My favorite myth here is that sleeping in a sealed room (i.e. windows and doors closed) at night with a fan on will kill you. People will point to newspaper stories and reports on TV. More educated people may say that their doctors tell them this (which they often do) or even point to a 2006 Korean Consumer Protection Board report which says:
"If bodies are exposed to electric fans or air conditioners for too long, it causes [the] bodies to lose water and [causes] hypothermia. If directly in contact with [air current from] a fan, this could lead to death from [an] increase of carbon dioxide saturation concentration [sic] and decrease of oxygen concentration. The risks are higher for the elderly and patients with respiratory problems. From 2003 [to] 2005, a total of 20 cases were reported through the CISS involving asphyxiations caused by leaving electric fans and air conditioners on while sleeping. To prevent asphyxiation, timers should be set, wind direction should be rotated and doors should be left open."
This seems really silly to me except when I read that the EPA actually says to not sleep in a room with a fan pointed at you. In case your wondering, it does seem a bit strange that EPA has a publication on this. Best I can tell, it does not mention the likelihood of death.
Given that I have never heard of any other country believing in the dangers of sleep with a fan, I will mark this one down as a myth.