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.
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Fan death is a popular myth and misconception, common to Korean culture, that running an electric fan in a closed room with unopened or no windows can lead to death. Based less on concrete evidence, fan death persists due to its popularity as urban myth or perhaps superstition.
Origins of belief
The genesis of the misconception is unclear, but fears 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 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".
Hyperthermia (heat stress)
Air movement will increase sweat evaporation, which cools the body. But in extreme heat – when the blown air is warmer than the body's temperature – it will increase the heat stress placed on the body, potentially speeding the onset of heat exhaustion and other detrimental conditions. The American Environmental Protection Agency (EPA) discourages people from using fans in closed rooms without ventilation when the heat index is above 32 °C (90 °F). The EPA does, however, approve of using a fan if a window is open and it is cooler outside, or when the heat index in a closed room is lower.
Hypothermia is abnormally low body temperature caused by inadequate thermoregulation. As the metabolism slows down at night, one becomes more sensitive to temperature, and thus supposedly more prone to hypothermia. People who believe this theory think a fan operating in a closed room all night can lower temperature to the point of causing hypothermia.
Empirical measurements (as well as simple thermodynamics) show that fans do not cause room temperature to drop; if anything, it should rise slightly because of friction and the fan motor's heat output, but even this is negligible. Fans actually lower body temperature by increasing the convection around a person's body so that heat flows into the air more easily, and by vaporization as perspiration evaporates from the body. No scientific study indicates that this effect could cause hypothermia, unless the temperature were already very low. Moreover, very few people would keep a fan running continuously in a room that is cold enough to induce hypothermia.
It is alleged that fans may cause asphyxiation by oxygen displacement and carbon dioxide intoxication. In the process of human respiration, inhaled fresh air is exhaled with a lower concentration of oxygen gas (O2) and higher concentration of carbon dioxide gas (CO2), causing a gradual reduction of O2 and buildup of CO2 in a completely unventilated room.
According to The Straight Dope website run by the Chicago Reader, asphyxiation is an unlikely cause of fan death because "few rooms are totally sealed, and the fan would tend to keep CO2 and other gases well mixed".
Curiously, this theory bears a similarity to a once-popular misconception which claimed that a person in a closed room with plants would asphyxiate if the room wasn't kept ventilated, as the plant's respiratory processes would supposedly consume all the oxygen in the room. 
During the summer, mainstream South Korean news sources regularly report alleged cases of fan death. A typical example is this excerpt from the July 4, 2011, edition of The Korea Herald, an English-language newspaper:
A man reportedly died on Monday morning after sleeping with an electric fan running. The 59-year-old victim, only known by his surname Min, was found dead with the fan fixed directly at him.
This article also noted there was "no evidence" the fan caused the death, however.
Ken Jennings, writing for Slate, says that based on "a recent email survey of contacts in Korea", opinion seems to be shifting among younger Koreans: "A decade of Internet skepticism seems to have accomplished what the preceding 75 years could not: convinced a nation that Korean fan death is probably hot air."
South Korean government
The Korea Consumer Protection Board (KCPB), a South Korean government-funded public agency, issued a consumer safety alert in 2006 warning that "asphyxiation from electric fans and air conditioners" was among South Korea's five most common summer accidents or injuries, according to data they collected. The KCPB published the following:
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.
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It's hard to imagine, because to die of hypothermia, [one's body temperature] would have to get down to 28 °C, drop by 10 degrees [Celsius] overnight. We've got people lying in snowbanks overnight here in Winnipeg and they survive. ... Maybe if someone was elderly and they were sitting there for three days, ... Someone is not going to die from hypothermia because their body temperature drops two or three degrees overnight; it would have to drop eight to ten degrees.
There are several things that could be causing the fan deaths, things like pulmonary embolisms, cerebrovascular accidents, arrhythmia or COPD. There is little scientific evidence to support that a fan alone can kill you if you are using it in a sealed room. Although it is a common belief among Koreans, there are other explainable reasons for why these deaths are happening.
