How To Clean A Commercial Kitchen Exhaust Hood | Deep Clean Steps

Grease hardens inside vents and can flash when heat spikes. A steady routine keeps flames off the menu, air breathable, and inspectors happy. This guide lays out safe prep, the full degreasing workflow, how often to do it, and the checkpoints that prove the job was done right safely.

What A Hood Cleaning Achieves

Done well, a deep service does more than shine metal. It strips flammable residue from every surface that handles cooking vapors and restores strong airflow. It also aligns with fire codes and health rules that require clean, sound, reliable ventilation.

Cleaning A Commercial Kitchen Exhaust Hood Safely And Thoroughly

The steps below mirror how top crews work. Adjust the cadence to your menu, volume, and fuel type.

Prep The Line And Power

Dial down heat and let appliances cool. Shut off gas where needed and kill power to the hood, lights, and fan. Pull back nearby food, utensils, and paper goods. Shield ranges and fryers with plastic or foil. Lay down floor mats and position a bin for greasy solids. Suit up: chemical-resistant gloves, goggles, and a respirator suited to degreaser mist.

Tools And Supplies You Will Need

Item	Purpose	Field Tip
Heavy-duty degreaser	Breaks down baked grease	Use hot water to boost action
Alkaline foamer	Clings to vertical metal	Apply from bottom up to avoid streaks
Scrapers & putty knives	Lifts thick deposits	Keep edges dull to avoid gouges
Non-sparking brushes	Agitates stubborn film	Pair with a long handle
Low-pressure sprayer	Applies chemicals evenly	Label for caustic use only
Rinse sprayer	Flushes soils & foam	Warm water helps release oils
Plastic sheeting & tape	Protects equipment & floors	Build a funnel to a collection bin
Filter soak tank	Deep cleans baffles	Heat to 60–70°C for faster results
Neutralizer	Balances residual alkalinity	Final rinse after degrease
Grease depth gauge	Measures film thickness	Flag anything near 0.08 in.

Remove And Soak Filters

Pop baffle filters out carefully and log their number and position. Drop them into a hot soak tank charged with a compatible degreaser. Give them time to loosen heavy soils, then brush along the channels. Rinse until runoff clears and set aside to dry. Damaged baffles should be replaced, not hammered straight.

Build A Containment Cone

Tape plastic along the hood edge and create a temporary chute into a drum or tote. That keeps slurry out of sinks and drains. Local rules often require grease waste to stay out of wastewater systems; the FDA Food Code includes language on cleaning vents and avoiding unlawful discharge, see the section on Cleaning Ventilation Systems.

Degrease The Canopy And Plenum

Spray a foaming alkaline cleaner onto the hood interior and plenum. Start low and move upward so fresh foam isn’t washing contaminants over cleaned areas. Dwell time matters; let chemistry work before scrubbing. Agitate with non-sparking brushes and scrape heavy ridges. Rinse to a light sheen. Repeat until a clean towel swipe shows no residue.

Open Access Panels And Treat Ducts

Find and remove access panels along duct runs. Apply foam, brush reachable surfaces, and rinse gradually so runoff flows to containment without flooding seams. Where ducts rise long distances, work in sections. Keep wiring and sensors dry. Film that measures near one sixteenth of an inch is a red flag; NFPA 96 requires cleaning before combustible soils build up, summarized in section 11.6.2 by many code guides, such as this plain-language note on NFPA 96 cleaning rules.

Service The Fan And Curb

Lock out the fan, then open the hinge kit to access the wheel and housing. Scrape the blades, degrease, and rinse while protecting the motor. Clear weep holes and confirm the curb has a sound grease-catch system with pads in place. Spin the wheel by hand to check for rubs and wobble before re-energizing.

Neutralize, Dry, And Reassemble

Apply a neutralizer rinse to bring pH back toward balanced. Towel dry the canopy and plenum, then air dry with fans if needed. Refit access panels and gaskets. Return baffle filters once fully dry and seated correctly with channels vertical. Restore power and gas. Run the fan to confirm steady draw.

Validate The Work

Two quick checks tell the story. First, a white-towel swipe on the plenum and early duct shows no gray smear. Second, a grease depth gauge reads under one thirty-second of an inch. Take photos of each section and log findings on your maintenance sheet. Many firms apply a dated sticker that lists the next target month for service.

