Start from the load, not from the calendar
Two kitchens with the same number of burners can build grease at very different rates. One runs steamed rice and blanched vegetables for a school canteen. The other runs griddles and woks for a delivery brand that peaks between 18:00 and 21:00. Grease accumulation follows the cooking method and the number of cooking hours, so those two inputs belong in your frequency record before anything else.
A practical first step is to log three numbers for each hood line over one month: daily cooking hours, the share of that time spent on high-oil methods such as frying, grilling and wok work, and whether the line is used in batches or in one continuous service. Once that data exists, frequency stops being an opinion and becomes something you can defend in a hygiene audit.
Inspect the hood in four places, on purpose
A quick visual check of the filter surface tells you very little on its own, because the visible face is often the cleanest part. Inspect four locations and record what you find at each one:
- The filter face and the mesh cells underneath it, where a sticky film turns into a soft deposit that no longer rinses off.
- The hood interior walls and the collection trough, where grease creeps past the filter edge.
- The fan housing and impeller, which you can judge from vibration, noise and a drop in capture performance rather than by eye.
- The first metre of duct beyond the hood, the section that collects the most residue and the one most often missed during a routine wipe.
Write down what you see using three fixed levels, for example light film, soft deposit, and hardened deposit. The trigger for a deep clean is the second level, not the third. Waiting for hardened grease means the crew is no longer cleaning, they are removing a build-up that has already narrowed the airflow.
What shortens the interval
A few conditions push the cleaning interval down and are worth checking whenever the schedule feels insufficient:
- Fried, grilled and wok-centred menus, plus sweet sauces and sugar-based marinades that turn into a hard coating rather than a soft film.
- Long service windows and shift-overlap cooking, where the hood never gets a cool, dry period.
- A hood that runs short of airflow for its cooking load, because weaker capture pushes vapour onto surfaces that the filter was supposed to protect.
- Cold kitchen operation, which keeps the grease in a condensable state instead of carrying it away as vapour.
- A shared duct serving several kitchens or several brands, which adds residue that your own production data does not explain.
What lengthens it
The same evaluation works in the other direction. A steam-heavy or baked menu, a hood matched correctly to the cooking load, and a short daily wipe of the filter face and hood lip all reduce the amount of residue reaching the interior. Operators in this position often find that their deep-clean interval can be extended while the quality of the result improves, because each visit now deals with a soft deposit instead of a hardened one.
Match the method to the deposit you found
Once the interval is set, the method decides how expensive that interval is. Soaking filters in a chemical bath works for light and soft deposits, but it takes the filters out of service, it needs a disposal route for the spent solution, and it does nothing for the hood interior, the fan housing or the duct.
For a central kitchen that cannot stop cooking during the day, central kitchen cleaning equipment built around high-temperature steam changes the workflow: the hood, the filters and the first section of duct can be cleaned in place while the kitchen is between services. The Fixed Steam Cleaning Machine PowerDe HW02 is the fixed-installation model we point buyers to for this kind of work. Its published parameters are 220 V supply, 6 kW heating power, a steam temperature of 160°C, a vapour pressure of 0.8 MPa and an 80 L SUS304 tank, with a switch between dry steam and wet steam. Heat does most of the work on cooked-on grease, so the crew spends its effort on wiping the released residue rather than scrubbing or scraping it.
The same machine also covers the surfaces around the hood. The plating counter, the stovetop surrounds, the trolley wheels and the floor directly under the cooking line all collect the same grease that leaves the hood, and they are usually cleaned with a different product and a different chemical. Using one commercial steam cleaning equipment unit across those areas reduces the number of consumables on the shopping list and gives the kitchen one cleaning procedure instead of four.
Turn the evaluation into a simple record
The output of this exercise is a one-page sheet per hood line, and it should be short enough that the shift leader actually fills it in:
- Cooking hours per day, and the share of frying, grilling and wok work.
- Deposit level recorded at the four inspection points, once a week.
- Date of the last deep clean, and what was cleaned on that date: filters only, hood interior, fan housing, duct section.
- Any change in airflow, noise or odour since the previous entry.
After eight to twelve weeks you will have a defensible interval for your own kitchen. If the deposit level reaches soft at week three, three weeks is your interval. If it stays light for eight weeks, extend the schedule and spend the saved labour somewhere else.
