A commercial exhaust hood is the one item of kitchen equipment most owners never see from the inside. Fryer, griddle and charbroiler vapour leaves the cooking line, cools against the first surface it meets, and gives up a film of grease. The filters catch part of it; the rest travels into the plenum, the duct run, the fan wheel and the terminal on the roof, all of it out of sight from the kitchen floor. When a cleaning company sends you a quote, the difference between a job that protects the building and one that merely looks tidy comes down to method and machinery, so the questions in this guide matter more than the price line.
Why this is a grease problem, not a surface problem
Grease inside an extract system builds in layers. The first layer is soft and wipes away. After weeks of heavy service it oxidises into a hard, tacky coating that a scraper only partly removes and that ordinary detergent struggles to break down. Three consequences follow from that coating.
- Fire load. The hood plenum and the first metres of duct sit directly above open flame and hot oil. Grease accumulated there is fuel placed where ignition is most likely, and a fire that starts inside a duct travels the extract path into parts of the building kitchen staff never enter.
- Airflow and working conditions. Deposits narrow the passage and unbalance the fan. Extraction falls, smoke stops being captured at the source, make-up air draughts across the line, and the kitchen runs hotter. Cooks feel the change long before any inspector documents it.
- Hygiene and pests. Grease is food. A coated hood and duct support cockroaches, and a saturated filter can drip onto cooking equipment and prep surfaces below it.
Ten questions to ask before you book
1. What method do you use, and what machine comes with it?
Ask whether the crew works with scrapers and degreaser alone, or brings restaurant exhaust hood steam cleaning equipment. Scraping removes the loose layer. Superheated steam softens oxidised grease and lifts it off louvers, plenum walls and fan blades, which is where the buildup actually becomes a hazard. Ask to see the machine rather than the detergent label.
2. What temperature and pressure does your machine deliver at the nozzle?
Grease removal is largely a temperature story, so ask for the outlet steam temperature and the working vapour pressure. Equipment in the professional class, such as the PowerDe HW02 steam cleaner, is specified at a steam temperature around 160 °C and a working vapour pressure of 0.8 MPa from a 6 kW heater. A cold pressure washer will move loose soil; it will not clear baked-on grease at any useful speed.
3. Does the quote cover the whole extract path?
Scope gaps cause most disputes after the invoice. Go through the price point by point: hood interior and plenum, filters and baffles, fan housing and wheel, horizontal and vertical duct runs, fire dampers, and the roof terminal and bird screen. Then ask who opens and reseals access panels, and who replaces a gasket that has perished.
4. How do you protect the kitchen while working?
Ask how the area below the hood is sheeted, how grease-laden condensate is collected rather than washed into floor drains, whether the work happens after service or overnight, and what has to be removed from under the hood beforehand. A crew that has done this repeatedly will describe containment without being pressed on it.
5. How much water does the job use, and when can we cook again?
Steam consumes far less water than pressure washing, which matters in a basement restaurant or an upper-floor site with limited drainage and no convenient gully. Ask how long the cleaned surfaces stay wet and at what point cooking may restart, so the schedule is planned around your service rather than theirs.
6. What paperwork do I receive afterwards?
Ask for a dated report that lists the sections cleaned, the access points that were blocked or missing, defects found such as a warped damper, an unbalanced fan wheel or a distorted filter, and before-and-after photographs. Insurers, fire assessors and environmental health officers ask for records. A job with no paperwork is very hard to defend afterwards, and the report is also what tells you when the next clean is genuinely due.
7. Who does the work, and what training do they hold?
Ask whether the crew is directly employed or subcontracted, whether they are trained for roof work and for opening a fan housing, and who signs the job off. Subcontracted crews hired on the cheapest rate are where quality quietly disappears.
8. What insurance covers the work?
Ask for a certificate of public liability cover, and ask the direct question: what happens if a fan motor, a fire damper or a stainless steel panel is damaged during cleaning. The answer usually tells you how the company is run.
9. What interval do you recommend for our menu?
A charbroiler and fry line loads a duct far faster than a reheating or banquet kitchen, and a venue open until two in the morning accumulates grease differently from one that closes at ten. Ask what frequency they propose for your volume and your cooking methods, and what signs should shorten that interval. A firm that offers every restaurant the same annual contract is selling a schedule, not an assessment.
10. Is the equipment yours, and is it maintained?
Ask whether the plant is owned and serviced by the company, whether it needs a mains supply or runs on battery, and how quickly a breakdown is replaced. A hired or neglected machine cannot hold temperature under load, and temperature is the whole job.
If your group cleans in-house, judge the machine on these points
Hotel groups, central kitchens and stadium operators sometimes run their own overnight cleaning with commercial steam cleaning equipment rather than hiring a contractor every quarter. The shortlist then looks like this:
- Outlet temperature and pressure. Read the steam temperature and vapour pressure, not just the power consumption. Heat is what releases a hardened deposit.
- Dry and wet steam in one machine. Dry steam breaks the crust, wetter steam finishes the rinse, and switching between the two without changing equipment keeps a night shift moving.
- Tank material and capacity. The HW02 carries an 80-litre SUS304 stainless tank, which stands up to hot, greasy water far better than a mild-steel tank that rusts from the inside out.
- Supply requirements. A fixed 220 V, 6 kW unit needs a proper circuit, while hand-pushed and driving-style battery models reach corners and outdoor areas where no power is nearby.
- Protection features. Leakage, short-circuit, high-temperature, high-voltage and water-shortage protection are worth having on a wet, greasy floor where the machine is operated by kitchen staff rather than engineers.
- Mobility. Fixed, hand-pushed and driving-style formats suit different floor plans. A machine that is difficult to move into position is a machine that stops being used.
One caution before you specify a machine: confirm the intended duty with the supplier. PowerDe's cleaning range is documented for vehicle, facility and equipment cleaning work, so check kitchen hood duty, the water inlet arrangement and your local food-safety requirements before committing to a model for that use.
Three warning signs when you hire
- A price quoted over the phone by the metre of duct, with no inspection of the hood, the fan or the access points.
- A crew that arrives with drums of degreaser and scrapers and no heated-water or steam plant at all.
- A finished job with no report, no photographs and no record of what was found inside the duct.
Ask these questions and you will quickly separate contractors who clean an extract system from contractors who wipe the visible part of one. The same discipline applies if you buy the machine yourself: ask for the temperature, the pressure, the tank, the protection features and the duty the equipment is actually built for, and get all of it in writing before the order is placed.
