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:
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.
Check: Hood Schedule and Appliance Documentation
Hood schedule must call out TYPE II and list the specific appliances served (dishwasher, steam kettle, low-temperature oven) with appliance type noted as light-duty or dishwasher.
Document NET cfm per linear foot on the schedule: 200 cfm/lf for light-duty appliances, 100 cfm/lf for dishwashers.
Note on M-001: if any appliance is changed to a grease-producing type after permit, the hood must be upgraded to Type I before occupancy.
Review Risk:
Type II hoods over appliances later changed to grease-producing types are the most common Type II inspection failure - lock in the final appliance list before the permit is filed.
Calling a Type II hood general exhaust without designating it as a commercial hood triggers a plan review
Missing NET cfm on the schedule is a consistent Type II plan review flag.
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.
Masterbuild QA Lens
Type II hoods for non-grease-producing appliances have different exhaust rate requirements than Type I. Confirm the appliance list under each Type II hood is complete - dishwashers, ovens, steam tables, steamers - and that the exhaust cfm is calculated from the correct table row. Adding a high-heat appliance to a Type II system after submittal requires a design change.
Drawing / Submittal Check
For Type II hoods (507.3): the drawings must call out that the hood is Type II and identify the appliances beneath it. Type II hoods serve heat- and moisture-producing appliances that do not produce grease-laden vapors (dishwashers, steam kettles, low-temperature ovens). If the appliance list changes to include a grease-producing appliance, the hood must be upgraded to Type I. Document the appliance list on the drawings.
Common Review Risk
Type II hoods over appliances that were later changed to grease-producing types are the most common Type II inspection failure. The building owner replaces a steam kettle with a griddle, and the Type II hood is now over a Type I appliance. This is an after-permit change that requires an amendment. Confirm with the kitchen operator that the appliance types are final before the permit is filed.
When To Escalate
Escalate when the kitchen operator cannot confirm the final appliance types before the permit is filed, specifically when there is a possibility of adding grease-producing appliances after occupancy. A Type II hood system that is later upgraded to Type I because the appliances changed requires a full duct replacement and fire suppression addition - one of the most expensive post-permit mechanical changes in kitchen work.
Load Assumption Check
Type II hood exhaust rates depend on the appliance type and the hood geometry. Confirm that exhaust CFM is calculated for each appliance under the hood and that the total matches the fan schedule - generic CFM-per-linear-foot values must be validated against the actual equipment.
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.