How often does NFPA 96 require hood cleaning?
Monthly for solid fuel, quarterly for high-volume kitchens, twice a year for most restaurants, once a year for low-volume. The full table, the grease-depth rule behind it, and what Oregon, Washington, and Portland add.
NFPA 96 sets the inspection interval by how you cook, not by the calendar on the wall. Solid fuel kitchens (wood, charcoal) are inspected monthly. High-volume kitchens (24-hour, charbroiling, wok cooking) quarterly. Moderate-volume kitchens, which is most sit-down restaurants, every six months. Low-volume kitchens like churches, day camps, and seasonal operations once a year. When the inspection finds grease at or above the standard's thresholds, the system gets cleaned [1].
That is the short answer. The rest of this guide covers the table itself, the grease-depth rule that actually triggers a cleaning, why every fire marshal in Oregon and Washington treats the table as a cleaning schedule, and what Portland adds on top.
What is the NFPA 96 cleaning frequency table?
NFPA 96 is the Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations. Chapter 12 covers how the exhaust system gets inspected and cleaned once it is in service, and Table 12.4 sets the inspection interval by cooking type [1].
- Solid fuel cooking. What that looks like in a real kitchen: Wood-fired pizza ovens, charcoal grills, smokers, live-fire steakhouses. Inspection interval: Monthly.
- High-volume cooking. What that looks like in a real kitchen: 24-hour kitchens, charbroiling, wok cooking, most fast food and QSR. Inspection interval: Quarterly.
- Moderate-volume cooking. What that looks like in a real kitchen: Most sit-down restaurants, hotel kitchens, cafeterias, pubs with a fryer. Inspection interval: Semiannually.
- Low-volume cooking. What that looks like in a real kitchen: Churches, day camps, seasonal kitchens, senior centers. Inspection interval: Annually.
Two things trip people up here. First, the table says "inspection," not "cleaning." The cleaning is required when the inspection finds grease at the thresholds below. In practice, every fire authority we work with in Oregon and Washington reads the table as the cleaning schedule, and Portland writes it into policy that way [2]. Second, the tier is set by the heaviest thing you cook on. One charbroiler in an otherwise moderate kitchen makes you a quarterly kitchen. Our crews see this every week: a cafe adds a flat-top and a fryer for a brunch menu, keeps its annual schedule, and the duct is packed by the second inspection.
What grease depth triggers a cleaning under NFPA 96?
NFPA 96 section 12.6.1.1 sets the trigger: 0.002 inches (50 micrometers) of grease on hoods, filters, and ducts, 0.078 inches (2 millimeters) on other interior surfaces, and 0.125 inches (one eighth of an inch) in the fan housing [1]. Those are thin. Two thousandths of an inch is the thickness of a sheet of paper. A duct that looks "a little dirty" to a manager is usually well past the limit.
Section 12.6.2 then says the hood, grease removal devices, fans, ducts, and other appurtenances shall be cleaned to remove combustible contaminants [1]. That is the whole system, hood to roof, not the canopy and the filters. When you hear "cleaned to bare metal," that is the industry shorthand for the result the standard is asking for. The standard itself does not use the phrase, so be suspicious of anyone who tells you NFPA requires bare metal. It requires the grease gone.
Does Oregon follow NFPA 96?
Yes. Oregon enforces the Oregon Fire Code, which is the International Fire Code with state amendments. Chapter 6 covers building services, and Section 606 covers commercial cooking equipment and requires the exhaust system to be operated and maintained per NFPA 96 [3]. Every city fire department and rural fire district in the state inspects to that standard. Salem Fire, Eugene Springfield Fire, Tualatin Valley Fire and Rescue, and the rest all start at the same table.
Portland goes further. Portland Fire and Rescue policy FIR-8.08 sets cleaning frequency directly: monthly for solid fuel and wok cooking, every three months for high-volume, fast food, 24-hour, and charbroiling kitchens, every six months for normal commercial cooking and baking, and as needed for infrequent cooking. It requires the system to be inspected by a certified person at least every six months regardless of tier. It requires a label on the hood showing the date, the servicing company, company and technician certification numbers, and areas not cleaned. And it requires the inspection and cleaning reports to be kept on site and made available to the Fire Marshal's Office on request [2]. If you run a Portland kitchen, the sticker and the report are not optional. Our Portland hood cleaning page covers the local specifics.
Does Washington follow NFPA 96?
Yes. Washington adopts the International Fire Code through WAC 51-54A-0606. Section 606.2 requires a Type I hood over any commercial appliance producing grease-laden vapors. Section 606.3 says commercial cooking systems "shall be operated, inspected, and maintained in accordance with Sections 606.3.1 through 606.3.4 and Chapter 12 of NFPA 96" [4]. Same table, same thresholds, same written-report rule. Vancouver, Seattle, Tacoma, and Olympia all enforce it through their fire marshals.
One difference worth knowing: Seattle Fire certifies kitchen hood suppression technicians, not hood cleaning companies [5]. So in Washington, "certified" rests on training and industry membership (IKECA, PWNA), not a city license. Ask any cleaner what their certification actually is.
Not sure which tier your kitchen falls in? Tell us what you cook on, how many hoods you run, and when it was last cleaned. Get a free estimate or call (800) 973-5573. A person answers, any hour.
Why does the frequency matter beyond the inspection?
Because the duct is where restaurant fires start. Cooking equipment caused over 60 percent of fires in eating and drinking establishments between 2014 and 2018, with more than 100 civilian injuries and about $165 million in property damage every year, according to NFPA data summarized by Ansul [6]. A flare-up on the line is normal. A flare-up that finds a quarter inch of grease in the plenum and rides it up the riser to a fan bowl full of the same stuff is a building fire.
