The 19 members of an elite team of firefighters battling a blaze in Arizona tried everything to save themselves before they tragically lost their lives Sunday, including using a device that looks like a foil tent. But what exactly are these devices and how are they supposed to work?

fire safety shelter

Fire shelter (Photo: National Interagency Fire Center)

All but one member of the Prescott-based Granite Mountain Hotshot crew died in what was the deadliest wildfire for firefighters in the U.S. in decades. Hotshot crews are highly trained and work long hours in extreme conditions.

Cronkite News out of Arizona State University had featured the crew as they demonstrated techniques to protect themselves in the fire safety shelters:

Phillip “Mando” Maldonado, a squad leader, shouts instructions as a dozen hotshots, firefighters trained to combat wildfires in extreme conditions, face a nightmare scenario: flames rushing in from all sides and their survival hinging on successfully unfolding and wrapping themselves in thin sheets of heat-reflecting material.

“Get down! Heads toward center!” Maldonado yells, the urgency in his voice rising.

Diving to the ground, crew members attempt to form a tight circle and point their feet toward the approaching flames. That will deflect heat and help protect their torsos. They clamp down on the edges of their emergency shelters to make sure fire, smoke and heat can’t get inside, and they keep their faces near the ground to breathe cooler air that won’t damage their lungs.

There’s nothing to do now but wait.

A guide by the National Wildfire Coordinating Group stated that since 1977 fire shelters had helped save the lives of more than 300 firefighters.

Arizona Firefigthers Used Fire Safety Shelters In Last Resort Survival Effort

The fire shelters come in a pack like this. (Photo: NWCG.gov)

To use fire shelters, firefighters are instructed to scrape the ground to soil, if time permits, to clear any additional fuel to the fire away from the area. There are very precise instructions for how to deploy and then enter the shelter, but essentially a firefighter can huddle inside with his or her mouth and nose to ground, hoping to ride out the fire.

fire shelter

(Photo: NWCG.gov)

The shelters are said to be a last resort when escape isn’t possible and are noted to perform optimally when not in direct contact with flames.

Arizona Firefigthers Used Fire Safety Shelters In Last Resort Survival Effort

(Photo: NWCG.gov)

The shelters work by “reflecting radiant heat and trapping breathable air,” according to the report:

The outer layer is aluminum foil bonded to woven silica cloth. The foil reflects radiant heat and the silica material slows the passage of heat to the inside of the shelter. An inner layer of aluminum foil laminated to fiberglass prevents heat from reradiating to the person inside the shelter. When these layers are sewn together, the air gap between them offers further insulation.

Cronkite News reported in its feature that training is a way of life for the crews that are on call during the whole fire season. It noted one rookie, Shane Arollado, who “fake died” twice during training as he learned to use the fire shelters saying his squad leaders — Maldonado and Clayton Whitted — “were really great at showing me where I went wrong.”

“There’s always someone trying to point you in the right direction,” he said.

But even with the training and the use of shelters over the weekend, as the NWCG guide put it ”the shelter will not protect firefighters under all fire situations.” A video shown during the training reported on by Cronkite News showed how six firefighters died in 1990 despite being inside the tents.

Watch this video from Cronkite News last year showing the training exercises:

Prescott Fire Chief Dan Fraijo said the 19, whose names had not been released, were a part of the city’s fire department. Of the tent-like safety shelters, Fraijo said “certain conditions there’s usually only sometimes a 50 percent chance that they survive.”

There are more than 100 hotshot crews in the U.S. who often hike for miles into the wilderness with chain saws and backpacks filled with heavy gear to build lines of protection between people and fires.

The Associated Press contributed to this report. The link to ASU’s Cronkite News feature has been updated in this story.