A steam lance going near a commercial exhaust hood is a different job from steaming a stovetop. The hood is not one surface but four: the canopy inner faces, the filters, the plenum above them, and the duct run behind the plenum. Each one answers a different question about temperature, water, electrical parts and fire risk. Before the machine is switched on, six items should be settled in writing, ideally in the kitchen's cleaning schedule rather than in a verbal instruction to the night crew.
1. The legal and insurer position on the duct
Start with the requirement, not the machine. In most jurisdictions a kitchen extract system has to be cleaned on a stated frequency, and that frequency follows how much fat loads the duct, which in turn follows cooking volume and cooking method. A charcoal grill line loads far faster than a steaming station. Some regimes set a higher standard of cleanliness where a duct passes close to a flue or through a protected structure. Get the rule that applies to your site, and get the insurer's wording on extract cleaning.
If the inside of the duct is contracted out, the kitchen still owns the canopy, the filters and the plenum, and any steam work in those areas has to be recorded alongside the contractor's certificate. Ask that contractor how they treat a hood that has just been steam-cleaned. Steam leaves a wetter surface than a scraper-only job, and their own sequence may have to change.
2. Which parts of the hood are in scope
Write the scope as a list of parts. A typical installation has filter frames and filters, the canopy interior and its grease trough, the plenum and its access panel, the fan housing where it is reachable, the light fittings, and the outer faces that staff and customers see. Each entry needs a stated method and a stated standard. Without the list, "clean the hood" becomes whatever the operator had time for, and afterwards nobody can prove what was done.
Decide separately whether filters are cleaned in place or taken away to a wash point. Filters soaked and brushed at a central kitchen degreasing bay come back straighter and cleaner than filters steamed while they are still hanging, and the run-off is caught in one place. On the hood itself, steam on the filter face mostly reaches the mesh that is still exposed; the corners and the frame channels are where the load sits.
3. Access, and when the hood has to come apart
Confirm that the crew can physically reach the work. Canopy interiors are shallow and dark. A wand held at arm's length inside a box under the ceiling gives a poor result and a scalded forearm. Confirm what has to come off: filter frames, access panels, the fan housing cover. Confirm what needs a platform, a ladder, or a second person holding a light.
Confirm the sequence against the other work on the hood. Fire suppression nozzles, their fusible links and the blow-off pipework normally sit on a separate inspection and re-set schedule. A hood with suppression pipework should not be steamed until the crew knows whether the nozzles have to be capped or removed, and who re-sets them afterwards. That is a question for the suppression contractor, not for the cleaning crew.
4. Isolating what is inside the box
Before steam enters the canopy: extract fan off at its isolator, with the isolator locked or tagged so nobody restarts it while someone is on a ladder; lighting circuits off, because the fittings sit inside the spray zone; gas to the appliances beneath the hood shut off; appliances cold. Steam onto a hot griddle or a hot fryer well flashes into vapour at once, the operator loses sight of the work, and that vapour carries loosened grease onto every cool surface in the room.
List the components that must never be sprayed, using the same wording every time: fan motors and their terminal boxes, light fittings and lamp holders, the high-limit sensor and its capillary, control knobs, and any printed label the crew might otherwise wash away. Write "wipe around" against those items. Where the hood maker has stated a restriction on water washing, put a copy of that restriction in the cleaning schedule and mark the affected tasks as wipe-only.
5. Temperature, distance and dwell, settled on a test panel
High-temperature steam is the tool for polymerised fat, which cold detergent and a scrubbing pad will not move. What needs confirming is what the machine delivers at the nozzle and what the hood surface tolerates. The Fixed Steam Cleaning Machine PowerDe HW02 page lists steam at 160 degrees with 0.8 MPa vapor pressure and a switch between dry and wet steam. Those are the figures to put in front of the hood manufacturer when you ask whether the canopy material and any coating accept them on a repeated basis.
Then run a test on one square metre in a place customers never see: the back of the last filter section, or the inner face nearest the duct entry. Record the distance the wand is held at, how long the nozzle stays on the deposit, how many passes it takes, and how the surface looks ten minutes later. Where the layer is thick, put heat in with the drier mode, let the fat soften, then use the wetter mode as a rinse instead of trying to strip the layer in one pass.
Look at the sealant and the joints during that same test. Old mastic, rivet lines and lap seams are where steam finds a way in, and driving water into a duct joint creates rust staining or a drip weeks later. If the test panel shows sealant lifting, the method for the whole hood changes: shorter dwell, greater distance, more wiping, less water.
6. Where the water and the grease go
Steam on a hood produces a small volume of very greasy liquid, and it has to be caught rather than allowed to run. Line the appliances and the floor beneath the hood, place trays or a catch basin under the drip line, and route the run-off into the site waste route through the grease interceptor. Run-off from a hood clean going into a prep sink or a surface drain is a blockage booked in advance. Have the interceptor checked and emptied around the same date as the hood work, because a full interceptor turns a compliant clean into a flood.
Confirm the water supply and where the machine will stand. A fixed unit plumbed to a tap near a wash point, such as the 220 V HW02 with an 80 L tank, keeps hoses off a working kitchen floor. A mobile unit from the Cleaning Equipment Series suits a site where one crew moves between several servery areas. Walk the hose and cable run against the layout before the shift, and record how much water the job actually uses, because that figure decides whether the next machine is bought fixed or mobile.
7. Drying, restart and the check that closes the job
Nothing in the canopy goes back on live until it is dry. Wipe what you can reach, then confirm that terminal boxes, lamp holders and the high-limit sensor show no standing moisture, and that no water has collected in the grease trough or at the low point of the plenum. Set acceptance criteria the crew can check in seconds: no visible fat film on the canopy interior, filter mesh open enough to see light through, no residue left in the frame channels, trough clear, no pooled water under the hood, no detergent smell on anything above food.
Restart in order. Suppression system confirmed back in service by whoever owns that duty. Fan isolator restored, fan run briefly to check it is quiet and not throwing oil. Lighting back on. Appliances cold-checked before gas is relit. Record the completed tasks, the date and who signed, and keep those sheets where a fire risk assessor or an environmental health officer can be shown them next to the duct contractor's certificate. Fat in a hood and its extract is a fire issue as well as a hygiene one, so the record is worth as much as the clean.
One more thing to confirm before the wand comes out: what the machine needs to keep producing that temperature. Where mains water is hard, scale collects in the heater and output drops well before the unit stops working, so a descaling interval belongs in the same schedule as the hood tasks. The HW02 page lists leakage, short-circuit, high-temperature, high-voltage and water-shortage protections. The crew needs to know they exist, and also that a machine tripping one of them is reported rather than reset again during a shift.
Confirming the set-up with the manufacturer
Hoods differ from site to site: box size, filter type, whether the plenum has an access panel, how the suppression pipework is arranged, what the canopy material tolerates. Shenzhen PowerDe Automation Precision Equipment publishes the parameters for each machine in the cleaning range, and customized steam cleaning equipment can be specified around your hood layout and the cleaning window you actually have. Send the hood dimensions, photographs of the worst deposits and your current cleaning frequency through the contact page, and ask for a machine configuration and a method matched to the site instead of adapting a catalogue page on the night.
