Restaurant Exhaust Fans 101: A Buyer's Guide for Kitchen Operators
New to commercial kitchen ventilation? This exhaust fans 101 guide covers fan types, CFM sizing, static pressure, motor options, and how to buy the right fan the first time.
The exhaust fan is the workhorse of your kitchen ventilation system. It pulls smoke, grease, and heat out of the hood, up through the duct, and off the roof — and if it is not sized and specified correctly, nothing else in your kitchen works right.
Here is what every operator, contractor, and buyer should understand before ordering one.
What a Commercial Exhaust Fan Actually Does
Your hood does not exhaust anything by itself. It is just a capture device. The exhaust fan, mounted on the roof (or occasionally on an exterior wall), is what creates the negative pressure that pulls air through the hood, through the duct, and out of the building.
Every commercial exhaust fan is defined by three numbers:
CFM — Cubic Feet per Minute. The volume of air the fan moves.
Static Pressure (SP) — The resistance the fan has to push against, measured in inches of water column ("w.c.). Longer duct runs, tighter elbows, and pollution control units all increase static pressure.
Fan Curve — The chart that tells you how much CFM the fan actually delivers at a given static pressure. A fan rated "2,000 CFM" only hits that number at one specific SP.
If a supplier quotes you CFM without SP, ask for the fan curve. Every reputable manufacturer publishes one.
The Main Fan Types
Upblast Centrifugal (Grease Duty) — The default for Type 1 grease hoods. Discharges up and away from the roof, hinges open for cleaning, includes a grease containment trough. Required by NFPA 96 for grease service (NFPA 96).
Downblast Propeller — For Type 2 condensate hoods and general building exhaust. Cheaper, lighter, but never legal for grease.
Inline / Utility Fans — Mounted in the duct run, often used when roof mounting is impractical (multi-story buildings, historic exteriors). Must be listed for grease duty in Type 1 applications.
Wall-Mount Exhaust Fans — Used mostly for food trucks, concession trailers, and small buildings where roof mounting is impossible. Usually direct-drive.
How to Size an Exhaust Fan (The Short Version)
Start with the hood CFM. A wall-canopy Type 1 hood typically needs 150-300 CFM per linear foot depending on cooking duty (medium-duty vs. heavy-duty vs. extra-heavy-duty).
Calculate system static pressure. Add up losses through the duct run, elbows, filters, fire damper (if used), roof cap or discharge, and any pollution control unit. Most restaurant systems land between 0.75" and 2.0" w.c.
Pick a fan that hits your target CFM at that SP. Read the fan curve — do not just match the "rated" CFM.
Confirm the motor is grease-duty rated for Type 1 applications (typically Class B insulation minimum, sealed bearings, and mounted outside the airstream).
Direct Drive vs. Belt Drive
Belt drive was standard for decades. Cheaper motor, adjustable RPM by changing pulleys, but requires belt inspection and periodic replacement.
Direct drive with an ECM or variable-frequency drive (VFD) motor is now the modern default. No belts, quieter operation, and RPM can be tuned electronically to hit exact CFM targets — a big advantage for utility bills and demand-control ventilation.
What You Actually Need to Order
Before you place a fan order, you should know:
Hood CFM requirement (per hood, if multiple)
Duct diameter or dimensions
Total system static pressure estimate
Voltage and phase available on the roof (115/1, 208/1, 208/3, 460/3)
Roof curb size and pitch
Whether you need a hinged base kit, grease containment box, or wind band
If any of that is unclear, ask your supplier — a good one will help you spec it before they ship.
Buy the Right Fan the First Time
Mr. Hood USA stocks upblast, downblast, wall-mount, and inline exhaust fans for restaurants, food trucks, and commercial kitchens. Every fan we ship is matched to your hood, duct, and static pressure so it actually delivers the CFM you paid for.