CHOOSING THE RIGHT COMMERCIAL KITCHEN VENTILATION HOOD, EXHAUST FAN, AND MAKE‑UP AIR UNIT

Why Ventilation Choices Matter

Grease‑laden vapors, smoke, heat, and odors rise from your cooking line every shift. A well‑matched ventilation hood, exhaust fan, and make‑up air (MUA) unit keeps that chaos out of the kitchen—and out of your diners’ lungs—while protecting equipment, employees, and your bottom line. Get any piece wrong and you invite comfort complaints, premature fan failure, and potential code violations.

1. START WITH YOUR COOKING EQUIPMENT

Duty Class | Typical Equipment | Required Hood Type | Baseline CFM per Linear Foot
Light‑duty | Convection ovens, steamers | Type II or low‑CFM Type I | 150–250
Medium‑duty | Griddles, open‑burner ranges, fryers | Type I | 250–400
Heavy‑duty | Charbroilers, woks, wood‑fired ovens | Oversized Type I | 400–600
(*Add 25–40 % more if the hood is an island canopy exposed on all four sides.)

Pro tip: The hood should overhang the cooking surface by at least 6 inches on every side. Measure your cookline, add the overhang, and you have the minimum hood width.

2. CALCULATE EXHAUST AIRFLOW (CFM)
Quick formula:
Total CFM ≈ Hood Length (ft) × Baseline CFM/ft
Example: A 10‑foot wall canopy over a mix of fryers and griddles (300 CFM/ft) → 10 ft × 300 CFM/ft = 3 000 CFM.
Keep a 10–15 % safety factor to cover filter loading and seasonal temperature swings.

3. MATCH THE EXHAUST FAN TO THE JOB
Fan Style | Best For | Key Advantages
Upblast centrifugal (roof‑mount) | Most restaurants, food trucks | Throws grease‑laden air upward, keeps roof clean, easy service access
Utility set fan (indoor or rooftop) | Long duct runs, high static pressure | Handles heavy resistance, quieter indoors with acoustical housing
Inline tubeaxial / mixed‑flow | Hidden installs, tight rooftops | Mounts inside the duct, compact footprint
Sizing checklist:
• Airflow rating ≥ calculated CFM
• Static‑pressure capability ≥ duct, filter, and hood resistance (often 0.6–1.5 in. w.g.)
• Grease‑rated construction for high‑temperature, grease‑laden air
• Speed control (VFD) lets you throttle back during slow periods and save energy

4. DON’T FORGET MAKE‑UP AIR (MUA)
Whenever you pull 400 CFM or more out of a building, most codes require replacement air. Starved kitchens suffer from:
• Doors slamming shut or refusing to open
• Smoke rolling into the dining room
• Pilot lights extinguishing (back‑draft)
• High energy bills from conditioned air being sucked outside
A make‑up air unit delivers tempered, filtered air—often 80–90 % of the exhaust rate—directly above or near the hood capture zone. In cold climates, add heat; in humid regions like Houston, consider cooling.

5. COMPLIANCE & BEST‑PRACTICE TIPS
Codes – Follow your local mechanical and fire codes (e.g., IMC, NFPA 96).
Ductwork – Welded 16‑gauge black iron or stainless; slope ¼ in./ft toward a grease reservoir.
Filters – Baffle filters at 45°; clean weekly or as grease load dictates.
Clearances – Maintain 18 in. from combustibles (or 3 in. with approved shielding).
Maintenance – Professional hood & duct cleaning at least every 3 months for high‑volume operations.

6. STEP‑BY‑STEP SIZING WORKFLOW
1. List cooking appliances and classify duty.
2. Choose hood type & style.
3. Measure hood length (include overhang).
4. Calculate exhaust CFM with duty‑based factors.
5. Estimate static pressure (duct length, elbows, filters).
6. Select an exhaust fan that meets CFM @ SP and is grease‑rated.
7. Size the MUA unit to 80–100 % of exhaust CFM, tempered as needed.
8. Verify compliance with your local authority having jurisdiction (AHJ).

REAL‑WORLD EXAMPLE
A 12‑ft island canopy over a charcoal grill and wok line in Houston:
• Duty: Heavy → 500 CFM/ft (island factor included)
• Exhaust CFM: 12 ft × 500 = 6 000 CFM
• Static pressure: 1.2 in. w.g.
• Fan: 6 000 CFM @ 1.5 in. SP, upblast, 3‑hp motor, VFD
• MUA: 5 000 CFM gas‑fired, 70 °F supply in winter, uncooled in summer
Result: balanced airflow, no smoky dining area, and happier cooks.

FINAL THOUGHTS
The right hood system is a marriage of capture, airflow, pressure balance, and code compliance. Investing the time to size each component properly pays back through lower utility bills, longer equipment life, fewer odor complaints, and a safer workplace.

Need help? Email info@airsupplycorp.com or call 832‑540‑7936.