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.
Verify equipment tag, connection detail, service access, and cleaning access before fastening.
Ask foreman
In Grease Duct, Kitchen Exhaust & Industrial Exhaust, I’m looking at: What do I do when not coordinating kitchen hood connection with hood installer? What should I verify before I cut, drill, seal, cover, move, or install?