Type 1 vs type 2 hood: the short answer
A Type I hood is used over cooking appliances that produce grease or smoke, and a Type II hood is used over appliances that produce only heat, steam, vapor, odor or condensate. The International Mechanical Code and NFPA 96 both build on that distinction, and almost every other difference between the two hoods follows from it.
Grease is a fuel. Once grease vapor condenses inside a hood and duct, it can ignite and burn through the system, so the Type I package is built to contain that fire: listed grease filters, a fire suppression system, and a fully welded grease duct with clearances to combustibles. Steam and heat are not fuel, so a Type II hood is a simpler capture device that removes moisture and heat to keep the kitchen comfortable and the ceiling dry.
If you remember one rule, make it this: the appliance and how it is used decide the hood, and the authority having jurisdiction (AHJ) has the final word.
Side-by-side comparison of Type I and Type II hoods
The table below compares the two hood types component by component. Values are typical and should be confirmed against the code edition adopted locally.
| Feature | Type I hood | Type II hood |
|---|---|---|
| Purpose | Capture grease vapor and smoke | Capture heat, steam, vapor, odor, condensate |
| Typical appliances | Fryers, ranges, griddles, charbroilers, woks, tilting skillets used for browning | Dishwashers, steamers, many ovens, pasta cookers, steam kettles used for boiling |
| Filters | Listed grease filters (commonly stainless baffle) | None required for grease; may have condensate baffles or none |
| Fire suppression | Typically required (wet chemical systems listed to UL 300 are common) | Typically not required |
| Duct | Grease duct: commonly ≥ 16-gauge carbon steel or ≥ 18-gauge stainless, continuously welded and liquid-tight | Ordinary sheet metal duct, often aluminum or galvanized for moisture; not a grease duct |
| Clearance to combustibles | Commonly 18 in., reducible with listed protection | Normal duct clearances |
| Duct velocity | Commonly at least 500 fpm; typical design 1,500 to 1,800 fpm | Set for comfort and moisture removal |
| Exhaust fan | Listed for grease exhaust (UL 762 fans are common), hinged for cleaning | General exhaust fan suited to moist air |
| Cleaning and inspection | Periodic grease inspection per NFPA 96 frequency | Routine cleaning of condensate and filters |
| Relative cost | Higher: filters, suppression, welded duct, rated enclosures | Lower |
For component detail, see the Type I grease hood and Type II hood pages.
Which hood type commonly applies to each appliance
The appliance list below shows how hoods are commonly assigned in US kitchens. It is a starting point, not a ruling: the AHJ decides, and the same appliance can move between categories depending on the food cooked and the volume.
| Appliance | Commonly | Why, and what can change it |
|---|---|---|
| Deep fat fryer | Type I | Produces grease vapor every time it runs |
| Range, open burners | Type I | Sautéing and pan frying release grease |
| Griddle / flat top | Type I | Burgers, bacon, eggs: steady grease load |
| Charbroiler | Type I | Heavy grease and smoke; one of the most demanding appliances |
| Wok range | Type I | High heat, oil, fast plume |
| Tilting braising pan | Usually Type I | Used for browning; Type II only if strictly used for steam cooking and the AHJ agrees |
| Commercial dishwasher | Type II | Steam and heat; some machines use a direct duct connection instead of a hood |
| Compartment steamer | Type II | Steam only |
| Steam-jacketed kettle | Type II when boiling | Moves toward Type I if used to brown meat or fry |
| Pasta cooker | Type II | Boiling water, starch-laden steam |
| Combi oven | Varies | Steam and heat, but roasting fatty proteins releases grease; listing and AHJ decide |
| Convection oven | Type II or Type I | Baking bread: Type II; roasting chicken or bacon: often Type I |
| Pizza deck or conveyor oven | Varies | Many AHJs accept Type II; some require Type I, especially for heavy cheese and meat volume |
| Wood or coal-fired oven | Type I, plus solid-fuel rules | Smoke, creosote and spark risk; separate duct and more frequent inspection |
| Rethermalizer | Usually Type II or none | Hot water bath with sealed product; light load |
| Rotisserie | Type I | Rendering fat from rotating meat |
| Panini press, countertop toaster | Often no hood or Type II | Small loads; heavy-volume use may change the answer |
Some electric appliances are listed for use without a hood, or with a recirculating ventless system, under specific conditions. That listing, not the appliance category, controls.
What changes in the duct, fan and building
Choosing a Type I hood changes far more than the hood itself, because the grease duct behind it is a fire containment system that runs all the way to the roof. A Type II duct is ordinary ventilation work.
Type I grease duct requirements
- Continuously welded, liquid-tight seams and joints; no screws or rivets penetrating the duct.
- Slope back toward the hood or to a grease reservoir so liquid grease drains.
- Access doors for cleaning at changes of direction and at the intervals the code requires.