Frequency is also what your insurance carrier is looking at. Underwriters and loss-control inspectors use NFPA 96 as the benchmark, and after a fire the adjuster pulls the cleaning log, the service tags, and the photos. If the last cleaning was the wrong interval or only touched the canopy, the carrier can argue the operator contributed to the loss [7]. The interval and the paperwork protect you twice.
How do I know which tier my kitchen is in?
Start with the heaviest appliance, then the hours. Here is how our crews tier a kitchen on the first visit.
- Wood, charcoal, pellets, or any solid fuel anywhere on the line: monthly. No exceptions, even if the smoker only runs on weekends.
- Charbroiler, wok range, open flame grill, or a kitchen that cooks more than about 16 hours a day: quarterly. Most fast food and QSR sits here because of the fryers and grills.
- Fryers, flat-tops, and ranges in a kitchen with normal hours: semiannually. Most sit-down restaurants, hotel restaurants, brewpubs, and cafeterias.
- Warming, light saute, a church kitchen that cooks on Sundays, a summer camp: annually.
If you are between two tiers, the inspection decides. Section 12.6.1.1 is the referee. We measure grease depth in the plenum and at the fan, and if the six-month kitchen is hitting the threshold at four months, it is a quarterly kitchen whatever the menu says. The schedule changes, and the sticker reflects it. Details on what a full cleaning covers are on the commercial hood cleaning service page.
What does a compliant cleaning have to leave behind?
The interval gets you inspected. The paperwork gets you passed. NFPA 96 requires three things after every cleaning [1]:
- A service label on the hood showing the date of service, the name of the person who did the work, and the company's name, address, and phone (section 12.6.13). It stays until the next service.
- A written inspection report and a written cleaning report delivered to the owner within two weeks (sections 12.6.14 and 12.6.15), listing areas above the grease limits, inaccessible areas that were not cleaned, accessible areas that were not cleaned, access panel locations, and duct leakage.
- Tags at each access panel that was opened (section 12.6.10).
Portland adds the certification numbers and the "areas not cleaned" line on the sticker itself [2]. After every job our crews leave a certificate, a dated hood sticker, and a photo report that covers the plenum, the duct, and the rooftop fan. The full breakdown is on the NFPA 96 compliance hub.
What about the exhaust fan?
The fan is part of the system and part of the inspection. NFPA 96 section 8.1.6.3 requires rooftop fans to be accessible for cleaning, with a minimum access opening of 3 by 5 inches or 4 inches round, and hinged upblast fans are the standard way to get there [1]. A fan that was never tipped back was never cleaned, and a fan bowl with an eighth of an inch of grease in it is past the threshold on its own. If your cleaner has never asked about roof access, the fan is not on their list. Belts, bearings, and the hinge get checked on the same trip through our exhaust fan maintenance service.
Frequently asked questions
How often should a restaurant hood be cleaned?
Most sit-down restaurants are moderate-volume kitchens under NFPA 96 Table 12.4 and are inspected every six months. Fryers and flat-tops keep you there. A charbroiler, a wok range, or 24-hour service moves you to quarterly. Any solid fuel moves you to monthly [1].
Is NFPA 96 the law in Oregon and Washington?
NFPA 96 is a standard, but both states adopt it through their fire codes. Oregon Fire Code Section 606 and Washington WAC 51-54A-0606 both require commercial cooking systems to be maintained per NFPA 96 Chapter 12 [3][4]. Fire marshals enforce it.
Does Portland have its own hood cleaning rule?
Yes. Portland Fire and Rescue policy FIR-8.08 sets monthly, three-month, and six-month cleaning intervals by cooking type, requires a label with the date, company, certification numbers, and areas not cleaned, and requires the reports to be kept on site for the Fire Marshal [2].
What if my kitchen is seasonal?
Seasonal and infrequent kitchens fall in the annual tier under NFPA 96. Portland allows infrequent operations (churches, lodges) to stretch the inspection to a maximum of two years [2]. Clean before the season starts, not after it ends, so the grease does not sit all winter.
Can I clean the hood less often if I only use it a little?
The tier is set by what you cook on and how long, and the inspection confirms it with a grease-depth measurement. A lightly used charbroiler is still a charbroiler. If the six-month inspection shows the system under the thresholds, you stay at six months. If it shows grease over the limit at three, you are a quarterly kitchen.
What happens if the fire marshal finds the hood overdue?
Expect a citation with a re-inspection date, and in some jurisdictions an order to stop cooking until the system is cleaned and documented. Get a full-system cleaning with photos and a written report before the re-inspection. Our guide on what to do after a failed fire inspection walks through the week.
Put your kitchen on the right schedule. Get a free estimate with your address, hood count, cooking equipment, and last cleaning date, or call (800) 973-5573 any hour.
Sources
- NFPA 96 Chapter 12 summary (Table 12.4 intervals, section 12.6.1.1 grease thresholds, 12.6.2 scope, 12.6.10 and 12.6.13 labels, 12.6.14 and 12.6.15 reports, 8.1.6.3 fan access), Facilitec Southwest (facilitec-sw.com, kitchenguard.com)
- Portland Fire and Rescue policy FIR-8.08, Fixed and Portable Fire Extinguishing Systems and Equipment (portland.gov)
- Oregon Fire Code 2022, Chapter 6 Building Services and Systems, Section 606 (up.codes)
- Washington Administrative Code 51-54A-0606, Commercial kitchen hoods (606.2 and 606.3) (app.leg.wa.gov)
- Seattle Fire Department certification packet (kitchen hood suppression technicians) (seattle.gov)
- Ansul, "Two NFPA restaurant fire stats," citing NFPA data for 2014 to 2018 (ansul.com)
- Kitchen Guard, "Why NFPA 96 certified hood cleaning protects your restaurant and insurance coverage" (kitchenguard.com)