You always see wildlife firefighters with drip torches. I understand they are used to control/suppress fires, but how does that work? Why does it work as a fire suppressant?
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If you burn the grass, it makes a region of “burnt grass” that won’t catch fire. So, you get in front of a fire, using your trucks, and burn up all the grass and easy to burn stuff. When the wildfire gets to that place, it goes out.
Firefighters also use this technique to burn “escape paths” for them to run away through if the fire turns unexpectedly.
Wildfires tend to start by burning dead plant material that ends up collecting on the forest floor. If there is a bunch of built up fuel then if/when a wildfire starts it is going to use that fuel to burn large and hot.
To avoid this humans can periodically set off controlled burns to reduce the amount of collected fuel in the forest. These deliberate wildfires are smaller due to the lower amount of fuel and are easier to control.
Starting those controlled wildfires involves people going out into the forest and setting it on fire, and a drip torch helps do that by dripping flaming fuel onto the ground.
the idea is; that if we can remove as much easily combustible material; we can slow or stop the fire.
its hard for a wildfire to ignite a living tree; its easy for a wildfire to ignite all the dead fallen branches/logs, old leafs, needles. (which then burn enough to ignite the trees) So firefighters can create fire lines that they control to burn back towards the main fire. This should slow or even stop the wildfire spread enough that other containment or extinguishing measures can be taken
Wood needs to heat up in order to actually burn. This is why you need tinder and kindling when starting a campfire; you use things that catch fire easily to heat up the firewood until the firewood is able to burn.
A wildfire is similar; it only spreads when it gets the nearby trees hot enough to burn. If there is a lot of natural tinder and kindling that becomes easier; heat those up a little and they start burning, which heats up the trees. This way, a fire can spread with just an ember landing in the wrong place.
By doing controlled burns, firefighters can remove a lot of the tinder and kindling without letting the trees get hot enough to burn. The wildfire can still spread, but it takes longer.
A drip torch is like the barber of the forest. It trims the small, flammable stuff so the big, bad fire can’t grow unruly.
Think if it this way.
If you have a cigarette lighter and you light it and hold it to a tree trunk, the lighter will run out before anything happens to the tree.
Now take that same lighter and hold it to all the dried leaves and foliage on the ground. You will start quite a bit fire very soon.
So these back burns aim to remove that dried material in a controlled fashion so that it isn’t a set on fire by the main fire. In forest fires, there are a lot of burning embers carried by the wind that travel in front of the main fire front. Of they land on a tree, nothing will happen. If they land in dried material, then can start other fires that join up to the main fire front. So removing this material is key to stopping a fire front progression.
It is also commonly used as a fire maintenance and mitigation tactic, where controlled burns reduce that amount of available material to start a fire.
It is not a new thing, indigenous peoples in Australia have used this technique for thousands of years.
The following article explains the benefits, and also has a video.
https://www.watarrkafoundation.org.au/blog/aboriginal-fire-management-what-is-cool-burning
Wildfires will typically burn with the wind blowing them along. This is called “head” fire. So to put one out, you get ahead of that location and light your own fire line using a drip torch. That line will spread and burn moving perpendicular (ideally) to the fire line. Firefighters will immediately put out the part burning with the wind (otherwise it will turn into another head fire). That can be done simply by shoveling dirt on that part of the line, raking all fuel away from it (ahead of time) or letting it run into a plow line of fresh dirt.
The other part of the fire line will burn against the wind direction. This is called “backing” fire, and it moves pretty slowly. Ideally, by the time the wildfire line meets the backing fire, there is a large section of already burned land, so the wildfire has nothing left to consume and will go out.
You can do all of this with matches or a lighter, but a drip torch makes it easy to set a nearly continuous line of fire instead of having to use lots of matches, etc. The fuel used inside is a mix of gasoline and diesel. Diesel won’t burn on its own, but pure gasoline is explosive. Mixing the two together allows the drip torch to put down drops that burn for a few minutes on the ground so that the surrounding fuel will start burning.
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