An urban legend states that when operated in closed rooms, electric fans cause sudden death, suffocating victims by stealing their oxygen.

Beliefs

The specifics behind belief in the myth of fan-death often offer several explanations for the precise mechanism by which the fan kills. However, as explained below, these beliefs do not stand up to logical and scientific scrutiny. Examples for possible justifications of belief in fan death are as follows:

• That an electric fan creates a vortex, which sucks the oxygen from the enclosed and sealed room and creates a partial vacuum inside. This explanation violates conservation of matter, as indoor fans are not powerful enough to change the air pressure by any significant amount.

• That an electric fan chops up all the oxygen particles in the air leaving none to breathe. This explanation violates mass conservation and well-known properties of molecules and gases.

• The fan uses up the oxygen in the room and creates fatal levels of carbon dioxide. There is no actual conversion of oxygen to carbon dioxide happening; unlike a candle, the electric motor in a fan does not alter the chemical composition of the air (apart from creating some ozone if the motor uses brushes, and outgassing from the materials).

• That if the fan is put directly in front of the face of the sleeping person, it will suck all the air away, preventing one from breathing. This explanation ignores the fact that most people point a fan towards themselves when using one, which causes air to move past the face but does not change the amount of air present.

• That fans contribute to hypothermia, or abnormally low body temperature.^[2] As the metabolism slows down at night, one becomes more sensitive to temperature, and thus supposedly more prone to hypothermia. If the fan is left on all night in a sealed and enclosed room, believers in fan death suppose that it will lower the temperature of the room to the point that it can cause hypothermia. Empirical measurements will show, however, that the temperature in the room does not fall, at least not due to the fan; if at all, it should rise slightly because of friction and the heat output of the fan motor, but even this is generally not significant. Fans actually make one cooler by increasing the convection around a person's body so that heat flows from them to the air more easily, and by the latent heat of vaporization as perspiration evaporates from the body. However, there is no scientific study which indicates that this effect would be sufficient to cause hypothermia unless the temperature were already very low (in which case, there would be no need for a fan anyway).

Electric fans sold in Korea are equipped with a "timer knob" switch, which turns them off after a set number of minutes: perceived as a life-saving function, particularly essential for bed-time use.

• That fans contribute to hyperthermia, commonly known as heatstroke.^[3] The U.S. Environmental Protection Agency warns that during excessive heat events, people should not "use a portable electric fan in a closed room without windows or doors open to the outside."^[4] The EPA's position is based on the fact that a fan alone will not prevent hyperthermia brought on by hot weather, not that a fan will exacerbate hyperthermia.

• That fans contribute to prolonged asphyxiation due to environmental oxygen displacement or carbon dioxide intoxication.^[3][5][6][7] 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.^[8] Other indoor sources of carbon dioxide include burning fossil fuels, such as a gas-fueled water heater, and seepage through foundations in areas of high CO₂ soil content.^[9] Carbon dioxide is a colorless, odorless gas, and because it weighs 1.5 times more than normal air,^[10] it tends to concentrate toward the floor,^[7] depending on temperature and air currents. In South Korea, some people sleep on traditional floor mats, called yos, while others prefer western-style beds, and floor vents may be absent when ondol radiant underfloor heating is employed.^[11] According to The Straight Dope website run by the Chicago Reader newspaper, 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."^[3]

South Korean government position

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 seasonal summer accidents or injuries, according to data they collected.^[12] Also included among the five hazards were air conditioner explosions, and sanitation issues, including food poisoning and opportunistic pathogens harbored in air conditioners. According to the KCPB:

"If bodies are exposed to electric fans or air conditioners for too long, it causes bodies to lose water and [causes] hypothermia. If directly in contact with [air current from] a fan, this could lead to death from [the] 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 [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."

Fan-related hyperthermia research

Research suggests that fan use may be a contributing factor in heat-related deaths such as fatal cases of hyperthermia.^[13] A U.S. Centers for Disease Control and Prevention study published in the Journal of the American Medical Association advises that "although the use of fans may increase comfort at temperatures less than 90°F (less than 32.2°C), fans are not protective against heatstroke when temperatures reach greater than or equal to 90°F (greater than or equal to 32.2°C) and humidity exceeds 35%,"^[13] and provides a similar but simpler warning to the public on their website.^[14] These temperature and humidity conditions are consistent with a death cited in an earlier article critical of fan death, which suggested that fan use was irrelevant.^[3]

Texts on industrial hygiene and ventilation will describe conditions when the use of a fan will increase a worker's heat load. Those conditions include very high temperatures found in foundries and similar industries like heat treating metals. Similar problems occur with high heat and high humidity.

A 2007 meta-analysis of studies on heat wave-related deaths explains that "a fan induces air movement that increases evaporation and lowers skin temperature, but in warm environments increased wind speeds of hot air can actually raise the skin temperature and thus produce opposite results by increasing core body temperature."^[15] The study concludes that definitive recommendations on fan use require further study.

An analysis of risk factors contributing to 700 "excess deaths" during a 1995 Chicago, Illinois, heat wave found no evidence that fans either increased or decreased mortality, but noted that "interpretation of the data on the use of fans is complicated by the need to take into account specific environmental factors (for example, whether the fan is used in a room with an open or a closed window) and the health status of individual subjects."^[16] Fear of crime was cited as a factor in people keeping windows and doors locked shut.

Media coverage

The phenomenon of fan death is accepted by many Korean medical professionals. In summer, mainstream Korean news sources regularly report on cases of fan death. A typical example is this excerpt from the July 28, 1997, edition of the Korea Herald, an English-language newspaper:

According to The Straight Dope website, when informed that the phenomenon is virtually unheard of outside of their country, "some locals claim Koreans are uniquely vulnerable due to a peculiarity either of their own physiology or of Korean fans."^[3]

Published professional opinion

Gord Giesbrecht, a professor of thermophysiology at the University of Manitoba in Canada,^[17] is a leading expert on hypothermia: Dr. John Linton at Yonsei's Severance Hospital, who attended medical school at Yonsei University, is licensed to practice medicine in South Korea:^[2] 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: He blames the Korean media for the persistence of the urban legend:

See also

• Contemporary culture of South Korea
• Urban legends

References

External links

• Korean news clip on fan death

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