Fire whirls are towering columns of flames that rise high, move slowly, and are difficult for humans to extinguish using direct methods.
Exploring the Mysterious Fire Whirl Phenomenon of Nature
Firefighters observe a fire whirl on the southern slope of Mauna Kea volcano in Hawaii, USA, on August 29. The fire whirl was created during a wildfire covering an area of 566 hectares. (Photo: National Geographic).
Fire whirls—also known as fire devils or flame vortices—are not a rare phenomenon. However, they are seldom documented in scientific literature. This observation comes from Jason Forthofer, an engineer specializing in wildfire research at the Montana Department of Natural Resources and Conservation in the USA. Recently, fire whirls appeared in São Paulo, Brazil, due to months of drought leading to numerous wildfires in the region.
According to National Geographic, Forthofer studies “fire devils” to protect firefighters.
“If we can identify the conditions that lead to the formation of fire whirls, it would provide valuable information for firefighters, as some have been burned by fire whirls,” he stated.
Fire whirls occur when air is highly turbulent in areas with extreme heat (such as during wildfires) and create swirling winds. These swirling winds can lift flammable gases and burning materials. A fire whirl consists of a core (where combustion actually occurs) and an area of air surrounding the core. The surrounding air continually swirls and supplies oxygen to the fire.
The core of a typical fire whirl usually has a diameter of 0.3 to 0.9 meters and a height of 15 to 30 meters. However, under favorable conditions, Forthofer notes that the core of a super-sized fire whirl can reach several meters in width and heights exceeding 300 meters.
“Super-sized fire vortices occur at least once a year in the United States,” Forthofer confirmed.
A fire whirl moves near the chimney of a burning building in an unidentified location in the USA in 2010. (Photo: National Geographic).
The temperature inside the core of a fire whirl can reach up to 1,093 degrees Celsius—hot enough to ignite debris that the wind lifts from the ground.
“This phenomenon is similar to the scenario where we burn flour. If a sufficient amount of flour rises into the air, we can ignite it. But we cannot burn the pile of flour on the ground,” he explains.
The flammable gases released by trees serve as fuel for most fire whirls.
When lifted by the swirling air, these flammable gases enter the vortex. When the vortex reaches an area with sufficient oxygen and high temperatures, it ignites. This is why the flames in the core can shoot up so high.
“Those gases cannot ignite until they mix with a large amount of oxygen. They can only mix with oxygen when they rise high,” Forthofer noted.
Fire whirls do not remain stationary, yet their speed never exceeds that of a person walking. They can incinerate everything in their path and blow burning debris into the air.
The winds generated by fire whirls can also pose dangers. Large fire whirls can produce winds reaching speeds of up to 160 km/h—strong enough to uproot trees. Fire whirls can last for over an hour, and humans cannot extinguish them using direct methods. The only way to extinguish or weaken a fire whirl is to remove its supply of oxygen.
