Hood and Grease Trap Cleaning Schedule for Restaurant Kitchens

Two pieces of kitchen equipment collect grease on purpose: the exhaust hood above the line and the grease trap or interceptor below it. Both work only if someone empties them, and both cause expensive trouble when nobody does. A neglected hood is one of the classic ways a kitchen fire gets into the ductwork and the building. A neglected trap backs up into floor drains, overflows into the sewer and earns a fine from the city.

This guide covers what the kitchen team does itself, what a contractor does, how often each happens, and how to keep proof. It is written for kitchens in the US and Canada, where NFPA 96 is the reference standard. Check with your local fire authority and wastewater utility, because they set the rules you are actually inspected against.

The parts of the exhaust system

It helps to be clear about what is being cleaned:

• Hood filters: the removable baffle filters in the hood canopy. They catch grease before it reaches the duct. These are the kitchen team's job.
• Hood interior and plenum: the surfaces behind the filters. Partly the team's job (wipe-down), mostly the contractor's.
• Ductwork: the enclosed duct running from the hood to the roof or wall. Contractor only.
• Exhaust fan: usually on the roof, with a grease cup or containment. Contractor cleans; the team or maintenance person can check the grease cup.
• Fire suppression system: the wet chemical system with nozzles over the appliances. Separately inspected by a licensed fire protection company, typically every six months. Not covered in detail here, but schedule it alongside hood cleaning.

Daily and weekly work for the kitchen team

Filters load up faster than most people think. A filter clogged with grease reduces airflow, the kitchen gets hotter and smokier, and the grease that does not stick to the filter goes into the duct.

Two habits make filter washing actually happen. First, keep a spare set of filters so one set can soak while the other is installed; a hood should never run with filters missing. Second, put filter washing on the closing list for a named station, not on the general "clean kitchen" line. If it belongs to everyone, it will be done when someone notices smoke. Our kitchen cleaning schedule has a template for assigning these by station.

How often the ducts and fan need professional service

NFPA 96, the Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations, sets how often the whole exhaust system must be inspected for grease buildup. The schedule depends on the type and volume of cooking:

The detail people miss is that this is an inspection schedule. The standard requires the system to be cleaned when the inspection finds it contaminated with deposits, so in practice the inspection and cleaning visits usually coincide, and most busy kitchens end up on a quarterly clean. A wood-fired pizza place is monthly whether or not it feels busy.

"Moderate" and "high volume" are not precisely defined, and kitchens tend to flatter themselves. If you run a fry station or a grill for most of a long service day, assume you are high volume and let the contractor's inspection tell you otherwise. If the contractor reports heavy buildup at every visit, the interval is too long.

Which edition of NFPA 96 applies depends on what your state, province or city has adopted. In Canada, provincial fire codes point to NFPA 96 for commercial cooking exhaust; Ontario's Fire Code, for example, requires these systems to be installed and maintained in accordance with it. Your local fire marshal can confirm the edition and any local additions.

Choosing a contractor and reading the sticker

NFPA 96 requires the cleaning to be done by properly trained, qualified and certified people acceptable to the authority having jurisdiction. In practice, ask the contractor:

• What certification their technicians hold (several industry bodies certify hood cleaners, and some fire departments keep an approved list)
• Whether they clean the full system, roof fan included, or only what they can reach from the hood
• Whether they provide before and after photos of the duct
• Whether they will tell you about access panels that are missing or sealed shut

After each service, the contractor should leave a label or certificate in the kitchen showing the company, the technician and the date. If any part of the system could not be cleaned (an inaccessible duct section, for example), that should be written down too, not quietly skipped. Inspectors check this sticker, and so do insurance adjusters after a fire.

The common failure is a cheap service that cleans the hood canopy and the first few feet of duct, polishes everything you can see, and leaves the horizontal runs and the fan untouched. Photos of the inside of the duct and fan, every time, are the easiest way to know what you paid for.

Grease traps and interceptors

Every drain carrying greasy water (pot sinks, prep sinks, floor drains near the line, sometimes the dish machine) should run through a grease trap or interceptor before reaching the sewer. The grease floats, the solids sink, and the cleaner water in the middle flows out. Once the trap fills with fats, oils and grease (often called FOG) and food solids, it stops separating and the grease goes straight into the sewer.

There are broadly two kinds:

• Small under-sink or in-floor grease traps, often sized in gallons per minute. These fill fast and are usually cleaned weekly or more often, either by the team or a service.
• Large in-ground interceptors, often outside the building and holding hundreds or thousands of gallons. These are pumped out by a licensed hauler, typically every one to three months.

The 25% rule

Many US municipalities require a trap or interceptor to be pumped when the combined FOG and solids reach 25% of its depth, or at a maximum interval, whichever comes first. The exact wording varies. Some measure against the liquid depth, some against the design depth, some look only at the final chamber, and maximum intervals range from weekly for small indoor traps to 90 days or six months for large interceptors. Sioux City, Iowa, for example, requires interceptors to be pumped quarterly or sooner if they hit 25%, and its smaller indoor traps weekly. Your local sewer use ordinance or FOG program is the only reliable answer for your address.

If your city has a FOG program, it may also require you to use a registered hauler, keep pump-out manifests on site for a set number of years, and submit them on request. Some cities inspect without notice and measure the trap themselves.

Habits that make the trap last longer

• Scrape plates and pans into the bin before they reach the sink
• Never pour fryer oil or pan grease down any drain; collect it for the rendering or used-oil service
• Do not use hot water or enzyme products to "flush" grease through; it re-solidifies further down the line, often in the city's sewer, which is exactly what FOG programs exist to stop
• Keep strainers in floor drains and sink drains

Keeping proof

Hood cleaning and grease trap service both generate paperwork that someone will ask for: the fire inspector, the wastewater inspector, the insurer, a landlord, or a franchisor's auditor. Keep it in one place, and keep it longer than you think you need to.

For each service, the record should show the date, the company and technician, what was cleaned or pumped, how much was removed (for traps), any problems found, and the next due date. Photos help. For the team's own filter washing, a simple signed line on the closing checklist is enough, as long as it is actually signed each day. A photo of the clean filters on the closing checklist is better still, and it is the sort of thing TenorOps was built to collect.

Set a reminder two weeks before each contractor visit is due. Kitchens rarely forget the first service; they forget the third one, after the manager who booked it has left.

A note for kitchens in India

NFPA 96 is not the governing standard in India, though some international chains and hotel groups use it internally. Restaurants here operate under the fire NOC issued by the state fire service, and the conditions on that NOC (and the National Building Code of India, which most states follow for fire safety) are what an inspection will check. Ask your fire consultant what cleaning frequency and records your NOC renewal expects, and keep the hood cleaning invoices with the renewal file. Grease trap requirements come from the local municipal body or pollution control board and vary widely by city.

Related reading

For the broader fire picture, see the US restaurant fire safety checklist or the Canadian version. For keeping service dates on one calendar alongside refrigeration and dish machine maintenance, the restaurant equipment maintenance checklist is a good starting point.

Official sources

• NFPA 96: Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations
• Ontario Fire Code, O. Reg. 213/07
• City of Sioux City: Understanding the grease removal and 25 percent rule
• US EPA: National Pretreatment Program