It is bushfire season again in Oz. Just last February a fire which destroyed 72 houses came within a few hundred metres of my home. I own numerous watercarts with watercannons so was better off than most people but didn't like putting my employees, myself or my equipment in the path of the fire. This meant it was down to just me and one truck on standby at the house but, as the fire danger lasted several days, it was pretty draining. If you left the exclusion zone for a rest you weren't allowed to return.

I have been approached several times over the years by companies spruiking superabsorbent gels designed to be sprayed over buildings, plants and so on which provide a considerable amount of fire resistance and longevity - especially compared to just plain water. This would be costly and messy but still could be a option for protecting your property while allowing you to decamp to safety.

The problem is that I could never put together a good business case for selling the stuff. You don't want to spray the gel over everything hours or days ahead of time when the fire may or may not even reach you - but neither do you want anyone workIng 1/2 hour or so ahead of a raging firefront.

My idea is to create a range of metre-high decorative mushroom shapes which could be strategically placed around one's yard. They would hold a quantity of this gel surrounding either a volatile compound or merely a compressed gas. When the ambient temperature reaches a pre-set threshold of, say, 65C then the whole lot is violently discharged up through an aperture or spinning nozzle on the top of the mushroom covering everything in the vicinity with fire protectant gel.

They could be any shape you wanted if mushrooms aren't your thing. Gnomes, unicorns, or abstract designs would all work equally well. I would like long snake shapes on either side of my roof crests. Firefighting koalas or beehives could be suspended in trees.

I am aware that it is possible to plumb up sprinkler systems and all that but it is an expensive option which requires pumps, multiple waterlines and an adequate supply of water and water pressure. Electricity is often cut in fire zones, water pressure drops and diesel pumps run out of fuel so the power source is problematic.

I'd be seriously interested in hearing any suggestions from my fellow HBers on how to best flesh this idea out.
-- AusCan531, Dec 30 2011

Wikipedia description of fire fighting gels http://en.wikipedia.../Fire-retardant_gel
[AusCan531, Dec 30 2011]

Fighting fire with explosives http://en.wikipedia.../wiki/Oil_well_fire
Do not try at home (unless you are a Hellfighter or a fully-qualified Halfbaker) [Alterother, Dec 30 2011]

Types of Fire Extinguishers http://en.wikipedia...i/Fire_extinguisher
Includes Fire Extinguishing Ball which is a similar concept. [AusCan531, Dec 31 2011]

The California version Borate_20Bouncing_20Bettys
[normzone, Jul 05 2021]

No moat?
-- zeno, Dec 30 2011


Brushfire season is dry. During dry weather, a moat is just ground that's a little lower than the ground to either side of it.

The exploding bit is easy to accomplish. First, use very highly compressed CO2, which will have a brief smothering effect in its own right. The discharge is triggered by a consumable seal on the pressure outlet that just melts at a certain tempurature (this is already baked, used in Xmas tree extinguishers and elsewhere). Channel the pressure however you want, as stated--through a directional or spinning nozzle, or simply blasting your gel all over the place. If the discharge is powerful enough, it might even extinguish the flames with concussion as well, such as the dynamite method used by hellfighters. <link>

[+]
-- Alterother, Dec 30 2011


[+] for exploding lawn ornaments.

//water cannons// Is there such a thing as a fog cannon ? A couple of those upwind would cool the air before it reaches the building, coat the building in water droplets and quench any ember light enough to be wafted in.
-- FlyingToaster, Dec 30 2011


//Is there such a thing as a fog cannon ?// Maybe a snow-making machine?
-- mouseposture, Dec 30 2011


I don't think I quite understood the meaning of dry. Here dry means the bit in between the rains, what you call rain, we call fog.
-- zeno, Dec 30 2011


That's what it's like here in Maine, too. 'Dry' means 'the sunny parts between the rain / snow / sleet / rhinoceroses / hail / all of the above at once'. But in Australia, amongst other parts of the world, 'dry' means 'one careless smoker can burn down half the continent'.
-- Alterother, Dec 30 2011


^^^//snow-making machine// that's what I was thinking of, using fogging devices instead of refrigeration apparati; outside of [AC]'s specs though.
-- FlyingToaster, Dec 30 2011


Actually, in warm weather, snowmakers like the ones used at the large ski resort not twelve miles from my house produce extremely fine mist that hangs in the air like fog. Not much good for firefighting, but maybe for prevention.
-- Alterother, Dec 30 2011


(D'oh! I knew that.)
I;m not sure that using a snowmaker would be best though: the particle size (in my sub-idea) should be small enough to simply be a fog that is carried to the fire-facing side of the building mostly by the wind.
-- FlyingToaster, Dec 30 2011


A snowmaker would be ideal in that application. The modern ones produce a very fine mist, almost a vapor, that freezes in the air. No artificial refridgeration is involved. By my observational estimate, they project a 60-degree fan or cone to a range of 20-30 yards, or a stream up to 50. The 'snow' thus produced drifts nicely on the wind (for hundreds of yards, sometimes), allowing one unit or a chain of units to cover several trails simultaneously if properly arranged. On bright, sunny days when the conditions are just right for snowmaking, the mountain looks like it's boiling with huge plumes of steam, like a frozen volcano.

Only drawbacks: extremely high pressure requirements, cannot be used in high winds, and they must have a continuous high-volume water source. If there are any interruptions or even drastic fluctuations in the flow, the entire system must be bled of air (I overhear the snowmaking crews bitching about it all the time).
-- Alterother, Dec 30 2011


I think the problem with snow would be the lack of volume of water...which wouldn't be much of a heat-sink.
-- not_morrison_rm, Dec 30 2011


Some snow machines spray both ice particles and water, others just water.
-- FlyingToaster, Dec 31 2011


There are such things as fog cannons (my company makes fogging systems) but would be inappropriate because of the wild, swirling super-heated winds usually associated with fire fronts. The problem with fine droplets (or snowflakes) or foams is that within 15 seconds they'd be either totally evaporated or blown to the next state. The answer is to have heavy, sticky droplets resistant to evaporation and somewhat resistant to blowing away. A moat just wouldn't suffice I'm afraid other than providing a place of refuge, if you have scuba gear, so you can watch your place burn.

It's hard to get across in words the nature of conditions but the video [link] I put up will help. Even my sticky gel would be windblown but if the house is surrounded by exploding mushrooms hopefully those upwind (which is where the fire and the heat would be coming from) would spatter their goo in the right direction onto the house.

Houses tend to go up either because of ember attack (where burning leaves etc get blown into crevices such as gutters or into evaporative airconditioners), burning trees falling onto the house or they simply burst into flames due to the intense radiant heat. I have cleared trees from near the house, built a screenmesh cover for my a/c and have everything I need to plug the gutters and fill with water. If I could cover the surfaces of the house and trees with enough gel to survive the most intense 1/2 hour when the firefront sweeps through I will have done all I could with this property. If I ever build a house in the bush I will design a fireproof one from the get-go.

But even if I eventually construct a totally fire-proof home/bunker for myself there will still be tens of thousands of houses needing a semi-automated gel spraying system. Awareness has never been higher after the last 2 years and any remedial solution for existing properties would be most welcomed.

The linked Wikipedia article on fire extinguishers does list "Fire Extinguishing Ball" which self-destructs when subject to heat but covers only about 5 sq.m. and is suitable for passive suppression but would be more suitable for indoor fire fighting.

Any ideas for really ramping up the spraying system other than just compressed CO2? I'm thinking solid propellant rocket motors to really give it some oomph as I want to move considerable mass quite a few metres into the air.
-- AusCan531, Dec 31 2011


Well, solid propellants typically involve a certain amount of, er, fire. Quite large amounts of it, actually. What you want is an explosive, not a propellant. I don't know how you'll deliver the gel without destroying it, though; that's a question for [8th] or [MikeD].
-- Alterother, Dec 31 2011


... asbestos house-cozy ?
-- FlyingToaster, Dec 31 2011


You know, we're making this harder than it needs to be. What if we just loaded up an 80mm mortar tube with this firefighting goop?
-- Alterother, Dec 31 2011


If we'd all just build like hobbits...

