How many CFM are needed for my stove or cooking surface?
For gas cooking surfaces or range, a minimum ventilation level of 100 CFM (Cubic Feet per Minute) per 10,000 BTU is recommended. However, the hood must have a minimum of 500 CFM of ventilation power.
Clearly, for a unit of 40 000 BTU, the range hood must have 500 CFM (100 CFM X 4 = 400, but the minimum required is 500 CFM). For a unit of 80 000 BTU, the hood must have 800 CFM minimum (100 PCM X 8 = 80 000).