Guide from the team
BESA publishes two related documents, TR19 and TR19 Grease, and many buildings need both. Here is how to work out which applies to yours.
Published 8 September 2026
Ask three facilities managers what “a TR19 clean” means and you may get three different answers. That is because BESA (the Building Engineering Services Association) publishes two related documents: TR19, which covers the hygiene of ventilation systems in general, and TR19 Grease, which deals specifically with grease in kitchen extract systems. They overlap in origin but not in scope, and knowing which applies to your building shapes what you should be buying, how often, and what paperwork you should expect at the end.
TR19 is BESA’s guide to good practice for the internal cleanliness of ventilation systems. It applies to the supply and extract ductwork that moves air around a building: offices, schools, hospitals, hotels, retail units, anywhere with mechanical ventilation. It sets out how systems should be inspected, how cleanliness is assessed, what methods a competent contractor should use, and how the work is verified and recorded afterwards.
The concern behind TR19 is air quality and system performance. Dust, debris and microbial growth accumulate inside ductwork over time, and a contaminated system pushes that contamination into occupied spaces while working harder to do it. Regular ventilation and ductwork cleaning keeps the system delivering what it was designed to deliver, and the plant that drives it benefits too: air handling units that are kept clean run more efficiently and last longer.
TR19 Grease was split out of the main document by BESA to deal with a distinct and more dangerous problem: grease accumulation inside commercial kitchen extract systems. Cooking loads the extract airstream with vaporised fat and oil, which condenses on the inside of canopies, ductwork and fans. Once a layer builds up, it is fuel. A fire that starts at the cooking line can be drawn into the duct and travel the full length of the system, often through parts of the building nobody can see.
Because the risk is fire rather than air quality, TR19 Grease works differently. It sets cleaning frequency by how many hours the kitchen operates each day: heavy use of 12-16 hours a day calls for a clean every 3 months, moderate use of 6-12 hours every 6 months, and light use of 2-6 hours every 12 months. It also defines when a system needs cleaning based on measurement: a mean grease deposit of 200 microns, measured by wet film thickness test, is the trigger point. We explain that test in more detail in how grease is measured in kitchen extract.
TR19 and TR19 Grease are industry guidance published by BESA, not legislation, and it is wrong to describe either as a legal requirement in itself. The legal duties sit underneath them. The Regulatory Reform (Fire Safety) Order 2005 requires the responsible person to manage fire risk, and grease-laden extract ductwork is a fire risk. The Workplace (Health, Safety and Welfare) Regulations, supported by the Approved Code of Practice L24, require workplace ventilation to be effective and maintained. A fire risk assessment for any premises with a commercial kitchen should address the extract system.
Cleaning to the relevant TR19 document is the recognised way of showing those duties have been met. Insurance points the same way: documented extract cleaning is a condition of cover in most UK commercial policies, though policies differ and you should check the wording of yours.
The two documents are not alternatives. A hotel has bedrooms and corridors served by general ventilation, and a kitchen served by extract: TR19 applies to the first, TR19 Grease to the second. The same is true of hospitals, schools with catering, office buildings with staff restaurants, and shopping centres with food courts. If your building both moves air and cooks food, you almost certainly need both disciplines, potentially on different schedules, and along with related fire-safety work such as fire damper testing they form one ventilation compliance picture.
Both documents put weight on proof. A TR19 clean should end with a report recording what was inspected and cleaned, the condition found, and photographic before-and-after evidence. A TR19 Grease clean adds deposit measurements and a compliance certificate, which is the document your insurer and fire risk assessor will ask to see. As a BESCA Vent Hygiene Associate member (BESCA is BESA’s certification body), our operatives are TR19 trained and our work is independently audited, so the certificates we issue are verified rather than self-declared.
The quickest way to find out is to let us look. Book a free survey through our contact page and we will assess your ventilation and extract systems and tell you plainly what applies and what condition they are in, or request a TR19 quote if you already know what you need. If you have an existing TR19 report from a previous contractor, send it over and we will read it for you.
TR19 is BESA’s guidance on the internal cleanliness of ventilation systems in general, covering supply and extract ductwork in any building with mechanical ventilation. TR19 Grease is a separate BESA document dealing specifically with grease accumulation in commercial kitchen extract systems, where the primary risk is fire rather than air quality. They set different measures, different cleaning triggers and different documentation.
No. TR19 and TR19 Grease are industry guidance published by BESA, not legislation. The legal duties come from elsewhere: the Regulatory Reform (Fire Safety) Order 2005 for fire risk, and the Workplace (Health, Safety and Welfare) Regulations with ACoP L24 for workplace ventilation. Cleaning to TR19 standards is the accepted way of demonstrating those duties have been met.
If your building has mechanical ventilation, TR19 applies to it. If it also has a commercial kitchen with an extract system, TR19 Grease applies to that system as well. Hotels, hospitals, schools and offices with catering typically need both, often on different cleaning schedules.
Documented cleaning of the kitchen extract system is a condition of cover in most UK commercial policies, and a TR19 Grease certificate with a supporting report is the standard evidence. Policies differ, so check what yours specifies. Because our BESCA Vent Hygiene Associate membership means our work is independently audited, the certificate you receive is verified rather than self-declared.
Send us your existing report or book a free survey. A named engineer replies within 24 hours.