How Often To Degrease Restaurant Exhaust Systems

Frequency tracks with fuel type and cooking load. Solid fuel work builds residue fastest, high-volume frying and charbroiling follow, and light kitchens are slower. Inspect on a set cycle and clean when grease levels approach the limit. Typical cycles used by many crews look like this:

Public health rules also require vents to be clean and to avoid creating a nuisance or unlawful discharge; see the Food Code’s wording linked earlier.

Typical Inspection And Cleaning Cadence

• Solid fuel appliances: check monthly; cleaning often monthly.
• High-volume lines (woks, charbroilers, 24-hour fryers): check quarterly; cleaning often quarterly.
• Moderate volume: check each half year; cleaning each half year in many kitchens.
• Low volume (seasonal or light duty): check yearly; cleaning around yearly if levels stay low.

These intervals match what many fire authorities apply when referencing NFPA 96.

Common Mistakes That Start Fires

Several patterns show up in incident reports. Skip them and risk drops fast.

Skipping Ducts

Shiny canopies hide dirty risers. If access doors are missing or sealed by paint, deposits can linger out of sight and ignite when flame flares.

Soaking Filters In The Sink

Greasy runoff sent to a food sink or floor drain can foul traps and clog sewers. Keep filter soaking to a dedicated tank and collect slurry for proper disposal. EPA materials on fats, oils, and grease remind operators to keep waste out of drains and manage interceptors correctly; see this quick deck on FOG management.

Using The Wrong Pads Or No Curb System

Fan curbs without absorbent pads end up streaked and slick. That residue can drip onto roofs and damage membranes.

Rushing Dwell Time

Strong foam still needs minutes to work. Scrubbing too soon wastes chemical and leaves a thin film that builds faster.

Leaving Caustic Residue

Alkaline cleaners that are not neutralized can haze stainless and irritate skin and lungs. Close with a balanced rinse.

Pro Technique: Step-By-Step Deep Clean

Here is a compact workflow you can adopt or hand to a service partner. It keeps steps clear and keeps the space tidy during the messiest parts.

1. Cool appliances and shut off gas, lights, and the fan.
2. Shield cooking gear and floors with taped plastic and mats.
3. Pull baffles; hot-soak in a degreasing tank and brush channels.
4. Build a plastic cone under the canopy to route runoff to a drum.
5. Foam the canopy and plenum; wait; brush; scrape; rinse.
6. Open duct doors; foam, brush, and rinse each reachable section.
7. Lock out the fan; hinge it back; clean wheel, housing, and curb.
8. Rinse with neutralizer; dry metal; reinstall panels and baffles.
9. Power up; run the fan; check airflow and listen for rubs.
10. Do towel and gauge checks; photograph; log the work; apply a dated sticker.

Grease Levels And Action Triggers

Use objective readings to decide when to schedule a deep service. This table links common gauge values to next steps.

Grease Film	Condition	Action
< 1/32 in. (≈0.8 mm)	Within safe range	Keep current inspection cycle
1/32–1/16 in.	Approaching limit	Schedule a full clean soon
> 1/16 in. (≈1.6 mm)	Over limit	Clean immediately; review cadence

Daily And Weekly Tasks That Slow Buildup

Small habits stretch the gap between big cleanings. Wipe the canopy lip and ledges at close each night. Launder hood skirts and change grease pads on a schedule. Empty and service grease interceptors per local rules. Keep fire suppression nozzles capped, free of foam, and aimed correctly.

Each week, pull baffles for a quick soak and rinse. Check that channels are clear and drain toward the hood interior, not the floor. Confirm the fan hinge pin isn’t bent and that the power whip has slack. Walk the roof for streaks near the curb; swap pads before they saturate.

When To Hire A Certified Service

Large systems with long vertical ducts, solid fuel appliances, or tight roof access often need a certified crew. A good vendor will set containment, clean all listed components, photograph each section, test fan balance, and leave a signed report with next target dates. Ask for proof of training, chemical SDS sheets, and confirmation that liquid waste is hauled to an approved facility.

Simple Recordkeeping That Satisfies Inspectors

Keep a binder or shared drive with dated photos, grease gauge readings, invoices, SDS sheets, and copies of the latest fire and health inspections. Tape the current hood sticker near the switch. Clear records shave minutes off visits and make it easier to hand tasks to new staff.

Final Pass: A Quick Self-Audit

Stand under the canopy with the fan running. Air should pull lightly at your cheeks. Surfaces should look clean, dry, and free of streaks. No drips should hit the roof. Filters should sit snug with channels vertical. If anything feels off, book a check before the rush swings back.