A commercial exhaust hood is the one appliance that works every hour the line is open and gets cleaned only when someone can no longer ignore it. Grease does not build up evenly. The canopy face looks bad within a week, the filters thicken over a month, and the plenum and fan housing quietly collect the heaviest deposit because nobody sees them. That is why a deep clean organized as one long weekend scrub usually goes wrong: the crew runs out of time before it reaches the parts that matter most.
Organizing the job properly means deciding four things in advance: what gets inspected, how often each part is done, who is responsible for each section, and what evidence you keep afterwards.
Inspect the system in the order the air travels
Walk the extract line with a torch before booking anything. Go in the order the air moves: canopy interior, filters, plenum, fan housing, duct access panels, grease cups and collectors, and finally the exterior discharge, rain flap and bird screen. At each point, note three things: how bad it is, whether the panel opens with hand tools, and whether the surface is actually reachable with your equipment.
Two facts change the plan more than anything else: what you cook and for how long. Charbroiling and open grilling lay down thick, sticky grease that shifts slowly even under a good degreaser. Steaming, boiling and light frying leave a thinner film that still hardens into a crust when it mixes with dust. Write down the appliance mix and the daily cooking hours for each hood. That record, not the calendar on the wall, is what sets a realistic interval.
Set the interval from cooking volume, not from habit
Fire codes and insurer requirements for commercial kitchens generally follow one logic: the higher the cooking volume and the greasier the menu, the shorter the interval. Frequencies commonly referenced in NFPA 96-style guidance range from roughly monthly for very high volume charbroiling operations, through quarterly for busy grill lines, to semi-annual for moderate cooking and annual for low volume, seasonal use. Those bands are a starting point only. Confirm what your local fire authority and your insurer actually require, because the wording differs by jurisdiction and by policy.
Whatever the schedule says, treat these as signs the work is overdue now:
- grease visible at an access panel, duct joint or fan housing seam;
- a baffle filter that no longer drains freely into the trough;
- a change in fan noise or vibration, or weaker capture over the grill;
- smoke drifting back into the kitchen instead of being pulled into the hood.
Split the job into four zones
Half-finished cleans happen because the job is defined as "the hood". Break it into zones that each have an owner and a defined stopping point:
- Canopy and filters. Baffle filters come off and soak hot, then wipe the canopy panels from the clean end toward the dirty end. Disposable mesh filters are replaced, not scrubbed.
- Plenum and fan housing. The part crews skip. Grease sitting in the plenum softens the next time the line fires up and drips back onto the cooking equipment.
- Duct runs. Clean what the existing access panels allow, and record honestly which sections cannot be reached without cutting new openings.
- Extractor fan and discharge. Blades, housing, rain flap and bird screen at the roof termination.
Work from the top down, and inside the ducts work toward the discharge point, so run-off never lands on a surface you have already finished.
Heat does the work that scrubbing cannot
Cold water on grease just moves it around. Grease only becomes mobile once it is hot, so the practical order is heat first, then dwell time, then light mechanical action. A filter that has sat in a hot soak for fifteen minutes needs a fraction of the effort of one scrubbed straight away with cold detergent. Crews that skip the dwell spend far longer on the scrub and still leave film behind.
The fixed parts of the system are where commercial range hood grease removal work usually stalls, because the plenum walls and fan housing cannot be taken away to a sink. Here, hot water and steam do the job a mop cannot reach. For kitchens handling a heavy grease load, a planned central kitchen degreasing routine built on high-temperature water shortens the scraping stage considerably and reduces how much detergent goes down the drain.
When you compare equipment, read the published parameters rather than the marketing line. The PowerDe HW02 fixed steam cleaning machine, for example, is listed at 6 kW heating power, 160 °C steam temperature, 0.8 MPa vapor pressure, an 80 liter SUS304 tank, 220 V supply and switchable dry or wet steam. Those figures describe a stationary unit that sits beside the kitchen or in a plant room, not something you carry up a staircase, which is exactly what a fixed extract system needs. One caution: the product listing itself describes vehicle, garage and equipment cleaning rather than kitchen ductwork, so confirm the intended application, water supply and drainage arrangement with the manufacturer before specifying any machine for a kitchen extract system.
The safety steps that decide whether service can restart
- Isolate the appliances under the hood. Anything touching gas supply or wiring needs a competent person, not the cleaning crew.
- Protect and dry the floor as you go. A wet kitchen floor is the quickest way to turn a hood clean into an injury claim that shuts the kitchen down.
- Gloves and eye protection, data sheet to hand for whatever degreaser is in the bucket, and never mix two products.
- Contain the run-off. Greasy water poured into a floor drain is how kitchens end up with blocked waste lines; route it to a drain that can take it, or collect and dispose of it properly.
- Leave the section out of service until it is dry and extraction has been checked at the grill line.
Keep records anyone can pick up
One page per clean is enough: date, zone, method used, who did it, a before and after photograph of the dirtiest access panel, and the next due date. Photograph the same panel every time, and the series tells you whether your interval is right without anyone guessing. Then split the work deliberately: filters, canopy panels and the surfaces directly under the hood usually stay with the in-house team on a short cycle, while the fan housing and long duct runs go to a contractor on the longer cycle.
What to do this week
- Open every access panel and photograph the worst one.
- Write down the appliance mix and daily cooking hours for each hood.
- Soak the filters tonight, and replace any that have stopped draining.
- Book the fan and duct stages as a dated job in the rota, not as a reaction to a complaint.
- Ask your insurer what cleaning frequency the policy actually requires, and put the answer on the same page as the log.
A hood gets deep-cleaned properly when every part of the extract line has an owner, an interval and a photograph that proves the work happened. Equipment matters, but it comes second: walk your own ductwork first, decide which zones you can actually reach, and then choose a machine whose published parameters fit those zones.
