What Is an Exhaust Hood? | Kitchen Ventilation Basics

An exhaust hood earns its keep the moment you sear a steak or boil pasta water. It draws contaminated air up and away from your kitchen, keeping grease off your cabinets, humidity off your ceiling, and smoke out of your lungs. Most Americans know it as a range hood or vent hood, but the technical term covers everything from residential over-the-stove units to industrial canopy systems built to handle a restaurant’s cooking load.

Understanding how one works comes down to three ideas: capture, transport, and removal. The hood’s shape captures the rising air, the ductwork or filter system transports it, and the fan pushes it outside or recirculates it through charcoal filters. How each piece gets sized and built depends heavily on whether the unit sits over a home range or inside a commercial kitchen.

How an Exhaust Hood Works

An exhaust hood captures contaminated air at the source rather than letting it circulate through the room. The fan creates negative pressure at the hood’s underside, which pulls grease-laden vapors, smoke, fumes, and steam into the capture zone.

From there, the system takes one of two paths:

• Ducted (vented) hoods push the air through metal ductwork to the outside of the building. This is the more effective option for heavy cooking because it removes moisture and grease completely.
• Ductless (recirculating) hoods pass the air through baffle or mesh filters to catch grease, then through a charcoal filter to absorb odors before releasing it back into the kitchen. Cheaper to install, but they leave heat and humidity in the room.

The Canadian Centre for Occupational Health and Safety notes that in industrial ventilation, the hood refers specifically to the point where contaminated air enters the exhaust system – the capture opening itself. In everyday kitchen use, the term covers the whole visible appliance above the stove.

Residential vs. Commercial Exhaust Hoods

The gap between a home range hood and a commercial kitchen canopy is enormous. Residential units, like those Whirlpool describes mounting above ranges and cooktops, focus on catching everyday cooking byproducts. Commercial systems, by contrast, must meet strict fire-safety and airflow codes because they handle far higher heat and grease volumes.

Commercial hoods split into two categories. Type I hoods handle grease-producing cooking like frying and grilling, and they require fire-suppression systems. Type II hoods handle heat, steam, and odors without significant grease – think dishwashers and ovens.

Material requirements for commercial units are also far stricter. Select Air Systems’ canopy hood spec, for example, calls for exposed surfaces in 18-gauge type 304 stainless steel with a #3 polish, welded liquid-tight per NFPA-96. Local government guidelines from Wanneroo and Gosnells similarly require rigid, noncombustible materials with smooth, sealed seams so grease has nowhere to hide.

Key Design Rules and Specifications

Proper hood performance depends on geometry, airflow, and duct sizing. The figures below come from U.S. county plan-check guidance and manufacturer specifications, which offer a reliable baseline for commercial installations.

A hood that sits too high or fails to overhang the cooktop loses capture efficiency, so the plume of grease and smoke escapes into the room. Duct size matters just as much: undersized ducts create excessive velocity and noise, while oversized ones let grease settle in the pipework. The Alameda County plan-check guidance also stresses that makeup air – the replacement air drawn into the kitchen when the hood exhausts – must be mechanically supplied and electrically interconnected on the same switch as the hood itself.

Installation and Maintenance Essentials

Installing an exhaust hood correctly starts with measuring the hood’s coverage so it overhangs the appliance by at least 6 inches and sits within the recommended mounting height. Next, size the exhaust flow using either the manufacturer’s spec sheet for UL-listed hoods or the applicable local code formula for custom units, and verify duct velocity lands in the 500–2500 FPM range.

Grease filters must be removable and sized so airflow through each filter stays within the manufacturer’s operating limits. CaptiveAire’s specification page, for instance, lists airflow requirements of 150 CFM per foot for 450°F cooking surfaces, scaling up to 250 CFM per foot at 700°F. Cleaning access also gets codified in some jurisdictions: the Wanneroo guideline requires exhaust openings at least 75 mm wide, spaced no more than 1 meter apart, so every filter is reachable for proper degreasing.

Common mistakes easily undermine a well-designed system. Confusing an exhaust hood with a laboratory fume hood is a notable one – fume hoods are sealed containment devices with sash fronts designed for hazardous chemicals, not cooking. Mixing residential and commercial rules is another. And skipping filter maintenance turns a safety device into a fire hazard, since accumulated grease ignites quickly.

If you’re shopping for a range hood for your own kitchen, our tested picks for the best exhaust hoods break down the top performers by size, airflow, and noise level.