A conservative estimate suggests your grill needs 1 CFM for every 100 BTUs (with a minimum of 1,200 CFM for the baseline), but this will vary between manufacturers. Basing your vent hood CFM off of your grill’s maximum BTU count is a rock-solid way to guarantee you can handle grill’s smoke production — even when it decides your lungs are hogging all the oxygen and tries to go full smokestack.