TR19 & standards
Three months, six, or twelve? The interval comes from how hard your kitchen works and what the grease readings show - not a number someone picked once.
The short answer
TR19 Grease sets starting intervals by how many hours a day the kitchen runs - heavy use every 3 months, moderate every 6, light every 12. But those are minimums. The real frequency is calculated from your cooking type, system condition and measured grease build-up, then reviewed at every visit so it tracks the actual risk.
The starting bands
The headline schedule is based on daily operating hours. Heavy use - roughly 12 to 16 hours a day - points to cleaning every 3 months. Moderate use, around 6 to 12 hours, every 6 months. Light use, 2 to 6 hours, at least every 12 months. Where there is no cleaning history to work from, the specification's Table 4 is used to establish that initial interval in the absence of pre-clean thickness data.
These bands are a sensible place to begin, but they are deliberately minimums. Two kitchens open the same hours can produce very different amounts of grease depending on what they cook, so the hours alone never settle the question - they just start it.
What refines the number
The interval is really a risk-based judgement made by a competent person. Heavy frying, grilling and wok cooking throw off far more grease than a kitchen reheating prepared food, so cooking type and volume push the frequency up or down. So does system condition and layout - long runs, tight bends and hard-to-cool sections load differently.
The objective measure is the grease itself. Periodic inspections read the thickness before and after cleaning and record the days between readings, which shows how fast the system is loading. If it is climbing toward the 200-micron mean quickly, the interval shortens; if it stays comfortably low, it can lengthen. Inspection intervals should not exceed 12 months, and insurers or a fire risk assessment may require more frequent attention on the highest-risk sections like the canopy and plenum.
The limit
The trap is booking a clean annually simply because that is what was done last year. Kitchens change - menus, volumes, hours and equipment all move - and a schedule set once drifts out of step with the real risk. TR19 frequency is about condition, not the calendar: the date in the diary should be the output of assessment and readings, and it should be revisited whenever the operation changes. A clean on the wrong interval is either wasted money or, worse, a system quietly past the limit.
Questions
As a baseline: heavy use (12-16 h/day) every 3 months, moderate (6-12 h) every 6 months, light (2-6 h) every 12 months. These are minimums - the real interval is set by cooking type, condition and grease readings.
A table in the TR19 Grease specification used to establish the initial cleaning frequency when there is no history of pre-clean grease thickness to work from. It gives a starting point that readings then refine.
Yes, significantly. Heavy frying, grilling and wok cooking generate far more grease than reheating, so two kitchens open the same hours can need very different intervals.
Through periodic inspections that measure grease thickness before and after cleaning and track how fast it builds. If build-up is quick the interval shortens; if slow it can lengthen. Inspection should happen at least every 12 months.
Only if assessment and readings support it. Annual cleaning by habit often fails to match real risk - a busy kitchen can exceed the limit long before twelve months are up.
Phoenix Duct Clean · by the numbers
We assess your usage and take baseline readings, then set a cleaning frequency that keeps you under the limit - reviewed each visit, not fixed and forgotten.