What range hood airflow should I plan, and does the candidate match its duct manual?
Start with HVI's width-based planning baseline, then use the higher of that baseline and the exact model manual minimum. A rated-CFM pass is not enough: the installed duct must also meet the manual diameter and equivalent-length limits.
Method
HVI uses 100 CFM per linear foot for a wall hood and 150 CFM per linear foot for an island hood. The duct ledger adds straight length to elbows multiplied by an editable manual-equivalent length; it does not claim actual delivered airflow.
Important limitation
This is pre-purchase planning, not code compliance, combustion-safety, make-up-air approval or an installed airflow test. Use the exact manual and a qualified installer for the final decision.