PHOENIX (AP) — When things go from bad to really bad for wildland firefighters, their last best hope rests with a folded emergency fire shelter they all carry wherever they go.
But the shelters are not a surefire way to live through a raging wildfire, as the deaths of 19 Arizona firefighters on Sunday shows. They work only under the best of circumstances, despite redesigns intended to make them more effective.
"It's an extreme measure that's taken under the absolute worst conditions," said Prescott Fire Chief Dan Fraijo. "Under certain conditions there's usually only sometimes a 50 percent chance that they survive."
Nineteen members of a 20-pershot Hotshot crew from Prescott's fire department died despite using their shelters, a tent-like contraption made of fire-resistant material. It is designed to reflect heat and trap cool breathable air inside for a few minutes while a wildfire burns over a person.
But its success depends on the firefighters being in a cleared area away from fuels and not in the direct path of a raging inferno of heat and hot gasses. That apparently wasn't the case Sunday in the hills about the community of Yarnell, about 95 miles northwest of Phoenix.
"If you're in an area with a lot of flame contact, high temperatures for a long duration, that's when it's most challenged," said Tony Petrilli, a Forest Service project leader in charge of shelters and protective equipment based in Montana.
Fire shelters have been used in the U.S. since the 1960s. The latest version of the shelter American wildland firefighters use was designed in the early 2000s and all state and federal crews were using it by 2010. Shelters often look like a small pup tent made of aluminum foil.
It's actually much more complex than that. The outer layer is made up of silica cloth that can withstand high temperature covered by aluminum foil. The inside layer is lightweight fiberglass also laminated to aluminum foil.
The shelter reflects heat but doesn't stand up well to direct flames, Petrilli said. Firefighters who are trapped and can't escape to a safe area are trained to identify spots where it can be best used in a pinch.
But they need to find a clear area away from a slope the flames are racing up, such as a cleared fire road or a rock slide area. And they've got to pick the spot quickly.
"Every situation is different," Petrilli said. "The best instruction we can give to firefighters is it's up to you to find your best deployment sites."
Investigators are just starting to review Sunday's deaths, and it could take months to determine whether the flames were just un-survivable. The glue holding the layers of the shelter together begins to come apart at about 500 degrees, well above the 300 degrees that would almost immediately kill a person.
Firefighters must be recertified in using their shelters once a year. A video profile of the Granite Mountain Hotshots produced by Arizona State University students for the Cronkite News Service last year shows the crew doing that training, unfurling and climbing into the shelters and wiggling to point their feet in the right direction — toward the oncoming flames.
For training, crew members used green tarps shaped and packaged like fire shelters. Once the hotshots got inside, other crew members yanked on the tarps to simulate the high winds they could face.