Sleeping With a Fan On?
The combination of cracking open a window and running a fan at night might sound like a smart strategy to keep you cool while you sleep, but it could be doing you more harm than good.
If you live in an urban environment where there's a lot of diesel emission particles, a fan can circulate these outdoor air pollutants indoors and direct them right into your upper airway, says Sam Huh, MD, chief of otolaryngology at Mount Sinai Brooklyn Hospital... More here.
I have slept with a fan on for many many years and always with the window open no matter what the temperature. Not doing both always feels stifling to me, but I was not aware of the potential downsides.