Sleeping with the gentle breeze of a fan on a hot summer night is one of life's greatest pleasures. Unless you subscribe to the belief of "fan death," that is, where this pleasure will leave you dead by morning. This superstition has been passed down through generations — and mostly in just Korean families, it appears.
According to folklore, the only way to survive sleeping with a fan on is to open the window or use a fan that has an automatic shut-off so it doesn't run all night. The origin of the killer fan story is murky, but does it have any kernels of truth? First, we'll look at all the ways your fan may be trying to murder you in your sleep.
One urban legend claims that a fan's blades actually chop up oxygen into carbon dioxide, making the air in your bedroom impossible to breathe and, therefore, fatal [source: Snopes]. Another says that a fan blowing on you all night can make your body temperature drop so low that it will cause hypothermia, and then death. Or, a fan constantly circulating very hot air won't actually cool you off; the hot air will eventually just suffocate or dehydrate you to the point of your demise. Fans can't cause hypothermia, though. They don't cool the air; they just circulate it. And because no house is air tight, you can't suffocate from hot air or a lack of oxygen.
The issue of "fan death" was such a concern that, in 2005, the Korea Consumer Protection Board issued a warning entitled "Beware Summer Hazards!" One of these warnings, regarding electric fans, advised leaving doors open when using a fan while sleeping, citing possible dehydration, hypothermia and decreased oxygen. The warning also attributed 20 deaths from fans in the years 2003 to 2005 [source: Levin]. However, nobody has been able to confirm these deaths [source: Lee]. Nevertheless, the belief persists even today.
How did this superstition begin? Some believe it grew from a 1970s campaign to conserve electricity. Or it could simply be coincidence — someone finds a dead body in a closed room with a running fan and makes a hasty conclusion. More likely, the person died from natural causes, such as a heart attack. In one case, a man fell asleep in front of a fan after a night of heavy drinking [archived source: Herskovitz].
Interestingly enough, however, the Environmental Protection Agency states in its Excessive Heat Events guidebook that people should not "direct the flow of portable electric fans toward yourself when room temperature is hotter than" 90 degrees Fahrenheit (32 degrees Celsius). This warning came about during the heat waves of the 1980s and 1990s when evidence suggested that fans in enclosed rooms could evaporate moisture from the body faster in heat indexes of 90 degrees Fahrenheit and higher.
So could that Korean grandmother be on to something, after all?