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Engineering the spark that starts the wildfire

Video of the ignition of pine needles by contact with a hot steel particle

Hot metal fragments can be created from power lines, overheated brakes, railway tracks or any other manner of metal-on-metal action in our industrialized society. Although these bits cool as they fall to the ground, they can ignite a flame that quickly spreads if they land on a prime fuel source like pine needles or dry grass.

Credit: James Linwood Urban, Combustion and Fire Processes Laboratory, University of California - Berkeley


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ignition of pine needle powder by contact with a hot molten aluminum particle

Some human-caused ignitions are on the decrease, such as those caused by cigarettes and arson. But fires that bloom from stray particles continue to be a problem, particularly around mid-sized populations where there is just the right cocktail of civilization and natural fuels.

Credit: James Linwood Urban, Combustion and Fire Processes Laboratory, University of California - Berkeley


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ignition of pine needles by contact with a hot steel particle

The engineers found relatively large fragments could ignite blazes even at low temperatures, if the fuel was of a certain type. Large shards might come from overheated vehicle brakes, bearings or result from sloppy welding.

Credit: James Linwood Urban, Combustion and Fire Processes Laboratory, University of California - Berkeley


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ignition of pine needles by contact with a small hot molten aluminum particle

Combustion is essentially a chemical reaction that is determined by temperatures and material makeup. For spot fire ignition, the situation becomes more complex, because environmental conditions play a big role.

Credit: James Linwood Urban, Combustion and Fire Processes Laboratory, University of California - Berkeley


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ignition of pine needle powder by contact with a large hot aluminum particle

Using elegant tabletop experiments, the engineers experimented with a variety of metals and fuels, attempting to replicate real-world conditions. Brass, stainless steel, copper and aluminum ranging in size from roughly a pencil tip to an eraser were heated to temperatures from 1,100 to 2,200 degrees Fahrenheit. The metals represent those used in activities or events that are known to cause fires, like welding, drilling, metal-cutting and power surges.

Credit: James Linwood Urban, Combustion and Fire Processes Laboratory, University of California - Berkeley


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While some human-caused ignitions are on the decrease, fires that bloom from stray metal particles continue to be a problem, particularly around mid-sized populations where there is just the right cocktail of civilization and natural fuels. Engineers supported by the National Science Foundation are learning what ingredients and conditions cause this type of fire-starting, known as spot fire ignition.

Credit: at the end of video


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