Tuesday, July 9, 2013

Fire

Like a lot of people in the US over the past couple of weeks, I've been thinking about the 19 firefighters who died in the Yarnell Hill wildfire in Arizona.

I have a friend and former student who has worked as a Hotshot.  I confess, it's the kind of job that is simply inconceivable to me.   Unbelievably difficult.  Incredibly dangerous.  Extraordinarily necessary.

I haven't been able to put it out of my mind since I read portions of Bill Streever's Heat: Adventures in the World's Fiery Places (2013).

I don't think I ever understood the dangers of wildfires, in any real, immediate sense.  Obviously, it's fire.  Obviously, fire is dangerous.

But wildfires carry a level of danger and unpredictability that it's hard for me to imagine.  Grappling with them--doing the job that the Hotshots do so well--is not just about showing up with a hose and a helmet and setting to work.

As Streever points out, as wildfires spread, they begin to create their own weather.  The heat dries any moist vegetation, creating its own fuel.  "The fire reaches the crest of a hill, with an updraft on one side, and a downdraft on the other":
The challenge is to come up with models coupling the reasonably static reality of the landscape with the overwhelmingly dynamic reality of an uncontrolled wildfire.  The challenge is to create a model that captures land burning with a ferocity capable of creating sounds that firefighters have compared to the sounds of trucks, trains, tornadoes, hurricanes, and volcanoes.
In the case of the Montecito Tea Fire in 2008, some homeowners had about 15 minutes of warning before their homes were engulfed in flames.

Streever describes the fire shelters that were deployed by the firefighters at Yarnell Hill:  "It is a tightly packed cube of folded foil and fabric, wrapped in plastic.  The firefighter's first line of defense is to avoid being caught by fire, but these shelters have saved the lives of more than 250 firefighters who were surrounded and burned over."

Shaped "like an oversized sleeping bag" when opened, "[t]he fabric is aluminum glued to a fiberglass frame."  Firefighters are trained to deploy them in less than 20 seconds.  "The idea is simple: when surrounded and at risk of being overwhelmed by fire, find a firebreak, set up the shelter, crawl inside, and hope for the best."

Nevertheless, as Streever points out, "[t]he shelter will not survive direct contact with flames."  It will melt, like anything else would under such conditions.  Temperatures in a wildfire can typically reach more than 2000 degrees.

The principle of a fire shelter is to hold the portion that faces the advancing fire with your feet and stay as low as possible, breathing close to the ground.  "This close to the flames, strong winds will tug at the shelter."

"Typical burn-overs, typical entrapments, last fifteen to ninety minutes."

May the men who died at Yarnell Hill rest in peace.

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