Review on Compact 4 Inch USB Desk Fan: Powerful Airflow, Quiet Operation - Perfect for Cooling Desktops at Office or Home by Chris Chincuanco

This fan is best used during a power outage. It runs on 5 volts (USB) and consumes little power. A small lithium power bank with USB port can run this fan for hours. The fan blows out an "air column" that can reach you from 6 feet away - the blades are perfectly curved to push the air straight out. The funnel-shaped airflow "spreads" the breeze so you don't get hit as hard. This means that the least energy is used for cooling. This fan is also quiet at high settings which, as you can imagine, means the fan doesn't convert power into noise.