I'm in PG county, and below is a link to my MUA solution (for a 1000cfm hood). So far it's working we'll - no CO poisoning, and no fireplace ash scattered about!

Here is a link that might be useful: My makeup air solution

BTW, what you need to do is find out for sure if your county enforces the 2009 IRC, section M1503.4, which states that range hoods capable of exhausting in excess of 400 cfm must have makeup air.

Hi scrappy25, I'm in Baltimore County, too - I would call and ask: 410-887-3353 - Permits, Approvals and Inspections.

Here is a link that might be useful: Baltimore County Gov't Permits, Approvals and Inspections

4 am blues, that is a really clever solution , thank you! Really great if anyone wants to have high CFM. And thanks for the advice to call the county. I can't believe that you actually know the IRC section in detail like that.

purplepansies, THANK YOU for that phone number. They were so easy to speak to. The inspector said that that requirement might be buried somewhere in the residential code, but unless it was a commercial type unit they had other priorities in the residential inspection, that's why those local contractors and architect had had to deal with that issue.

Lesson learned is not to be afraid to pick up the phone to speak to the inspectors of your area. Of course it is much easier when the phone number is provided on a silver platter. I love GW!