Updated 2026-09-11
Anyone reading about kitchen extract cleaning for the first time meets two names in quick succession: TR19 and NAAD21. Both are guides to good practice for controlling grease in commercial kitchen extract systems. Both are published by industry associations rather than by government. Both use a risk-based cleaning frequency, deposit measurement and a documented report. They are not rival legal codes, and a kitchen does not have to choose between them; but the distinction matters when an insurer, a landlord or a tender document names one of them, so it is worth being clear about what each is.
Who publishes what
| TR19 Grease | NAAD21 | |
|---|---|---|
| Publisher | BESA, the Building Engineering Services Association | NAADUK, the National Association of Air Duct Specialists UK |
| Status | Industry specification and guide to good practice | Industry guide to good practice |
| History | Kitchen extract content of BESA's long-standing TR19 guide, published as a standalone specification in 2019 | First published in 2022, revised as NAAD-21:2025 |
| Scope | Kitchen extract systems only; general ventilation is covered separately by TR19 Air | Part 1 covers grease in kitchen extract; Part 2 covers indoor air quality in general ventilation |
| Contractor scheme | BESCA Vent Hygiene Elite scheme and Vent Hygiene Register | NAADUK membership and training for member companies |
| Recognition | The document most often named in insurance conditions, leases and fire risk assessments | Recognised as an alternative standard with a comparable approach |
Where they agree
On the points that decide whether a kitchen burns, the two documents point the same way. Both treat the whole system, from canopy to discharge, as the unit to be cleaned rather than the visible hood. Both set the cleaning interval from the intensity of use rather than a calendar habit. Both expect grease deposits to be measured rather than eyeballed, with readings taken before and after the clean. Both require adequate access to the ductwork and a report that records what was done, with photographs, and what could not be done. A contractor who works properly to one would recognise every requirement in the other.
Where they differ
The differences are mostly about who stands behind the document rather than what it asks for. TR19 Grease has the longer history and the wider footprint: when an insurer writes a cleaning condition into a policy, it usually says "in accordance with TR19" or "to a recognised standard", and fire risk assessors and environmental health officers tend to reach for the TR19 frequency table by default. NAAD21 is newer and comes from a smaller association, and its two-part structure means it also addresses indoor air quality, which TR19 handles in a separate document. There are differences of emphasis in how measurement and photographic evidence are described, but we would rather not characterise the detail of either text beyond what is published, and the practical outcome is the same: a competent contractor, a verified clean and a report you can produce on demand.
Which one do you need?
Start with whoever will read the certificate. Check the wording of your insurance policy, your lease and any franchise or brand standard; the insurance requirements guide explains where the condition usually sits. If a document names TR19, ask for a clean carried out and reported to TR19 Grease. If it says "a recognised standard", either will do, and a report that references both is the most robust position. Whichever you choose, the frequency should follow the same usage bands: heavy use at twelve to sixteen hours of cooking a day means every three months, moderate use at six to twelve hours every six months, and light use at two to six hours every twelve months. A loss adjuster is far more interested in whether the interval was kept and the ductwork measured than in which trade body's logo is on the report.
What to ask a contractor
- Which standard will the report reference, and can they show a sample from a comparable kitchen?
- Are they on BESA's Vent Hygiene Register, a member of NAADUK, or both?
- Will the readings be taken by Wet Film Thickness Test or Deposit Thickness Test at set points in every section?
- Will the report list any unreached sections and say why?
The choosing a contractor guide expands the list. The TR19 Grease guide and the post-clean report guide describe what a compliant document looks like in practice.
How Extract Cleaning UK handles this
We arrange cleans; we do not write the reports. The partner contractors we work with clean and document to TR19 Grease as standard, and many are also familiar with NAAD21 where a client asks for it. If your insurer has specified a particular standard, tell us when you request a quote and we will make sure the contractor we assign reports against it. A short description of your kitchen is all we need to begin.
Read next: Cleaning Frequency · Kitchen Extract Cleaning Cost · Ductwork Cleaning Cost
Frequently asked questions
Does NAAD21 replace TR19?
No. They are separate guides from separate associations, and both remain current. NAAD21 did not supersede TR19 Grease, and BESA continues to publish and update TR19. Most insurance conditions and fire risk assessments still name TR19, so it remains the reference point for the majority of UK kitchens, with NAAD21 accepted as an alternative approach by many of the same readers.
Will my insurer accept a NAAD21 report?
Usually, if the policy condition says "a recognised standard" or similar, and the report contains measured readings, photographs and a next-due date. If the policy specifically names TR19, ask the insurer in writing before relying on a report that references only NAAD21. Getting that confirmation takes one email and removes the argument before it can start.
Is a contractor who follows NAAD21 less qualified?
Not necessarily. The competence that matters is the ability to measure grease deposits, reach and clean the whole system, and document the result properly, and companies working to either guide can do that. Ask to see a sample report and proof of insurance rather than judging on the acronym alone.
Do I need two separate cleans to satisfy both standards?
No. A single clean, verified by measurement and documented with photographs, can be reported against both standards if the contractor chooses to reference them. The physical work is the same. What you should avoid is paying for a document that references either name without the measurement and evidence behind it.