The ventilation system is the most expensive piece of equipment you'll never think about. Until it fails. Then it's the only thing you think about. A kitchen without a working hood is a kitchen that can't cook. The health department shuts you down. The fire marshal red-tags your equipment. Your staff walks out because it's 110 degrees on the line.
I've seen restaurants learn this the hard way. Their hood system was undersized for the equipment underneath it. Smoke and grease accumulated on the ceiling. The fire suppression system triggered during a busy Friday night service. The Ansul system discharged, coating the entire line in chemical suppressant. They were closed for 3 days for cleanup and re-inspection. Lost revenue: $45,000. The correct hood system would have cost $3,000 more upfront.
Industry Data & Sources:
Energy Star provides efficiency ratings and buying guides for commercial kitchen equipment.
NSF International certifies commercial foodservice equipment for safety and sanitation standards.
Type I vs Type II Hood: Quick Comparison
| Feature | Type I (Grease Hood) | Type II (Heat/Vapor Hood) |
|---|---|---|
| Required for | Ranges, fryers, griddles, charbroilers | Dishwashers, steamers, coffee brewers |
| Grease filters | Required (baffle filters) | Not required |
| Fire suppression | Required (Ansul system) | Not required (most jurisdictions) |
| Exhaust fan | Required | Required |
| Makeup air | Required | Required |
| Cost (10-ft hood) | $8,000-$15,000 installed | $3,000-$6,000 installed |
| Annual maintenance | $500-$1,500 | $200-$500 |
Types of Hood Systems
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Type I Hood (Grease Hood)
Required for equipment that produces grease, smoke, or heat. This includes: ranges, griddles, fryers, charbroilers, woks, tilting skillets, conveyor ovens that cook greasy products.
Type I hoods include: grease filters (baffle filters that capture grease particles), fire suppression system (Ansul or similar, required by code), exhaust fan (pulls air through the hood and out of the building), makeup air system (brings fresh air in to replace exhausted air).
Type II Hood (Heat/Vapor Hood)
Required for equipment that produces heat or steam but no grease. This includes: dishwashers, steamers, pasta cookers, coffee brewers, convection ovens (if not cooking greasy products).
Type II hoods are simpler and less expensive. No grease filters. No fire suppression required (in most jurisdictions). Just exhaust and makeup air.
Ventless Hood Systems
Self-contained units that filter and recirculate air. No ductwork to the outside. No makeup air required. Limited to electric equipment only. Limited to low-volume cooking.
Best for: small cafes, coffee shops, food courts, locations where ductwork is impossible (historic buildings, basements). Not suitable for: gas equipment, high-volume frying, charbroiling, or any heavy grease production.
CFM Requirements
What is CFM?
Cubic Feet per Minute. The volume of air the exhaust fan moves. Higher CFM = more air exhausted = better capture of smoke and grease. Too low CFM = smoke and grease escape the hood. Too high CFM = excessive energy costs and negative building pressure.
Calculating Required CFM
The basic formula:
Capture velocity factors: light-duty (ovens, steamers): 150-200 CFM per linear foot, medium-duty (ranges, griddles): 200-300 CFM per linear foot, heavy-duty (charbroilers, woks): 300-400 CFM per linear foot, extra-heavy-duty (solid fuel, wood-fired): 400-550 CFM per linear foot.
Example: A 10-foot hood over a range and fryer (medium-to-heavy duty). 10 feet × 300 CFM = 3,000 CFM required.
The Overhang Rule
The hood must extend 6 inches beyond the equipment on all sides. If your equipment is 8 feet wide, your hood must be at least 9 feet wide. This ensures the hood captures smoke and grease from the edges of the equipment.
The Height Rule
The bottom of the hood should be 6.5-7 feet from the floor. Lower = better capture but may interfere with tall cooks. Higher = worse capture. The hood should be no more than 4 feet above the cooking surface.
Makeup Air
Why You Need It
Your exhaust fan pulls 3,000 CFM out of your kitchen. That air has to come from somewhere. Without a makeup air system, it comes from: your dining room (creating drafts and making customers cold), your front door (making it hard to open), your water heater and furnace flues (backdrafting carbon monoxide into your building, which is dangerous).
