Metal sparks are a common cause of wildfires in California, mainly due to equipment use during the hot dry Mediterranean Summer weather pattern.

The most important requirement for this type of ignition is the receptive fuel bed. Sparks are generated of different sizes but usually possess heat values greater than the 450 deg F. required to ignite cellulose fuels. The dryness of the fuel, heat of the day, and relative humidity, associated with the size of the spark emitted, determines whether a fire will start. Obviously hot afternoons, rather than cool evenings, are an important part of the heat requirement to ignite the available fuel.

California has enacted laws (PRC 4427) concerning required fire clearances for welding grinding and other operations during the time when burning permits are required since this is not an uncommon occurrence. Striking a metal stake with a metal hammer is not addressed in the statute since it is not a common ignition source but can happen as determined in the cause of the Ranch Fire. Watch those survival shows on TV. It doesn't take much of spark from a fire starting flint stick as long as the fuel is dry and the fuel is receptive to receive the spark.

Fire causes from sparks that I determined included, grinding, grading with heavy equipment, rock strikes with metal tracked equipment, exhaust particles from vehicles and locomotives, horseshoe strikes on rocks, and electrical sparks form energized distribution lines. What all these fires had in common was the dryness of the receptive fuel bed the sparked landed in associated with high heat and low relative humidity.

Monty Messenger