Code & Compliance

Commercial Kitchen Exhaust Systems: A Contractor’s Guide to Type I, Type II, and California Code

Restaurant exhaust is where a lot of kitchen projects get red-tagged, and where contractors who actually know the code stand out. Get the hood type, the make up air unit, and the fire suppression system right and you pass inspection the first time; get them wrong and the job stalls while the kitchen sits closed and the owner loses money every day. This guide breaks down what California’s mechanical and fire codes expect from a commercial kitchen exhaust system, the difference between Type I and Type II hoods, how the make up air unit keeps the building from going negative, and the mistakes that cost contractors their re-inspection. Whether you’re bidding a full kitchen buildout or swapping a single hood, this is the baseline that separates a specialist from a generalist, and the kind of work SearchLocalPro matches license-verified pros to every week.

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Type I vs Type II, get this right first

The hood type is decided by what’s cooking under it.

  • Type I handles grease and smoke, anything that produces grease-laden vapor: fryers, griddles, charbroilers, ranges, woks, broilers. A Type I commercial kitchen exhaust system requires grease filters/baffles, a welded liquid-tight grease duct, exterior discharge, and a fire suppression system. This is the regulated, inspected, fire-rated category.
  • Type II handles heat, steam, and moisture only, no grease: dishwashers, steam tables, some ovens. No grease filters or fire suppression system required, but it still needs to be permitted and vented correctly.

Putting a Type II hood over grease-producing equipment is one of the fastest ways to fail plan check.

The make up air unit, the part generalists miss

Every CFM you exhaust has to be replaced, or the building goes negative, doors that won’t close, pilot lights that blow out, backdrafting. California code requires a make up air unit sized to the exhaust, typically replacing the large majority of exhausted air, often tempered so you’re not blowing cold air across the line in winter. Larger systems also trigger Title 24 requirements like demand-control kitchen ventilation (DCKV). If your bid doesn’t account for the make up air unit, your number is wrong and your inspection will catch it.

Fire suppression system, non-negotiable on Type I

Type I hoods require an automatic wet-chemical fire suppression system (e.g. Ansul R-102 style), interlocked to shut off fuel/power to the appliances and tied into the building fire alarm where required. This is governed by NFPA 96 and NFPA 17A, plan-checked by the fire department, and inspected separately from the mechanical work. Coordinate it early, it’s a common scheduling bottleneck.

Permits & inspections, who signs off

A commercial kitchen exhaust system typically clears three authorities, and missing one stalls the whole job:

  1. Building/Mechanical, the mechanical permit (CMC Chapter 5 governs exhaust systems)
  2. Fire Department, the fire suppression system plan check and test
  3. Health Department, finishes, clearances, and that the system is part of the approved kitchen plan

Pull them in parallel, not in sequence, and confirm your local AHJ’s specifics before you bid the timeline.

Five red-tag mistakes to avoid

  1. Wrong hood type for the equipment duty
  2. Undersized or missing make up air unit
  3. Grease duct that isn’t welded liquid-tight or lacks required access panels
  4. Insufficient clearance to combustibles
  5. Fire suppression system not coordinated with the mechanical scope, blowing the schedule

Frequently asked questions

Do I need a Type I hood over a commercial dishwasher?
No, a dishwasher produces heat and steam, not grease, so it falls under Type II. Type I is for grease-producing cooking equipment. Confirm the full equipment lineup before you spec the hood.
How big a make up air unit does a commercial kitchen need?
It’s sized to the exhaust volume, you’re replacing the air you pull out, with most systems supplying the large majority of the exhausted CFM (often tempered). Exact figures depend on the hood, the equipment, and your local code, so size the make up air unit against the current CMC and your AHJ, not a rule of thumb.
Who inspects a commercial kitchen exhaust system?
Usually three: building/mechanical for the exhaust system, the fire department for the fire suppression system, and the health department as part of the kitchen plan. Each is a separate sign-off.
How often does a commercial kitchen exhaust system need cleaning?
NFPA 96 sets the cadence by cooking volume, roughly monthly for solid-fuel and high-volume operations, quarterly to semi-annually for moderate use, and annually for light-duty kitchens. The owner is responsible for keeping it on schedule, but contractors who offer or coordinate cleaning often turn a one-time job into a recurring relationship. Confirm the interval against NFPA 96 and your local AHJ.
Can I reuse the existing hood and ductwork in a restaurant remodel?
Sometimes, but only if it meets current code. A change in cooking equipment or use can trigger bringing the whole commercial kitchen exhaust system up to today’s NFPA 96 and clearance requirements, and a worn grease duct or outdated fire suppression system usually has to be replaced. Have the AHJ confirm what can stay before you bid reuse into the job.

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