When a restaurant group or a central-kitchen operator plans a deep clean of the extraction system, the conversation usually starts and ends with the filters. Hood faces and filter cartridges are the parts a crew can reach, so they set the scope. What gets left out is the duct run behind the wall: horizontal sections, the vertical riser, the fan housing and the discharge termination. Those surfaces accumulate the same cooking aerosol as the hood, only harder to see and harder to reach. This article sets out how a procurement or facilities team can organise that work as a defined, checkable job, and where a commercial steam cleaning equipment solution fits into the workflow.
Start from an inventory, not from a schedule
A duct cleaning contract priced per kitchen is unreliable because the work content varies with duct geometry. Before any date is fixed, the site should produce a one-page inventory: every hood and the appliance line it serves, the access panels already fitted to the duct, the location of the fan (inline or roof-mounted), whether the duct passes through occupied space, and whether the run terminates at a roof, a wall or a shared shaft. Where a drawing does not exist, a walk with a phone camera and a tape measure will produce the same information. The inventory is what makes the scope comparable between two suppliers.
The inventory should also record what the site cannot open. Many ducts are sealed, insulated internally, or routed above ceilings that would have to be dismantled. If the run cannot be entered along its length, then "deep cleaning" means access-panel cleaning, brush-and-scrape from the open ends, and an honest statement of the remaining uncleaned length. A quotation that promises a clean duct without identifying access points is describing an aspiration, not a task.
Separate the job into four work packages
Splitting the job into packages prevents a single line-item price from hiding the parts nobody wants to touch. The four packages are: hood and filter bay, accessible duct interior, fan and motor housing, and discharge terminations plus the roof or wall penetration. Each package has its own labour content, its own waste stream and its own acceptance method, and each can be scheduled on a different frequency.
- Hood, plenum and filter bay: degreasing of internal faces, filter frames, the grease trough and the collection container.
- Accessible duct interior: scraping and removal of soft, workable deposits from the surfaces reachable through existing or newly fitted access panels.
- Fan housing and wheel: deposit on the blades and casing, plus a check on balance, bearing noise and belt condition where belts are fitted.
- Discharge termination, bird screen and the roof or wall penetration, including the condition of the flashing and the screen mesh.
Writing the packages separately in the purchase order also lets a site keep the cheap, frequent work monthly and put the duct interior and fan on a longer cycle. That is the pattern most kitchen operators end up with, because the deposit rate at the hood face is much higher than several metres downstream.
Decide the method per surface, and write the reasoning down
There is no single correct method for the whole system. A hand tool with a scraper and a degreasing agent is normal for a straight horizontal run that a person can reach. Robotic and whip-line methods exist for runs that cannot be entered. Chemical gel products are sold for softening hardened grease, and their suitability depends on the duct material, the joint type and how the residue will be rinsed and drained afterwards. What matters for procurement is that the chosen method is named in the quotation, together with how the loosened material will be captured.
Heat is the variable that changes labour content most on the accessible parts of the system, which is why kitchen operators ask about steam. For the hood faces, filter frames, troughs and the parts that come off and can be worked on a bench, high-temperature, high-pressure equipment softens cooked-on grease so that wiping replaces hard scraping. Our Fixed Steam Cleaning Machine PowerDe HW02 is rated at 160 degrees C steam temperature and 0.8 MPa steam pressure, with 6 kW of heating power, an 80 L SUS304 tank, dry and wet steam modes plus a vacuum function, and a 220 V supply. Those are machine-side figures taken from the product page; the temperature that actually reaches a grease film a metre from the nozzle depends on hose length, ambient loss and dwell time, and is something you should measure on your own parts during a trial.
The same product page lists the intended applications as vehicle exterior cleaning at fuelling and parking sites, interior vacuuming and disinfection, and engine-compartment cleaning. Duct interiors are not on that list, and we are not claiming they are. Before a steam unit is written into a duct-cleaning specification, the supplier should answer in writing whether the machine and its nozzle set are suitable for the specific surfaces involved, how long it can run continuously on one tank, and how water and loosened grease are to be contained on a kitchen line that has to reopen the next morning.
