual lies face down. The ground protects the underside of his body. He breathes the cooler, cleaner air trapped near the ground. The shelter has four straps in the corners, which allow it to be held down by hands and feet when the flames and wind arrive.
RADIANT HEAT travels in a straight line through space without heating the space itself. It turns into heat when it contacts a cooler surface. CONVECTIVE HEAT requires air movement. When flames or hot gasses move by air past a surface, the hot air transfers the heat to that surface.
The fire shelter protects primarily by reflecting radiant heat and trapping breathable air inside. The new shelters have two layers. The outer is aluminum foil bonded to silica cloth. The foil reflects radiant heat and the silica slows the passage of convective heat to the inside of the shelter. An inner layer of aluminum foil laminated to fiberglass prevents heat from radiating to the person inside. When the layers are sewn together, the air between offers further insulation.
The outer layer reflects 95% of the radiant heat. Convective heat, however, may be absorbed, allowing the temperature of the material to rise. At 500 degrees (F), the bonding of the layers begins to break down. Fire temperatures may exceed 1,500 degrees. (Goggles and helmets melt at 320 degrees.) Above 1,000 degrees, the risk to the individual in the shelter increases significantly.
Here is an excerpt from my book One Foot in the Black (Amazon) which describes the moments after a burnover, where a crew has been trapped, tries to escape, and deploys fire shelters. It´s fiction, but this is the way it happens:
I dimly saw deployed fire shelters and a couple of bodies lying face down, gloved hands holding helmets over their heads. I lay against the rock and felt the unbearable heat of the fire. My lungs fought for the small quantity of oxygen that remained near the ground. I was certain I would die from inhaling superheated air. I smelled burnt hair. It was mine.
The firestorm reached the top of the ridge where it paused for a few seconds in the cross winds, then blew past us down the other side of the mountain. I heard hissing and popping, rocks exploding from the intense heat. Silence. I had survived. We had survived.
I sat up coughing and vomited the banana and my breakfast onto my shirt. We struggled to clear our lungs and to breathe. My chest hurt, my eyes burned. Everyone was blackened with ash. Hector was on his hands and knees, saliva dripped from his mouth, black snot and soot ran from his nose. Luis sat, legs crossed, staring straight ahead. Blood ran down Red Eye´s forehead.
Wildland firefighters are often faced with deadly fire behavior which may result from a change of wind direction which puts them in the path of a fast moving fire, or preheating, in which a whole area may simultaneously burst into flame. Given the nature of wildland firefighting, the men are often on terrain where it is difficult to flee. All wildland firefighters identify a safe (escape) zone before starting their work, but it isn´t always accessible. A fire shelter is a mandatory item of PPE (personal protective equipment) for all wildland firefighters, and is the last line of defense in saving one´s life.
The fire shelter is carried in a package at the firefighter´s hip. The general rule is that when needed, the shelter must be deployed in 30 – 60 seconds. That´s how fast an oncoming fire moves. The shelter is approximately 80 x 120 inches and when deployed, is in the shape of a tunnel closed at both ends.
The individual lies face down. The ground protects the underside of his body. He breathes the cooler, cleaner air trapped near the ground. The shelter has four straps in the corners, which allow it to be held down by hands and feet when the flames and wind arrive.
RADIANT HEAT travels in a straight line through space without heating the space itself. It turns into heat when it contacts a cooler surface. CONVECTIVE HEAT requires air movement. When flames or hot gasses move by air past a surface, the hot air transfers the heat to that surface.
The fire shelter protects primarily by reflecting radiant heat and trapping breathable air inside. The new shelters have two layers. The outer is aluminum foil bonded to silica cloth. The foil reflects radiant heat and the silica slows the passage of convective heat to the inside of the shelter. An inner layer of aluminum foil laminated to fiberglass prevents heat from radiating to the person inside. When the layers are sewn together, the air between offers further insulation.
The outer layer reflects 95% of the radiant heat. Convective heat, however, may be absorbed, allowing the temperature of the material to rise. At 500 degrees (F), the bonding of the layers begins to break down. Fire temperatures may exceed 1,500 degrees. (Goggles and helmets melt at 320 degrees.) Above 1,000 degrees, the risk to the individual in the shelter increases significantly.
Here is an excerpt from my book One Foot in the Black (Amazon) which describes the moments after a burnover, where a crew has been trapped, tries to escape, and deploys fire shelters. It´s fiction, but this is the way it happens:
I dimly saw deployed fire shelters and a couple of bodies lying face down, gloved hands holding helmets over their heads. I lay against the rock and felt the unbearable heat of the fire. My lungs fought for the small quantity of oxygen that remained near the ground. I was certain I would die from inhaling superheated air. I smelled burnt hair. It was mine.
The firestorm reached the top of the ridge where it paused for a few seconds in the cross winds, then blew past us down the other side of the mountain. I heard hissing and popping, rocks exploding from the intense heat. Silence. I had survived. We had survived.
I sat up coughing and vomited the banana and my breakfast onto my shirt. We struggled to clear our lungs and to breathe. My chest hurt, my eyes burned. Everyone was blackened with ash. Hector was on his hands and knees, saliva dripped from his mouth, black snot and soot ran from his nose. Luis sat, legs crossed, staring straight ahead. Blood ran down Red Eye´s forehead.
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