I bought a total of two fans of this type. The first one worked fine for 4 months (~4 hours per day) and then stopped working. I thought I was just unlucky and bought the same fan again because I liked its construction, as I had it placed on a window. Unfortunately, the second fan only lasted for 15 days with the same usage. Out of personal curiosity, I decided to take a look and see if I could understand why this happened. I discovered that the blades of both devices were rubbing against the casing (pipe) during rotation, which could potentially lead to gradual overheating of the motor and ultimately its burning out. Unfortunately, the product needs to be redesigned by the manufacturing company in order to be reliable and justify its relatively high cost.