Type II Hoods for Heat, Steam and Vapor

What a Type 2 Hood Handles

A Type 2 hood is the hood category for appliances that give off heat, moisture, steam or odor but not grease-laden vapor or smoke. It keeps dish rooms and steam cooking areas from turning into a sauna, protects ceilings from condensation and mold, and carries cooking odor out of the building.

Because no grease is involved, a Type II hood does not need listed grease filters, a wet chemical fire suppression system or a welded grease duct. That makes it lighter and less costly than a Type I grease hood. The trade-off is that the design challenge shifts from fire and grease to water: large volumes of hot, saturated air that condense the moment they hit a cooler surface.

Designs are prepared with the locally adopted mechanical code and the appliance manufacturer data in mind. The authority having jurisdiction (AHJ) decides whether a given appliance needs a Type II hood, a Type I hood or no hood at all.

Appliances That Typically Go Under a Type II Hood

The appliance decides the hood type. The table below lists equipment that commonly ends up under a Type II hood, with the design issue each one brings. Treat it as a starting point; the cooking process and local code can move an appliance into the Type I column.

The comparison with grease hoods is covered in detail in our Type 1 vs Type 2 hood guide.

Type 2 Hood Styles: Condensate Hoods and Heat Removal Hoods

Type II hoods come in two working styles, and picking the wrong one is a common cause of dripping ceilings in new kitchens.

Condensate hood

A condensate hood is built for wet loads. It has a perimeter gutter that runs around the inside lower edge and catches water that forms on the hood walls. Many designs add internal baffles that slow the air and give moisture a place to condense and drain, rather than letting it ride up into the duct. The gutter connects to an indirect drain. This is the right style over dishwashers, steamers and pasta cookers.

Heat removal hood

A heat removal hood is a simple canopy for dry heat, such as bake ovens or warming equipment. It captures the rising thermal plume and sends it to the exhaust. It does not need a gutter, though a small lip is sometimes added as insurance.

Dishwasher vent collars

Some conveyor dishwashers are made with exhaust collars at each end. Where the manufacturer and the AHJ allow it, ducting straight from those collars can replace a full canopy. The ductwork must still be sealed and sloped for condensate.

Sizing Exhaust for a Type II Hood

Type II exhaust is sized to capture the vapor or heat plume before it spills, and the biggest variable is how the appliance releases its load. A steady heat source behaves very differently from a dishwasher that releases a burst of steam every time a rack exits.

• Hood footprint: the canopy should extend beyond the appliance on open sides, and past door swings and conveyor ends where steam escapes. Six inches of overhang on open sides is the commonly referenced minimum for canopy hoods; dish rooms often benefit from more.
• Manufacturer data: dishwasher manufacturers often publish recommended exhaust rates at each end of the machine. Those numbers are a good baseline.
• Room conditions: cold make-up air dropped into a dish room creates fog and condensation. Tempered supply, or supply placed away from the hood, helps.
• Mounting height: the lower the hood, the better the capture, but staff need headroom to load and unload racks.

For general hood dimension rules, see the commercial hood sizing guide. Type II rates are usually lower than Type I rates for the same hood length, but an undersized dish room hood is one of the most visible failures in a kitchen.

Materials, Gutters and Drains on Type 2 Hoods

Type II hoods live in a wet, corrosive environment, so material choice and drainage details matter more than appearance. Stainless steel is the usual choice for dish room and steamer hoods because detergent-laden vapor attacks lesser metals. Some codes permit other materials for Type II hoods; check before value-engineering.

Details that keep water where it belongs:

• Continuous gutter with sealed corners and a drain fitting at the low point.
• Drain line routed to an indirect waste receptor, not tied straight into sanitary.
• Sealed seams so condensate cannot wick into the ceiling cavity.
• Light fixtures rated for wet locations.
• Duct collar placed so condensate from the duct runs back into the hood gutter or a duct drain, not onto a worker.

Type II Exhaust Duct Is Not a Grease Duct

The duct that serves a Type 2 hood is a general exhaust duct, not a grease duct, and it should never be connected to a grease exhaust system. Mixing the two would spread grease into a duct that is not built, cleaned or protected for it.

That said, a dish room duct carries a lot of water. Good practice includes:

• Sealed joints so moisture does not drip from seams.
• Corrosion-resistant material, commonly stainless or aluminum, where the vapor load is heavy.
• Horizontal runs sloped to drain back toward the hood or to a drain point.
• Insulation where the duct passes through cold spaces, to cut condensation inside and outside.
• An exhaust fan suited to moist air, with a discharge located away from intakes.

The rest of the exhaust train is covered on our kitchen exhaust systems page.

When a Type II Hood May Not Be Required

Not every heat or steam appliance needs a hood. Codes and AHJs allow exceptions in specific cases, and knowing them can save money, but they need to be confirmed before the design is final.

• Some dishwashers with built-in vapor condensers or heat recovery are designed to reduce vapor release, and the AHJ may accept them without a Type II hood.
• Low-heat appliances, such as some countertop warmers, may fall below the threshold that triggers a hood requirement.
• Some electric ovens are listed for use without a hood when installed exactly per their listing.

Each exception rests on the product listing, the local code and the inspector. We flag them during review but never assume them. If the general exhaust and the room air balance cannot handle the released heat and moisture, a hood is the better answer even where code does not insist.

Cleaning and Inspecting a Type II Hood

A Type II hood needs less cleaning than a grease hood, but it is not maintenance-free. Mineral scale, detergent film and mold are the usual problems, and they build up out of sight on the upper hood walls and inside the duct collar.

• Wipe the hood interior and baffles on a regular schedule with a cleaner that is safe for stainless steel.
• Flush the condensate gutter and check that the drain runs freely; a blocked drain turns the gutter into a drip tray that overflows at the corners.
• Look for rust streaks at seams, which point to a failed sealant joint.
• Check fan belts and bearings, since moist air shortens their life.
• Verify the exhaust still starts with the dishwasher or steam equipment, if the two are interlocked.

Routine service visits can cover Type II hoods alongside grease hoods; see our hood service and maintenance page.

Getting a Type 2 Hood Specified Correctly

The quickest path to a correct Type II hood is to send cut sheets for the dishwasher and steam equipment, along with the dish room layout and ceiling height. With that, an engineer can choose condensate or heat removal style, set the overhang at doors and conveyor ends, and size the exhaust and drain.

Use our quote request form to send drawings. If a Type I hood is on the same project, we size both so the make-up air and fan selections work together.