The University of Louisville’s men’s basketball team will play Saturday in the Final Four, and Metro Police are warning fans to celebrate without lighting couches on fire, as fans are sometimes wont to do.

West Virginia University lays claim to the tradition of lighting a couch on fire after the local team wins the big game…or loses a game…or even plays any game…ever. But the trend has spread. Last year, there was a string of couch burning across Lexington after the Kentucky Wildcats advanced throughout the NCAA tournament, and sports-related couch fires have been spotted in Michigan, California and Texas.

“It’s a very bad idea,” says Arlene Blum, the executive director of the Green Science Policy Institute. A recent study showed that a majority of American couches tested positive for halogenated flame retardants, which are toxic. Even though they’re called flame retardants, these chemicals won’t stop a couch from burning, and Blum says their presence makes the burning even more dangerous.

“If a couch with flame retardants burns, these halogenated flame retardants convert to dioxins, and dioxins are among the most cancer-causing and toxic and persistent chemicals we know,” she said.

“Dioxins go into the environment and they stay forever,” she said. “They don’t break down. So when you add dioxins to the environment, it’s a really long-term issue. And they stay in our bodies for a really long time, too.”

And if all that isn’t enough to dissuade you from lighting a couch on fire after the game, any local revelers caught burning couches could face arson, disorderly conduct or property crime charges.