With five speeds and a boost mode, the HushJet Mini Cool goes up to 55mph, making it the most powerful personal fan I've tested. Dyson/Jeffrey Hazelwood/CNET CNET’s key takeaways  At $100, Dyson’s HushJet Mini Cool comes in three colors and includes a “neck dock” (lanyard) and charging stand. The Mini Cool has five speeds and a boost mode that reaches 77.5 dBA, which, in my opinion, makes it too loud for shared indoor spaces. While it charges in 3 hours, you get only 6 hours of battery life at speed 1, and even less at higher speeds. However, you can use it at speed 1 while it charges. I Tested Dyson’s 55MPH Handheld Fan. Here’s Why I’m (Mostly) Sold My experience with the Dyson HushJet Mini Cool The specs Dyson HushJet Mini Cool vs. Shark ChillPill CNET’s buying advice During hot yoga, the room is heated to 110 degrees Fahrenheit, and I often dream of having something, anything , to keep me cool.…