Charcoal filters are used for converting your range hood to ductless. This is when you are not ducting to the outside of your home. Charcoal filters are made of activated charcoal carbon that is designed to remove contaminants and impurities from the air before recirculating the air back into the home.
Charcoal filters come in a set of two. It is best to replace your charcoal filters at least 6-8 months or less if needed.