Fan Death

Well, I'll be. I learn something new every day:

Many people in South Korea believe that, when operated in closed rooms, electric fans do not bring heat relief but sudden death... The belief is that an electric fan, if left running overnight in a closed room, can result in the death (by suffocation, poisoning, or hypothermia) of those inside. This belief also extends to air conditioners and the fans in cars. When the air conditioner or fan is on in a car, some people are apt to leave their car windows open a crack to avoid "fan death." Fans manufactured and sold in Korea are equipped with a timer switch that turns them off after a set number of minutes, which users are frequently urged to set when going to sleep with a fan on.

Moreover:

The explanation of fan death is accepted by many Korean medical professionals. In summer, mainstream Korean news sources regularly report on cases of fan death, even if more likely causes (e.g. heart attack, gunshot, alcohol poisoning) are evident.

(h/t Steven)