Kitchen extract systems divide into two very different cleaning jobs on the day: the inner duct run and fans, which normally go to a specialist contractor, and the parts a kitchen crew or in-house maintenance team can reach — the hood filters, the grease cups and collection trays, the hood interior and periphery, the exposed sections of pipework near the fan, the dampers and the exterior of the canopy. Those accessible surfaces are the ones that decide whether the system still pulls air between contractor visits, and they are also where most crews get the mode wrong: one steam setting used everywhere, and either a sticky wet mess on light deposits or a heavy deposit left almost untouched.
Choosing between dry and wet steam on those surfaces is a deposit question, not a machine preference. The practical rule: put heat into the deposit first, move it second, and use water only where the surface and the run-off route can take it. This article sets out how to make that call surface by surface, and which questions narrow the machine choice.
Name the surface before naming the mode
Write down what is reachable without scaffolding, a lift or cutting a duct access panel, and put each item on its own line. In a typical kitchen that list is: filters and filter frames; the grease cup or collection tray under the hood; the hood interior shell and the inside of the upper cone; the hood exterior and the perimeter where grease migrates; the visible duct sections and any accessible flex; the fan housing exterior and the fan access door; backdraft and fire dampers; and the wall and floor zone around the line. Each of those has a different deposit thickness, a different material, and a different run-off path, and the mode follows from those three facts.
Read the deposit, then choose
Three deposit states cover almost everything on an extract system:
- Fresh grease, loose, still mobile. Recent splatter and light film on filters, the hood exterior, and the top of the canopy. Little heat is needed; the water side of the job does the work.
- Soft built-up emulsion. A few weeks to a few months of accumulation: dull, brown, squeezable, usually on filters, grease cups, the hood interior and damper blades. Heat helps release it, and some carry-over water helps flush it away.
- Polymerised, varnished, tar-like. Hard, dark, glossy, bonded to the surface, typically on the hood shell near the exhaust, on older duct sections, on the fan housing and on anything that has been heated and cooled many times. Water alone will not move it; heat has to break the bond before anything else happens.
A dry and wet steam cleaner covers both halves of that work with one machine. The drier mode carries more heat to the surface and leaves less free water behind, so it is the starting mode on the polymerised class — it softens the coating so a scraping or brushing step can lift it, and the crew can see what has released. The wetter mode then acts as a rinse on the surfaces that can take it: filters laid flat, grease cups, and open sections that can be flushed into a tray. Working in that order, heat then limited water, is what keeps run-off and dwell time down on a kitchen extract job.
Dry steam first on bonded coating and on surfaces that must stay serviceable
Use the drier mode where any of these apply:
- The deposit is hard and glossy rather than soft, so heat and dwell matter more than flushing.
- The surface sits next to electrical parts — the fan housing exterior, the fan access door, motor terminals, wiring runs, light fittings, control panels, damper actuators — where free water has nowhere to go.
- The surface is overhead or vertical and there is no tray or drain to catch a wet run-off.
- The item has to go back into service quickly, because the kitchen cannot afford the extraction stopped while the assembly dries.
Set the working distance close enough that the steam condenses on the deposit rather than dissipating in the air gap, hold it there for a defined dwell, and make a fixed number of passes on the worst panels. Write those three numbers down after a trial on one hood so the second shift repeats the same result rather than improvising.
Wet steam on removable parts that can be laid flat
The wetter mode belongs on parts you can take off, put on a trolley or into a wash bay, and wash without run-off reaching the room: filters and frames, grease cups and trays, splash panels, and the flat of the hood underside once the loose material has been lifted. Laying a part flat changes the physics — the water carries the released grease along the surface into a tray instead of dripping across the kitchen. That is the point at which a commercial range hood grease removal routine actually shortens, because the scrubbing step disappears and only the heat-and-flush sequence is left.
Keep the wetter mode off the fan housing, off any assembly with a motor or terminal box, and off duct joints and sealant you have not checked. Where a joint looks soft or a sealant bead is lifting, stop and record it; a cleaning job is the moment those defects get found, not the moment they get worsened.
