DDL series centrifugal fan with square structure, direct drive, fan outlet installed in any position and direction, and do not need to stand with iron angle iron brackets. Have the advantages of a large amount of wind, moderate pressure, low noise, small size and easy installation. Applicable to kitchens for exhausting and sending fresh air, as well as for ventilating in mining enterprises, entertainment and other occasion basement. It also can be widely supporting the use in the production equipment like the food package machinery, chemical machinery, plastics machinery. It is an ideal ventilation fan for environmental engineering facilities. DDL-I fan have two structural forms: A-type direct drive and E-type belt drive, using efficient forward multi-blade centrifugal impeller. Equipped with explosion-proof motor and aluminum (stainless steel) material impeller. It can be made explosion-proof type. DDL-II fan with A-type direct drive, equipped with efficient backward curved centrifugal impeller and unique silencing function. It can be made anti-corrosion type or explosion-proof type according to the customer requirement.