Aside from their decorative aspects, extractor hoods can prove very useful when you're cooking. They help make your food healthier by sucking up the grease and odour-laden vapours produced during the cooking process.
This is why it's important to regularly clean the metal filters on extractor hoods with soapy water. Another extra little advantage they offer is that they can usually be cleaned in a dishwasher, depending on their size. If your extractor hood is the type that does not vent to the outside, you'll need to replace the carbon filters once every three to six months, depending on both the particular model and the type of cooking you do.
Other parts may also need to be replaced over time, such as the light bulb in the hood (if it no longer lights up); the metal grease filter (if it gets too fouled up); and the ducting and non-return valve (on ducted extractor hoods), if your appliance is no longer extracting as it should.