Run-off and drainage decide how much water you can use
Before choosing the wetter mode anywhere, answer where the water comes from and where the greasy run-off goes. Grease-laden wash water belongs in the site's waste route through the grease interceptor, and that interceptor has to be checked and emptied on a stated interval — a full interceptor turns a compliant clean into a flooded kitchen. If the only drain available is a prep-area sink or a surface gully, the answer on the floor and under the hood is the drier mode, with run-off absorbed into trays and removed as waste. Trays, absorbent granules, and a labelled waste oil route belong on the task sheet next to the mode, not in someone's memory.
Water supply constrains the machine as much as the mode. A fixed unit plumbed to a tap supply at a wash point beside the line keeps crews off long hose runs across an aisle; a mobile unit from the Cleaning Equipment Series suits sites where several servery areas share one crew, or where the cleaning happens at night and the machine has to be moved to the work. Where the site has neither a wash point nor convenient power, say so in the plan and let that constraint pick the configuration.
Isolation and cooling come before either mode
No task on an extract system is executable without the isolation step written into it: the fan switched off at the isolator and, where the site runs a permit system, locked and tagged; the extraction stopped and confirmed stopped; the hood and ductwork cooled before heat is applied. Steam onto a hot surface flashes immediately, scalds the operator and removes their sight of what they are holding. State how long cooling takes and who confirms it. Also state who covers the cooking line, dry goods and open chemicals before steam is generated, because vapour travels and settles on everything in the room.
Questions that narrow the machine choice
Once the surfaces and deposit states are on paper, the buying questions get short and specific:
- Where is the nearest power supply, and is it adequate for the duty? Published electrical data for each machine in the Cleaning Equipment Series settles this before delivery rather than after.
- Is there a tap feed at the wash point, or does the tank have to be filled and carried? Tank capacity and fill method decide how many hoods one crew can do before a refill.
- Does the unit need to move between floors or sites, or does it stay beside one line?
- Do you need both modes, or only the drier one? If the accessible work is all bonded coating and electrical-adjacent surfaces, a mode you will never use is cost.
- Which consumables wear out — seals, nozzles, hoses, brushes — and who holds spares so a failed hose does not stop the schedule?
- What is the local water hardness? Scale collects inside a heater and output falls well before the machine fails, so a stated descaling routine belongs in the plan.
On a fixed machine, ask what protections the unit has and what the crew should do when one trips. The PowerDe HW02 steam cleaner page lists leakage, short-circuit, high-temperature, high-voltage and water-shortage protections among its safety designs; a machine that trips one of them during a shift has to be reported and investigated, not reset repeatedly until it runs.
Acceptance criteria the operator can check without arguing
"Clean" cannot be enforced on a schedule. Write checks that take seconds: filter mesh visible with no sealed coating across it; grease cup empty and not coated in hard residue; no bare metal lost to over-aggressive work, but no glossy tar-like film left on the hood shell; damper blades free to move and not glued shut by deposit; no pooled water in a joint or on the fan housing; the fan back up to normal airflow with the difference recorded; and the room floor dry within a stated radius of the work. Record the date, the surfaces done, the mode used and who did them. On an extract system that record matters as much as the clean itself — deep deposits on cooking equipment and extract lines are a fire issue as well as a hygiene one, and inspectors and fire risk assessors ask for the paperwork, not for a verbal assurance.
Where to start if you have never done it in-house
Pick one hood and its first metre of accessible ductwork. Clean it in both modes, timing each, and record dwell, distance, passes, water used, run-off collected and the drying time before the fan was restarted. Two or three cycles on that one hood give you real numbers for the whole site and show which mode you actually reach for. Shenzhen PowerDe Automation Precision Equipment publishes parameters for each machine in the Cleaning Equipment Series and specifies customized cleaning equipment against site layout and duty cycle. Send the surface list, photographs of the worst deposits, and your power and water situation to the contact page and ask for a mode-and-configuration recommendation matched to the kitchen rather than a catalogue page.
