Kitchen Exhaust Duct Cleaning: When to Do It and What TR19 Requires

For this reason, having a kitchen exhaust duct cleaning schedule isn’t just a housekeeping nicety. In the UK, the TR19® specification is the industry-standard benchmark expected by insurers and environmental health officers (EHOs). Ignore it, and you’re not just risking a telling-off from the EHO, you’re risking a fire, a voided insurance policy, and a hygiene rating that’d make your nan cover her eyes. This blog covers exactly what TR19 requires and when your ductwork needs to be cleaned.

What is the TR19 standard and why does it matter?

TR19® is the industry standard set by the Building Engineering Services Association (BESA) that sets out the requirements for the internal cleanliness of ventilation systems. For commercial kitchens specifically, the relevant document is TR19® Grease, a standalone specification focused entirely on kitchen extract systems, covering fire safety and hygiene in one go.

The crux of it comes down to grease that builds up inside your ductwork, which is so highly flammable that it’s essentially fuel sitting in your ceiling. TR19® Grease sets a clear threshold for kitchen safety: ductwork must be cleaned when grease deposits exceed an average of 200 microns. To put that in perspective, that’s roughly half the thickness of a standard paper business card. Not much, is it?

What counts as a kitchen extract system?

The extract system covers the full path that air travels from your cooking equipment upwards and outwards, including the canopy filters, the ductwork, the fan unit and the discharge point. TR19 applies to all of it, not just the bit you can see when you wipe down the canopy. Grease travels through the whole system; the further it gets, the harder it is to shift – and the greater the fire risk. This is why TR19 kitchen requirements exist as a specific framework, rather than general ventilation guidance.

The severe risks of ignoring TR19 compliance

Non-compliance with TR19 carries three serious consequences, and none of them is the sort of thing you want to find out about after the fact.

1. Fire: Grease accumulation inside ductwork is one of the leading causes of commercial kitchen fires. Once ignited, a grease fire inside a duct system travels fast and is very difficult to extinguish. Your canopy suppression system won’t reach it. Only the fire service will.
2. Voided insurance: If a fire does break out and you can’t produce a valid TR19-compliant certificate showing your kitchen extract cleaning was up to date, your insurer is very likely to decline the claim. No certificate, no payout.
3. Hygiene ratings and EHO inspections: Poor extraction leads to poor indoor air quality, which affects your staff’s health and comfort during service. It also affects grease migration onto surfaces, into food preparation areas, and into the air your customers breathe. EHOs do look at the condition of extract systems. A blocked or filthy duct can contribute directly to a lower Food Standards Agency (FSA) food hygiene rating, and that score is public.

There’s also the matter of your staff. Working in a poorly ventilated kitchen with compromised extraction is an occupational health issue.

When to do it: recommended cleaning frequencies

How often your kitchen exhaust ducts need cleaning depends on how hard your kitchen works. TR19® Grease sets out minimum extraction duct inspection and cleaning frequencies based on usage levels:

1. Heavy use – 12 to 16 hours per day: Clean every 3 months. This covers 24-hour operations, fast-food kitchens and high-volume frying operations.
2. Moderate use – 6 to 12 hours per day: Clean every 6 months. Standard restaurants, pub kitchens and school canteens typically fall here.
3. Light use – 2 to 6 hours per day: Clean every 12 months. Small cafés, light-use hospital catering and occasional-use facilities.

These are the minimum cleaning schedule requirements under TR19, so they’re not targets to aim for, but floors not to fall below.

When to act sooner

There are situations where you shouldn’t wait for the next scheduled cleaning, regardless of where you are in the cycle:

• Excessive smoke or persistent odours during or after service
• Noticeable reduction in airflow or extraction performance
• A mean average deposit thickness test (DTT) reading above 200 microns across the system
• A single DTT reading exceeding 500 microns at any point in the system (requiring immediate spot cleaning)
• Following any kitchen fire, however minor

If your kitchen is smelling like something’s taken up residence in the ducts, or your chefs are complaining about smoke hanging around, that’s your extract system waving a white flag.

What does TR19 require? The cleaning process explained

A TR19-compliant clean goes a good deal further than wiping down the filters and calling it done. Here’s what a proper kitchen exhaust duct grease removal process actually involves.

Access panels

TR19 requires that ductwork has sufficient, correctly sized access panels installed at regular intervals throughout the system. Without them, a thorough clean simply isn’t possible. If your ductwork doesn’t have adequate access, a compliant contractor will flag this. In some cases, panels will need to be fitted before cleaning can proceed.

The cleaning process itself

A full TR19 duct system clean covers the entire extract system in four stages:

1. Manual wiping to remove surface deposits
2. Hand-scraping of heavy grease build-up
3. Application of chemical degreasers to dissolve residual grease
4. Mechanical brushing and vacuuming to clear the ductwork thoroughly

Post-clean verification and certification

This is where TR19 gets firm. After the cleaning, you must receive:

• A detailed written report of the work carried out.
• Before-and-after photographic evidence.
• Deposit Thickness Test (DTT) or Wet Film Thickness Test (WFTT) measurements confirming grease levels are below 50 microns across all tested surfaces.
• A TR19-compliant hygiene certificate.

That certificate is your proof of compliance. It’s what you show your insurer and your EHO. Keep it somewhere you can put your hands on it quickly.

Who cleans commercial kitchen exhaust ducts?

Because of the legal, insurance and technical requirements involved, this isn’t a job for your general cleaning team or a willing pair of hands with a pressure washer. TR19 duct cleaning requires specialist, certified contractors.

Competent technicians should be trained to BESA-recognised standards and should be able to demonstrate their credentials before they start work.

That’s where KDC Food Hygiene Ltd comes in. We provide professional TR19-compliant deep cleans for commercial kitchens across London and beyond, supplying the full certification package you need to satisfy your EHO, your insurer, and your own peace of mind. 

How we can help

Regular duct cleaning is how you prevent fires, protect your team, keep your food hygiene rating intact and stay on the right side of your insurance policy.

Don’t wait for a failed inspection – or worse. Get in touch with KDC Food Hygiene Ltd today to book a full duct inspection and TR19-certified clean. Give us a call. We’ll bring the elbow grease, you keep cooking.

FAQs

How often does a commercial kitchen exhaust duct need cleaning?

It depends on how many hours a day your kitchen runs. Heavy-use kitchens (12 to 16 hours) need cleaning every 3 months, moderate-use (6 to 12 hours) every 6 months, and light-use (2 to 6 hours) once a year. These are the minimum frequencies set out under TR19.

What happens if grease deposits exceed 200 microns?

That’s your trigger for an immediate clean, regardless of when the last one was carried out. At 200 microns (roughly half the thickness of a paper business card) grease inside your ductwork becomes a serious fire risk, and TR19 requires action.

Will my insurer pay out if I haven’t got a TR19 certificate?

Almost certainly not. If a fire breaks out and you can’t produce a valid TR19-compliant certificate, most commercial kitchen insurers will decline the claim. Keeping your certification up to date is necessary for protecting your business.

Can my regular cleaning staff carry out a TR19 duct clean?

No. A TR19-compliant clean requires specialist, certified contractors trained to BESA-recognised standards. General cleaning staff aren’t equipped for it, and a clean carried out without proper certification won’t satisfy your insurer or an EHO inspection.

What do I get after a TR19-compliant clean?

You should receive a full written report, before-and-after photographs, Deposit Thickness Test (DTT) readings and a TR19-compliant hygiene certificate. If a contractor can’t provide all of that, they’re not delivering a compliant clean.