... . 4)Simple and easy installation. The roof ventilation fan applies the theory of convection between natural ... into vertical so as to improve the indoor ventilation. The hot air rises and cold air falls ... can effectively remove indoor soot, smoke, odor, moisture, heat, decorative harmful gas, dust, human matabolism and other ... : 500mmBase Plate Dimension:750mm*800mm 500mm Heat Recovery Roof Fan Exhaust