The Tempura Flakes on Sushi Rolls Are Spontaneously Combusting and Starting Fires

Last week, the Lantana Cafe in London's Fitzrovia neighborhood caught on fire shortly after it had closed for the day. It took the London Fire Brigade almost two hours to get the flames under control and, after a brief investigation, they suggested that the blaze was started by a pile of freshly laundered towels that had been stacked in the cafe's kitchen. Yes, towels.

"Sometimes when materials are cleaned, put in tumble dryers and then folded and stacked, the heat from the tumble drying cannot escape. This can result in a high enough temperature allowing it to build up to a point where it smolders and eventually ignites," a Fire Brigade spokesperson said in a statement. That freakish kind of fire has a tendency to happen to fabrics that have previously been stained with cooking oils, like on the towels, tablecloths, and chef whites you'd find in a restaurant.

But don't post on the /TodayILearned subreddit yet—because oil can seemingly self-heat when it's elsewhere in the kitchen, even in edible ingredients like tempura flakes. Two sushi restaurants in Madison, Wisconsin have caught on fire since April, and the city's fire investigators believe that both incidents were caused by deep-fried tempura flakes. (Yes, the same delicious bits that top any sushi roll that the menu describes as 'crunchy.')

According to Wisconsin Public Radio, no one was hurt during the April 5 fire at Sumo Steakhouse and Sushi Bar or during the May 10 blaze at Takara Japanese Restaurant, but the two incidents caused a combined $575,000 in damage. The owners at the Sumo Steakhouse had heard of spontaneous tempura combustion before, but had never seen it until they watched their own surveillance footage from the night of their fire.

"Restaurant staff report that flour is routinely deep-fried for use in some of their sushi products," the Madison Fire Department wrote in its report. "After being deep-fried, the flour is left to drain and cool for a day. In this case, the deep-fried flour ignited on its own overnight, resulting in a fire that caused at least $250,000 in damages." (Four days after the fire, Sumo Steakhouse posted a stock photo-ish close-up of two knives on a flaming grill on its Facebook page. Super weird flex.)

The Madison Fire Department has recently released a warning about tempura flakes, and is urging everyone from professional chefs to at-home cooks about their potential for DANGER.

"Cooking oils, especially soybean oil and canola oil, are known to have a propensity to self-heat under certain circumstances. For example, rags saturated with cooking oil residue can self-heat and undergo spontaneous combustion after being laundered," its bulletin states. "Because the 'crunch' product is heated during the cooking process, then placed in a bowl or colander to cool and drain, the ability for the heat to dissipate is compromised. These conditions can create an environment for a fire to occur."

During their investigation, Madison fire investigators learned about one other tempura-related fire in the state of Wisconsin, and two others nationally. It's also encouraging anyone who makes tempura 'crunch' to spread it on a baking sheet to cool, instead of leaving it in a metal bowl or in a colander, where the heat can continue to build. They also suggest not leaving it unattended in a restaurant overnight.

Oh, and if you're doing a restaurant's laundry, you might not want to fold and stack it right after it comes out of the dryer. Sometimes it's cool when the roof is on fire, but not when it's that of your restaurant.