"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 fan blowing air is good. When consumers buy electric fans, to see the instructions to see if the mandatory certification quality system certification, whether there is inspection standards certification; and now promote "green carbon", depends on whether the level of energy efficiency standards. For "24V DC Cooling Fan" safety requirements, national standards set forth in a very detailed, consumers can be a simple test. Qualified "24V DC Cooling Fan", general adult fingers can not touch the fan grille and front, families with young children should choose dense fan grille.