Fan death is death caused by leaving an electric fan on with the window closed for an extended period of time. The same also occurs with air conditioners. There are several theories that have been suggested by professionals how this phenomenon occurs.
1) The fan sucks the air out of the room, causing a vacuum, and therefore suffocating the poor, stupid fool who fell asleep with the fan on.
2) The cool air causes hypothermia, thus causing death.
3) The fan chops up the oxygen molecules in the room, suffocating that poor fool.
4) Some odd combination of all these factors
Several deaths every summer are declared as Fan Deaths, and thus the media proliferates this.. idea.
For more information regarding Fan Death, please visit these web sites
Oh, and as a side note. This is not just an urban legend to Koreans. This is hard science. It is taught in school, and Americans here have had to to teach it to thier students. Don't you love teaching lies?