Dr. Lee Yoon-song is a professor at Seoul National University's medical school and works with the school's Institute of Scientific Investigation. He has conducted autopsies on some of the people who have been described in Korean media as having succumbed to fan death and said,
When someone's body temperature drops below 35 degrees, they do start to lose judgment ability. So if someone was hiking and later found dead, that could be part of the reason. But we can't really apply this to fan accidents. I found most of the victims already had some sort of disease like heart problems or serious alcoholism. So hypothermia is not the main reason for death, but it may contribute.
Korean reporters are constantly writing inaccurate articles about death by fan, describing these deaths as being caused by the fan. That's why it seems that fan deaths only happen in Korea, when in reality these types of deaths are quite rare. They should have reported the victim's original defects, such as heart or lung disease, which are the main cause of death [in these cases]. If a Western doctor investigated these deaths, he would say what really caused the death, and say that a fan was beside the victim.
- Culture of South Korea
- Culture-bound syndrome
- List of common misconceptions
- Sudden unexpected death syndrome
- Jennings, Ken (Jan 22, 2013). "Is Your Electric Fan Trying to Kill You? Fan death in Korea, the dangers of wearing red in the Philippines, and other momisms from around the world.". Slate.
- "Strange Harm From Electric Fans", Jungoe Ilbo (Domestic and International Daily), July 31, 1927, "The rotating fan blades create a vacuum directly in front, and the intensity of the resulting air flow always results in an insufficient supply of oxygen to the lungs." (Korean)
- "Fan Death". Snopes.com. 6 June 2011.
- Herskovitz, Jon; Kim, Jessica (2007-07-09). "Electric fans and South Koreans: a deadly mix?". Reuters. Retrieved 2013-07-21.
- Excessive Heat Events Guidebook, United States Environmental Protection Agency. "Annex B: Use of Portable Electric Fans During Excessive Heat Events ... Don't Use a portable electric fan in a closed room without windows or doors open to the outside. ... Don't Use a portable electric fan to blow extremely hot air on yourself. This can accelerate the risk of heat exhaustion. ... Annex C: Excessive Heat Events Guidebook in Brief ... Don't direct the flow of portable electric fans toward yourself when room temperature is hotter than 90 °F."
- Surridge, Grant. (2004-09-22). "Newspapers fan belief in urban myth." JoongAng Daily, via joongangdaily.joins.com and archive.org. Retrieved on 2007-08-30.
- Adams, Cecil (1997-09-12). "Will sleeping in a closed room with an electric fan cause death?". The Straight Dope. Chicago Reader, Inc. Retrieved 2007-08-02.
- Watanabe, Toshifumi, and Masahiko Morita. (1998-08-31). "Asphyxia due to oxygen deficiency by gaseous substances." Forensic Science International, Volume 96, Issue 1, Pages 47–59. Retrieved on 2007-09-06.
- Gill, James R., Susan F. Ely, and Zhongxue Hua. (2002). "Environmental Gas Displacement: Three Accidental Deaths in the Workplace." The American Journal of Forensic Medicine and Pathology, 23(1):26 –30, 2002. Retrieved on 2007-09-06.
- "Concentrated Carbon Dioxide in Western Pennsylvania." The Pittsburgh Geological Society. Retrieved on 2007-09-06.
- Sleeping With Plants, Danit Brown, Indiana Public Media, retrieved July 19 2016 at http://indianapublicmedia.org/amomentofscience/sleeping-with-plants
- "Summer death revives fan death myth". The Korea Herald. 2011-07-04. Archived from the original on 2011-11-26.
- "Beware of Summer Hazards!" (Press release). Korea Consumer Protection Board (KCPB). 2006-07-18. Archived from the original on 2007-09-27. Retrieved 2007-09-01.
- "Fall 2005 Curriculum (Archive), Learning Series Session (Sept. 21, 2005): Keep Your Head Up: A Primer on Cold Water Immersion and Near-Drowning." (Website). Smartrisk Navigator. Retrieved on 2007-09-01.