One of the many approaches of fighting forest fires involves dropping water from aircraft into the fire and the trees in its path. This cools the fire and slows its progress giving ground crews more time to create firebreaks and evacuate people as well as helping quench the fire.

As the payload of 'planes and helicopters is limited it is important that they carry the material that most inhibits the fire. Foam starves fire from Oxygen but is ineffective in an intense fire. Water cools the fire but evaporates quickly and disperses as water vapour.

Chunks of solid Carbon Dioxide (dry ice) dropped just ahead of the path of the fire would take more heat from the fire per unit mass than water and, when turned to gas, would hug the ground better than other components in air, starving the fire of Oxygen.

It's not an instant solution but could provide a few more minutes for the ground crews.
-- st3f, Dec 29 2001

(?) Homes Renewed by Fire http://www.halfbake...Renewed_20by_20Fire
A way to abandon and rebuild homes rather than defend them. [Aristotle, Dec 30 2001, last modified Oct 04 2004]

How about liquid nitrogen?
-- bristolz, Dec 29 2001


Good grief Mr Sealy, You're a mind-reader. I almost put a brief predictive pedant prevention note at the end on exactly that topic but deemed it superfluous. How wrong I was.

Had I put it in, the gist of it would have been that anybody in the area would, of course, have to wear breathing apparatus.

bristolz: Liquid nitrogen would also work. I prefer CO2 as it's easier to manufacture, safer to handle and, being heavier in gaseous form, hugs the ground better. Liquid Nitrogen does have better cooling, though, so it might be more effective than Carbon Dioxide if dropped directly into the fire.
-- st3f, Dec 29 2001


Why would it kill the trees?
-- bristolz, Dec 29 2001


Freeze them and damage the cells such that thawing out wouldn't help. Trees often 'explode' when frozen, thus scattering splinters and other easily ignitable bits of wood.

Might work if one sprayed the liquid nitrogen from above, rather than dropping it like water. It would have boiled into gas by the time it hit all but the highest leaves, and may still help put out the fire. More expensive, though.

CO2 isn't a bad idea, if you could get big enough blocks of it to let it sublimate for a while...Problem is that fire isn't two dimensional, and the upper part of the trees would still burn...Plus the aforementioned problem with ground personnel.
-- StarChaser, Dec 29 2001


I doubt that it would freeze the trees, at least with the quantites that can be carried aloft. The boiling off, the gas, the suffocating nitrogen, is what you want (plus the cooling effect), yes?
-- bristolz, Dec 29 2001


If we are talking about UB's part of the world, I am told dead trees would not be a problem as they grow up again (cannot think of the right word) all too soon and if they had been chopped or burnt at a better time of year in the first place,there would not be the problem there is now.
-- po, Dec 29 2001


While heat is one third of what makes fire, it's not the one that's usually fought against. It's more denying oxygen than cooling. I think the gas by itself is more useful than the heat removal. But since air is 80% nitrogen already, I don't know how useful nitrogen might be.

If you took a bucket of the sort used in firefighting, insulated it and filled it with liquid nitrogen, then dumped it all in one place as the water is done <Not one point, but one relatively small area> I think it would hold together well enough to kill a couple of trees.
-- StarChaser, Dec 29 2001


saplings. maybe.
-- bristolz, Dec 29 2001


I don't think this would work. Water not only squelches the fire itself by cooling and smothering, it tends to hang around to retard flare-ups.

Both of the gases mentioned have extremely low boiling points. Both would begin to become gaseous on contact with air. I would tend to think that either might put out a fire in the immediate area (if dumped in solid form), but then be boiled off and carried up and away by the heat generated by the remaining fire. And I doubt that much of the liquid forms - dropped from a plane - would make it to the ground at all.
-- phoenix, Dec 30 2001


While I appreciate the sentiments, realistically... WIBNI
Pretend it did work... Environmental impact on life forms other than trees would have too many consequences. Alarmists would come a-knockin'
Forest Fires are actually a necessary part of Natures self-maintenance. Alarmists...
All structures should be pretreated with Fire Retardants. If not all, certainly those in susceptible regions.
While on the subject of Fire Retardants, I would advise each halfbaker to equip their home/office/car(s) with appropriate fire extinguishers if not so equipped, check and recharge if need be if already equipped.
Pop and Grandpop (whom I never met) were Fire Chiefs/Water District Managers.
-- thumbwax, Dec 30 2001


Hadn't considered the other critters in the woods, at least some of whom could outrun the fire, but few would be able to outrun an oxygen-excluding gas...
-- StarChaser, Dec 30 2001


They don't realize that the fires ARE part of nature in the area.

Doesn't make it better, means they're idiots. Which we already knew...

I said blocks to let it sit and keep providing for a while, rather than little bits that would pretty much instantly go 'foof' and be gone in the updrafts. California has problems with brushfires too, some of them at least as large as yours...And Florida has had even larger ones.
-- StarChaser, Dec 30 2001


I agree wholeheartedly that the fires are part of nature. In fact I've added a new idea to propose the way I feel people should adjust to them (see link).
-- Aristotle, Dec 30 2001


AfroAssault must be on vacation. ¯UnaBubba: Wonderful explanation of flash fire, explained quite a bit to me. Would some high explosive devices suspended in sclerophyll or melaleuca thickets set to detonate at the flashpoint of vaporized sap serve the dual purpose of depriving the fire of oxygen and dispersing plant oils? Bonus, things are knocked down and blown to bits!
-- reensure, Dec 30 2001


How's about an iceberg trebuchet? You just launch are really really big iceberg at a wildfire and let it cool down the fire! I just hope whoever fires the thing misses my house.
-- Willie333, Oct 10 2005


*gets to work on Iceberg TrayBucket*
-- shapu, Oct 10 2005



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