First, name the surfaces you are actually standing in front of
Walk the system from the cooking line outwards and write each surface on its own line. Most restaurant extraction systems fall into five groups, and operators are usually surprised by how much of the list they had never looked at closely.
The canopy or hood gives you the filter band, the front lip, the internal baffle faces, the upper shoulder that faces the ceiling void, and the exterior panels that everyone can see but nobody reaches. The duct gives you access panels, inspection hatches and the change-of-direction sections. The fan and its housing gives you the casing, the blade surfaces on fans that are built to be cleaned, and the mounting frame. The fixings and junctions give you flanged joints, rivet lines, seams, dampers and the flexible connectors between rigid sections. And the building interface gives you the wall and roof penetrations, the fire dampers, and the ceiling tiles or trunking that sit within reach of whatever you spray.
Anything on that list you cannot reach safely, cannot see, or cannot get a hose and lance to without a ladder, a scaffold or a roof access permit, is not a cleaning task yet. It is a separate job with its own method, its own fall-arrest decision and, in most buildings, its own permit. Establishing the reach line honestly at the start prevents the very common situation where an operator agrees to a job they physically cannot finish with the equipment in hand.
Second, type the soil, because restaurant soil is three different problems
Not every brown film on an extraction system behaves the same way, and treating it as one substance is the main reason cleaning jobs stall.
Fresh aerosol deposit is the soft, sticky layer that forms on the underside of a canopy within days of a deep clean. It is still mobile. Nearly any method with some heat and some dwell will move it, and the operator's real constraint here is how quickly it can be taken off before it turns into the next category.
Build-up that has thickened and darkened is deposit laid down over weeks that has picked up dust, char and burnt crumbs. It is softer at the core and harder at the surface. It responds to heat and dwell, but it needs a rinse and a lift afterwards; vapour alone will loosen it and leave it sitting there, which looks like a failure the following morning when it has run to the edges and dried grey.
Hard, baked-on layers on hot surfaces, around gas burners, on the tops of griddles and on the parts of a canopy nearest the flame, have been cooked onto the metal. They are polymerised. They are the soil most often described as "the steam did not work", when in fact the method chosen was never going to remove them and a mechanical or chemical step is the honest answer. An operator who can tell these three apart on sight can decide a method in seconds; an operator who cannot will keep re-passing and blaming the equipment.
Non-grease matter also lives in these systems: dust and lint in the duct, corrosion pitting on older galvanised sections, and insect activity in sections close to an outside air intake. Steam is a heat-and-dwell method, not a sweeping method, and it does not deal with dry particulate or with a section that has lost its metal.
Third, inspect the condition of the system before choosing a method
This is the step almost always skipped, and it is the one that decides whether the job ends cleanly.
Older galvanised or zinc sections that have been in service for years, especially in damp coastal sites, often show white corrosion product and a rough, lifted surface. Once that layer has gone, more of the metal underneath will be exposed. On painted exterior panels, check for scratches, previous repairs and paint that has already been stripped by harsh cleaning. On any section with a coating of unknown history, do not assume it will behave.
Check the joints. Mastic and sealant at flanged connections is frequently brittle or partly missing by the time a system is three or four years old, and once it has failed, driving water at that seam pushes it into the ceiling void. Check the insulation on lined duct sections, including the jacketing and the exposed edges at cut-outs, because insulation that has been wetted once rarely dries inside a duct. Check flexible connectors for tears and for the fabric's condition; check dampers and their linkages; check nameplates, direction arrows and safety markings, which are printed or etched and are easily destroyed.
Check anything electrical within reach: fan motors, their terminal boxes, cable glands, VSD enclosures, light fittings inside the canopy, sensors and their probe tubes. These items belong in an exclusion list, not in a cleaning pass, and the exclusion list has to be written down before the job, together with what will be used on those items instead.
Fourth, decide heat and dwell against water volume, row by row
The choice an operator is really making on an extraction system is not "strong versus gentle". It is how much heat and dwell a surface can accept, and how much liquid that part of the system can tolerate and drain away.
Upward-facing surfaces on a canopy and its filter band hold heat well and can take a longer dwell, and they are where a longer dwell pays. Vertical panels shed heat quickly, so dwell has to be maintained by working in small areas. Horizontal internal duct surfaces are the worst case, because whatever you release has nowhere to go but along the floor of the duct. Insulated and lined sections take up water. Sections with no fall and no drain point will simply hold it.
