Answer: South Korea

If you’re an expat living in South Korea, it would be easy to assume the reason nearly all fans are equipped with a timer knob is because South Koreans are very energy conscious and want to ensure that fans aren’t left running needlessly when there’s no one there to enjoy the cooling breeze.

In reality, however, the timers were introduced long before energy consumption was of any concern and the real reason for their ubiquitous presence on electric fans is a very long running and persistent Korean urban legend. This urban legend, taken as gospel by generations of South Koreans, states that sleeping in a closed room with an electric fan will kill you via “fan death”. How this fatal interaction occurs varies based on the retelling, but the common tales center on either the idea of the fan introducing hypothermia (on the false premise that the body is very poor at temperature regulation during sleep) or on the even more outlandish idea that the fan movement displaces oxygen and causes the sleeper to suffocate in a bubble of their own exhaled carbon dioxide (which is certainly nonsensical given that the constant fan use would do more to mix and homogenize the air in the room than if there was no fan running).

Although the urban legend has circulated throughout South Korea since the introduction of electric fans around the 1920s, it wasn’t given any sort of official support until the 1970s when newspapers began reporting alleged fan deaths and government agencies talked about the phenomenon in official documents (a practice that has persisted to this day). Some South Korean conspiracy theorists believe that the then-sitting President of South Korea, Park Chung-hee, took advantage of the urban legend to decrease energy dependence during the global energy crisis in the 1970s and, in the process, gave it an undeserved air of legitimacy.

Before we leave this bit of trivia though, let’s share a useful (and legitimate) caution against fan use that can in fact harm you. The American Environmental Protection Agency (EPA) cautions against using a fan in a closed room when the heat index of the room is above 99 °F (37 °C) because the movement of the air created by the fan will increase the evaporative cooling that lowers the temperature of your body, but the air itself will not be cooler (no matter how it might feel moving over your skin), and such an arrangement can in fact increase the heat stress on a person’s body and potentially speed up the onset of heat exhaustion. Simply opening a window or only using a fan in a closed room when the heat index is at or below 90 °F (32 °C) will alleviate the risk.