Kitchen Extract Grease Assessment and WFTT Surveys
Independent ventilation hygiene assessors · No cleaning services
Grease in kitchen extract systems is a distinct fire risk and needs a different assessment from general ventilation ductwork. We inspect the whole extract route, measure grease deposits with Wet Film Thickness Testing (WFTT) and give you independent evidence of condition and cleaning need.
Established 19992,500+ assessmentsSafeContractor approvedBOHS Affiliate MemberLondon & South East
Why kitchen extract is assessed separately
Cooking releases grease that condenses and builds up inside canopies, filters and ductwork. Unlike dry dust, it is combustible and can spread fire through the extract route. BESA publishes separate guidance for these systems, TR19® Grease, with its own measurement methods and cleaning frequencies.
What we inspect
We inspect the whole extract route.
- Canopies and grease filters
- Horizontal and vertical ductwork
- Risers
- Extract fans
- Discharge points
- Access panels, including whether there are enough of them to allow cleaning and inspection
How grease is measured
Wet Film Thickness Testing (WFTT) uses a comb gauge to measure the depth of wet or soft grease deposits, in microns. It is the method for greasy deposits, where Deposit Thickness Testing is not suitable. We take readings at representative locations along the extract route and photograph each one.
| Deposit | Method | Guidance |
|---|---|---|
| Wet or soft grease | WFTT | TR19 Grease |
| Hardened or dry deposits in kitchen ductwork | Assessed case by case; we explain the method used | TR19 Grease |
| Dry dust in general ventilation ductwork | DTT or vacuum test (EVT) | TR19 Air |
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Typical assessment frequency
TR19 Grease links frequency to how heavily the kitchen is used. As a guide: heavy use (12–16 hours a day) every 3 months, moderate use (6–12 hours) every 6 months, light use (2–6 hours) every 12 months. We recommend a regime for your kitchen based on its use and risk assessment.
How an assessment works
A kitchen extract assessment follows five steps.
Review
We review previous cleaning records, drawings and any insurer requirements.
Plan
We agree access, timing around service hours and the route to be inspected.
Inspect and measure
We inspect the route from canopy to discharge and take WFTT readings at representative locations.
Report
We report condition, readings, access issues and whether cleaning is needed, with a defined scope.
Verify
After cleaning by your contractor, we can re-test to confirm the result independently.
Limitations and what this assessment cannot tell you
- Readings describe accessible, tested locations; inaccessible sections are recorded
- Where access panels are missing, parts of the route cannot be assessed until access is improved
- It is an assessment of grease condition, not a full fire risk assessment of the premises
What your report includes
- Extract route plan from canopy to discharge
- Access-panel schedule, including gaps
- WFTT readings at each location
- Photographs linked to locations
- Condition against TR19 Grease criteria
- Cleaning scope, if needed
- Recommended assessment frequency
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