"24V DC Cooling Fan" major component making noise is the motor, in the selection of fan must listen whether the noise when the motor is running, to see it in operation whether jitter is stable; good motor let you in quiet environment, only to hear the wind, "whispers", ultra-quiet air supply is good "24V DC Cooling Fan". Odor is "24V DC Cooling Fan" odor varnish coating on the copper produced at the time of the operation, in the purchase of fans have to smell it, to see this paint is environmentally friendly, whether through quality testing, let you in the fresh enjoy the wind in the air cool.