Range hoods should be ducted to the outside of the home. While non-ducted filters trap some of the grease and odors from normal cooking, the humidity, smoke and heat will all be re-circulated back into the home. If the non-ducted filters are not regularly replaced, eventually the grease and odor catching effect will no longer protect your home from impurities.
High BTU gas cooking equipment should always be ducted to the outside of the home. If this is impossible, high performance convertible hoods and filters are available in some models. Contact the Technical Support Group for more information.