In order to determine the proper amount of range hood air flow required for your cooking equipment, you must first know how many BTU’s (british thermal units) your gas range emits.  Then, with a simple calculation you can determine the amount of CFM (cubic feet per minute) required by your range hood.  For example if your cooktop emits 90,000 BTU’s you would divide 90,000 by 100 which indicates your venthood should have a kitchen hood blower capable of exhausting 900cfm.  This means that 900 CFM or more would efficiently exhaust your range.
 
Electric and Induction range tops:

For electric and induction cooktops choose a blower with a minimum of 200 CFM per 12 inches of cooktop width. Remember, it’s always a good idea to round up vs. down.


Range hood blower location options:

The other choices you should then decide on is do you want an internal range hood blower system, this means where the actual blower or blowers are inside the body of the hood or an inline range hood blower system where the actual blower motor is in the duct run or finally where the range hood blower is external to the home, either on an external wall or the roof.

Range hood height above the range: