I also had a range hood that recirculated air in my home (an integrated KitchenAid model with built-in microwave). I had no idea it recirculated the air until I started measuring PM2.5 in the house and noticed it would spike like crazy any time we cooked and didn't seem to change when running the range hood fan. There was a tiny metal grease filter in it, but I can't imagine these do anything for indoor air quality. Feels borderline unethical.
On my unit you can reconfigure it to vent out the back (if the unit just happens to align perfectly between the studs -- which mine didn't) or you can configure it to vent up through a duct. I had a duct run through the roof. My air quality is definitely better when running the range hood now; it still gets bad when I cook, but just less-bad than before.
On my unit you can reconfigure it to vent out the back (if the unit just happens to align perfectly between the studs -- which mine didn't) or you can configure it to vent up through a duct. I had a duct run through the roof. My air quality is definitely better when running the range hood now; it still gets bad when I cook, but just less-bad than before.