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.
Confirm system type, contents, material, labeling, and who is authorized before modifying anything.
Ask foreman
In Grease Duct, Kitchen Exhaust & Industrial Exhaust, I’m looking at: What do I do when not escalating when grease/industrial detail is missing? What should I verify before I cut, drill, seal, cover, move, or install?