Phoenix Journal · Ductwork
The dirtiest, most fire-critical ductwork in a commercial kitchen often sits where a person cannot easily stand, turn or get out - which makes it a confined space in law, and changes how the clean must be planned.
Confined-space duct cleaning
Some of the dirtiest, most fire-critical ductwork in a commercial kitchen sits in exactly the places a person cannot easily stand up, turn around or get out of in a hurry.
Long horizontal runs above a ceiling void, vertical risers between floors, plant enclosures on a roof - these are where grease gathers and where cleaning is hardest to do well. They are also, in law, often confined spaces. That changes how the work must be planned, who is allowed to do it and what has to be in place before anyone opens a panel. Getting this right is not box-ticking. It is the difference between a clean, compliant system and a genuinely dangerous job carried out without the controls that keep people alive.
Under the Confined Spaces Regulations 1997, a confined space is not simply somewhere tight. It is a place that is substantially enclosed and where there is a reasonably foreseeable specified risk. Both parts of that test have to be met. The regulations list five specified risks: fire or explosion; loss of consciousness from gases, fumes, vapours or oxygen deficiency; loss of consciousness from raised body temperature; drowning from rising liquid; and asphyxiation or entrapment from free-flowing solids.
Grease-laden kitchen extract ductwork ticks more of those boxes than people expect. The deposits themselves are combustible, so fire and explosion are foreseeable. Cleaning chemicals and solvents give off vapours in an enclosed run with little natural ventilation. Larger plant enclosures and risers can hold a poor atmosphere long after the extract fan is off. So the moment a duct is enclosed enough that entry means committing your body to it, and any one of those risks is present, you are working to confined-space rules whether the ductwork looks dramatic or not.
Kitchen extract is a fire risk first and a hygiene issue second. Around 70% of fires in commercial kitchens are linked to grease build-up in the extract system, which is why the BESA guidance most operators know as TR19 - now split into TR19 Grease for fire-risk extract and TR19 Air for supply and general ventilation - matters so much. Cleaning to a recognised standard is how you demonstrate you are meeting duties under the Regulatory Reform (Fire Safety) Order 2005 and the Health & Safety at Work etc. Act 1974, and it is increasingly what insurers ask to see.
The catch is that thorough grease removal and safe entry pull in the same direction only if the system was designed for it. TR19 expects access panels along the ductwork at regular intervals, roughly every 2 metres and at every bend and change of direction, so that internal surfaces can actually be reached and cleaned to bare metal. Where those panels exist, much of the run can be cleaned from outside by hand and by machine without anyone entering at all - which is always the safest outcome. Where they do not, cleaners are tempted to climb in, and that is where an ordinary clean quietly becomes a confined-space entry that nobody planned for.
The safe system of work
The legal hierarchy is blunt and it is worth stating plainly. First, avoid entry to the confined space altogether if the work can reasonably be done another way. Only if entry is genuinely unavoidable do you move to a safe system of work, and even then you must have suitable emergency and rescue arrangements in place before the job starts. For duct cleaning that order of priority shapes everything: we design the clean around not entering wherever the ductwork and its access panels allow, and we treat entry as the exception that carries its own controls.
Where entry cannot be avoided, the controls are specific. A risk assessment identifies the hazards in that particular run. The atmosphere is tested and monitored - oxygen first, then flammable gases and vapours, then anything toxic - because a run that has held solvent or been isolated can read very differently from the room outside. Mechanical ventilation clears vapours before and during the work. A permit-to-work records who is entering, for how long and under what conditions, and a trained attendant stays outside in constant contact with the person inside.
Rescue is the part that gets underestimated. Regulation 5 requires suitable and sufficient arrangements to recover someone in an emergency, planned before work begins and matched to the actual space. HSE guidance in the ACOP L101, Safe Work in Confined Spaces, is explicit that you should not rely on the emergency services to be your rescue plan - they may not arrive quickly enough, and they may not be equipped for that specific space. That means the right tripod, harness and recovery kit on site, and people trained to use it, before the first panel comes off.
A competent contractor makes the confined-space question part of the survey, not an afterthought on the morning of the clean. Before quoting, the system is walked and mapped: where the long enclosed runs are, where risers pass between floors, where plant sits in an enclosure, and crucially where access panels already exist and where they are missing. That survey decides how much of the work can be done without entry and where entry controls will be needed, so there are no surprises and no shortcuts improvised on site. If your ducts were never designed with cleaning in mind, the fix is often to fit compliant access panels so future cleans can be done from outside - the same thinking that goes into planning safe, accessible duct routing from the start rather than retrofitting it under pressure.
The clean itself should leave evidence, not just a shiny inspection hatch. TR19 Grease is measured, so a proper job records grease-deposit thickness before and after, with photographs at accessible points along the run and a post-clean report and certificate stating what was cleaned, what was not reachable and why, and when the system is next due. Verification to bare metal at the points that can be reached is the standard to hold your contractor to. Cleaning frequency follows usage: heavy use of twelve to sixteen hours a day points to roughly quarterly cleaning, moderate use to around every six months, and light use to annually.
The runs that fail this test are almost always the confined, hard-to-reach ones - out of sight above a ceiling, behind plant, easy to skip and easy to sign off on trust. That is exactly the pattern an honest inspection exposes, as in this audit that uncovered years of missed cleaning hiding in the parts of a system nobody could see. If you cannot get eyes or a report on the whole run, assume the worst part is the part being left undone.
Questions
It can be, and often is. The Confined Spaces Regulations 1997 apply a two-part test: the space must be substantially enclosed and carry a reasonably foreseeable specified risk such as fire, explosion or loss of consciousness from vapours or oxygen deficiency. Grease-laden extract runs, risers and plant enclosures frequently meet both parts, so entry to them must be treated as confined-space work with the controls that go with it.
Not usually, and avoiding entry is the legally preferred outcome. Where TR19-compliant access panels are fitted along the run - roughly every 2 metres and at every bend - most surfaces can be reached and cleaned to bare metal by hand and machine from outside. Entry only becomes necessary when access is inadequate, and where that happens it needs a permit, atmospheric monitoring, ventilation, an attendant and a rescue plan before work starts.
TR19 - now published as TR19 Grease for fire-risk extract systems - is BESA guidance that sets how kitchen extract ductwork should be cleaned and verified. It expects cleaning to bare metal at accessible points, measurement of grease-deposit thickness before and after, and a post-clean report and certificate. Meeting it helps demonstrate compliance with the Regulatory Reform (Fire Safety) Order 2005 and is commonly required by insurers.
Regulation 5 of the Confined Spaces Regulations requires suitable and sufficient rescue arrangements planned before work begins and matched to the specific space. HSE guidance in ACOP L101 is explicit that employers should not depend on the emergency services alone, because they may not arrive quickly enough or be equipped for that particular space. In practice that means trained people and recovery equipment such as a tripod and harness on site from the outset.
Phoenix Duct Clean · by the numbers
Phoenix surveys and cleans kitchen and building ductwork to the TR19 standard - measured, cleaned and certificated, UK-wide.