Part of your recirculating rangehood, charcoal filters are designed to remove grease and odours from cooking vapours, allowing clean air to return to the kitchen. It is recommended that these filters be replaced every three to six months, depending on use, as grease-saturated filters can become a barrier to air movement that impedes the rangehood's performance, or even create a fire risk. Keeping a spare filter handy gives you peace of mind and means that you won’t need to cook without your rangehood while waiting for a new filter that you've ordered to arrive when you need one.