I'm looking at my kitchen design and it includes a recirculating downdraught extractor, located to the rear of the hob, which itself is located in the island unit.     As we're planning an airtight, energy efficient home, we'll be having a MVHR system,  Am I correct to assume that the carbon filters in the very expensive down draught fan will remove the odours etc and the MVHR system will deal with the fresh air side of things.