How Often Should You Clean a Commercial Kitchen Hood? NFPA 96 Frequency Guide for Ontario Kitchens

If you’ve searched this question, you’ve probably already gotten three different answers from three different people — your landlord says once a year, your last cleaner said quarterly, and your insurance broker just says “per code.” None of those are wrong exactly, but none of them are complete either, because NFPA 96 doesn’t set one interval — it sets several, based on what and how much you’re cooking.

We’ve been cleaning hoods, ducts, and rooftop fans for commercial kitchens across the Greater Toronto Area for 12 years — everything from single-hood independent restaurants to multi-unit QSR chains — and this is the single most common question we get on the intake call, usually right before “can you get someone out this week?” So here’s the technical answer, not the marketing answer.

The Short Answer

NFPA 96 (2021 edition, Table 11.6) ties cleaning frequency to cooking volume and cooking method, not to a calendar date everyone follows. The table breaks down like this:

That’s the code minimum. It’s a floor, not a ceiling — and the “moderate volume” and “low volume” categories are where most of the confusion (and most of the fire risk) actually lives, because two restaurants that both call themselves “full-service” can generate very different grease loads depending on what’s actually on the menu.

Why “It Depends on the Menu” Isn’t a Cop-Out

Grease accumulation isn’t about hours open — it’s about what’s passing under the hood. Two kitchens open the same number of hours per week can have completely different cleaning needs:

• A wok station or charbroiler throws off aerosolized grease at a much higher rate than a kitchen doing mostly bake and steam work. That grease condenses inside the ductwork, not just on the filters, which is why NFPA 96 puts wok cooking in the quarterly-minimum bracket even if the kitchen isn’t open 24 hours.
• Deep fryers and flat-top grills produce more airborne grease than convection ovens or steam tables, even at similar ticket volumes.
• Filter type matters. Baffle filters trap grease more effectively than older mesh filters, but even well-maintained baffle filters only catch a portion of the grease — the rest travels into the duct and settles as it cools, which is exactly the material a fire feeds on.
• Duct run length and geometry affect where grease settles. A short, straight run to a rooftop fan collects differently than a long run with multiple turns — more turns mean more surface area for grease to condense on, often in sections that are harder to reach and get skipped by less thorough cleanings.

This is the part a generic “clean every 6 months” answer misses: the interval on the NFPA table is a starting point for classification, not a substitute for someone actually looking at your hood, filters, and duct access points and telling you where your kitchen actually falls.

How to Tell If Your Kitchen Is Overdue Right Now

You don’t need to wait for a scheduled date to check. These are the signs we look for on every inspection, and any one of them means the system is due sooner than your last interval suggests:

1. Grease dripping from the hood lip or filters when the exhaust fan is running. If you can see it, the ductwork behind it has more.
2. A burnt or greasy smell that shows up when the cooking line has been running for a while, especially near the ceiling.
3. Weak suction over the cook line — smoke or steam lingering instead of pulling straight up into the hood. This usually means the fan or duct interior is restricted enough to reduce airflow, which also makes the kitchen hotter and less comfortable to work in.
4. Grease residue on walls or ceiling tiles near the hood, even if the hood itself still looks clean. This is often the first visible sign that the exterior is being wiped down (by staff or a janitorial service) while the interior duct and fan are being missed entirely.
5. A fan that’s noticeably louder, or a fan belt that needs replacing more often than it used to. Grease-caked fan blades throw the assembly off balance, which increases wear on the motor.

If you’re seeing two or more of these, the honest answer is: clean it now, then figure out the right ongoing interval — don’t wait for the “next scheduled” date.

A Practical Frequency Chart by Kitchen Type

Based on NFPA 96’s categories and what we actually see across the restaurant types we service in the GTA:

These are starting points, not guarantees — a “quarterly” kitchen that adds a wok station or extends hours can move into a shorter interval without anyone updating the paperwork. This is why we do a short intake assessment (cooking volume, hood layout, filter type, duct access) before quoting a schedule, rather than quoting a flat rate off the phone.

