This is a picture of an extract air valve I found in a kitchen, pretty disgusting isn’t it! You would think that it came from a house that had disgusting hygiene standards but not at all. The house was beautifully clean though but maybe unusually for today’s standards they did cook every day and used quite a bit of gee.

What this is showing is that it is always better to put a filter on the kitchen extract. The type of dust that is usually found in extract through out the rest of the house will mostly move through the ducting to be caught by the filter in the the MVHR unit, however, in the kitchen oil and grease used in cooking become air borne when the water in cells of vegetables boil and bust the puff of steam takes oil and fat into the air. As we all know the tops of kitchen cupboards get covered with a layer of dusty grease that is difficult to clean, we need to prevent this from getting into the ducting.2