A kitchen exhaust and make-up air scope covers replacing or repairing the exhaust fan and the make-up air unit, wiring their interlocks so they run together, and balancing airflow so the kitchen stays slightly negative to the dining room. It does not include hood cleaning, grease duct cleaning or fire suppression, and the scope should name the separate party responsible for each of those.
- Exhaust and make-up air are one system. A scope that replaces one fan without addressing the other usually moves the problem somewhere else.
- Hood cleaning, grease duct cleaning and fire suppression are separate trades with their own certifications. The scope should say who owns them instead of leaving a gap.
- Interlocks decide how the system behaves on a bad day: fire alarm, suppression discharge, fan failure. They belong in the scope in writing.
- Balance is measured, not assumed. Ask for before and after airflow readings and a stated dining-room pressure condition.
- Permit and inspection items under the California Mechanical Code vary by jurisdiction, so the scope should say who pulls the permit.
What this scope covers, and what it deliberately leaves out
Most kitchen ventilation disputes begin with a vague line item such as "service hood system." That phrase can mean cleaning grease, replacing a fan, fixing a door that will not stay shut, or all three. This page is about one slice: the mechanical equipment that moves air, namely the exhaust fan and the make-up air unit (MAU), plus the controls that tie them together and the balance work that proves they behave.
Davinci's work here is the kitchen ventilation and make-up air service: fans, MAUs, their mechanical connections and controls, performed by our own UA Local 250 crew. The scope below is written so a restaurant group, landlord or general contractor can drop it into a bid package and compare proposals fairly.
Hood and grease duct cleaning, fire suppression system service and testing, and any new hood or duct fabrication are separate scopes. Davinci does not perform hood cleaning or fire suppression. The owner or GC should name the licensed, certified party for each so nothing falls between trades.
Who owns what on a kitchen ventilation job
The cleanest way to prevent finger-pointing is a responsibility table in the bid documents. A starting point:
| Item | Typical responsible party | Scope note |
|---|---|---|
| Exhaust fan replacement, curb, wiring from disconnect | Mechanical contractor | Confirm who provides the disconnect and any new circuit |
| Make-up air unit replacement and gas or electric heat | Mechanical contractor | Gas piping extension is a plumbing or gas-fitting item in some jurisdictions; name it |
| Primary electrical service, feeders, panels | Licensed electrician named by owner or GC | Davinci does not perform this work |
| Hood and duct cleaning | Certified hood cleaning company | Access panels must be reachable after the work |
| Fire suppression and shunt trip | Licensed fire suppression contractor | Interlock points are coordinated with mechanical |
| Roof penetrations, flashing, structural framing | Roofer or GC | Mechanical contractor sets equipment, does not warrant the roof |
| Airflow balancing report | Named in the scope | Davinci takes readings on its own installed equipment; an independent test-and-balance agency is a separate item |
If you are writing the bid package from scratch, start with how to write a commercial HVAC scope of work and then tighten this section against the clarifications and exclusions checklist.
Exhaust fan replacement: what to specify
The existing fan is a poor guide to the new one. Fans get swapped over the years for whatever fit, and the nameplate may reflect a unit that was never right. Before ordering, the scope should require field verification of the following.
- Hood type and the airflow the hood was designed and listed for, taken from its label, not guessed from the fan.
- Fan style: upblast on the roof or utility set inside, and whether the existing curb, vented base or hinge kit can be reused.
- Motor and drive: belt or direct, single or variable speed, and whether the new fan changes electrical load enough to affect the disconnect.
- Grease containment, access for cleaning and any drain arrangement at the fan base.
- Discharge clearances from air intakes, property lines and walkable roof areas as required by the California Mechanical Code and the local authority. Confirm current requirements with the building department.
A reused curb is a quiet source of change orders. If the scope assumes reuse, state that a mismatch will be handled as a documented change order once the old fan is unbolted and the curb is seen.
Make-up air unit replacement and the air you cannot see
Every cubic foot a hood pulls out has to come back in from somewhere. If the MAU is weak, the kitchen borrows from the dining room, the back door, the roof drains and the gas appliances' flue spillage paths. The result is cold drafts, hard-to-open doors, pilot lights that misbehave and cooks who say the hood "doesn't pull."
Decisions the scope should settle
- Direct-fired, indirect-fired or unheated make-up air, with the heating source and who extends gas or power to it.
- Whether supply is delivered at the hood, as a short-circuit or perimeter supply, or into the kitchen space, since this affects capture and comfort.
- Filtration and coil or burner protection for a unit that breathes air near a grease-producing roof.
- Cooling or tempering of make-up air, which is often cut in budget reviews and then regretted in July.
- Curb adapters and the crane or lift plan. See equipment removal, crane and rigging.
Interlocks: how the system behaves when something goes wrong
Interlocks are the least visible and most consequential part of the job. They should be listed one by one, with who wires each end.
- Exhaust and make-up air start together: the MAU is enabled only when the exhaust fan proves it is running, using a current switch, airflow switch or fan status relay.
- Make-up air shuts down on exhaust fan failure so the kitchen is not pressurized with hot air or a firing burner.
- Fire alarm and suppression signal: define whether the MAU shuts down, the exhaust fan continues to run, or both, according to the approved design and code. Do not assume; point to the drawings or the authority having jurisdiction.
- Gas shutoff coordination where cooking appliances are tied to the hood proof-of-flow, handled by the party that owns the gas train.
- Manual override or test switch location, labeled, reachable and noted for the fire inspector.
Where the building has automation, add the points that should report to it. See building automation controls upgrade scope for how to write that piece.
Dining-room pressure and balance
A kitchen should sit slightly negative to the dining room so cooking odor and heat drift toward the hood, not toward guests. Too negative and the front door whistles and the rooftop HVAC unit serving the dining room starves for air. Too neutral and smoke gets out.
A good scope asks for a measured, documented condition rather than a general promise. Readings to request:
- Exhaust airflow at the hood and fan, before and after.
- Make-up air supply airflow, with all hoods and the dish machine vent running.
- A stated pressure relationship, kitchen to dining, with doors in their normal operating position.
- Notes on any door, transfer opening or dining unit adjustment made to reach the condition.
These readings are recorded against each fan and MAU and kept in the DaVinci Portal so the next technician starts from the commissioned condition, not from scratch. The restaurant-side view of the same problem is covered in kitchen heat and refrigeration performance.
Sample scope language and closeout
Contractor shall furnish and install one replacement exhaust fan and one replacement make-up air unit at the locations shown, reconnect existing ductwork at the new equipment, and furnish control wiring to interlock the make-up air unit with exhaust fan operation. Contractor shall measure and record exhaust and supply airflow before and after the work and adjust equipment speeds to reach the airflow stated in the Owner's design documents. Hood and duct cleaning, fire suppression work and primary electrical service are excluded and shall be furnished by the parties Owner designates.
Closeout for this scope is short but should not be skipped: marked-up equipment tags, airflow readings, interlock test results signed off with the kitchen manager, a note on filter and belt maintenance, and photos of the finished installation. Confirm with the local building department which inspections apply to your jurisdiction and permit.