According to the induction site (http://theinductionsite.com/) you estimate cfms according to the width of your cooktop, at the rate of 100 cfms per foot of cooktop. So for 30" you would need 250 cfms.

IMO this is too low. We have 720 cfm for a 36" cooktop. We seldom need this but on the rare occasion when I have several pots all cooking briskly, I run the hood at top speed. It keeps residue from building up around the cooktop, and smells from drifting through the house.

Cheryl

For a good discussion of cfm rules of thumb, follow the Greenheck KVS Guide link in my "clippings."

Other estimation approaches relating to effluent velocity are also possible, but tedious to describe.

For recirculating systems, function is critically dependent on cleaning or replacing the filters regularly. High flow rate is probably not possible with standard units due to their small physical size for filter enclosure. An effective high flow rate recirculating system is theoretically possible, but I am not aware of any being offered for sale.

kas

If it is a recirculating hood, it doesn't matter.

A 120 cfm vented hood will be more use than a 1200 cfm unvented one. We're in a temporary apartment with an unvented hood now and it just adds insult to injury by blowing the smoke and grease back into your face. You may not be able to get a 10" vent out, but there's almost always a way to get a 4-5 " duct out

Be aware Viking has had quality problems with products in the past and this range will have to develop a good track record to overcome their rep.
Even a Panasonic bathroom exhausting fan system would be better than most recirculating fans.
This Vent A Hood is an option-

Here is a link that might be useful: Vent A Hooda

Yes, I'm thinking re: Viking but have my reasons.
Not everybody here may know: In some places (including mine), external venting is *not permitted* by government and/or coop/condo associations with force of law. So I'm asking not b/c I love or want recirculating, but b/c there isn't an alternative except no vent at all. My hope is that GW-ers can help with the best of a bad lot. (And - with total price of Vent a Hood ARS being upward of 2K with filteretc, even though it's longlasting, something less expensive.) (The bathroom vents are in an entirely different place.)

I understand the 'no-vent' rules that some places have.

I would suggest buying the least expensive recirculating unit that meets your appearance criteria.

Condo/coop rules can be overturned - especially if they violate local law or codes. Someone posted a while back that they had succeeded in getting their condo rule overturned.

Helpful approach, Weedmeister. What is your opinion about cfms in my sitatuion - also doesn't matter? and baffles - which seem to raise price a lot but help a lot with cleaning?

I have a 30" 600cfm Bosch hood, vented, that is plenty adequate for my 30" cooktop.