Last year my informant had a Korean room mate who would get nervous whenever they had the air conditioner on in their room at night. As they were going to sleep, he would ask, “Are you leaving that on?” and would insist my informant turn it off. This inspired my informant to ask why, from which he learned, “the air conditioner will suck all the oxygen out of the room, so you’ll suffocate when you sleep at night”. My informant would comply, and if he forgot to turn it off before going to bed he would often wake up in the middle of the night and turn it off. Though my informant is not aware of this belief’s origin, he believes it could be of Korean descent, due to learning it from his Korean room mate.
When my informant told me this belief, I was immediately reminded of fan death, which I also heard had come from Korea, so my informant’s room mate having this belief did not surprise me as much. Though this belief is slightly tweaked from that of fan death, involving an air conditioner unit instead of a fan, the idea is the same, in that there is danger to leaving an air unit on over night because it will tamper with the air and make it “unbreathable”.
Like other popular folk beliefs I came across (shot cure), there are elements to the belief that sound scientific – the mention of oxygen is especially potent, the specific elemental reference reminding people of chemistry or other science classes they might have taken long ago in school. The belief plants itself in one’s head next to other, half-remembered “scientific facts”, and by association gains credibility. Even if one has slept with an air conditioner or fan before (as both my informant and his room mate ended up doing), a person might become suspicious upon hearing this belief, thus allowing it to spread further.