American Standard S9V2B080D4VSAB Installer's Manual page 43

All air from outdoors The confined space shall be provided with two
permanent openings, one commencing within 12 inches of the top and
one commencing within 12 inches of the bottom of the enclosure.
The openings shall communicate directly, or by ducts, with the
outdoors or spaces (crawl or attic) that freely communicate with the
outdoors. Refer to the Minimum Free Area in square inches for
confined spaces table, for minimum open areas required.
18-CE03D1-1F-EN
F F u u r r n n a a c c e e G G e e n n e e r r a a l l I I n n s s t t a a l l l l a a t t i i o o n n
CONFINED SPACE
AIR FROM OUTDOORS
CONFINED
SPACE
CONFINED SPACE
AIR FROM VENTILATED ATTIC/CRAWL SPACE
CONFINED
SPACE
ALTERNATE
INLET AIR
CONFINED SPACE
AIR FROM VENTILATED ATTIC
CONFINED
SPACE
OUTLET
OUTDOOR
AIR DUCTS
INLET
ATTIC LOUVERS
TO OUTDOORS
OUTLET
AIR
INLET
AIR DUCT
ATTIC LOUVERS
TO OUTDOORS
OUTLET
AIR
INLET
AIR DUCT
43