I have a large natural gas burner (60,000 BTUs) in my brewing room. My vent fan is marginal (900 cfm - largest size that would fit the space), but effective at humidity and temperature control since it ports directly out the side of my basement wall. I have a decent sized open-air basement (half is my brewing area) and I leave the door to the upstairs open for my source of makeup air (plus, I have windows that I can open), so it's not a "confined space," per se. And I have a combination smoke and CO detector about 15 ft away from the burner (recommended distance.)
Just like going to our KK expert, Dennis, for advice on things, have a certified HVAC specialist help you design the venting system for your new kitchen.