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.

I have followed the discussion with interest. I am genuinely puzzled as to why fire bunkers, shelters, call 'em what you will, are not employed more widely in the bush/suburban interface.

Susan, you are in Australia, as I am? Well, you know the scale of the disaster and the cumulative factors that triggered the firestorms.

Four years of drought, a huge fuel load, drying winds all conspired to produce the Perfect Firestorm.

Cost as at five days after Black Saturday:

181 lives lost. Many others seriously burned.

1100 homes destroyed.

200,000 hectares burnt, uncounted numbers of stock lost and farms destroyed.

There will be a Royal Commission and Coroners Courts, but there's no doubt this mega-fire was way beyond any human agency to combat. There is no sight more pitiful than someone standing on their roof [ usually in shorts and T shirt ] spraying water around with a half inch hose.

Which brings me back to the bunker/shelter. One or two canny people had shelters, and they survived. These weren't even professionally designed. But they gave that vital protection, just for that 15 or so minutes that it take for a firefront to pass.

There's a guy who lives a few miles from me [south of Sydney ] who has built two reinforced concrete dome shelters on his rural property. He's a Rural Fire Service veteran and says he would obviously trust his shelters with his life.

Simple, proved fire protection, which gives him the option to fight the ember attack against his home until the last minute before retreating into shelter.

Hello, Peter! No, I'm not in Oz, just in western Washington State, USA.

I am a great fan of Bill Mollison, and while I don't agree with a few of his opinions and ideas, he has provided much incredibly good information.

Some people don't realize that earth-sheltered homes or survival bunkers take a long time to heat up, and if they're all or partly underground, the cooler soil temperatures will help to mitigate above-ground temperatures, even if they are extreme.

The simple half-underground survival domes that architect Nader Khalili came up with over 40 years ago, created with just a shovel, sandbags and a roll of barbed wire would be workable structures for most of the households in the entire world. They are fireproof and earthquake-stable. I haven't been able to find photos of those first shelters, just his current crop of above-ground shelters shown at his website http://calearth.org/.

But the premise is simple: mark a 10-ft circle on flat ground. Start digging straight down within the circle, filling the sandbags with the soil from the circle. Stack the sandbags alternating brick-style just outside the marked circle. Allow for a doorway. Lay two strands of barbed wire between each layer of sandbags to prevent shifting. Gradually move the sandbags inward to form a dome. Frame the doorway and add a door. In fire areas, I would use ferro-concrete 'timbers' with door hardware built into it. In areas of heavy rain, I would cover the dome with heavy plastic or a layer of concrete, then cover the entire thing (not the door) with a thick layer of soil, one to two feet thick. Plant it with something with a good root system like clover to keep it cool and keep the soil in place.

Sue