By Mai Martinez

(CBS) — A raging wildfire continues to burn and grow in Arizona and is now being called the deadliest fire in U.S. history in the past 30 years.

19 firefighters died yesterday while fighting the fire about 85 miles northwest of Phoenix. They were members of an elite team called the “hotshot” crew.

The firefighters apparently knew they were in trouble and tried to save themselves by using special pop up fire shelters.

CBS 2’s Mai Martinez has a look at what these fire shelters are and how they work.

Lt. Tom Flader of the Lake & McHenry Co. Wildland Fire Task Force says that using a fire shelter, “is truly a last resort item because no human can outrun fires. Every wildland firefighter in the U.S. has a fire shelter with them at all times.”

Made of fire resistant, not fire proof, materials the shelters serve one purpose: To buy trapped firefighters more time until help can get to them or the fire passes.

Curtis Martin of the Lake & McHenry Co. Wildland Fire Task Force says that a fire shelter can be deployed in, “Under a minute.”

As they showed CBS 2 in a drill using practice shelters. Martin says that, “When we can deploy shelters we want our feet to be at the fire and our head away from the fire for obvious reasons to protect our airways.”

Flader explained that in a fire shelter, the firefighter will tuck in all the corners as tight as possible and keep their mouth close to the ground where there is the coolest air.

Martin said the shelters are generally used when a fire as taken an erratic turn or because of weather conditions.

It’s too soon to know if that is what happened in Arizona, but Martin says now is not the time to analyze, but mourn.

“It was devastating, anytime we lose a brother or sister. First thing I did this morning was give my wife a big hug,” said Martin.

Since 1977, fire shelters have been credited with saving more than 300 lives.

The firefighters CBS 2 talked to today, say fortunately, they have never had to use the shelters while fighting wild-fires, but consider them an invaluable piece of equipment.

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