A range hood is more than a light over the cooktop. It captures smoke, grease, and moisture near their source, before they spread across cabinets or settle on a nearby window. The IRC benchmark in the subtitle is a useful starting point: 100 CFM for intermittent operation or 25 CFM for continuous operation. CFM measures airflow in cubic feet per minute. That matters.
These figures describe different operating patterns, not two settings that work equally well in every kitchen. An intermittent hood runs when cooking; a continuous system runs at a lower rate over time. The right choice depends on the appliance, cooking habits, hood placement, and duct route. A long or restrictive duct can reduce airflow, even when the fan’s rating looks adequate on paper. Quiet operation is helpful, but weak capture is not.
Check the locally adopted code edition and ask the building department or a qualified installer about applicable requirements. Local amendments may differ, and installation details matter. The hood should exhaust outdoors through an approved duct, not simply recirculate air, where the code requires an exhaust system. Also confirm whether added ventilation or makeup air provisions apply to your project. The numbers are a baseline, not a guarantee of good performance. A quick check before buying can prevent a noisy hood that still leaves a haze above the stove.