A cookline can only run as clean as its air handling. Exhaust fans and make-up air units work together to pull heat, grease-laden vapor, and combustion byproducts out of the kitchen while replacing that exhausted air so doors don’t slam and burners don’t starve for oxygen.
How Exhaust Fans and Make-Up Air Work Together
Your exhaust hood’s fan pulls air (and grease vapor) up and out of the building, but every cubic foot exhausted has to be replaced with fresh air or the kitchen develops negative pressure — causing doors to stick, pilot lights to struggle, and comfort-cooling systems to work harder. A properly sized make-up air unit supplies conditioned or tempered replacement air to balance the system.
Exhaust Fan Types
| Type | Best For |
|---|---|
| Upblast centrifugal fan | Standard Type I hood exhaust, most cookline setups |
| Utility/inline fan | Longer duct runs, Type II low-grease exhaust |
| Direct-drive fan | Compact installs, lower maintenance (no belt) |
Sizing and Code Considerations
- Exhaust and make-up air volumes must be balanced according to your hood’s rated CFM and local mechanical code.
- Make-up air is often required to be tempered (heated or cooled) in climates with extreme outdoor temperatures.
- Fan motors and belts should be accessible for service without full hood removal.
- Grease-rated fans and ductwork are required for Type I hoods handling grease-laden vapor.
Signs Your System Needs Attention
Doors that are hard to open near the kitchen, a hazy or hot cookline despite the hood running, and pilot lights that struggle to stay lit are all classic signs of an unbalanced exhaust and make-up air system — not necessarily a failing fan. Before replacing equipment, have the system’s CFM balance checked; sometimes the fix is a make-up air adjustment, not a new fan.
What is make-up air and why do I need it?
Make-up air replaces the air your exhaust hood removes from the building, preventing negative pressure that causes door problems, pilot light issues, and reduced hood performance.
How do I know if my exhaust fan is properly sized?
Fan CFM should match your hood manufacturer’s rated exhaust requirement for its length and type — an undersized fan won’t fully capture grease vapor, while an oversized one wastes energy and can overload make-up air supply.
Does make-up air need to be heated or cooled?
In many climates, yes — tempered make-up air keeps the kitchen comfortable and prevents cold drafts in winter or heat gain in summer. Requirements vary by local code and climate zone.
How often should exhaust fans be serviced?
Motors, belts, and bearings should be inspected at least twice a year, with grease buildup on fan blades and ductwork cleaned per your local fire code (often quarterly for heavy-use kitchens).
Keep your kitchen’s air system balanced and code-compliant.