My heart is heavy with the loss of the 18 HotShot Firefighters. Something went terribly wrong for them to get caught in that after all their advanced training. Their fire retardent covers didn't do the job they needed to have done. I think they were surrounded by fire when winds shifted and they found themselves trapped in it.
They all sound like exceptional men and they died heros. Giving their lives to save wildlife, the ecology and any homes that might be threatened. 3 of them were from this area. All wanted to be firefighters from an early age. Two had fathers who were Fire Captains at different city Fire Stations. God Bless them.
BBM
Those fire shelters are not actually flame retardant and they aren't designed to be. They are actually heat resistant. Under the best conditions, they give a 50% chance of survival. Which is why they are the strategy of last resort.
The problem is the same one backpackers face: hotshots often have to hike into the area where they are establishing firelines and every ounce has to be considered in terms of the trade off between additional safety vs the drain on energy required to carry it.
The theory is that in a blowup, the fire itself is creating a strong updraft, so if a trapped firefighter can just survive the heat and oxygen depletion they are unlikely to have embers falling on them.
This last ditch method of survival came from the Mann Gulch Fire where one of the survivors deliberately lit a backfire, waited by it and when the blowup came, stepped into the good black (charred ground that no longer has any fuel source) and burrowed into the ground as deeply as possible. He survived where 13 other men did not.
It was a stroke of the genius of pure desperation because no one had ever tried anything like that before. Sadly, he was reviled for surviving in the investigation of the incident. It was another 10 years before research showed that his moment of genius really did work and could have saved all 13 of his fellow firefighters had they joined him.
The reason why fire shelters are not designed to be fireproof is because of weight. If a firefighter is caught in a blowup, their best chance of survival is to run to a safe(r) place. In the South Canyon Fire, 12 of the 14 people killed were hotshots. All 12 were found with their tools either under their bodies or right next to them, indicating that they can carried their tools with them.
In the investigation of the incident, an expert demonstrated that if the 12 who died had simply dropped their tools, it would have increased their speed such that they would have survived (by running uphill and crossing over the crest of the ridge, as the survivors did).
Since hotshots typically never believe that they themselves will be killed fighting fires, it is important to keep the last resort fire shelter weight down so that they will continue to carry them (versus "mysteriously" losing them at the first opportunity). Let's be real, we're talking about young adrenaline junkies here--of course they don't think they could be the one to die because they just don't believe it. In the worst case scenario, every ounce they have to carry can be the difference between life and death.
It is a tough choice and I'm glad I'm not the one to have to make it. It is a choice, though, informed by a century of intensive research and compilation of statistics.