The answer to how much MUA is needed depends on what negative pressure the house (kitchen) gets down to when running the blower at some power level. The more negative you get, the less cfm are actually moved from the hood to the outside, the harder it is to capture and contain all of the cooking effluent, and the easier it is to backdraft any combustion appliances that depend on getting their effluent up a chimney using passive means. Open windows (with screens) may be ok, depending on the area opened, the blower fan curve, and resistance of the screens (are they clean?). Window opening of the order of the area of the hood aperture might be needed, certainly half the aperture, to assure that the negative pressure is not a problem for the other combustion appliances (a mere 0.03 inches of water column lower pressure can backdraft some appliances.) . If such appliances, where used, are not connected to the air in the kitchen, and no one is using a fireplace, then the pressure loss through a too-narrow window restriction can be tolerated, so long as the odor and grease continue to be evacuated for the blower setting in use. In general, CFM for blowers is specified for zero static pressure, and without knowing all of the pressure losses, starting with the aire getting into the house and ending with getting out of the house, along with the fan curve of flow vs. pressure loss, and including the baffle/mesh pressure loss, one cannot possibly predict what CFM are actually being moved. In particular, wheither a 600 cfm rated unit actually moves more cfm than a 700 cfm rated unit cannot be determined without measurement. All else being equal (which rarely is the case), the two Finnish papers noted in my Clippings have comparisons of upward velocity and volume rate from different cooking surfaces that will likely indicate a difference between gas and induction, but I wouldn't expect in most kitchen scenarios that the hot burnt gas that rises from around the pan being heated adds a lot the to hood requirements if the requirements are based on large-diameter hot cooking surfaces generating significant greasy effluent. kas

Breezygirl: I just got through talking with the dealer that I ordered the Faber Hood from and luckily I found out that they ordered the wrong one. I didn't realize that they ordered a30" Hood instead of the 36". So now they are going to find another 36" hood with at least 1000 to 1200 CFM's for me. Thank you for your advice. If it were not for you I would have been totally surprised when a 30" hood was delivered to my door to go with my 36" CC rangetop. I had a 36" Faber before and it is a beautiful hood and was powerful enough for my 36" Dacor cooktop but it would not have been enough CFM's for my CC.

Forget the induction part. How much CFM do you have now and is it enough? If it is, and you don't plan on cooking more smokey fishy stuff, it's probably fine to go with about the same. If it helps, I had a 650 (maybe 600) CFM slideout over a 36" induction cooktop and it was totally fine. Personally, I'd take 600 over 300 but if the Zephyr looks that much better or has other features you prefer, it's most likely fine.

It is not impossible for a surface sized hood to operate successfully, just not possible under all conditions. As a test with the hood on full blower power, take a pan on a hob/burner at the edge of the cooking zone and heat peanut oil to the smoke point (~ 450F). Observe whether all of the plume is captured or some gets past the hood edges. If the "cook" walks around, or others walk around the area, does the capture efficiency change? There is much information in the threads on this site w.r.t. hoods and make-up air that can improve insight into these topics. With that background, one can ask targeted questions that have not been adequately covered -- at this point mostly questions specific to architectures, or help with calculations.