We are in a middle-of the-building townhouse with no windows in the kitchen and no possibility of external venting through the wall or through the roof. So, we had thought we could only do a recirculating hood. Then, I started to read some older threads here and discovered one from 13 years ago where people discussed tapping into other existing venting to vent their range hood. I'd like to know what people's thoughts are on more unconventional ways to get venting. Here is what I found:

"Here's my setup:
30" GE induction cooktop (love it, love it, love it)
Faber Inca HC SS Insert (we did a wood decorative hood).

The Faber Inca HC has 540 CFM blower and comes in 30 or 36" size installations. We have been very pleased with the amount of suction it has.

To recirculate the air, we took venting up through the decorative hood, did a 90 degree turn between floor joists, went above & over to the end of the cabinets (only about 2' for us) and then vented out into a round ceiling heat register for the air vent. It looks fine and works fine, despite all my worrying about it's looks and effectiveness." This solution I think was just a way to at least get the air from the vent fan out of the kitchen and not necessarily outside the house.

and, this one from Buehl:

"Two different solutions were proposed. One plumber (the $550 estimate) involved tapping into the toilet waste pipe w/a sanitary T. However, the other plumbers were uncertain that it would pass inspection, so they proposed tapping into the 2nd floor main waste pipe and venting up the wall into the attic where, it turns out, we have a "whole house" vent stack. The 2 estimates we got for that were $925 & $1,000. We went w/the $925 bid since they also offered drywall repair (another $500) and the other one did not. However, we did not need it as the bay to the attic was completely clear so they were able to feed the vent pipe up to the attic w/o cutting through any drywall.

Our contractor kept saying there's no way that will pass code/inspection and that we HAD to go through the roof to be sure it would pass...(they wanted $4,800!)

Well, we went w/the $925 bid/solution anyway and yes, it did pass inspection...I even asked the inspector about the toilet waste pipe solution and he said that would have passed as well!" This one I think actually ended up with real outside venting.

Do any of you have any thoughts about unconventional ways to achieve outside venting in a situation where we have always thought we couldn't do it? After a lot of thinking about this, we are finally getting to the point where we need to make some actual final decisions and purchase a hood. Thanks.