It’s fascinating when an entire country succumbs to a collective belief that is provably false everywhere else. One wonders if the rules that govern reality are flexible in this way, providing exceptions to physics, chemistry, cosmology if a certain density of people believe something (belief in this phenomenon could explain fundamentalism at a psychological level).
Take South Korea and the famed "Fan Death" phenomena. Cheap plastic electric fans can barely cut off your fingers if you remove the protective grating and stick them right in the blades (don’t try this). But the idea that electric fans can remove oxygen from a room is utterly ridiculous.
The only realistic risk to consider from fans is that they don’t actually lower your temperature. They just increase evaporation rates from your skin to cool you off. In extreme temperatures, they’re no substitute for really cooling down and staying hydrated.
Aside: There’s a trick I discovered as a kid that can turn an ordinary fan into a real cooler, which could be fun for your kids next summer (use your own judgment for safety considerations, and do not try this within X miles of the South Korean Fan Death zone).
Build an air-tent by tucking a large cloth bedsheet (or several sheets duck-taped together, depending on the bed size) around the edges of a bed. Tape the foot end of the sheet around the fan, such that the fan blows in and inflates the air-tent. Leave enough slack in the tent that you can comfortably sleep inside, sit up, move around, etc… I didn’t do anything elaborate for getting in and out, just untuck and tuck the sheet as needed. I think cheap flat sheets work best, but try fitted if you like.
I believe you’ll find an actual temperature drop inside the air tent. I figure it’s because it slightly increases pressure (pV=nRT) for air entering the tent and decreases it for air escaping through pores in the sheet, carrying heat away as it re-expands. It’s a simple heat pump.
In fact, as a kid, I needed to sleep with a winter blanket inside my little air tent all summer, it was that cold. I did not run out of oxygen, but it sucks if the power goes out. And be warned, unlike real A/Cs, it doesn’t pump the heat outside, just away from your bed.