Square axial flow fan, featuring a low-noise motor specifically designed for direct drive; the entire unit is shaped square for an aesthetically pleasing appearance and easy installation with pre-drilled square holes in walls; equipped with self-hanging louvers at the exhaust to prevent rainwater and wind from entering the room; boasts advantages such as strong installation, low vibration, low noise, and smooth operation, widely used for wall-mounted exhaust in industrial and mining enterprises, residential buildings, stadiums, and animal husbandry. The DFBZ-I model uses an internal rotor motor with direct drive structure, the DFBZ-II model uses an internal rotor motor with belt drive structure, and the DFBZ-III model uses an external rotor motor with direct drive structure. Corrosion-resistant and explosion-proof models can be produced upon customer request.