There Certification: When consumers buy "24V DC Cooling Fan", to look at 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 meet the national energy efficiency standards. Noise: "24V DC Cooling Fan" making noise of the main components of 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 a quiet environment, only to hear the wind, "whispers", ultra-quiet fan blowing air is good.No odor: odor is the smell of varnish coating on the fan copper produced during 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.Electrical Safety: The "24V DC Cooling Fan" safety requirements, national standards set forth very detailed, consumers also can be a simple test. Qualified fan, general adult fingers can not touch the fan grille and front, families with young children should choose dense fan grille.