Type II hoods are the "steam + heat + combustion" side of commercial kitchens. Not a grease system, but still a code-driven hood + duct + airflow package.
Plain English: Plain-English Highlights
507.3 when Type II is required, Type II hoods go over:
Light-duty cooking
Dishwashers
Heat/moisture appliances that do NOT produce grease/smoke
Also: install Type II over appliances producing products of combustion (without grease/smoke).
Type I is allowed in place of Type II if it meets Type I installation rules. If a Type I hood serves ONLY dishwashers and Type II-only appliances, it does NOT need fire suppression or grease filters.
507.3.1 materials for Type II hood construction:
Steel: min 0.0296 in (22 ga)
Stainless: min 0.0220 in (24 ga)
Copper: min 24 oz/sf
Or other approved material/gage
507.3.2 supports: Supports must handle hood load + unsupported ductwork + effluent load + potential personnel load.
507.3.3 joints/seams/penetrations
Follow Chapter 6.
Seal on the interior.
Must be smooth, readily cleanable, and watertight.
507.3.4 capacity (NET exhaust)
NET = total exhaust minus any air supplied directly to the hood cavity.- 507.3.4.1 light-duty airflow minimums (cfm per linear ft)
Wall-mounted canopy: 200
Single island canopy: 400
Eyebrow: 250
Double island canopy: 250 per side
Backshelf/pass-over: 250
507.3.4.2 dishwasher airflow minimums
100 cfm per linear ft of hood length
On Plans: Why it matters
Common redlines: calling a Type II hood "general exhaust," missing NET cfm, using grease-type assumptions on a dishwasher canopy, and not detailing duct sealing for wet/moisture-laden airstreams.
Code Path: Where to show it
Hood schedule: Type II, material/gage, appliance type (light-duty vs dishwasher), OA, EA, and NET cfm.
M-101: duct routing + note "INTERIOR SEALED / WATERTIGHT PER CH. 6."
Details: hood support method and cleanable interior seams.
Field Tip: Field tip
On your hood schedule, add 3 quick columns for Type II:
APPLIANCE TYPE (LIGHT-DUTY / DW) | NET CFM/LF | MATERIAL/GA.
It eliminates 80% of Type II plan-review back-and-forth.
Comment "IMC507-P5" if you want a paste-ready Type II hood schedule row + M-001 note.
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.