The purpose of having a ductless range hood? 
(not vented outside)

If you have a choice between buying either a ductless range hood or none at all, we would strongly recommend the former. Yes, we know we said that ducted range hoods are far superior to ductless range hoods, however, it’s still much better to have a ductless range hood than none at all. Why? Chances are you are going to pan fry or sauté something. Part of the oil will go airborne. We're not talking about spilled oil, but rather about these fine, aerosolized oil particles which aren't always visible. Without a range hood, these oil particles will have free rein to spread and stick to everything in the near vicinity. This will leave you with sticky cabinets and other surfaces. Not only is it really unhygienic, gross and smelly, it will leave you with very hard-to-clean yellow stains. Ductless range hoods will pass these oil particles through a charcoal filter and/or an aluminum mesh filter, which in turn will capture them. . The former one will take away some of the odors, while the latter one is geared towards capturing grease. So, if you plan to cook more than mac ‘n cheese, do your future self a favor and get a range hood, even if that means you need to buy a ductless one.