Fan death is a putative phenomenon generally accepted only in South Korea, in which an electric fan left running overnight in a closed room can cause the death of those inside. Fans 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.
While the prevalent explanations given by lay Koreans, such as suffocation or hypothermia, are generally incorrect, this does not render the phenomenon itself fallacious; an electric fan running directly on a human body in a hot, enclosed room can accelerate hyperthermia, although this could only occur in a humid atmosphere at temperatures near or exceeding body temperature (such as indoors in the summertime).
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, none of these beliefs stand up to logical or scientific scrutiny. Examples for possible justifications of belief in fan death are as follows:
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. The KCPB actually 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.
Whenever conditions are present which cause heat exhaustion or heat stroke, it is important to realize that a fan does not lower air temperature. It is unsafe to rely on a fan to relieve heat stroke. In fact, technically, fans actually raise air temperature, since their motors produce heat, though by extremely small amounts that would be far from showing up on thermometers. In most conditions fan use will reduce body temperature through evaporation, but it does so at the cost of body fluids, which can increase health risk. Once the body is completely dehydrated and loses the mechanism to control body temperature, the risk of hyperthermia is dramatically elevated. Particularly vulnerable are infants, the elderly and the intoxicated. There are cases of extreme heat and humidity where a fan can actually push heat onto the human body, but the circumstances where moving air exaerbate the problem are extremely unlikely.
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 summer weather in Korea, which is often very hot and humid. These temperature and humidity conditions are also 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.
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.
Dr. Lawrence Kalkstein, a professor of biometeorology at University of Miami and former president of the International Society of Biometeorology, [said in an interview]:
"When the room temperature is high and the fan is on in an enclosed room, the room's heat becomes concentrated on the person and causes the body temperature to rise. As the breeze from the fan takes away body fluids from the exposed skin, it could lead to death."
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 ten 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:
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.