Seriously though good idea. It should vent its gas/foam directly towards the strongest heat signature.
-- 2 fries shy of a happy meal, Dec 31 2011


//other than just compressed CO2 ?// how about moving boilers into the woods ? when enough pressure has built up a pressure-valve breaks, steam rushes through the pipe and blows off the gel for that area.
-- FlyingToaster, Dec 31 2011


//The answer is to have heavy, sticky droplets resistant to evaporation and somewhat resistant to blowing away.//

Tapioca pudding, then?

I recall having to eat it at boarding school and it making you feel like you'd swallowed a few kilograms of lead shot.
-- infidel, Dec 31 2011


Everyone loves 80mm mortar tubes [Alterother]. That's a given. But where's the whimsy I ask? Where is the whimsy?

99.999% of the time these devices are going to just be sitting around the yard. Would your better half be receptive to surrounding your abode with mortars clearly aimed at the house? Mine's twitchy enough with my good ideas now.

[FT]'s idea of boilers in the woods is good but rather than water I'd prefer some other volatile that undergoes phase change at less than 100C.
-- AusCan531, Dec 31 2011


Ether, perhaps? Maybe not...
-- infidel, Dec 31 2011


// Would your better half be receptive to surrounding your abode with mortars clearly aimed at the house? //

Probably, but The Good Fairy Jenny is an exceptional woman. I'm not saying she wouldn't go around and double- check that I'd removed all the warheads, of course.
-- Alterother, Dec 31 2011


////The answer is to have heavy, sticky droplets resistant to evaporation and somewhat resistant to blowing away.//

break a gazillion eggs, spray them over the building, heat gets used up folding the proteins and making it cooked, and then everyone can have an omelette after the event...
-- not_morrison_rm, Dec 31 2011


Broken eggs and half bacon?
-- AusCan531, Dec 31 2011


..and you could probably use potatoes in foil as a kind of protective wall...the heat gets used up cooking the potatoes...how much am I getting paid for these again?
-- not_morrison_rm, Dec 31 2011


Potatoes? They're pretty cheap.
-- infidel, Dec 31 2011


Damn, there goes the patent
-- not_morrison_rm, Dec 31 2011


Sir Francis Drake got there first. They're about a 66c a pound these days, for orders of a ton and up.
-- infidel, Dec 31 2011


That's ok, my appearances here are strictly pro bono
-- not_morrison_rm, Dec 31 2011


I can't stand him, the sanctimonious Irish git.
-- infidel, Dec 31 2011


//Everyone loves 80mm mortar tubes [Alterother]. That's a given. But where's the whimsy I ask? Where is the whimsy?//

Use gels in a variety of gay fluorescent colors: Green, pink, blue, orange, red... oh, wait...
-- Whistlebritches, Jan 01 2012


//Use gels in a variety of gay fluorescent colors// Now we are cooking... oh, wait...

I think [Alterother] is correct and what we need is a verrry slow burn explosive. Something which could drive a piston with enough power to forcefully eject 150 litres of gel through a nozzle in less than 2 minutes. [8th]?
-- AusCan531, Jan 02 2012


+ when I’m cruising * random*, I wonder how I have missed so many great ideas!
-- xandram, Jul 05 2021


Thanks [xandram]. I briefly did some research on this idea with the half-assed notion of baking it in real life. For a self-contained propellant I looked at buying airbag gas inflators on Alibaba but couldn't calculate how many I'd need to go off in succession to create the pressure I needed. The whole idea is now relegated to the part of my mind labelled 'maybe someday projects'. (Think of a hoarder's garage).
-- AusCan531, Jul 15 2021


//What if we just loaded up an 80mm mortar tube with this firefighting goop?//

...And then train everyone in their use! Not only will the nation be safe against fire, it will be resistant to fire bombing and to a lesser degree to actual invading armies.
-- Voice, Jul 15 2021


//Houses tend to go up either because of ember attack (where burning leaves etc get blown into crevices such as gutters or into evaporative airconditioners), burning trees falling onto the house or they simply burst into flames due to the intense radiant heat.//

So the problem is clear: houses should not be built of material that easily catches fire. A reinforced concrete dome covered in a shell of copper should show some resistance, especially if the copper is continued into a large moat.
-- Voice, Jul 15 2021



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