Type II hoods are not "grease ducts," but the exhaust still has to be built and terminated like a real system, not a loose note on the plan.
Plain English: Plain-English Highlights
506.4 scope: Commercial kitchen exhaust serving Type II hoods must follow 506.4.1 and 506.4.2.
506.4.1 ducts
Ducts and plenums must be rigid metallic.
Construction, install, bracing, and supports follow Chapter 6.
If the duct is under positive pressure or carries moisture-laden or waste-heat-laden air, it must be constructed, joined, and sealed in an approved manner.
506.4.2 terminations: Terminate per the hood manufacturer and also meet these placement rules:
Minimum 3 ft from openings into the building.
Minimum 10 ft from property lines or buildings on the same lot.
Minimum 10 ft from outside air intake.
Minimum 10 ft above grade.
If above roof: minimum 30 in above roof surface.
Minimum 30 in from exterior vertical walls.
Protect against local weather.
Do not discharge onto walkways.
Meet IBC requirements for exterior wall opening protectives.
On Plans: Why it matters
Common redlines: nonmetal duct called out, no sealing shown for positive pressure runs, and terminations too close to doors, windows, intakes, property lines, or pedestrian paths.
Code Path: Where to show it
M-001: "TYPE II HOOD EXHAUST" note stating rigid metallic ductwork, Chapter 6 construction, and sealing for positive pressure or moisture or heat laden runs.
M-101: Duct routing plus a clear termination callout with distances to openings, grade, walls, and property line where applicable.
Roof plan or exterior elevation: Outlet location and discharge direction, with "DO NOT DISCHARGE TO WALKWAYS" where it could be a conflict.
Check: Do
Treat Type II exhaust as a fully detailed duct system, not a generic exhaust arrow.
Show termination clearance compliance on the drawings, not only in specs.
Review Risk: Don't
Don't use flex or nonmetal duct for Type II hood exhaust.
Don't place the outlet where it can recirculate to openings or create a nuisance at sidewalks.
Field Tip: Field tip
Before you finalize the roof plan, run a quick "3-10-10-10-30" check for every Type II outlet: 3 ft from openings, 10 ft from property lines or same-lot buildings, 10 ft from outside air intakes, 10 ft above grade, 30 in above roof and 30 in off walls. If any one is tight, relocate the outlet now, not during inspection.
Comment "IMC506-P5" if you want a paste-ready Type II note for M-001.
Masterbuild QA Lens
Exhaust systems need a source-to-discharge story. Identify what is being captured, how it is captured, how it is routed, where it terminates, and what interlocks or separations protect the building.
Drawing / Submittal Check
Verify source classification, hood or pickup point, duct material, route, cleanouts or access, fan selection, discharge location, make-up air, controls, and required coordination with fire protection or alarms.
Common Review Risk
The expensive miss is treating all exhaust the same. Grease, dryer, dust, hazardous, smoke control, battery, and specialty exhaust systems carry different proof requirements.
When To Escalate
Escalate when exhaust involves grease, hazardous materials, combustible dust, battery charging, smoke control, rated shafts, energy recovery, or any discharge that can re-enter the building.
Load Assumption Check
For load-driven decisions, make the assumptions visible: weather basis, orientation, envelope, occupancy, ventilation, equipment gains, and any existing-building limitations that affect capacity.
Kitchen Exhaust Coordination
For kitchen exhaust, tie the hood schedule, appliance lineup, grease duct route, cleanouts, fan discharge, fire suppression interface, and make-up air strategy into one reviewable story.