Confirm whether this is grease duct, kitchen exhaust, lab exhaust, industrial exhaust, or normal exhaust.
Check the approved drawings/spec/submittal.
Look for cleanout/access, clearance, enclosure/wrap, weld/seal, slope/drainage, and inspection requirements.
Trace what equipment it serves and ask the foreman to confirm the system type.
Ask foreman
In Grease Duct, Kitchen Exhaust & Industrial Exhaust, I’m looking at: What do I do when not recognizing grease duct versus regular exhaust duct? What should I verify before I cut, drill, seal, cover, move, or install?
