This picture from Wikipedia bears the following caption:
Electric fans sold in South Korea are equipped with a “timer knob” switch that turns them off after a set number of minutes. This is perceived as a life-saving function, particularly essential for bedtime use.
The reason for this? Electric fans are dangerous:
[F]ears about electric fans date almost to their introduction to Korea, with stories dating to the 1920s and 1930s warning of the risks of nausea, asphyxiation, and facial paralysis from the new technology.
One conspiracy theory is that the South Korean government created or perpetuated the myth as propaganda to curb the energy consumption of South Korean households during the 1970s energy crisis, but Slate.com reports that the myth is much older than that — dating almost as far back as the introduction of electric fans in Korea, and cites a 1927 article about “Strange Harm from Electric Fans.”
If bodies are exposed to electric fans or air conditioners for too long, it causes bodies to lose water and hypothermia. If directly in contact with a fan, this could lead to death from increase of carbon dioxide saturation concentration and decrease of oxygen concentration. The risks are higher for the elderly and patients with respiratory problems.
From 2003-2005, 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.
I suspect this belief to be less prevalent in North Korea, where there are only eight electric fans and they all belong to Kim Jong-un. Then again, possessing one under those circumstances might be hazardous to your health should the Dear Leader find out.