Somewhere between the insurance renewal form and the fire risk assessment, every owner of a building with mechanical ventilation meets the same three letters: TR19. The renewal form asks whether the kitchen extract is cleaned to it. The fire risk assessor asks who did the cleaning and where the certificate is. A tender asks for a ‘BESA TR19 registered’ contractor without explaining what that actually means. Behind those questions sit two specifications and one register, and the evidence they expect from you is specific. Here is the plain-English version.
TR19 Air and TR19 Grease: two documents, one family name
BESA, the Building Engineering Services Association, has published the industry specification for the internal cleanliness of ventilation systems since 1991, and for years a single TR19® document covered everything. It has since split into two specifications that do different jobs.
TR19® Grease, published in 2019, is the fire document: the specification for managing the fire risk from grease accumulation in kitchen extract systems. It is measurable by design. Mean grease deposits across the system must stay below 200 microns between cleans, a reading of 500 microns at any single point triggers a local clean, and a compliant clean takes the system below 50 microns. The numbers come from Wet Film Thickness Testing with a calibrated comb gauge, which is exactly what our kitchen extract grease testing service measures.
TR19® Air, now in Version 2 (published March 2026), is the air quality document: the specification for internal cleanliness and hygiene management of ventilation systems, covering supply and extract ductwork and the air handling plant that feeds them. It works alongside BS EN 15780, the European standard that assigns a building a cleanliness quality class (low, medium or high, depending on use) and sets the deposit limits each class allows.
The distinction matters because the risks differ. Grease in extract ductwork is fuel, and a grease-lined duct is a route for fire to leave the kitchen. Dust in supply ductwork degrades indoor air quality and feeds microbial growth. But the compliance logic is identical in both documents: defined limits, measured deposits, documented verification. Neither specification is satisfied by an invoice that says ‘ducts cleaned’.
What ‘BESA TR19 registered’ actually means
TR19® is a specification, not a qualification. Any contractor can buy the document and quote it in a proposal; being able to evidence work against it is another matter. That gap is what the Vent Hygiene Register exists to close.
The register is operated by BESCA, the certification body within the BESA Group. It began life in 2019 as the Vent Hygiene Elite (VHE) scheme, built around kitchen extract cleaning, and was relaunched as the Vent Hygiene Register (VHR) in 2022. Member companies undergo third-party audits of their technical and commercial competence, their operatives train against the specifications, and each compliant clean is logged through the BESCA portal, which generates a certificate. That last step is the point: the paperwork is independently traceable rather than self-declared. The specifications the register enforces are recognised by the RISCAuthority and the London Fire Brigade, and the register is used by facilities managers, insurers, NHS trusts, local authorities and principal contractors when they specify ventilation hygiene work.
In March 2026 BESCA extended the scheme with VHR Air, a certification pathway for air-side ventilation hygiene against TR19® Air. The timing is deliberate: the Building Safety Act expects duty holders to evidence that work affecting building safety was carried out by demonstrably competent contractors, and VHR Air gives ventilation hygiene an auditable route to exactly that.
So when a specification, an insurer or a landlord asks for a ‘BESA TR19 registered’ contractor, the practical translation is: a company on the BESCA-run Vent Hygiene Register, whose completed work generates certificates you can verify rather than promises you have to take on trust.
The evidence insurers and landlords ask for
When the renewal questionnaire arrives, or worse, when a loss adjuster does, this is the file that answers:
- A pre-clean survey with numbers. Grease depth in microns at representative points for kitchen extract; deposit levels assessed against the building’s BS EN 15780 class for general ventilation. A clean without a before reading proves very little.
- Post-clean verification. The same points re-measured against the post-clean thresholds, with photographic evidence. The certificate should record the readings, not just the visit.
- A certificate that traces. For VHR member contractors, the clean is registered on the BESCA portal and the certificate it generates can be checked, which is precisely what insurers want after a duct fire.
- Frequency evidence. Records showing the cleaning interval actually matches how hard the system works, not how the budget felt that year.
Insurers have moved from asking to insisting: TR19® Grease-compliant maintenance is now written into many kitchen policies as a condition of cover, and claims have been cut down or refused after duct fires where no maintenance records existed. For landlords and employers the duty runs wider than the policy schedule: the responsible person under the Fire Safety Order 2005 must show the grease fire risk is being managed, and the Workplace (Health, Safety and Welfare) Regulations require mechanical ventilation to be kept clean. All of it lands in the same fire risk assessment file.
Cleaning frequencies by system type
Kitchen extract runs on cooking hours. The TR19® Grease benchmark intervals are:
- Heavy use (12-16 hours’ cooking a day): clean every 3 months
- Moderate use (6-12 hours a day): clean every 6 months
- Light use (2-6 hours a day): clean every 12 months
Treat those as starting points rather than a substitute for measurement. Grease testing between cleans shows whether your interval genuinely holds the system under 200 microns: some kitchens need cleans more often, others are buying cleans they do not yet need.
General ventilation runs on cleanliness class, not the calendar. BS EN 15780 assigns the class by use (an operating theatre is not an office), recommends inspection intervals for each, and lets inspection results trigger the cleaning. TR19 Air compliance is therefore inspection-led: deposit levels measured on schedule, cleaning when the numbers demand it, and certificates recording both. Our ventilation hygiene team surveys before quoting for exactly this reason, and will tell you honestly if your ductwork does not need cleaning yet.
Where fire dampers come into it
The ductwork that needs cleaning is the same ductwork that punches through your compartment walls, and fire dampers exist to close those holes when it matters. The two regimes belong together: dust and grease are exactly what stop a damper blade closing, BS 9999 says dampers should be drop tested at least annually (more often in high-risk settings such as hospitals and commercial kitchens), and the access panels cut for cleaning are the same panels an engineer needs to reach the damper. A hygiene contractor who vacuums around a seized damper and moves on has left the most important fire safety device in the duct exactly as they found it. Our fire damper testing runs on the same discipline as the cleaning: every damper dropped, photographed, and fixed rather than merely reported.
Five questions for your ventilation hygiene contractor
- Are you on the Vent Hygiene Register, and can I verify the registration online?
- Will I get measured before-and-after results (microns for grease, deposit levels against a BS EN 15780 class for air), or just an invoice that says ‘cleaned to TR19’?
- Who installs the access panels where the system cannot currently be reached?
- Do you test the fire dampers in the same ductwork, and do failures get fixed or just listed?
- Will the paperwork answer my insurer’s renewal questions without a scramble?
As a BESA member, Gemini AMPM works to the published specifications this article describes: grease measured in microns to TR19® Grease, ventilation cleaned and verified against BS EN 15780, and fire dampers drop tested to BS 9999, with the certificates recording numbers rather than assurances. One survey establishes where your building stands across all three. Request a consultation or call 0330 043 0080.