- Enclosure in a fire-rated shaft or protection with a listed wrap or factory-built grease duct system where it passes through the building.
- Its own dedicated path: a grease duct does not connect to other exhaust systems.
- An upblast or utility fan suited for grease, commonly discharging at least 40 in. above the roof, with grease containment at the fan.
Type II duct
Type II duct is designed to carry moisture without corroding or dripping. Aluminum, stainless or galvanized duct is common, joints are sealed against condensate, and the duct is often pitched to drain. It does not need fire-rated enclosure for grease, though normal fire and smoke damper rules for ductwork still apply.
The grease duct system page covers Type I duct in more depth.
What changes in fire suppression and controls
A Type I hood over grease-producing appliances typically requires an automatic fire suppression system, while a Type II hood does not. Wet chemical systems listed to UL 300 are the common choice in US kitchens. The system protects the appliance surfaces, the hood plenum and the duct entry.
Suppression brings controls with it. On discharge, fuel gas and electric power to the appliances under the hood must shut off, and the fan operation follows the code and the suppression system design. A manual pull station is placed along the path of egress. Make-up air interlocks may also apply. None of this exists on a typical Type II hood, which usually needs only a fan switch or interlock with the dish machine.
Moving one appliance from a Type II zone to a Type I zone can therefore require new nozzles, new detection, new gas valves and new interlocks, not just a larger hood.
Common hood type misclassification mistakes
Most hood type errors happen when the appliance list is read without asking how the appliance is actually used. These are the mistakes we see most often:
- Putting a combi or convection oven under Type II when the menu roasts meat. Grease vapor from roasting will coat a Type II duct that was never built to contain it.
- Treating a tilting skillet as a steam appliance. If it ever browns ground beef, it is a grease appliance.
- Adding a fryer to a Type II line after opening. Menu changes quietly turn a compliant kitchen into a non-compliant one. Any new grease appliance needs Type I protection.
- Connecting a Type II hood or dish exhaust into a grease duct. Grease ducts serve only Type I hoods; mixing systems is generally not permitted.
- Assuming a ventless label covers any appliance. Recirculating systems are listed for specific appliances and conditions.
- Leaving the AHJ out until plan review. Borderline appliances such as pizza ovens and rethermalizers get decided differently from one jurisdiction to the next. Ask early.
When a decision is unclear, many designers simply extend the Type I hood over the questionable appliance. That costs more up front but leaves room for menu changes later.
How to confirm the right hood type for your kitchen
The reliable way to settle Type I versus Type II is to list every appliance with its fuel, size and the food it will actually cook, then review that list with the AHJ or in the plan submittal. Include planned future equipment, not just opening-day equipment.
From there, the hood sizes and exhaust rates follow the appliance duty classes described in the hood sizing guide. Inspection frequency for Type I systems is covered in the NFPA 96 requirements guide. If you want a second opinion on a specific equipment list, send it through request a quote and an engineer will mark which appliances commonly need which hood.
Type I and Type II Hood Questions
- Can one hood be both Type I and Type II?
- A single hood is either Type I or Type II. A long hood can be built in sections, but if any grease-producing appliance sits under a section, that section must be Type I with grease filters, suppression and grease duct. Many kitchens simply put all appliances under one Type I hood for flexibility.
- Does a pizza oven need a Type I or Type II hood?
- It depends on the oven, the fuel and the AHJ. Many electric and gas deck or conveyor pizza ovens are placed under Type II hoods, and some are listed for use without a hood. Some jurisdictions require Type I because of cheese and meat toppings. Wood or coal-fired ovens follow solid-fuel rules and typically need Type I with a separate duct.
- Is a Type II hood required over a commercial dishwasher?
- Commonly yes, unless the dish machine has a listed direct exhaust connection or is a low-temperature or ventless model that the manufacturer and AHJ accept without a hood. The aim is to remove steam before it condenses on ceilings and walls. Check the machine's installation instructions and the local code.
- Why is a Type I hood so much more expensive than a Type II hood?
- The hood itself is only part of the difference. A Type I system adds listed grease filters, a fire suppression system, welded heavy-gauge grease duct, rated shaft or wrap protection, a grease-rated fan with containment, and periodic professional cleaning. A Type II system uses ordinary duct and a simpler fan.
- Can I convert a Type II hood to Type I later?
- Usually not economically. Conversion would require grease filters, a fire suppression system, a new welded grease duct and possibly a new fan and shaft protection. In most cases a new Type I hood is installed. If a menu might grow, specify Type I from the start.
- Who decides whether an appliance needs a Type I or Type II hood?
- The authority having jurisdiction, usually the local building or mechanical official and the fire marshal, makes the decision based on the adopted mechanical code, NFPA 96, the appliance listing and the intended cooking. Designers and manufacturers can recommend, but the AHJ approves the plans and the installation.