You can email the dept. from a gmail account. :)

Nobody mentioned it when I did my remodel. I suspect every city will be different.

But really, isn't it better to know about it before you fail inspection and have to retrofit it? Just ask them. If you need it, you will need it. It's not like they'll go "o yeah we forgot about that but now that you mention it..."

What bay area town are you in?

In San Jose, the rule is:

"Buildings with gravity appliances such as water heaters, furnaces, gas fireplace inserts, etc, within the conditioned envelope must provide make up air if the combined exhaust rate of the two largest exhaust fans (including clothes dryers and kitchen hoods) exceeds 15 cfm/100 sq ft. "

Not sure whether it gets enforced. Probably depends on who shows up to inspect.

I am a bit further north in the Peninsula in Los Altos.

Was not an issue for me in San Jose. Gut and rebuild of our kitchen with a 1600cfm hood added. The inspector, who was so picky that he wanted to see the specs on our faucet to make sure it had proper check valves.. the faucet was a Kohler bought from Home Depot and carries multiple certifications all with identical check valve requirements as the city.. well he didn't bat an eye at the hood. Never even asked what the air flow rating was on it.

I think it all depends on the inspector because a lot of people still don't pay much attention to MUA. If you had to pull a permit and your inspector is aware of these codes you might be in for some trouble.

You can buy a MUA kit for less than $200 but installing will most likely cost quite a bit more than the unit itself.