We have an atmospheric boiler in a closet in a garage behind some bypass doors. It's combustion air vents are in the wall next to it and zone plumbing running directly in front of those vents. Can the combustion air supply vents be moved out of the closet to the other side of the garage? Is there a distance limit between the boiler and it's air supply vents? How could we improve upon the carboard box shutoff approach someone employed here? Thanks. Brendan.