Originally Posted by
John Thompson
is drawing combustion air into a utility closet from the attic through a six inch pipe. ... Is this OK?
Absolutely not.
The minimum size of *each* combustion air vent is 100 square inches. A round pipe would need to be a 12 inch diameter pipe (a 10 inch diameter pipe would be too small and they don't make an 11 inch diameter pipe (or, if they do, those 11 inch diameter pipes are had to find).
And, they need two of those 12 inch pipes. One within 12 inches of the ceiling and one within 12 inches of the floor.