For best results the hood should extract the cooking odours to the outside of the property. However, your Hoover hood can be used to recirculate if out side venting is not possible for some reason Check that the installer has not set it up to recirculate the air back into the cooking area. If this is the case then the optional charcoal filters will need to be fitted to get rid of the cooking odours. Should you require filters you can purchase them via the spares section of this website
Please refer to the fitting instructions for your hood which can be downloaded from this web page.