"8x 10 townhouse kitchen has ducting for OTR microwave."

I don't get why you are asking this question, if you say your townhouse has ducting for OTR MW. In any case, why don't you call your local Building Department and ask this question.

Yep, check with your local building department or inspector office.

I ask because the kitchen cabinets are going to be replaced and I want to remove the soffit which has venting for the OTR MW. Unfortunately, the building dept is not opened to the public due to Covid and has a message on the phone that they will only respond to inquires via email within 10 business days. Still waiting to hear from them on my other inquiry .

If it's been over 10 buisness days, try emailing the office again. Maybe try calling again to see if the office is open for further inquiries.

Where in CA is this? Sometimes municipalities can have additional codes than the regular state codes.

"Second, you absolutely should not forego the ability to duct your kitchen exhaust to the outside. This is a non-starter. Stop even going down that path, it makes no sense whatsoever."

This ↑↑↑↑↑↑

More: https://bamasotan.us/range-exhaust-hood-faq/

@opaone, wow, thanks for posting that link, I have not read all but very informative.

@Shannon_WI@opaone The reason I am considering going down that path is to eliminate a 12" soffit that spans 10 feet across a small kitchen. I don't quite following the logic that removing the soffit should not remove the ability to vent your OTR MW. In this particuluar case, the outside vent is not adjacent to the upper duct cabinet as set forth in your illustration. If it was adjacent, I would agree. In this case, the electric stove is at the mid-point of the wall and the duct extends 5 feet (half of the soffit length) to the outside wall.

Although unstated, I assume the statement that removal should be a "non-starter" and making "no sense whatsoever" is due to inside air quality concerns. Opaone, thank you for posting the interesting article about air quality and kitchens. Admittedly, my level of concern regarding interior air quality was not as high as bamasotan's as the kitchen will be primarily used for microwaving Trader Joe's frozen food. I guess the essense of my question was really one of legality and practicality. If there is a way to elimate most of the soffit and maintain the duct, I would be interested in knowing.