How Commercial Kitchen Ventilation Systems Fit Together
A commercial kitchen ventilation system is a loop of air: exhaust leaves through the hood, duct and fan, and the same volume of air comes back in through make-up air and transfer air. If any link in that loop is undersized or out of balance, the whole system underperforms, no matter how good the hood is.
| Component | Job in the system | Main design input |
|---|---|---|
| Hood | Captures and contains the cooking plume | Appliance duty class, hood style, overhang |
| Grease duct | Carries grease-laden air to the outside safely | Exhaust CFM, velocity, route, clearances |
| Exhaust fan | Moves the design airflow against system resistance | CFM and total static pressure |
| Make-up air | Replaces exhausted air without disturbing capture | Exhaust CFM, climate, diffuser placement |
| Controls | Interlocks fans, suppression and fuel shutoff | Code requirements, energy goals |
The exhaust rate is the number everything else is sized from. Get it from the appliances and hood type first, then size the duct, the fan and the make-up air unit to that figure.
-
Kitchen Exhaust Systems
The full exhaust path from hood collar to discharge: design velocity, duct routing, static pressure, roof or wall termination and demand-controlled ventilation. Learn more -
Exhaust Fans
Upblast, utility set and inline kitchen exhaust fans: drive types, hinge kits, grease containment, UL 762 listing and selection against static pressure. Learn more -
Make-Up Air Systems
Replacement air sized to the hood exhaust: tempered or untempered units, direct or indirect gas heat, and discharge styles that support capture instead of fighting it. Learn more -
Grease Duct Systems
Welded steel or listed factory-built grease duct, sloped to drain, with cleanouts, rated enclosures or wraps, code clearances and a leak test before it is covered. Learn more
Where the Parts Interact (and Where Problems Start)
Most kitchen ventilation complaints come from the interfaces between components, not from a single failed part. A hood that captures perfectly in a test can spill smoke in a real kitchen if the make-up air blows across its face.
- Hood and duct: the duct collar size sets the velocity entering the duct. Too large and grease settles; too small and static pressure climbs.
- Duct and fan: every elbow, transition and foot of duct adds resistance the fan has to overcome. A fan picked from CFM alone, without static pressure, will underdeliver.
- Fan and make-up air: the two are interlocked so replacement air runs whenever the exhaust runs. If one is variable speed, the other usually has to follow.
- Make-up air and hood: supply air that enters too fast or too close to the hood disrupts capture.
- Kitchen and dining room: the kitchen should stay slightly negative so cooking odors flow in, not out to the guests.
These links are why we treat the complete exhaust path and the supply side as one design problem.
Balancing Exhaust and Make-Up Air
Balancing is the field process of measuring and adjusting airflows until the system delivers what was designed. It happens after installation, with all fans running and the kitchen in its normal configuration.
A typical target is for the make-up air unit to supply most of the exhausted air, often in the range of 80 to 90 percent, with the remainder transferred from adjacent spaces. That keeps the kitchen slightly negative without making doors hard to open. Confirm the approach against the mechanical code adopted locally and the building HVAC design.
What a balancing visit usually covers
- Exhaust airflow at each hood, measured or calculated from readings
- Fan speed and amp draw compared with the fan selection
- Make-up air delivery and diffuser throw
- Pressure relationship between kitchen and dining room
- Visual smoke capture test with appliances at cooking temperature
Rebalance whenever the cook line changes, a hood is added, or the building HVAC is modified. A kitchen that worked on opening day can drift out of balance after a remodel next door.
Codes and Standards Behind Kitchen Ventilation
Kitchen ventilation in the US is designed around NFPA 96 and the mechanical code adopted by the jurisdiction, most often the International Mechanical Code. ASHRAE Standard 154 adds guidance on exhaust rates by appliance duty class. Equipment carries its own listings: UL 710 for hoods, UL 1978 for factory-built grease duct, UL 762 for restaurant exhaust fans and UL 300 for wet chemical suppression.
The authority having jurisdiction has the final say on which editions apply and how they are interpreted. Our NFPA 96 requirements guide covers the points inspectors check most often, and the guide to how kitchen ventilation works explains the airflow principles in more depth.
Designing a Ventilation System for Your Kitchen
A ventilation design starts with the equipment schedule and the building, and ends with a balanced, inspected system. We work from your drawings, or from a site visit for existing kitchens, and size every component to the same exhaust figure.
- Review appliances, hood layout and building constraints.
- Calculate exhaust per hood and total system airflow.
- Route the grease duct and calculate static pressure.
- Select the exhaust fan and make-up air unit together.
- Coordinate controls with suppression, fuel shutoff and building systems.
- Install, test, balance and document.
The pages below go deeper on each part of the system. If you have a project in hand, send drawings for a ventilation quote or ask to talk to an engineer.
Kitchen Ventilation System Questions
- Can I upgrade just the exhaust fan to fix a smoky kitchen?
- Sometimes, but a bigger fan alone often makes things worse. More exhaust without more make-up air pulls the kitchen further negative, and the hood may still spill if supply air disturbs it. Measure what the system is doing first, then decide whether the fan, the make-up air, the hood or the duct is the limiting part.
- Who is responsible for balancing the ventilation system?
- Usually a test and balance contractor or the ventilation installer, depending on the project specifications. The mechanical engineer of record often requires a written balance report. On smaller projects the installer may balance the system and document readings for the inspector and owner.
- Does every kitchen need make-up air?
- Any kitchen exhausting a meaningful volume of air needs that air replaced. Whether it comes from a dedicated make-up air unit, the building HVAC or a combination depends on the exhaust rate, the climate and the local mechanical code. Most commercial kitchens with Type I hoods end up with a dedicated unit.
- How often should a kitchen ventilation system be checked?
- Grease buildup inspection follows the NFPA 96 frequency for your cooking volume, from monthly for solid fuel to annually for low-volume kitchens. Airflow and balance should be checked after any change to the cook line or HVAC, and whenever staff notice smoke spilling, drafts or hard-to-open doors.
- Can one exhaust fan serve several hoods?
- It can, when the hoods are on the same floor and the code and duct layout permit combining them. The duct has to be designed so each hood receives its intended airflow, and the fan must be selected for the combined airflow and the longest path static pressure. Separate fans give more independent control.