It is fitted and working and recycles the air back into the kitchen as we do not have it extracting to the outside. Now, I am not sure if it is blowing correctly. The only filter is a mesh filter it came with - I don't know if I need a different kind of filter added to it e.g. a carbon or grease filter. I don't understand the carbon and grease filter differences. There is a plastic catch inside the lid which has 2 positions: one position blows the air more strongly back down towards the cooker while the other position blows less powerfully but it is not obvious where it is blowing to. I am not sure what is happening and I don't have instructions to show the purpose of the different positions of the catch or even if they make a difference. There is no obvious updraught so I cannot be sure it is functioning as it should though I do not believe it is broken. What can I do? Also, should I fit a carbon filter to it or is the original mesh filter packed with it sufficient? My wife simply says she does not think it is doing what it should do.