Grease Duct Buildup and Cleaning Interval (NFPA 96)

Monthly for solid fuel, quarterly for high volume operations -- twenty four hour cooking, charbroiling, wok cooking -- semiannually for moderate volume, and annually for low volume such as churches, seasonal businesses and day camps. Getting the category right is the whole scheduling decision, and a charbroiler in an otherwise moderate kitchen moves the whole system into the quarterly column. THE SCHEDULE AND THE MEASUREMENT ARE TWO SEPARATE TESTS AND THE MEASUREMENT GOVERNS. An inspection at the interval is required whatever the system looks like, and a cleaning is required whenever measurable grease is found, whatever the schedule says. A system inspected on time and found with grease is cleaned on the spot; a system found clean is still inspected again at the interval. Neither test substitutes for the other, and reporting only the schedule is how a system that needed cleaning in month two gets cleaned in month six. The depth criterion is where the two meet: a measurement at a designated inspection point carries a far tighter trigger than the general one, because that point is chosen to represent the system and a small reading there implies a large accumulation elsewhere. THE SCOPE TRAP IS THE ONE THAT LEAVES BUILDINGS ON FIRE. Cleaning means the ENTIRE system -- hood, filters, the full length of duct including horizontal runs and every access panel, the fan, and the roof discharge -- and a cleaning that addresses the hood, the filters and the first accessible section of duct has cleaned the part that is easy to reach and left the part that burns. The fan housing and the roof curb accumulate heavily and are routinely skipped, and a certificate that does not say what was cleaned has not said anything. A schedule check and a depth comparison. It does not determine the cooking volume category, which is a judgment about the operation; it does not address the access panel spacing and placement that make a full cleaning possible in the first place, which is a design and installation matter; and it does not cover the fire suppression system, its inspection interval, its nozzle placement relative to the appliances beneath, or the semiannual servicing that is a separate requirement. Cleaning method, chemicals, containment of the runoff, and the certification of the cleaning contractor are all outside it. NFPA 96 as adopted, the authority having jurisdiction, and the certified cleaning contractor govern.

months overdue = months since the last inspection - the interval for the cooking volume; the cleaning trigger is the general depth criterion, or the tighter designated-inspection-point criterion where the measurement was taken at one.

The NFPA 96 inspection intervals by cooking volume, by name -- monthly for solid fuel, quarterly for high volume (24 hour, charbroiling, wok), semiannually for moderate, annually for low volume -- with the depth criterion commonly 2,000 micrometres generally and 50 micrometres at a designated inspection point. The schedule and the measurement are separate tests and the MEASUREMENT GOVERNS. Cleaning scope is the entire system: hood, filters, the full duct, the fan and the roof discharge. NFPA 96 as adopted, the authority having jurisdiction, and the certified cleaning contractor govern.

One subtraction and one comparison on a measurement the reader takes; no NFPA text is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: inspection_interval_months, months_since_inspection, measured_thickness_um, cleaning_trigger_um, inspection_point_trigger_um, is_designated_point, months_overdue, next_inspection_months, inspections_per_year, applicable_trigger_um, thickness_margin_um, thickness_ratio, measured_thickness_in

• The cooking volume category is a judgment and it sets the whole schedulethe authority having jurisdiction
• The measurement governs over the schedule any measurable grease means cleaning, whatever the interval saysNFPA 96 as adopted
• Scope is the entire system the fan housing and roof curb are routinely skippedthe certified cleaning contractor