Commercial Kitchen Ventilation & Hood Sizing

Ventilation is where most wok-line projects go wrong, and it is the one system you cannot fix cheaply after the slab is poured and the gas is run. A Panda® wok range throws off far more heat and combustion product per linear foot than a standard fry-and-griddle line, and the hood, the makeup air and the fire suppression all have to be sized around that reality from the first drawing. This guide walks through how to specify the exhaust system for a high-BTU Chinese cooking line so it captures grease and heat, satisfies mechanical code, and passes inspection the first time.

Type I vs Type II: pick the right hood first

The single most important classification is grease. A Type I hood is required over any appliance that produces grease-laden vapor or smoke — wok ranges, roasters, fryers, broilers and charbroilers. It carries listed baffle grease filters, a welded grease gutter and cup, and a fire-suppression system. A Type II hood handles only heat, steam and moisture with no grease, so it belongs over dishwashers, steamers and some rice-cooking equipment. Any wok range that sears, stir-fries or seasons a wok is unambiguously Type I. Do not let a value-engineering pass downgrade a wok hood to Type II — it will fail plan review and it is a genuine fire hazard.

Calculating exhaust CFM

Hood airflow is driven by two things: the duty of the equipment below it and the geometry of the hood itself. In practice engineers size the exhaust from the hood's capture length and cooking-duty category rather than from BTU alone, but BTU tells you which duty category you are in. Wok ranges are extra-heavy-duty cooking — the hottest category — so they demand the highest airflow per linear foot of hood, typically several hundred CFM per foot for a wall-canopy configuration and more for a single-island canopy. A short four-foot wok hood can therefore pull well over a thousand CFM, and a full production line can run several thousand.

A few variables move the number materially. Longer overhang and lower hood mounting height improve capture and let you reduce airflow. Higher menu volume, back-to-back burners and open wok wells push it up. Because a wok flame is intermittent and vertical, capture velocity at the front lip matters more than raw volume, which is why hood length and overhang beyond the appliance face are as important as the fan you spec.

• Confirm the cooking-duty category — wok ranges are extra-heavy-duty and set the CFM floor.
• Size CFM from hood length and configuration (wall canopy vs single/double island), not BTU alone.
• Add overhang: extend the hood 6 to 12 inches past each end and beyond the appliance front where possible.
• Set mounting height low enough to capture the plume but high enough to clear the tallest wok work.

Makeup air: the half everyone forgets

Every cubic foot you exhaust has to be replaced, or the kitchen goes into negative pressure — doors that won't open, pilot lights that snuff out, back-drafting water heaters and cold drafts pulled through the dining room. Makeup air (MUA) should replace roughly 80 to 90 percent of exhaust volume, with the building's general HVAC supplying the small remainder so the kitchen stays slightly negative relative to the dining room but not to the outdoors. In cold climates the MUA unit usually needs to be tempered or heated so you are not dumping winter air onto the cooks. Balance this on paper before you order fans; an oversized exhaust with undersized makeup air is the most common cause of a hood that 'smokes' despite pulling plenty of CFM.

Capture, containment and fire suppression

Capture and containment is the test that matters in the field: the hood must both catch the plume as it rises and hold it inside the reservoir until the filters pull it out. A hood can move enough air on paper and still spill smoke if it is too short, mounted too high, or fighting a cross-draft from an HVAC diffuser or an open door. Keep supply diffusers from blowing across the hood face, and give the hood enough overhang and reservoir depth to hold the plume.

Fire suppression is mandatory on a Type I wok hood. A wet-chemical system with nozzles aimed at each wok well, the duct collar and the plenum discharges on heat detection, and it must be interlocked to shut off gas to the appliances on activation. Listed baffle filters, a fusible-link damper and clearance for duct cleaning access are all part of the same package. Suppression, hood and gas shutoff are inspected together, so coordinate the mechanical, plumbing and fire trades early.

Code, power and inspection basics

Hoods are governed primarily by the mechanical code and NFPA 96, layered with local amendments — so the authority having jurisdiction has the final word. Plan review wants a hood schedule with exhaust and makeup CFM, duct routing and clearances, appliance BTU inputs, and the suppression cut sheet. On the electrical side, remember that a modern wok line is rarely all gas: automation, exhaust fans and induction wells may need dedicated circuits and often three-phase service, so verify amperage and phase against your panel before the equipment arrives. Panda-built equipment is NSF, CSA and ETL listed, which streamlines the equipment side of plan review, but the hood system is approved on its own merits.

If you are laying out a new wok line and want the exhaust sized against real appliance heat loads and connected loads, our team can work from your floor plan and menu volume. Contact us with your drawings and we will help you match hood length, CFM and makeup air to the equipment before anything is ordered.