Why Ventilation Comes First
Ventilation is the first system to plan and the last thing you want to improvise. Cooking produces heat, grease-laden vapors, smoke, and combustion gases that a building cannot absorb without engineered exhaust. Beyond comfort, commercial kitchen ventilation is governed by code — NFPA 96 for fire safety and the mechanical code for airflow — and your health and building inspectors will verify it before you open. Because the hood determines where cooking equipment can sit, mistakes here are expensive to fix.
Type I vs Type II Hoods
- Type I hoods serve grease-producing equipment: fryers, griddles, broilers, ranges, and ovens that see fat. They must include grease filters, a fire suppression system, and ductwork built to grease-service standards.
- Type II hoods handle heat, steam, and moisture without grease: dish machines, steamers, and some ovens. They do not require grease filters or fire suppression, but they must handle condensation and heat.
A full-service kitchen almost always needs a Type I hood over the cooking line. Know which appliances sit under which hood before you order, because a fryer placed under a Type II hood is a code violation and a fire hazard.
Sizing the Hood: CFM and Capture Area
The hood must physically cover the cooking equipment — most installations extend at least 6 inches beyond the equipment footprint on exposed sides — and the exhaust fan must move enough air. As a rule of thumb, engineers size exhaust at roughly 100 CFM per linear foot of hood for wall-mounted installations and more for island hoods, but the actual number depends on the equipment, the building, and local code. Get a mechanical engineer or the hood manufacturer to calculate it; an undersized system will not capture smoke, and an oversized one will waste conditioned air.
Fire Suppression Systems
Every Type I hood needs a wet chemical fire suppression system — the familiar ANSUL-style arrangement of nozzles over the cooking appliances, the hood, and the duct. The system activates automatically and can also be triggered by a manual pull station. Code requires:
- Professional installation and a visible inspection tag.
- Monthly visual inspections by staff.
- Professional inspection and service every 6 months, with records kept on site.
- Kitchen staff trained on the manual release and on turning off gas and electricity during a fire.
Never buy a used suppression system for a new installation; they must be certified, and the certification rarely transfers.
Makeup Air
Exhaust only works if air can replace it. Without a makeup air unit, the kitchen goes into negative pressure: doors become hard to open, cold drafts pour in, and gas water heaters and furnaces can backdraft dangerous carbon monoxide into the building. Makeup air is typically sized at 80 to 100 percent of the exhaust rate, and it should be tempered so the kitchen is not blasted with outside air in winter. Some hoods integrate makeup air into the hood body; others use a separate rooftop unit.
Exhaust Fans, Ductwork, and Roof Terminations
Grease duct runs from the hood to a roof-mounted upblast exhaust fan. The duct must be welded or gasketed to be grease-tight, pitched to drain, and fitted with access doors so it can be cleaned. Where the duct passes through walls or floors, it needs a fire-rated enclosure. This is engineered work: get drawings, permits, and a licensed installer, and keep the cleaning schedule documented for the fire marshal.
Grease Management
- Clean or replace baffle filters on the schedule the manufacturer sets — daily in heavy use.
- Keep grease drip trays emptied.
- Have ducts professionally cleaned per NFPA 96, typically quarterly to yearly depending on volume; high-volume fryer kitchens land on the aggressive end of that range.
- Route sink water through a grease trap sized to your flow so fats do not clog the sewer line.
Buying New vs Used
Vent hoods are one of the few equipment categories where buying used rarely pays. Hoods are often custom-fabricated to fit the space, they corrode and accumulate grease in ways that are hard to assess, and they must meet current code in your jurisdiction. Buy the hood, ductwork, and suppression system new from manufacturers such as CaptiveAire or Gaylord through a licensed installer. Exhaust fans are the one component a savvy buyer might source used and have reconditioned, but only after an electrician verifies the motor and voltage.
Working With the Spec Sheet
Every hood has a spec sheet: dimensions, filter count and type, CFM rating, and the UL listing that tells you it is rated for grease service. Look these up on CookBidSpecs and compare them against your equipment lineup and building constraints before you sign anything. Ventilation is not the glamorous purchase in a build-out, but it is the one that keeps the kitchen legal, safe, and actually usable.