Why duct geometry and layout come first
A kitchen extract system usually starts above the line, runs through a ceiling void, makes one or two turns and exits at the roof. Every change of direction creates a place where grease settles, and every ceiling void creates a place that is hard to reach. Before anyone talks about cleaning method, the drawings and a physical inspection should answer three questions: how long is each duct run, where are the access panels, and does the duct have a slope that lets softened grease drain somewhere it can be collected?
Steam works by applying heat close to the deposit, letting the grease soften, and then wiping or flushing it away. That process depends on how far the lance can reach from an opening and how straight the duct is in that section. A long straight run with access panels every few metres can be treated from the inside. A duct that turns twice before the fan, with no panels on the horizontal section, usually means parts have to come down and be cleaned separately. If the site cannot provide safe access along the whole route, that limitation belongs in the specification before the machine is chosen.
The condition of the ductwork itself
Older galvanized ducting that is still mechanically sound tolerates heat and wiping. Ducts with lifted seams, failed sealant, corrosion at the joints, or insulation that has been exposed will not respond well to any wet cleaning method, because cleaning exposes the weakness rather than causing it. Inspect the joints and the interior lining first. Where the interior is coated or lined, ask the installer what the coating is and how it should be cleaned; some linings are not designed for high moisture.
Grease that has been left for years does not behave like fresh grease. Thick, oxidised deposits harden and no longer soften easily, so the deposit may need to be scraped or the section replaced, with steam used afterwards on the remaining film. A sensible programme treats the first clean as a survey: it shows what the build-up looks like and how quickly it returns, which then sets the realistic interval for the next visit.
Equipment ratings and site services
A machine that produces steam needs three things on site: electrical supply, water, and somewhere for the run-off to go. The supply matters because a small portable unit plugged into a distant socket will lose voltage at the cable and the operator will compensate by slowing down. Confirm the available voltage and the location of distribution boards before specifying a fixed or trolley unit. Our fixed steam cleaning machine page lists the electrical and water connections of the HW02, so the site conditions can be checked against the machine rather than assumed.
Water quality affects the machine more than most operators expect. The HW02 takes a tap-water inlet, but in areas with very hard supply the scale that forms inside a heater is a maintenance problem for whoever owns the machine. A softened or filtered feed lengthens service intervals. Run-off from the duct is grease and hot water; a drain route has to exist near the work. These are not minor details. They decide whether a duct clean is a planned task or a job that gets postponed.
How the kitchen operates around the work
A restaurant kitchen does not stop. Duct cleaning creates a wet floor, a smell of hot grease, and equipment moved out of the way, so the schedule is a site condition as much as the duct is. Most operators clean outside service hours, section by section, so that the line can reopen. That means the cleaning method has to be reasonably quick and produce limited water on the floor, which is one of the practical reasons commercial kitchen steam cleaning is chosen over methods that flood a surface: the heat does most of the work and the operator controls how much moisture is applied.
Ventilation during the work matters too. With the fan off, the kitchen fills with vapour and steam condenses on cold surfaces. A temporary extract fan, doors held open, and a plan for the extraction system being out of service for a defined window are all part of a normal brief. Anyone specifying steam cleaning for a live kitchen should expect to describe these arrangements in the method statement, not discover them on the day.
Cooking method and the type of deposit
Two kitchens of identical size can produce completely different deposits. A site frying continuously gives finer aerosol that travels further along the duct and reaches the fan and the vertical riser. A site doing mostly grilling produces heavier droplets that settle near the canopy. The deposit that travels farthest is the one that ends up in the hardest place to clean. For a kitchen exhaust duct grease cleaning programme, the cooking method should set the inspection points and the frequency, not just the number of covers in the dining room.
Filter maintenance upstream changes what reaches the duct. Canopy filters that are cleaned or replaced on a schedule, and a canopy lip that is wiped daily, keep most of the grease in the canopy where it is easy to reach. A kitchen that lets filters clog pushes grease into the ductwork and turns a routine weekly task into an occasional heavy one.
Access, safety and what has to be isolated
Work above a kitchen line needs a platform or a scaffold deck, not a ladder balanced on a wet floor. Roof access, ladders to the fan, and the route for carrying equipment through a customer's dining area all form part of the site conditions. Electrical isolation of the fan, and a lock-off that nobody removes during the work, is a basic requirement. Hot surfaces, steam at the lance, and hot run-off mean the operator needs gloves and eye protection, and the kitchen team needs to be told when the area is hot and wet.
Fire-related requirements vary by location and by the client's insurer. Rather than assume a frequency or a standard, check what the property's own compliance documents ask for and what evidence they expect after the work. Cleaning reports, photographs before and after, and a record of access panels opened are what most clients keep.
Weather, temperature and timing
Ambient temperature changes how steam behaves. A cold duct in winter absorbs heat from the steam quickly, so the lance has to move more slowly and the operator sees condensation on the sheet metal. Warm-up time for the machine, and for the duct surface, is real working time. In summer the same job runs faster. A programme that cleans in one season should not assume the same duration in another, and a schedule built around a quiet month in a cold climate carries a time penalty that should be priced.
Machine choice follows from the survey
Once the duct length, access, supply, water and discharge are known, the machine decision becomes simple. A fixed unit sited close to the work gives continuous steam and a larger water tank, which suits a full duct route. A mobile unit on wheels suits sites where the equipment has to travel through a building, up steps, or between floors. PowerDe builds both arrangements; the PowerDe cleaning equipment range covers fixed, hand-pushed and driven machines, each with different tank capacity, heating power and steam output. If your site has unusual constraints, send us the duct layout and the available services and we will match the machine to the job instead of asking you to fit the job to a catalogue model.
In short: duct layout and access decide whether steam can reach the deposit; the condition of the ductwork decides whether it should; the site services decide what machine can run there; and the cooking method decides how often the whole thing has to be repeated. Get those four points documented before the quotation and the cleaning programme holds up.
