No, there's no saftey risk to not venting to the outside but if you have the option to vent out then that's what you should do. Recirculating hoods are better than nothing but you really want to vent the smoke, grease, heat, steam and odors to the outside and not recirculate them in your kitchen. There are dampers you can put on the vent pipe to prevent cold air from entering your kitchen.

Bumping this up :) I have a similiar concern. I often crank my freestanding range (no vent hood) up to 500 degrees to bake baguettes/french bread etc, and I set off the smoke detector everytime I open the oven door. I hope to have a wall oven with a separate cooktop/vent hood a couple of feet away, but will definitely consider a range for the new kitchen if this is going to be a problem? Dawn

Would you recommend plaster or stucco for cladding a vent hood? And why? I need to let my contractor know today.... Thank you!

My original issue with VaH (a decade ago) was their specious CFM claims that did not provide any "fan curve" information that would allow one to calculate actual CFM given some duct losses and MUA losses. More recently, I have seen some appropriate data published for their ducted units. However, checking just now, I see that they provide "n/a" for CFM for a representative ARS model. This is unconscionable. The ARS, being a closed system, has a volumetric airflow rate unaffected by exterior effects. They need supply only one easily measured number. How would one know if the flow rate is suitable for a particular cooktop / cooking style without knowing the specific (CFM/sq. ft.) flow rate of the hood? Given time and budget and no access to a residence exterior, I would probably research commercial solutions to this problem and adapt a filter to a conventional hood and blower. Sheet metal shops can easily build the needed "duct/filter" structure. On the plus side, recirculating systems do not need heated MUA and thus are more energy efficient. They avoid having a lot of house, basement, or attic space taken up with a powerful MUA system. On the negative side, for a given hood entry aperture flow rate, they will be noisier than an external blower with intermediate silencer.