Why the duct is the dangerous part
Grease leaves the cooking surface as vapour. The filters catch some of it. What gets past them travels up the duct, cools, and condenses on the inside walls. Over months that builds into a layer of solid grease along the entire run, thickest at bends and on horizontal sections where airflow slows.
That layer is fuel. When a flare-up on the cooktop sends flame into the canopy, a clean duct carries hot air. A greased duct carries fire, and it carries it to the roof, through the ceiling space, past whatever else is up there. This is the mechanism behind most serious commercial kitchen fires, and it happens above the ceiling where nobody has looked in years.
Access is everything
You cannot clean what you cannot reach. Duct cleaning depends entirely on access panels, and a great many Sunshine Coast kitchens, particularly older fitouts and those where a duct was extended during a renovation, have long runs with no panels at all.
Where panels exist, each one is opened and the duct is scraped and degreased in both directions as far as can be reached. Where they do not, there are two honest options: cut new panels in, which is a separate job with its own cost, or record the unreachable section as a defect on the report.
What should never happen is a report that says the duct was cleaned when half of it was never opened. If a contractor's report does not mention access at all, ask.
What gets done
- Locate every panel. Ceiling access, roof space, plant room, external wall.
- Open and inspect. Build-up depth is checked and photographed before anything is touched.
- Scrape. Heavy build-up is physically removed first. Chemical alone does not shift a centimetre of set grease.
- Degrease. Hot alkaline degreaser applied, allowed to dwell, agitated, rinsed. Wastewater contained.
- Bends and horizontals. Given extra attention because they hold the most.
- Panels resealed. With a fire-rated seal where required, so the duct stays sealed under fire conditions.
- Photograph and report. Every section, before and after, with any unreachable sections listed.
How much is in there
People are consistently surprised. A duct that has never been opened above a busy kitchen can carry grease in kilograms rather than grams, layered like tree rings from every year of trading. On the Sunshine Coast, coastal humidity keeps that grease soft and mobile longer, so it flows further along horizontal runs before it sets, and it holds salt against galvanised steel, which corrodes the duct from the inside.
That corrosion is worth knowing about. A duct that has rusted through is a duct that leaks grease into the ceiling space, which is a worse fire risk than the duct itself.
Interval
Ductwork loads more slowly than the canopy but with far higher consequence. Annual duct cleaning is a common baseline, with high output kitchens on six monthly cycles. The standard ties intervals to usage rather than fixing one number, so a charcoal grill and a sandwich bar are not on the same schedule.
If the duct has never been done and the kitchen has been trading for years, treat the first clean as urgent regardless of schedule.
Check the current requirements before you rely on this
This page describes kitchen exhaust cleaning standards and practice as they stood in September 2026. Standards are revised, and what applies to a particular venue depends on its equipment, its building, its council and its insurer.
AS 1851 is published by Standards Australia at standards.org.au. Food premises requirements in Queensland sit under the Food Act 2006 and are administered by your council, Sunshine Coast Council at sunshinecoast.qld.gov.au or Noosa Council at noosa.qld.gov.au. Building fire safety is administered by Queensland Fire Department. Where anything here differs from those sources, they are right and we are not.
We are not fire engineers, council officers or insurers. For what applies to your venue, speak to your council's environmental health team, your insurer or a fire safety adviser.