In Korean superstition, an electric fan is sometimes believed to cause death when left running in a closed room. This belief is widely known as fan death.
The superstition became prominent in South Korea during the twentieth century and has been associated with warnings in newspapers and instructions attached to fans. Proposed explanations have included hypothermia, suffocation, and carbon-dioxide buildup, but ordinary household electric fans do not remove oxygen from a room or create a known lethal mechanism in the way the legend claims.
South Korean authorities and scientists have repeatedly challenged the idea, although some people still use timers or open windows while sleeping with a fan. The story is a classic example of a modern urban legend: a familiar appliance is linked to unexplained deaths, and a warning is repeated until it gains cultural authority.