May need new charcoal filters
If your hood is set to recirculation and venting back into the kitchen then it will have charcoal filters fitted inside to clean and purify the air by removing smells. Charcoal is really good at removing odours however filters will require regular replacement. Should you require replacement 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.