A "fire bunker," field proven:

http://www.babble.com.au/2009/02/09/nagging-wife-saves-family-from-bushfire/

Egads, you read the little quote in that link and the owners are saying that the "fireproof" door to the bunker was already warped and buckled from heat and wouldn't close properly in the time it took for them to realize that they needed to seek shelter? That's a lot of heat!

Actually, one of the points that I've read a number of times is just how fast these wildfires spread--much, much faster than is typical. That seems to be a primary reason why so many people were overcome by flames in their vehicles. These weren't necessarily people who waited "too late" or were trying to fight the fire and then fled at the last second. They could have been people who usually leave early and who are accustomed to living with the danger of fire but the flames were there before anyone knew what was happening.

I read one interview where the person was saying that initially, they saw a fire burning in the distance that would normally take a day to reach their position. However, in this case, it took less than an hour to be at their doorstep. Can you imagine? One minute, you see a distant fire and then you could be on the other side of your house, loading up the car, getting ready to bug out with plenty of time to spare, and next thing you know, there's a huge wall of flame roaring towards you from different sides.

That's frightening stuff. Actually, every wildfire here in Southern California, you always see people interviewed on TV who aren't planning on fighting the fire and have their car all loaded up, ready to go, but they insist on staying until the last second before evacuating. I'm a homeowner, too, and I could never understand that thinking.

It is said that firestorms create their own wind, and even their own tornados.

Australian Bill Mollison ('father' of the permaculture movement), said every homestead should have an underground bunker for these fires. He recommended an adobe-type dogleg wall in front of the door to help reflect the severe radiant heat from the fire.

Sue

Yep,and put a heat reflector in front of your $1000 fireproof door so that it doesn't take a direct blast. That was a nice design otherwise, having it attached to a water tank probably kept the inside temp a bit lower.

I'd like to hear comments from the people with firefighting experience on this temperature question.

I recall reading that human lungs are extremely fragile with respect to hot air - temperatures that are readily survivable on other parts of the body are fatal if air at that temperature is inhaled for even a single breath.

I'm wondering about the usefulness of a "wildfire shelter" that doesn't keep the interior air "cool" as the fire passes by. If the air is heated to 1832F that it's going to expand (create a wind) and try to enter through cracks and such in any shelter.

I've ridden out several hurricanes on the waterfront and think most (not all) hurricane evacuations are unnecessary, but I'm not sticking around for any fire of any size.

PS. I prefer to reserve the word "luck" to mean "opportunity meets preparation". When someone survives in spite of themselves that's not luck, that's an accident: "Joe defended his home from the inferno with a garden hose but survived by accident"

Wildland fires can and do get large enough to create their own localized weather systems (as the Australian fires are certainly large enough to do). There can be enough heat to generate updrafts that can take a flaming pine cone aloft and carry it several kilometers downwind. Wildland firefighters during entrapments have said that the flame front sounded like an oncoming train - that's a lot of air movement.

"When the first fire front came across us, I would estimate that the winds were probably in excess of 70 miles per hour.The sense of power that you had around you, that energy release that we had around us was just absolutely incredible. It was a very humbling experience. I mean you felt very small and very insignificant at that point.
- Entrapment survivor

"Tornado" is a little misleading...think "firewhirl" which is like a dust devil, but with flame instead of dust. Firewhirls demonstrate atmospheric instability and the potential for extreme fire behavior but are typically small (maybe 10 meters high?), short lived (a few seconds) and their associated danger is their potential for blowing a control line.

Hmmm...I can only answer this qualitatively, but the fire shelters that wildland firefighters carry are designed to reflect radiant heat and create a cooler air space to help protect the lung tissues. This refers to the portable shake-and-bake fire shelter, not the fire bunker in the previous post. Fire guys (and gals) are trained to lay in the shelter face down with their face in cooler earth.

"They found in testing fire shelters set up in prescribed burns that air temperatures increase at a rate of 9ºF. per inch rise above the floor of the shelter." (link below, and please note that was for a prescribed burn, not a firestorm)

A dry bandana may be used to help screen out smoke, dust, etc...but it has to be dry since steam carries a lot more heat than dry air. What is stressed over and over again in training is that the fire shelter's only purpose is to create a cooler air space to protect the lung tissues. Yes, I repeat myself. Yes, it's that important.


"If you go into a steam room, 130 degrees is about as hot as you can stand it," says Putnam. "In a dry sauna, though, you can take 180 degrees. You can tolerate hot dry air better than moist air." (not talking about lung tissues though)

The single breath deal is when you get a gasp of something not-nice (smoke, superheated air, whatever), that's going to trigger a gag reflex...and so you inhale again...and again...

There's a fair amount of literature out there about the environmental and physiological effects of wild land fire. Google "fire shelter" and pay attention to any research coming out of Missoula.

http://wildfirenews.com/fire/articles/ted.html

Found the fire shelter instructions:

http://www.nwcg.gov/pms/pubs/fireshelt01.pdf

"I'm wondering about the usefulness of a "wildfire shelter" that doesn't keep the interior air "cool" as the fire passes by. If the air is heated to 1832F that it's going to expand (create a wind) and try to enter through cracks and such in any shelter."

The shelter that Mollison advised is like an underground bunker. It is at least halfway dug into the ground, with a non-wood structure over it (filled sandbags would be good, forming a dome over the hole). Then the structure is covered with a foot or two of soil (preferably planted to something with a good root system, like white clover).

With a shelter like this, it will help you to survive a moving firestorm. Only the temps outside are that high. It would take quite a while of sustained heat to heat up the soil around the shelter to the point that it would be a real oven. The moving flames might also use all the oxygen in the area, which I understand can cause you to pass out for a while. (This is why you are advised, when wading into a watersource from a local fire, that you may pass out and drown when the oxygen in the air is depleted.)

I had also read somewhere that someone built an underground shelter and had an open pipe extending from the shelter down into a hand-dug well (above water level). Since heat, by its very nature, must rise, the air inside the well would be cooler, and would/might provide oxygen for the shelter. I don't remember if this was actually done, actually tested, or was just theory. I'm just tossing it out here as an idea to consider. Maybe someone else here can say if it's a viable plan.

Sue

Can you cite a source (sources)? I'm not trying to be antagonistic, but this is something I'd really like to learn more about. Your first safety zone in a wildland fire really is a body of water.

Well, it's official now. The Orange County Fire Authority, which had said last year that it was reviewing the appropriateness of stay-and-defend for Orange County, California, decided against endorsing the policy or providing any formal training for home owners. They've had a couple public meetings in communities, like hard hit Yorba Linda yesterday, and announced the decision.

I believe that OCFA already came to this conclusion even before the recent disaster in Australia, but I'm sure that the loss of life there only reinforces their decision.

I have yet to run across any news articles about folks who did stay-and-defend and came out OK in this latest round of Australian fires. It's possible that the fires this time were just too much even for a well-prepped, well-equipped homeowner and homestead. Well, or maybe the media is focussing elsewhere, like on the tragic loss of life.