I am an O2 fan guy..Portable to put where ever you need the flowing air..I have 3-5" battery operated and 1-10"(soon to be 2) AC/DC and battery operated..By a window they suck in the outside air and above a heat source they circulated the air...When the electricity went out at the house,I used the 10" to circulate the wood stove heat throughout the house.
On a picnic table outside, they help keep the skeeters away whom are poor at flying in a breeze..For smokers they blow the smoke out a window...
Quiet and reliable..