How often should restaurant hoods be cleaned?
The answer everyone repeats is monthly, quarterly, twice a year or yearly, depending on your cooking. That is right as far as it goes. What it leaves out is that NFPA 96 schedules inspections, not cleanings, and that your local fire marshal may set a different number.
The short answer
NFPA 96, the fire standard for commercial kitchen ventilation, sets how often the exhaust system must be checked for grease build-up, by the kind of cooking it serves. As quoted by the Massachusetts and Utah state fire marshals:
| Cooking served by the system | Frequency |
|---|---|
| Solid fuel — wood or charcoal | Monthly |
| High volume — such as 24-hour cooking, charbroiling or wok cooking | Quarterly |
| Moderate volume | Twice a year |
| Low volume — such as churches, day camps, seasonal businesses or senior centres | Annually |
Most sit-down restaurants fall in the twice-a-year band. A kitchen with a charbroiler or a wok station is high volume however many covers it does, and anything burning wood or charcoal is monthly.
The part most guides leave out: it's an inspection schedule
NFPA 96's table is a schedule for inspecting the system for grease. Cleaning follows from what the inspection finds. In the words of the Massachusetts State Fire Marshal: "Based on the results of the inspection, a determination is made by the inspector if the system needs to be cleaned." Utah's fire marshal puts the consequence plainly: where grease is found, "the contaminated portions of the exhaust system shall be cleaned."
In practice, a kitchen inspected on schedule usually needs cleaning on roughly the same schedule, which is why the two get treated as one. But it explains two things owners run into:
- A cleaner can't certify a schedule for you without looking. The frequency in your service contract is an estimate of when your system will need it.
- If inspection finds build-up sooner, the system needs cleaning sooner, whatever the table says.
Your local code can change the number
NFPA 96 is adopted by states and cities, sometimes with changes. Portland Fire & Rescue's policy, for example, sets cleaning frequencies directly:
| Portland, Oregon (FIR-8.08) | Clean |
|---|---|
| Solid fuel or wok cooking | Every month |
| High-volume fast food, 24-hour cooking, charbroiling | Every 3 months |
| Normal commercial cooking or baking | Every 6 months |
Two differences from the NFPA table: wok kitchens move from quarterly to monthly, and Portland requires a certified person to inspect every 6 months, with infrequent use (a lodge or church) extendable to a maximum of two years. Your local fire marshal's office is the authority, and it will tell you which edition and which local amendments apply.
What "cleaned" means
- The whole system, not just the hood. NFPA 96 covers the hood, the ductwork and the exhaust fan. Grease in a rooftop fan or a duct run you can't see is still grease.
- To bare metal. Utah's fire marshal: "Anything less than bare metal clean should not be considered acceptable."
- Access to the ducts. Utah's guidance requires access panels no more than 20 feet apart, and no more than 10 feet apart at changes of direction. A duct with no access can't be cleaned, whatever the invoice says.
The sticker on your hood
After a cleaning, the company should put a label on the hood. Utah and Portland both specify what it shows:
- The service company's name, and the technician's certification number.
- The date of service.
- The type of service and system.
- Any areas not cleaned, and major deficiencies.
Read that last line. "Areas not cleaned" is where an inaccessible duct section or a fan that couldn't be reached gets recorded, and it is what a fire inspector or insurer will look at after a fire. Utah also says the owner should receive a completion or deficiency report, before-and-after photos and an itemised invoice.
Who is allowed to do it
NFPA 96 calls for a properly trained, qualified and certified person, and many jurisdictions license them:
- Massachusetts requires a Certificate of Competency from the State Fire Marshal. A Type 1 certificate is for businesses, needs at least 500 hours of experience, and is the only type allowed to do inspections. A Type 2 certificate lets an owner clean only systems on their own property.
- Portland requires a Certificate of Fitness issued after a Fire Marshal's Office exam.
Ask a hood cleaner for their certification and check it with your local fire marshal's office before booking.
What it typically costs, from public bid results, is in what does hood cleaning cost.
Records
Keep every cleaning and inspection report. Massachusetts requires owners to keep them for at least three years, and Portland requires them on site for the Fire Marshal's Office. In Massachusetts, a cleaner who finds the system non-compliant must notify the local fire department in writing within 48 hours, with a copy to the owner.
Between cleanings: what the kitchen does
From Utah's fire marshal guidance:
- Run the exhaust fans whenever cooking equipment is on.
- Never run the system with filters missing, or with gaps or separations between them. Those gaps let grease past the filters into the duct.
- Keep replacement-air openings clear while cooking.
Cleaning the filters regularly is what keeps grease out of the ductwork in the first place.
The fire suppression system is separate
The wet-chemical fire suppression system over the cooking line — often called an Ansul system after the best-known brand — has its own schedule. The Kansas State Fire Marshal requires it to be serviced at least every 6 months by a certified firm, including testing, checking the automatic fuel or power shut-off, and updating the service tag. A hood cleaning doesn't count as a suppression inspection, and the other way round. What the 6-monthly service covers, and the monthly checks the owner is responsible for, are in our Ansul system inspection guide.