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Comment by jabretti | Hacker News Reader

This is naive. A bushfire is huge, hot, and fast-moving, consuming entire trees in seconds. Your mains-pressure water sprinkler will not deter an onrushing wall of flame in the least... and worse, an automated system would take water away from where it's needed.

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It won't save the house if everything around is afire, but pictures like the burnt-down HP historical archive building[1] look like it could have been saved with a sprinkler wall. (For god's sake, the trees next to it are perfectly OK.)

[1] http://www.pressdemocrat.com/business/7559762-181/hewlett-pa... (see picture 3)

Indeed, some people in the recent fires were able to save their homes with a garden hose (!) depending on the intensity of the fire in their area, particularly when the fire was spread by flying embers. That's not unusual in wildfires, though only some fraction of buildings can be saved this way.

I'd argue some fraction is enough. It still represents millions saved in damages.

Yeah, I think it could be a very valuable precaution!

> only some fraction of buildings can be saved this way

In Australia, ember attack is responsible for 90% of the houses lost to bushfires. If you can prevent flying embers from igniting a house, you eliminate most of the risk to the building.

Embers are a big problem, and another one is vegetation near your house. If you have a big dry bush just outside your patio door and it starts to burn, the infrared coming off it can go right through the glass and catch the inside of the house on fire before the outside starts to burn. This is why we preach defensible space (no vegetation within 30-50 feet of the structure).

Here in Australia, external bushfire sprinkler systems are becoming more common. Their main purpose is to defend a house against flying embers, which are the most common way that homes ignite during a bushfire.

They are pressurised using a diesel generator, and each sprinkler head consumes 6 to 20 litres per minute (a typical installation will include 20-30 sprinkler heads) from an independent water supply (not mains - you can rely on that failing in a fire).

A bushfire front will typically pass within five to ten minutes, because as you pointed out, they are fast-moving. This limits the amount of radiant heat a sprinkler system has to cope with.

While fire suppression systems don't seem to me like a good startup model (more of a small-to-medium business), there are good software opportunities for automated and remote-triggered sprinkler activation (because people still evacuate hours earlier, and need a way to turn on the sprinkler system remotely).

Perhaps. But does it have to be water? How do you know something won't work until you try it?

Even with all the fire retardant sprayed onto massive wildfires from the sky, we're unable to stop them. Why wouldn't a different approach work?

If you read about the Napa fires, some neighborhoods in Santa Rosa were entirely burned to the ground not because of a wall of gushing fire, but because some embers from further away landed on dried up brush and leaves and started the fire in that area.

For low, slow fires like grass fires, it does not have to be water. Watery foam with bubbles of CO2 or another fire-inert gas can work well for smothering the fire. But the equipment to make foam properly is expensive and finicky and not all fire departments have it. And foam won't help much as a heat sink which is where water really shines. Heat sinks are what you need for big fires. Lots and lots of water.

Forest fires are never put out with water--you just can't get enough water where it's needed. Instead, you use small amounts of air-dropped water and fire breaks to steer the fire where you want it to go and let it run out of fuel.

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