Depending on the type of cooking and the location of the range, the recommended ventilation for a kitchen range hood can vary greatly.  Hoods which are mounted directly over the cooking surface are much more effective at capturing and exhausting the heat and odors...at a much lower air volume.  A downdraft ventilation will need a higher volume and speed to accomplish the same function.  While the style of a downdraft may be more aesthetically pleasing, and in areas where the location will not permit an overhead hood, a downdraft system may be the answer.

According to guidelines set by the Home Ventilating Institute, for a range set against a wall, a ventilation rate of 100 CFM is recommended for every linear foot of range, with a minimum of 40 CFM per linear foot of range.  For island ranges, 150 CFM is recommended per linear foot, with a minimum of 50 CFM per linear foot of range.  For professional style ranges, HVI recommends checking with the manufacturer for the specifications that will best serve their product.

These numbers are factored on ducted ventilation, as non-ducted recirculating hoods do not actually provide ventilation.  For additional information visit the HVI website.