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.