DTBU damper

If a cooker hood has been connected to the ventilation unit, extract air will increase during cooker hood operation in order to draw air through the cooker hood. At the same time, extract air from the bathroom and the lavatory will also increase, which is entirely unnecessary.
  
However, by installing a DTBU damper, you can regulate air extraction, so it is not increased in other rooms but only in the kitchen via the cooker hood where it is necessary. 

DTBU dampers are available in the following sizes: Ø125 mm, Ø160 mm and Ø200 mm.