Published on September 1, 2019.

Flakes Aflame

Spontaneously combusting tempura flakes spark blazes, recalling 2018 nacho incident 


Sushi lovers, take note: those deep-fried tempura flakes that give your maki rolls that delicious crunch can go up in flames.

In July, the New York Times reported on a series of restaurant fires linked to deep-fried tempura flakes. The fires occurred in multiple states—most of them, for reasons yet unknown, occurred in Wisconsin—prompting an investigation by the United States Bureau of Alcohol, Tobacco, Firearms, and Explosions.

Investigators found that the fires were the result of a familiar dynamic: spontaneous combustion involving edible oils.

“The crunchy flakes are made by ladling drops of batter into a deep fryer—canola and soybean oils are commonly used,” the Times reported. “[Wisconsin Fire Investigator Kara] Nelson said that both vegetable oils have a propensity to self-heat and that keeping the mix densely piled in a pot or bowl does not allow the heat to dissipate.” The restaurants had reportedly left the flakes in bowls to cool, creating conditions for heat to build up and for spontaneous combustion to occur.

The propensity of edible oils to self-heat in certain conditions was also a factor in a story NFPA Journal reported a year ago: the tale of spontaneously combusting boxes of tortilla chip dust stored outside a chip factory in Texas (“Nacho Typical Fire,” September/October 2018). Firefighters were twice called to the facility as the boxes of ground-up chips ignited, the result of self-heating of residual oils.

Following the Texas incident, Guy Colonna, senior director of Technical Services at NFPA, offered an example of fires that have occurred in commercial laundromats where oily linens from restaurants were washed and dried, then folded and stored before they were allowed to cool. “The culprit turned out to be the cooking oil that accumulated on the linens,” Colonna said. “Because the linens were not cooled before folding and storing, they retained heat that reacted with the oil residue that had not been fully laundered out. The self-heating process continued until ignition occurred.”

A 2011 NFPA report on spontaneous combustion is available online at

ANGELO VERZONI is a staff writer for NFPA Journal. Top photograph: Getty Images