Phoenix Journal · Ductwork
Mould thrives on the warmth, moisture and grease inside a busy kitchen extract system, and the spores it releases travel deep into the lungs. Here is how that risk builds, and how a proper deep clean shuts it down.
Air quality & health
Mould does not need a neglected building to take hold - it needs warmth, moisture and something to feed on, and a busy commercial kitchen offers all three in abundance.
Every grease-laden extract run, every washed-down wall, every warm cupboard behind a range gives fungal spores a foothold. The spores themselves are microscopic - fine enough to stay airborne for hours and small enough to travel deep into the lungs when someone breathes them in. For most healthy adults an occasional lungful is shrugged off, but in a kitchen where staff spend eight or ten hours a shift, day after day, the picture changes. Repeated exposure is what turns a nuisance smell into a respiratory problem.
This matters more now than it did even a couple of years ago. The UK Health Security Agency’s 2024 guidance, “Understanding and addressing the health risks of damp and mould in the home”, reset the national conversation by telling landlords and local authorities to treat mould as a health hazard rather than a lifestyle failing. The same shift in thinking runs straight through workplace duty of care. If you run or maintain a catering extraction system, the condition of that ductwork is part of the air your team breathes.
Understanding the route from a damp corner to a wheeze on the night shift makes the fix obvious. Work through it in order and you close off each stage before it becomes a health issue.
Occupational asthma is one of the most common work-related lung conditions in the UK, and catering sits squarely among the trades where it shows up. Flour, cleaning chemicals and cooking fumes all play a part, but mould belongs on that list too. When spores are inhaled repeatedly they can trigger or worsen allergic airway disease - the familiar cough, wheeze and breathlessness - and in sensitised people they contribute to more serious conditions such as allergic bronchopulmonary aspergillosis and severe asthma with fungal sensitisation. There is also extrinsic allergic alveolitis, sometimes called hypersensitivity pneumonitis, an inflammation of the tiny air sacs deep in the lung driven by an allergic response to inhaled mould and organic dust.
The scale is not trivial. Analysis of English housing linked damp and mould to roughly 5,000 cases of asthma and around 8,500 lower respiratory infections in a single year, and while those figures describe homes, the biology is identical wherever spores meet lungs. A kitchen actually stacks the odds higher: the warmth, the humidity and the grease give mould a richer food supply than most bedrooms ever will. Charities such as Asthma + Lung UK and Allergy UK have been consistent on the point - the people most at risk are the young, the older, and anyone with an existing respiratory or immune condition, and a professional kitchen employs plenty of all three.
The legal weather has changed as well. Awaab’s Law, which came into force for the social rented sector on 27 October 2025, was named after a two-year-old who died from a respiratory condition caused by prolonged exposure to damp and mould. It sets hard deadlines - significant mould hazards investigated within ten working days and made safe within five - and while it applies to housing rather than catering, it signals the direction of travel. Regulators and the public increasingly treat avoidable mould exposure as negligence. For an employer, the parallel duty already exists under the Control of Substances Hazardous to Health Regulations and the general requirement to provide a safe workplace. HSE’s catering guidance is equally plain that extraction must be cleaned and maintained so it keeps working - a blocked, mould-friendly system fails that test on air quality as surely as it does on fire risk.
The reassuring part is that mould in an extraction system is entirely preventable. It grows because grease and moisture are allowed to sit undisturbed, and it disappears when the food source and the damp are removed and the airflow is restored. None of that requires guesswork - it requires access, a proper deep clean and a schedule matched to how hard the kitchen works. Do that, and the air your team breathes on a double shift stops being a slow, invisible health cost and goes back to being just air.
Think of it the way you already think about fire risk. You would never leave grease to build to a hazard, and spore load deserves the same steady attention. A kitchen that is cleaned to standard protects the lungs of everyone in it, satisfies your duty of care and keeps you comfortably on the right side of a tightening regulatory mood.
Questions
Yes. Mould inside grease-laden ductwork releases microscopic spores that stay airborne and can be inhaled deep into the lungs. Repeated exposure across long shifts can trigger or worsen allergic airway disease such as asthma, and in sensitised people it contributes to more serious conditions like aspergillosis. Staff with existing respiratory or immune conditions are most at risk.
The clearest signs are a persistent musty or earthy smell when the system runs, visible dark growth around canopies, filters or access panels, and grease-heavy dust. Because the worst deposits usually sit above the ceiling line where nobody looks, the only reliable way to be sure is to open access points along the full extract run and inspect it properly, rather than judging the system from the canopy alone.
It will, provided two things happen together. You have to remove the source of moisture - a leak, condensation or trapped humidity - and strip out the grease and organic film that feed the mould back to clean metal. Wiping the surface alone spreads spores and the growth returns within weeks, so a thorough deep clean of the whole accessible system, on a schedule matched to how hard the kitchen runs, is what keeps it clear.
Phoenix Duct Clean · by the numbers
Phoenix surveys and cleans kitchen and building ductwork to the TR19 standard - measured, cleaned and certificated, UK-wide.