with two-way type ventilator 250-300 mm more appropriate.

The trick with the ventilation fan buy indoor use,kitchen ventilation fan and bathroom with three.
1, bathroom general smaller, about 2-4 square meters, the choice of open-fan 150-200 mm.
2, kitchen options unscreened with 250 mm exhaust fan, such as when the kitchen is equipped with a hood off, time to install ventilation fans.
3, bedroom and living room area is generally about 12-16 square meters,

with two-way type ventilator 250-300 mm more appropriate.