Fan death is a South Korean urban legend which states that an electric fan, if left running overnight in a closed room, can cause the death (by suffocation, poisoning, or hypothermia) of those inside. Fans manufactured and sold in Korea are equipped with a timer switch that turns them off after a set number of minutes, which users are frequently urged to set when going to sleep with a fan on.
The belief in the myth of fan-death often offers 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 would result in more air being blown towards them, not sucked away.
- That fans contribute to hypothermia, or abnormally low body temperature. 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 vaporisation 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).
- That fans contribute to hyperthermia, commonly known as heatstroke. 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." 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. 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. 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. Carbon dioxide is a colorless, odorless gas, and because it weighs 1.5 times more than normal air, it tends to concentrate toward the floor, 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. 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."
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. 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. 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%," and provides a similar but simpler warning to the public on their website. 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.
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." 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." Fear of crime was cited as a factor in people keeping windows and doors locked shut.
 Media coverage
The explanation[clarify] of fan death is accepted by many Korean medical professionals. In summer, mainstream Korean news sources regularly report on cases of fan death.
The heat wave which has encompassed Korea for about a week, has generated various heat-related accidents and deaths. At least 10 people died from the effects of electric fans which can remove oxygen from the air and lower body temperatures...
On Friday in eastern Seoul, a 16-year-old girl died from suffocation after she fell asleep in her room with an electric fan in motion. The death toll from fan-related incidents reached 10 during the past week. Medical experts say that this type of death occurs when one is exposed to electric fan breezes for long hours in a sealed area. "Excessive exposure to such a condition lowers one's temperature and hampers blood circulation. And it eventually leads to the paralysis of heart and lungs," says a medical expert.
"To prevent such an accident, one should keep the windows open and not expose oneself directly to fan air," he advised.
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."
Published professional opinion
Many people say that these victims die from lack of oxygen, but that is not true. Hypothermia does not only occur in the winter when it is cold. The symptoms can also take place if a person has been drinking and turns on a fan in a closed room. Most people wake up when they feel cold, but if you are drunk you will not wake up, even if your body temperature drops below 35 degrees Celsius, at which point you can die from hypothermia. It doesn't matter so much about the temperature of the room. If it is completely sealed, then in the current of an electric fan, the temperature can drop low enough to cause a person to die of hypothermia.
It is likely that the symptoms discussed by this doctor are actually due to excessive alcohol consumption, which can decrease body temperature.
It's hard to imagine death by fan, 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 in a sealed room with an electric fan turned on. 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 10 degrees." In addition, "the only way to verify whether someone had really died of hypothermia during the night would be to take a core body temperature the following morning. Waiting three days while the body was in the morgue wouldn't work because the corpse's temperature can drop during that time.
There are several things that could be causing the fan deaths, things like pulmonary embolisms, cerebrovascular accidents or arrhythmia. 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:
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.
He blames the Korean media for the persistence of the urban legend: