Newbury Kitchens 617 247-1234 has imported from Italy a Rex Electrolux slide-out far more discrete / invisible than the ones you have seen above. They may get you or another GW'er in to see it in operation on a job site if you move fast. The one in the showroom is not wired. I always think hearing the blower in operation is better than buying "sight unseen' or noise unheard. When pushed back into the dormant position, its front angles up into the cabinet. When slid out to capture smoke it angles down slightly so it could be positioned as low as a sneeze guard -- between your eyes and your hands. Many upper cabinets are installed 18" above the counter so this design makes sense to me. If you are tall, it will naturally end up below your eyes anyway whether it's installed low or not. The others you mentioned above all slide out horizontally, at eye level or at head level, so you still have the same obstacle to work around as if it were a solid headbanger, although they are less likely to give you a concussion since they move around when you hit them. The shape of the capture canopy counts for a lot, so this design (angle) makes sense for this reason too. About sizing. For many people, 300 CFM is plenty, adequate, fine, acceptable, a-ok. For others, they feel they need double that. High end manufacturers, such as those antss referred to, make some vents that pull as much as 550 and 600 CFM but not many models that pull more than that. Some people want quadruple that, and American and Canadian vent manufacturers sell them what they want. Feel free to say no to having more CFM, and feel free to say yes to having more. A lot depends on your duct size. How much make-up air are you able to provide? The more air is sucked out of the house, the more "make up" is needed. Air is not compressible (unless under a lot of pressure) so you need to replace every cubic inch you send out of the house. Make-up air (MUA) could be provided by opening up a window. If your house is well built and well sealed, you may be limited by the MUA factor and not by your duct size. In your climate, is it an option to open a window in wintertime? If you have a full house air exchanger like an ERV or HRV, you may have enough MUA without opening a window. Your duct size. How big is the diameter of your round duct, or what dimensions is your rectangular duct? E.g. if round: 5", 6", 7", 8"? If rectangular; 3" by 10", 3.5" by 14"? HTH -David Here is a link that might be useful: See sweeby's remark Feb 14 on MUA, in this range hood duct size question

Our solution is buying a vent hood that comes with telescoping chimney part for standard 8 foot ceiling or higher. We ended using only one of the 2-piece telescoping chimney. This is so we do not need to have a metal fabricator (cost too much) cut down the size of another hood with single piece chimney we bought. The piece we used was actually 1-2 inches longer than recommended but bypass having to recess into the ceiling.

As far as I know, no, there are not separate downdrafts that work with anything but a cook top. Are you having cabinets above on that wall? You could use a completely integrated hood and run the duct through the top of the cabinets. It takes a lot more work than building a box but it would look better. You could then run it through the pantry. Look at Broan and Faber Here is a link that might be useful: Broan Power Pack

Normally, the street sewer to which one's DWV plumbing is connected has a clear air path from under the street to the residence roof via the house DWV. Through this path, and the many others in the development, toxic and/or odoriferous gasses pass. The gasses are kept from the household air by water traps at the points of use. To have any chance that the gasses would not get into the kitchen hood and thence the kitchen when the hood system blower is off, a set of well sealed and powered dampers interconnected with the hood blower would be needed. I doubt even that would pass modern building codes, but it could function. Other houses' DWV would potentially be part of your venting system.