What Happens If You Clean Less Often Than the Table Says

Two things, and both matter more than most operators expect:

Fire risk. Grease is a fuel source. NFPA 96 exists specifically because grease-laden ductwork lets a small cooking-line fire travel through walls and ceilings before anyone notices — that’s the mechanism behind most serious commercial kitchen fires, not the stove fire itself.

Compliance and insurance exposure. In Ontario, fire inspectors check for a current NFPA 96 compliance sticker and dated cleaning certificate — not just a visually clean hood — during routine inspections. Separately, most commercial kitchen insurance policies require proof of cleaning on schedule as a condition of coverage. If a fire investigation finds the ductwork was overdue for cleaning, that’s grounds for an insurer to deny or reduce a claim, even if the fire wasn’t directly caused by the grease. A dated service report with before-and-after photos is the paperwork that protects you in both situations — the cleaning itself is necessary but not sufficient without documentation.

How to Set an Interval for Your Kitchen (Without Guessing)

1. Identify your cooking method category using the NFPA 96 table above — solid fuel, high-volume, moderate-volume, or low-volume.
2. Check your filter type and duct access points. Kitchens with harder-to-access duct runs need a technician who can confirm those sections are actually being cleaned, not skipped.
3. Track visible warning signs between scheduled cleanings — grease drip, smell, weak suction — as a signal your interval needs to shorten, not just a note for next time.
4. Ask your cleaner for dated documentation every time, with before-and-after photos of the hood, filters, duct, and fan — not just the hood interior. This is what an inspector or insurer will actually ask to see.
5. Put it on a recurring schedule, not a “call when we remember” basis. The kitchens that end up with the worst duct buildup are almost always the ones cleaning reactively instead of on a set interval.

Frequently Asked Questions

Does a fire suppression system change how often I need to clean the hood? No. A suppression system is there to put a fire out if one starts — it doesn’t reduce the grease that fuels one. NFPA 96 requires both a maintained suppression system and a regular cleaning schedule; one doesn’t substitute for the other.

If my hood exterior looks clean, does that mean the duct and fan are fine too? Not necessarily. Grease collects in ductwork and rooftop fans at the same rate as the hood, but those sections are out of daily view. A hood that looks spotless on the outside can still have significant buildup in the duct run, which is exactly what a general janitorial wipe-down won’t catch.

Can I just clean more often than NFPA 96 requires to be safe? Yes, and for high-volume kitchens this is often the right call — the table is a minimum, not a maximum. The cost of an extra cleaning is almost always lower than the cost of a duct fire, a failed inspection, or a denied insurance claim.

Who decides the actual interval for my kitchen — me or the cleaning company? It should be a joint decision based on an actual inspection of your hood, filters, and duct access, not a flat rate quoted without seeing the kitchen. A technician who assesses cooking volume and duct condition in person (or from photos) can tell you which NFPA 96 category you actually fall into.

Getting an Interval Set for Your Kitchen

If you’re not sure which category your kitchen falls into, that’s normal — it’s genuinely not a one-line answer, and guessing wrong in either direction costs you (too infrequent risks a fire or a failed inspection; too frequent wastes money). We do a quick phone or photo-based assessment before quoting anything, look at your hood, filters, duct access points, and cooking line, and set a schedule that matches your actual grease load — with a dated report and NFPA 96 documentation after every visit.

Hood Cleaning Masters has serviced commercial kitchens across Toronto, Vaughan, Concord, Mississauga, Richmond Hill, North York, Scarborough, Hamilton, Barrie, and surrounding Ontario communities for 12 years, for restaurant groups, hotels, and QSR chains including Tim Hortons, Wendy’s, and Burger King locations.

📞 Call +1-647-333-5455 for a free assessment, or book a service.

This article reflects NFPA 96 (2021 edition) guidance and general Ontario Fire Code practice. Specific inspection intervals and insurance requirements vary by municipality, occupancy classification, and individual policy — always confirm requirements with your local fire authority and insurer.