There's a deeply-rooted superstition in South Korea that sleeping with a fan on in an enclosed room can cause extreme health problems, and even death.
Have you ever slept with a fan on to combat the heat? Guessing you survived to tell the tale?
South Koreans believe that sleeping in an enclosed room with a fan on can cause extreme health issue or even death.
"I've heard on the news and through rumours that people have done that and died," a young South Korean told NBC Left field.
Another of his compatriots said: "If you sleep with the fan, you can die. My grandparents told me that often."
NBC's Yohan Yoon, who recently visited his family in South Korea, investigated where the superstition originates from and why it has endured for so long.