Commercial Kitchen Hood Product

Overview

A commercial kitchen hood is the capture device at the top of a restaurant's grease exhaust system. Cooking with fats produces an effluent plume of vapor, smoke, and aerosolized grease particles that is both a health problem and, once it condenses inside ductwork, a severe fire hazard. A Type I hood — the grease-rated class, as opposed to Type II condensate hoods over dishwashers and ovens — captures this plume, strips the bulk of the grease out of it, and passes the rest to a welded grease duct and rooftop exhaust fan. Design, construction, and clearances are governed by NFPA 96 and the International Mechanical Code, and factory-built hoods are listed to UL 710.

The hood consists of the Canopy Shell, the Grease Filter Bank, the Exhaust Collar & Plenum and plenum, an integrated Fire Suppression Interface, sealed Hood Lighting, Grease Collection hardware, and a Hood Control Panel panel.

Capture and containment

The thermal plume rising off a cook line expands as it climbs, so the Canopy Skin must overhang the appliances — at least 150 mm per side and about 300 mm at the front — and hang with its lower edge 1.98–2.13 m above the floor. Vertical End Panel closures markedly improve capture by blocking cross-drafts, and often allow a lower exhaust rate to be approved. The shell is brake-formed 18-gauge stainless with continuous liquid-tight welds at exposed seams, hung from building structure by threaded rod at the Hanger Bracket points, with a Wall Standoff holding code clearance from the wall behind.

Exhaust rates depend on appliance duty: roughly 300 m³/h per metre of hood for light-duty steam equipment, rising to 1,000 m³/h per metre or more over solid-fuel charbroilers. Every cubic metre exhausted must be replaced by tempered makeup air, which is why hood exhaust dominates the energy bill of a commercial kitchen.

Grease extraction

Air entering the hood turns sharply through the Baffle Grease Filter bank — rows of interlocking vertical baffles mounted at 45–60° in Filter Track rails. The repeated direction changes centrifugally throw grease droplets onto the baffle surfaces; UL 1046 listed baffle filters capture roughly 70–85% of particles above 8 µm. Mesh filters are prohibited in grease service because they load up and become a fire path. Collected grease runs down the baffles into the Filter Drip Rail, along the Grease Trough, and into removable Grease Cup containers that NFPA 96 limits to one litre so staff actually empty them. The filters themselves lift out by hand for a daily trip through the dishwasher.

Behind the filters, the Exhaust Plenum equalizes suction along the hood's length before air exits through the welded Duct Collar into the grease duct, which must hold 7.5–10 m/s so grease stays entrained rather than settling. A locking Balancing Damper is set once at commissioning — closable dampers are forbidden in grease ducts — and a gasketed Duct Access Panel admits the duct-cleaning crew for the degreasing that fire codes require on a 3- to 12-month cycle depending on cooking volume.

Fire suppression

The hood is the front line of kitchen fire protection. The built-in Fire Suppression Interface is a UL 300 wet-chemical system: Agent Nozzle heads aimed at each appliance, the plenum, and the duct, fed through fixed Agent Distribution Piping from a pressurized agent tank. Detection is a tensioned cable threaded through Fusible Link elements rated 138–232 °C; when one melts, the release mechanism fires the system. A wall-mounted Manual Pull Station gives staff a manual trigger. Discharge does three things at once via the Gas Valve Interlock and the System Microswitch contacts: fuel gas closes, electric appliances shunt-trip, and the exhaust fan is forced on to pull combustion products out. The potassium-based agent saponifies burning grease into a smothering foam crust, which is why water-based systems alone are not acceptable over fryers.

Lighting and controls

Recessed Vapor-Proof Light Fixture cans with tempered Glass Globe covers and 9–15 W LED Lamp sources put 500 lux on the cooking surface while keeping wiring out of the grease stream. The Hood Control Panel panel ranges from simple fan and light switches to demand-control ventilation: the DCV Controller Board reads Duct Temperature Probe sensors in the exhaust collar (and often optic sensors across the hood face) and slows the exhaust and makeup fans when the line is idle, saving 30–50% of fan and conditioned-air energy while still forcing full speed whenever cooking is detected — an arrangement now required by many energy codes for larger hoods.