How Much You Need
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Makeup air should be 80-90% of exhaust CFM. If you're exhausting 3,000 CFM, you need 2,400-2,700 CFM of makeup air. The remaining 10-20% creates slight negative pressure in the kitchen, which prevents cooking odors from migrating into the dining room.
Heated vs Unheated
In cold climates, makeup air must be heated. Bringing in 2,500 CFM of 20°F outside air will make your kitchen freezing. A makeup air heater (direct-fired or indirect-fired) heats the incoming air to 60-70°F. Cost: $2,000-5,000 for the heater unit plus gas line and installation.
In warm climates, unheated makeup air may be acceptable. In hot climates, you might even want cooled makeup air (expensive but appreciated by your kitchen staff).
Fire Suppression Systems
Ansul R-102
The industry standard. A wet chemical system that discharges when a fusible link in the hood melts (at 360°F or 450°F depending on the link). The chemical suppressant coats the cooking surface and reacts with hot grease to form a soap-like layer that prevents re-ignition.
Coverage: nozzles over every cooking appliance under the hood. The system also shuts off the gas or electric supply to all equipment under the hood.
Inspection Requirements
Semi-annual inspection required by code. A certified technician checks: fusible links (replace if corroded), nozzle caps (replace if missing), chemical tank pressure (recharge if low), gas shutoff valve (test function), manual pull station (test function). Cost: $200-400 per inspection.
Manual Pull Station
A red pull station located at each exit from the kitchen. Pulling it manually discharges the system. Train every kitchen employee on where it is and when to use it (flames reaching the hood filters, fire that can't be controlled with a fire extinguisher).
Installation Costs
New Installation
Type I hood with exhaust fan, makeup air, and fire suppression: $15,000-35,000 for a typical 10-12 foot hood. Breakdown: hood and ductwork $5,000-10,000, exhaust fan $2,000-4,000, makeup air system $3,000-6,000, fire suppression $3,000-6,000, electrical connections $1,000-2,000, gas connections $500-1,500, permits and engineering $1,000-3,000.
Replacement
Replacing an existing hood system: $8,000-20,000. Less expensive because ductwork, electrical, and gas connections may be reusable.
Ventless System
Ventless hood system: $5,000-12,000 installed. No ductwork, no makeup air, no roof penetration. Lower installation cost but higher filter replacement cost ($500-1,000 per year for filter packs).
Health Department Requirements
What the Inspector Checks
Hood is the correct type for the equipment underneath. Hood extends 6 inches beyond equipment on all sides. Filters are in place and clean (no grease dripping). Fire suppression system has current inspection tag (within 6 months). Exhaust fan is operational (they'll turn it on). Makeup air is operational (they'll check for negative pressure). No grease accumulation on the hood, ductwork, or roof.
Common Violations
Grease accumulation on filters or hood surfaces. Expired fire suppression inspection. Hood not extending far enough beyond equipment. Equipment added under the hood that wasn't in the original plan (adding a fryer where a steamer was planned). Exhaust fan not working or undersized. No makeup air system.
FAQ
Can I install a hood system myself? No. Hood installation requires: licensed mechanical contractor, licensed electrician, licensed gas fitter (if gas equipment), licensed fire suppression technician, engineering drawings stamped by a PE, building permit, health department approval, fire marshal approval. This is not a DIY project.
How often should I clean my hood filters? Weekly for moderate-volume restaurants. Twice weekly for high-volume or heavy-grease operations (fried chicken, burgers). Run filters through the dishwasher or soak in degreaser overnight. Dirty filters reduce airflow and increase fire risk.
How often should I clean the ductwork? Professionally cleaned every 6-12 months depending on volume and grease production. The ductwork from the hood to the roof accumulates grease. This is a fire hazard. A duct fire is 3x more dangerous than an open-flame fire because it's hidden inside the building structure where it can spread undetected for minutes before detection.
What's the most common mistake in hood system design? Undersizing the makeup air. The exhaust fan is correctly sized, but the makeup air system is too small. This creates negative pressure that causes drafts, door problems, and backdrafting. Always size makeup air at 80-90% of exhaust CFM.
Related: Essential Restaurant Equipment List · Commercial Range Buying Guide · Restaurant Licenses & Permits
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