How Do You Clean Kitchen Exhaust Fans?
Kitchen exhaust fan cleaning is the systematic removal of grease from a kitchen's exhaust equipment using containment, chemical dwell, mechanical agitation, and controlled rinsing, worked in an order that stops loosened grease from re-soiling finished surfaces. The short answer: contain the area first, pull the filters, clean from the fan back down through the duct and plenum to the canopy, capture every drop of wash water, and dry and reassemble before restoring power. This guide covers the method and the tools, and it is candid about where doing it yourself stops making sense.
What is the correct sequence for cleaning a kitchen exhaust system?
Clean from the top of the system downward, because grease released upstream drains onto everything below it. Anyone who starts at the canopy cleans it twice.
Set the order before touching anything, and treat it as fixed. Isolate the electrical supply and confirm the equipment is dead. Contain the cook line and the floor. Remove the filters and get them into a soak so they are working while you are. Move to the fan and the top of the duct. Work back down the duct run, section by section, through each access point. Do the plenum cavity behind the filter bank. Do the canopy interior. Finish with the grease trough, the canopy exterior, and the stainless around it. Rinse, dry, refit the filters the right way around, and restore power last.
Two parts of that sequence get skipped most often, and they are the two that decide whether the job counts. The plenum is one: it sits behind the filters, it is out of sight from the kitchen floor, and it holds more grease than the canopy people can see. The duct run is the other. A duct is cleaned through its access panels, and if a building has none, or a renovation covered them over, the honest position is that the duct has not been cleaned, whatever the invoice says.
Pace the work by chemistry rather than effort. Wet a section, let the degreaser dwell while you set up the next one, then come back and agitate. Working the surface too early just moves softened grease around. Working it too late means the product has dried and has to be reapplied. Rotating between two or three sections keeps dwell time productive instead of idle.
What tools does the job actually need?
Barrie Hood Cleaning's kit is weighted toward containment and capture rather than scrubbing, because controlling where the grease goes is most of the work.
The list that matters: plastic sheeting and tape to seal off the cook line and the floor run. A catch basin or collection tray positioned at the system's low point. A pressure source with a way to contain overspray. An alkaline degreaser matched to the surface being cleaned. Plastic or brass scrapers that lift hardened deposit without scoring stainless. Long-handled brushes sized to the duct. Good directional lighting, because a duct interior gives up nothing to a phone torch held at arm's length. Access hardware, including replacement panel gaskets and fasteners. And personal protective equipment that is actually worn: sealed eye protection, chemical-rated gloves, and non-slip footwear.
What is missing from that list is as informative as what is on it. There is no wire brush, because wire scores stainless and leaves a rougher surface that loads with grease faster afterwards. There is no oven cleaner decanted into a spray bottle, because product on the wrong surface at the wrong concentration takes finish off aluminium and paint. And there is no ladder standing in for roof access on a commercial job, because a fan on a curb is height work with its own requirements. Product selection for each surface is covered in the guide on which cleaner works best.
How is the kitchen protected while the work happens?
Containment goes up before a single container is opened, and it covers the cook line, the floor path, and anything that will be food contact tomorrow.
Sheet the cook line completely, tape the edges, and take the sheeting far enough past the hood that overspray has nowhere to land. Cover the floor along the whole route between the hood and the exit point, because the carrying is what spreads grease, not the cleaning. Move or wrap anything portable that touches food: pans, containers, cutting boards, utensil racks. Seal or cover open drains that are not part of the capture plan.
Then think about the handback rather than the cleaning. A commercial kitchen has to be food-ready the next morning, which means every surface a degreaser touched needs rinsing and wiping, filters need refitting the right way around so they drain into the trough, and the floor needs to come back non-slip. A job that leaves a film on the pass or a slick patch by the fryer has created a different problem to the one it solved. The descriptive account of how a crew sequences that handback is in the guide on what happens on the night.
Where do the water and the chemicals go?
Capture wash water at the low point and put it into the building's grease-handling stream. Never send grease-laden runoff down a roof drain, a storm drain, or across a lot.
This is the part of the method that separates a professional job from an enthusiastic one, and it is invisible in the finished result. Water used to rinse a grease-loaded system comes back grease-loaded. Sent down a roof drain it damages the membrane and reaches a storm system it should never enter. Sent across a parking lot it becomes somebody's slip hazard and somebody's environmental complaint. The answer is a capture setup at the low point of whatever section is being cleaned, sized so it is never the thing that overflows.
Chemical handling has its own rules. Alkaline degreasers work by saponifying grease, which is why they cut so well and why they are hard on skin, eyes, and bare aluminium. Use the labelled dilution rather than a stronger one, keep product wet for its dwell instead of letting it dry, ventilate the space, and never mix products in the hope of a better result. Store and transport containers so nothing gets decanted into an unlabelled bottle that ends up under a kitchen sink.
On a Barrie roof there is a seasonal wrinkle worth planning for. Between December and March a rooftop fan can sit under packed snow and ice, and meltwater on a cold membrane refreezes where it lands. That is one of the reasons rooftop work here gets pulled forward of freeze-up. Where grease reaching the membrane is a recurring problem, a containment unit at the fan is the durable fix rather than a better mop, and that is covered on the rooftop grease containment page.
DIY vs professional: where does self-cleaning stop being sensible?
