TR19 Grease: designing kitchen extract that can actually be cleaned

What is TR19 Grease?

TR19 Grease is BESA's specification for managing the fire risk from grease in kitchen extract systems. It sets out how grease deposits should be measured, how often systems should be cleaned, and how a clean should be verified and recorded.

It matters because grease in ductwork is fuel. A fire that starts on the cooking line can get into the extract and travel through the building inside the duct. That is why insurers take it so seriously: many policies expect kitchen extract to be cleaned to TR19 Grease, and after a fire, the first thing an insurer asks for is the cleaning records.

Grease in a duct is fuel waiting for a spark. You can't see it, so it's easy to forget about. Until it isn't.

Why we don't clean ductwork

We design, fabricate and install kitchen ventilation. Duct cleaning is a specialist trade in its own right, with its own equipment, training and certification, and we leave it to the specialists.

When choosing a cleaning contractor, look for membership of BESA's Vent Hygiene Elite (VHE) scheme or equivalent, cleaning to TR19 Grease, and a proper post-clean report for every visit (see below). Be wary of the cheapest quote: a clean that only covers the parts you can see is not a TR19 clean.

Designing a system that can be cleaned

A duct that cannot be reached cannot be cleaned. Cleanability has to be designed in from day one:

• Grease-tight access panels at regular intervals along the duct, typically at 2 m centres
• Access at every change of direction, and either side of fans, attenuators and odour control equipment
• Panels large enough to clean through, not just to look through
• Fans with access to the impeller and casing
• Grease drainage at low points where appropriate
• Duct routes planned so panels remain reachable once the building is finished

If you can't get to it, you can't clean it. And if you can't clean it, you've got a fire risk hidden in your ceiling.

Stop the building closing in

The biggest problem we see is not missing panels, it is panels that cannot be reached. After the ductwork goes in, the building closes in around it: pipework, cable trays, suspended ceilings and boxing-in. Architects understandably prefer not to see access hatches, so panels end up buried.

At design stage, we ask architects and builders to allow access hatches in ceilings and boxing below every duct access panel, and to keep other services from running directly across the duct. It costs very little at the start and saves a lot of money and disruption later.

Details we avoid

Some details make cleaning difficult or impossible, so we avoid them in grease extract wherever we can:

• Flexible ductwork, which cannot be cleaned effectively and should never be used for grease extract
• Long horizontal runs with no access
• Tight or awkward bends with no access either side
• Equipment boxed in with no service space

Fans, attenuators and odour control

The cleaning regime covers the whole system, not just the duct. Fans, attenuators and odour control units all collect grease. Who looks after each part should be agreed up front: typically the duct cleaning contractor cleans the ductwork and fans, while odour control equipment such as ESPs and carbon filters is serviced by the specialist supplier on its own schedule. Grease that gets past the canopy filters will end up in all of them, which is one reason good grease removal at the canopy pays for itself.

How often should ductwork be cleaned?

It depends on how much grease the cooking produces and how many hours the kitchen runs. As a guide, EMAQ+ gives these intervals:

Source: EMAQ+ (2018). Your cleaning contractor will set intervals for your system based on measurement.

TR19 Grease goes further: it expects grease deposits to be measured, so cleaning is triggered by what is actually in the duct rather than by the calendar alone. In our experience, busy kitchens running long hours, takeaways with heavy frying and anywhere using solid fuel are the most likely to fall behind.

What neglected ductwork looks like

When we survey existing systems, we regularly find ductwork that has clearly not been properly cleaned for a long time: thick grease in the first sections after the canopy, grease pooling at low points and leaking from joints, and fan impellers so coated they are out of balance. Very often the canopy and the first metre of duct look spotless, and everything beyond it does not.

A shiny canopy tells you nothing about what's going on in the duct.

Canopy-only cleaning

Cleaning just the canopy, filters and the visible end of the duct is common, and it gives a false sense of security. The grease that matters most for fire spread is in the ductwork you cannot see. If your cleaning certificate does not cover the full system, from canopy to discharge, it is not telling you the whole story, and it may not satisfy your insurer.

Fire, insurance and paperwork

After a kitchen fire, the insurer will want to see evidence that the extract system was cleaned to TR19 Grease at the right frequency. An operator who cannot produce it may find the claim reduced or refused.

We have replaced fire-damaged systems for insurers, including at the George and Dragon in Clifton, where we rebuilt the system to the original design basis and current standards. Nobody wants to be in that position, and good records are what protect you if you are.

A proper post-clean report should include:

• A schematic of the system showing where it was accessed
• Before and after photographs
• Grease deposit measurements before and after cleaning
• A clear list of any areas that could not be accessed or cleaned, and why
• The recommended interval before the next clean

Read the "not accessible" section carefully. If parts of your system cannot be reached, that is a problem to fix, not a line to ignore.

How we help: planned works

Although we do not clean ductwork, we carry out planned works that make proper cleaning possible on any system, not just our own:

• Retrofitting access panels where there are too few, or where existing ones cannot be reached
• Fan replacements and upgrades
• Replacing damaged or leaking duct sections
• Upgrading grease filtration to reduce how much grease reaches the duct

These jobs usually come to us when a cleaning contractor reports areas they could not access, or after an insurer or landlord asks questions. Retrofitting access is usually straightforward and is often done out of hours to keep disruption down.

What we hand over

Every system we install comes with O&M documentation and maintenance charts, so the operator and their cleaning contractor know what is installed, where it is, and what needs looking after. We make sure the system is set up from day one for a cleaning contractor to do a full TR19 clean.

One piece of advice

Treat duct cleaning as fire safety, not housekeeping. Book it at the right frequency, use a proper specialist, and read the report.

Get it right from the off: design it so it can be cleaned, then make sure it actually gets cleaned.

This guide is general information to help you plan. It is not a substitute for design of a specific system. Standards are revised from time to time, so always check the current edition.