Reference
Definition
What the word means. This is not a work instruction.
Start at the equipment or main trunk and follow the duct toward the branch, VAV, diffuser, grille, return, or exhaust point. Look for arrows, labels, equipment tags, damper handles, and airflow notes on the print.
On supply air, the duct usually leaves the air handler or VAV and heads toward diffusers. Return and exhaust usually pull air back toward a fan or shaft.