Two rules hold across all of these and are worth writing into the method. First, a low-moisture pass with dwell followed by a physical wipe or lift will remove far more than a wet pass that is wiped away, because the loosened soil has to be taken off the surface, not diluted on it. Second, the temperature that matters on the surface is what the surface actually receives, not a figure on a datasheet. Air gap, distance, angle, how long the lance stays in one place, and the fact that the metal itself is warm or cold all change what happens at the interface. Testing on a small marked patch, photographed as it stands before anything is applied, is the only reliable way to settle this on a specific system.
Fifth, plan the water and the run-off before the equipment moves
Extraction systems are the place where run-off planning stops being paperwork and becomes an actual constraint.
A canopy sits directly above the cooking line. Anything released from it falls onto equipment, food preparation surfaces, electrical fittings below the canopy, and the floor. It has to be contained at the point of release, with absorbent media and a collection tray under the work area, and the kitchen's drains have to be identified in advance so that the operator knows which drain each section discharges to and where the liquid stops.
Inside a duct, liquid pools. Every section needs a defined entry point, a defined exit, and a decision about who physically removes the released soil from the bottom of the duct, because it will not leave on its own. Where the duct passes through a ceiling void, a roof space or a corridor, wetting the structure on the outside of the duct is a building defect waiting to appear, so the containment has to be on both sides of the sheet.
The soil being removed is a grease-laden waste. Its route off site and into a waste stream is a compliance question for the building owner, not something the operator can leave open. Write it down alongside the water supply: the water point being used, the hose reach from that point to the highest work position, and the volume the room can actually accept without closing service.
Sixth, decide with the customer what is excluded, and name the replacement
A realistic extraction-system job has exclusions, and the operator who admits that in advance keeps the job. Exclusions that come up on almost every restaurant system include duct sections with no access panel and no inspection hatch, the fan motor and its electrics, lined or insulated sections with damaged jacketing, fire dampers and their trip mechanisms, printed markings and safety labels, older galvanised sections showing active corrosion, and any duct run inside a ceiling void or roof space that requires opening the building fabric.
Each exclusion should be recorded with the method that will be used there instead and what that trade costs the customer: a mechanical scrub, a chemical step, a panel cut and reinstated, or a section left as it is. An exclusion with no replacement is how a partially cleaned system gets reported as fully cleaned.
Seventh, run one bounded patch and let that settle the argument
Before committing to a whole canopy or a whole duct run, mark a small area with tape, photograph it from a low angle that reveals the texture of the deposit rather than shooting straight on, apply the chosen method, and record what changed. Then check the following day, after the kitchen has run a full service, because extraction soil reappears on day two if it was loosened but never actually removed.
Write the stop conditions before the first pass, not after the first surprise. Reasonable ones are water appearing beyond the containment, damage to a coating or a joint, the run-off route failing, or the deposit lifting but staying on the surface. Take the cycle time from the second run rather than the first, since the first run is where the operator learns where everything is.
What an operator should have in writing before agreeing to the job
Pull the seven preceding steps into one document: a surface list in the site's own words with reach marked per row; the soil type per row; a condition column flagging anything corroded, lined, sealed or marked; an exclusion column with a replacement method named; a containment and run-off plan naming the drain for each group; the exclusion list for electrical items; the access and permit position for anything high or inside the building fabric; and a named acceptance standard, which for extraction work combines what is visible, what is felt with a gloved hand, and the next-day check after service.
The honest answer to "is steam right for this system" is that it suits the softer deposit groups on surfaces that are reachable, sound and drainable, and fails on baked-on layers, dry particulate, damaged fabric and duct runs that cannot be entered. That judgement is made on the site, from the surface list, and from one bounded trial. If you want it made against a specific system, customized steam cleaning equipment can be discussed using your own surface list rather than a generic description. For the wider range of machines built for this kind of work, see industrial steam cleaning equipment. Where a fixed installation with defined water and power at the working position is the more likely arrangement in a permanent kitchen, Fixed Steam Cleaning Machine PowerDe HW02 is the listing to read; every published figure on it belongs to that machine, and the utility and consumption rows for your own duty have to be confirmed with the supplier against your surface list instead of read across from a page.
