There are several reasons given as to how a fan can kill:
- It is believed that an electric fan creates a vortex, which sucks the oxygen from the enclosed and sealed room and creates a partial vacuum inside.
- The fan uses up the oxygen in the room and creates fatal levels of carbon dioxide.
- 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.
- Fans can cause hypothermia. As the metabolism slows down at night, one becomes more sensitive to temperature, and more prone to hypothermia. In other words, if the fan is left on all night in a sealed and enclosed room, it will lower the temperature of the room to the point that it can cause hypothermia.
- Often, it is claimed that a combination of these factors is responsible. For example, it might be explained that the fan lowers the oxygen level in the room while raising carbon dioxide levels, which could prove fatal to a sleeping person already weakened by hypothermia.
From
http://en.wikipedia.org/wiki/Fan_death
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Going back on topic, a hypothetical situation I can think of would be waking up in a dream and not realising that you were still asleep. Then you would do mundane ordinary things in the dream, thinkng you were awake, then you'd fall asleep in the dream. Assuming you did nothing remarkable in the dream and the period of time that passed in the dream was negligible, and also that your waking up the second time in the dream coincided with your waking up in reality, you would never know that a small part of your life had been a dream and you would go on believing for the rest of your life that it was real.