Sequence the job so the kitchen can reopen
On an operating site the schedule is a constraint, not a preference. A practical sequence runs from the dirtiest, most removable work first: strip and clean filters and the filter bay, then the hood interior and plenum, then the accessible duct, then the fan, then the discharge. Cleaning the hood before the duct means the crew is not working over a surface they have just finished. Where the kitchen must reopen the following morning, the fan and discharge packages are the ones to move to a later date, because they do not block the cooking line.
- Confirm the shutdown window with the kitchen manager in writing, including who locks off the fan and the lighting circuits.
- Protect the cooking line before any panel is opened: sheeting over appliances, and a defined route for soled parts and waste.
- Book the utilities the method needs before the crew arrives: power at the required supply, water, and a lawful route for the rinse water and grease waste.
- Inspect and photograph before the protection is removed and the kitchen is handed back, not afterwards.
Water is the item most often left unresolved. Steam-based work uses far less water than a pressure-wash approach, which is one reason it is attractive on a kitchen line that cannot be flooded, but the water that is used still carries grease and has to go somewhere. The product page for our machine records a tap-water inlet with a half-inch internal-tooth fitting; it does not state water consumption per hour or the permitted drain route, so both must be settled with the supplier and with whoever controls drainage consent on your site.
Fix the acceptance method before the order is placed
Acceptance for a duct you cannot enter has to be defined in terms you can actually observe. Four checks are workable on most sites: a wipe test with a light cloth along the accessible length of duct and inside the plenum; photograph of the same access point before and after, taken from the same position; a visual check through each access panel with a lamp, and where a camera is used, the camera images delivered with the report; and a functional check after restart, listening for a change in bearing noise and confirming the fan still moves air as it did before the work.
Do not accept a report that describes the unseen length as clean. The honest form records which sections were reached, which were not, and what remains. That record is what lets you plan the next cycle and is what a surveyor or insurer will ask for if the system is ever questioned. If your site keeps a cleaning register, the report should be filed against the asset number, not filed under a date.
Bring the routine work in-house, keep the access work outside
Most operators land on a split. The weekly and monthly work at the hood face, on filters, on the trough and on the appliance tops is done by the kitchen team, and this is where equipment bought outright pays for itself in labour rather than in any measurable cleaning claim. The work inside the duct, at the fan and on the roof stays with a contractor, because it needs access, lifting equipment and a waste route.
For the in-house half, the machine you specify should match the space. The fixed 220V steam cleaning machine is a trolley-mounted unit measuring 1,200 by 800 by 1,200 mm including handles, which needs a store, a 220 V supply and a water point. Where a back-of-house corridor or a tight service yard is the only route, a hand-pushed unit or a battery-powered mobile machine may be the practical choice; our hand-pushed HMW3 is listed at 4.5 kW heating power with a 50 L clean-water tank on a 48 V battery, and its published application is hospital beds and medical machinery rather than kitchen ducts, so treat it as a form factor to evaluate, not as a proven duct tool.
The product page lists protection functions for the fixed machine covering leakage, short circuit, high temperature, high voltage, water shortage and high-pressure explosion protection, without stating test values. Ask for the test records for each of those items at acceptance. The page does not publish steam output per minute, water use per hour, continuous run time, hose and wand length, weight, accessory list or noise level; those gaps belong in the request for quotation, and a supplier who answers them in writing is much easier to compare against a competitor's quotation.
What to put in the request for quotation
Send the same inventory to every supplier and ask the same questions, so the returns are comparable. The request should state the duct inventory and the access points, the shutdown window, the utilities available, and the four work packages, and then ask each bidder to answer the same short list: the method for each package, how deposits will be captured and removed from site, which sections will not be reached and why, the acceptance evidence to be delivered, and the price split package by package.
If you are buying equipment for the in-house half rather than hiring a contractor, the request is different: send the appliance and hood photographs, the store and corridor dimensions, the available supply, and the list of parts your team removes each week, and ask for the machine and nozzle configuration that matches that work. We build customised cleaning solutions to a site's stated duty, and our engineering team handles sample development and hardware testing, so a trial on your own hood parts is possible before any decision. The contact page is the way in; include the inventory and the questions you need answered, and we will respond with the specification gaps our product page leaves open.
