Buy DC Axial Fan to be a little cautious

Heat no "DC Axial Fan" is one of the most suffering day hot sun shone regarded black leather skin, heat stroke and other problems have emerged, and for the beauty of the crush, are reluctant to go out, preferring to stay at home and enjoy air conditioning treatment, that is how happy thing, however negative "DC Axial Fan" is one of the parts of air conditioning, optional suction fan first look at dust and waterproof rating, second fan, part manufacturers with plastic blades and stamping stainless steel, aluminum die cast aluminum fan blades instead, because the lower cost of the kind of fan, die-casting blades are about 7.5 kg weight, so the cost is relatively high. Plastics and stamping wind. However, no for good "DC Axial Fan" can be used on any issue for 20 years, and a large amount of wind, but also energy-efficient, so how do we choose a good suction fan of it?