I haven't used it yet, but I recently bought a 10-inch portable fan with a built-in battery. In fits in my pack that I carry on. I bought it for three reasons. First, I often stay in hotels in Europe with no air conditioning, and merely opening the window doesn't get enough cool air in the room, even if it is 60 degrees outside; I figure even a small fan placed in the window will help. Second, European trains are always 80 degrees, winter and summer. And third, sometimes airplanes are insufferably hot. I'm headed to Europe in March and we'll see how it works. The legs come off.