TR19 Grease vs TR19 Air: A Plain-English Glossary

Option A

TR19 Grease

TR19® Grease is the specification for fire risk management of grease build-up inside commercial kitchen extract systems - the canopy, filters, riser and horizontal ductwork that carry cooking vapour up and out. Grease is flammable, and a poorly maintained duct is a proven route for a hob fire to spread into the fabric of a building. This standard exists to keep that deposit under control and to prove, on paper, that it has been.

The headline numbers are about thickness. TR19 Grease asks that grease is not allowed to exceed a mean average of 200 microns across the system between cleans - that is the point at which fire risk climbs sharply. After a clean, remaining deposits should sit below a mean average of 50 microns, roughly half the width of a human hair. Verification is done with a Deposit Thickness Test at representative points, and a compliant report pairs before-and-after readings with photographs and a system schematic.

It matters because it is the yardstick your insurer and fire risk assessor will reach for. Under the Regulatory Reform (Fire Safety) Order 2005, the “responsible person” must manage fire risk, and a TR19 Grease report is the recognised evidence that the extract system has been dealt with properly.

Pros

• Directly targets the biggest hazard in a kitchen duct - flammable grease.
• Gives a clear, measurable pass mark (below 50 microns mean average post-clean).
• Widely accepted by insurers and fire risk assessors as proof of compliance.
• Post-clean reporting is standardised, so certificates are easy to audit.

Cons

• Covers only kitchen extract - it says nothing about your fresh-air or comfort ventilation.
• Cleaning frequency depends on how hard the kitchen works, so there is no single “annual” answer.
• Access panels are sometimes missing on older ducts, which can add remedial cost before a clean can even be verified.

Option B

TR19 Air

TR19® Air is the specification for the internal cleanliness and hygiene of general ventilation systems - the supply, extract and recirculation ductwork that moves air around offices, schools, healthcare settings, gyms and the front-of-house side of hospitality. Its concern is not fire but indoor air quality: dust, debris and microbial growth that a dirty system can push into the air people breathe. The 2024 re-release, and the 2026 Version 2, sharpen the focus on health and on verifiable record-keeping.

Rather than grease, TR19 Air measures dust accumulation, again using a Deposit Thickness Test. The trigger levels differ by system type: a mean of around 60 microns flags a cleaning requirement for supply and recirculation ductwork, rising to about 180 microns for extract. It also leans on the cleanliness quality classes defined in BS EN 15780, so everyone agrees up front what “clean” means for a given system. TR19 Air now references the Ventilation Hygiene Register and includes a dedicated section on post-clean reporting.

It matters because clean ventilation is a health and duty-of-care issue as much as a comfort one. For most non-kitchen ductwork, TR19 Air is the standard your facilities team, occupational health and building insurers will expect you to be working to.

Pros

• Covers the ventilation most of a building relies on, not just the kitchen.
• Ties cleanliness to recognised BS EN 15780 classes, so expectations are agreed in advance.
• Strong on indoor air quality, which links to occupant health and productivity.
• Updated reporting and register requirements make ongoing compliance easier to demonstrate.

Cons

• Not designed for grease - it will not satisfy a fire risk assessor for a kitchen extract.
• The class-based approach needs a clear brief up front, or the scope can be argued over later.
• Systems that have never been surveyed can throw up a long list of access and remedial works.

The short version

Which one do you need?

The quickest test is to ask what the duct carries. If it carries cooking vapour and grease from a commercial kitchen, you are in TR19 Grease territory and the driver is fire safety. If it moves general air around the rest of the building, you are in TR19 Air territory and the driver is hygiene and air quality. Many sites need both - the kitchen extract under Grease, everything else under Air - handled as separate scopes with separate certificates.