Take a closeup look at the DynaTrap's powerful vacuum action fan. Once flying insects have been attracted to the Dynatrap by warm UV light and CO2, the DynaTrap's powerful (yet whisper-quiet) fan serves two functions. It is first used to draw insects into the retaining cage. It then keeps those insects from escaping using the vacuum action created by the continuous cycle of the fan. The Dynatrap is energy-efficient and is designed to run continuously. The fan is so quiet, it's hardly noticeable.