Barrie Hood Cleaning's honest split: a kitchen crew owns the filters, the canopy, and the trough, and a contractor owns the plenum, the duct, the fan, and the paperwork.
| Question | Doing it in-house | Bringing in a contractor |
|---|---|---|
| How much of the path gets reached | Filters, canopy interior, trough, visible stainless. Realistically stops at the filter bank. | Canopy, plenum, full duct run through every access point, and the rooftop fan. |
| Access panels | Usually left closed, because opening and resealing them is its own skill. | Opened, cleaned through, resealed. Missing panels get flagged as a gap rather than ignored. |
| Containment and capture | Improvised. Wash water often ends up on the kitchen floor or the roof. | Planned before the job starts, with a capture point sized for the section being cleaned. |
| Working at height | The stopping point for most kitchens, and rightly so. | Routine, with the equipment and the WSIB coverage that goes with it. |
| Evidence produced | A cleaner-looking kitchen and nothing on paper. | Before-and-after photos of each surface plus a signed certificate referencing NFPA 96. |
| What an inspector accepts | Not sufficient on its own. Barrie Fire and Emergency Service enforces the Ontario Fire Code, which adopts NFPA 96, and the question is dated evidence of the whole path. | The photo set and certificate are exactly the record an inspector and an insurance adjuster ask to see. |
| Cost shape | Staff hours after close, plus product, plus the risk of a repair caused by the attempt. | A known number. Commercial single-hood visits start from $385 and multi-hood kitchens from $725, quoted in writing first. |
| Best use of it | Keeping the system slow to load between scheduled visits. Genuinely valuable. | Meeting the NFPA 96 interval for the whole system and producing the record that proves it. |
The two are not rivals. Nightly and weekly in-house work makes the scheduled visit go faster and the system stay cleaner. What in-house work cannot do is satisfy the NFPA 96 requirement on its own.
How is an industrial kitchen vent different?
Scale changes the method: long horizontal runs, shared risers, and missing access panels turn a straightforward clean into a job that needs an access plan first.
Institutional and industrial kitchens around Simcoe County, meaning college serveries, hospital and long-term care kitchens, base and municipal cafeterias, and school board kitchens, tend to share three traits. Their duct runs go horizontally for long distances before turning up. Several hoods often feed one riser. And their access panels were either never fitted or were drywalled over during a renovation nobody documented.
So the sequence gains a step at the front: map the system and confirm how each length of duct will actually be reached, before any product comes out. Where a section cannot be reached, the choice is to fit an access panel or to record that section as not accessible. Quietly certifying an unreachable run is the failure mode worth naming, because it produces a clean-looking certificate over an uncleaned duct.
The shared riser deserves its own warning, and it applies to multi-tenant plazas as much as to institutions. Cleaning one tenant's hood and duct does not clear a riser that several kitchens feed. Each kitchen on that riser needs its own cleaning and its own record, or the building still has a loaded shared path. Institutional work also carries a paperwork requirement before anyone starts: proof of liability insurance and WSIB coverage, with the board or municipality named as additional insured on request.
Cleaning kitchen exhaust fans: frequently asked questions
Method questions that come up before a first attempt.
What is the correct order to clean a kitchen exhaust system in?
Work downstream to upstream and top to bottom within each section: contain the area, pull the filters, clean the fan and the upper duct, then the duct run, then the plenum, then the canopy, and finish with the trough and the surrounding stainless. Cleaning the canopy first wastes it, because everything loosened above it drains straight back down onto the surface you just finished.
What tools does the job actually need?
The real kit is containment and capture more than it is brushes: plastic sheeting and tape, a catch basin or collection tray at the low point, a pressure source and a way to contain the spray, an alkaline degreaser suited to the surface, scrapers that will not gouge stainless, long-handled brushes for duct reach, lighting, and full protective equipment including eye protection, chemical gloves, and non-slip footwear. Access hardware matters too, because a duct with no access panels cannot be cleaned properly no matter what is in the bucket.
Where does the wash water go?
Wash water has to be captured and disposed of properly, never sent down a roof drain, a storm drain, or across a parking lot. Grease-laden runoff is a pollution problem and a liability problem, and on a roof it also damages the membrane. Capture it at the low point of the system with a basin or a collection setup, and put it into the building's grease-handling stream rather than the nearest opening.
Can a restaurant clean its own exhaust system?
A kitchen crew can genuinely handle filters, the canopy interior, and the grease trough, and doing that well slows everything downstream. What a crew usually cannot do is the plenum behind the filter bank, the duct run, and the rooftop fan, because those need access hardware, containment, height safety, and capture. A self-clean also produces no photo record and no signed certificate, so it does not answer the question an inspector is actually asking.
How is an industrial kitchen vent different from a restaurant one?
Scale changes the method more than the chemistry does. Industrial and institutional vents in college serveries, hospital kitchens, and base cafeterias tend to have long horizontal duct runs, multiple hoods feeding a shared riser, and access panels that were never fitted or were sealed over during a renovation. Those systems need an access plan before any cleaning starts, and they are cleaned in sections so that each length of duct can actually be reached and photographed.
For a fan already loaded with grease, the recovery steps are in the oily exhaust fan guide. Full-system service detail sits on the kitchen exhaust cleaning page.