Duct Cleanliness Testing and Condition Surveys
Independent ventilation hygiene assessors · Focused on impartial evidence
If you are not sure whether your ductwork needs cleaning, a duct cleanliness test gives you the answer before anyone sells you a cleaning programme. We inspect and test your systems, tell you what condition they are in and recommend only what the evidence supports.
Established 1999 · 2,500+ assessments · SafeContractor approved · BOHS Affiliate Member · London & South East
Do I need duct cleanliness testing?
Testing is worth considering if any of these apply.
- Visible dust around grilles and diffusers
- Recurring odours when the system runs
- Staff or tenant complaints about air quality
- Construction or fit-out work nearby or inside the building
- Taking over a building or FM contract with an unknown maintenance history
- A lapse in planned maintenance or filter changes
- An insurer, landlord or auditor has asked for evidence
- Suspected poor filtration or contamination
Survey or cleaning?
Cleaning is only justified when the evidence shows it is needed. This is how we help you decide.
| Situation | Recommended first step |
|---|---|
| No recent inspection record | Condition survey with quantitative testing |
| Visible contamination or complaints | Targeted survey linked to the complaint, with IAQ testing if needed |
| Cleaning already quoted by a contractor | Independent pre-clean survey to confirm the need and scope |
| Cleaning just completed | Independent post-clean verification |
| Routine compliance evidence needed | Planned TR19 Air assessment |
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Do I need a ventilation hygiene survey? 60-second check
1.Has it been more than 12 months since your ventilation systems were last inspected — or do you not know?
2.Can you see dust or staining around grilles and diffusers?
3.Have staff or tenants complained about stuffiness, odours or dust?
4.Has there been construction, fit-out or refurbishment work in or near the building since the last inspection?
5.Have an insurer, landlord, auditor or client asked for TR19 evidence?
6.Has a contractor recommended cleaning without showing you measured results?
7.Has ductwork recently been cleaned without independent verification?
8.Does the building have a commercial kitchen?
Your result
- Kitchen extract: assess grease with WFTT under TR19 Grease.
- Independent post-clean verification is recommended.
- Get an independent pre-clean survey before approving the quote.
- A formal TR19 Air assessment will give you the evidence requested.
- A condition survey with quantitative testing is recommended; we may add indoor air quality testing if complaints are involved.
- A routine TR19 Air assessment is due.
- Your systems may not need a survey yet. Keep annual inspections in your PPM schedule, and check again if anything changes.
This check is a guide only and does not replace an assessment.
Independent assessor or cleaning contractor?
| Independent assessor (Green Air Monitoring) | Cleaning contractor who also inspects | |
|---|---|---|
| Sells cleaning | No | Yes |
| Decides whether cleaning is needed | Based only on measured results | Often linked to cleaning service provision |
| Cleaning scope | Defined and handed to you to tender | Usually quoted by the same company |
| Post-clean sign-off | Independent re-test at the same locations | Often self-certified |
| Tells you when cleaning is NOT needed | Yes, and records it | Based on contractor service scope |
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Independent post-clean verification to TR19 Air Version 2
Version 2 of TR19 Air (March 2026) formalises what should be reported after cleaning. When your contractor has finished, we check the work independently rather than relying on self-certification.
- We re-test at the same locations as the pre-clean survey, using the same method
- We review the contractor's Post-Work Verification Report, including before-and-after photographs, test results, site plan and access-point details
- We confirm the outcome for each system: Full Clean, Partial Clean, Inspection (Outcome 'Clean') or Inspection (Outcome 'Not Clean')
Free buyer guides
Use our practical guides to check a TR19 report or compare assessors before approving work.
How we test
We combine inspection with the quantitative method that suits your ductwork.
- Visual inspection of accessible sections
- Photographic and, where useful, video inspection
- Deposit Thickness Testing (DTT) on suitable flat metal surfaces
- Vacuum testing (EVT) where a gravimetric result is needed or DTT is unsuitable
- Wet Film Thickness Testing (WFTT) for grease in kitchen extract systems
- Microbiological surface sampling — swab or contact samples from duct and AHU surfaces, analysed in a laboratory for bacteria and fungi, where hygiene concerns, odours or visible growth justify it.
- Indoor air quality testing where the problem needs it
What you get
Every survey gives you a clear basis for decisions.
- Clear evidence of the condition of each system
- Defined boundaries of what was and was not surveyed
- A proportionate cleaning specification, only where needed
- An audit-ready report you can share with insurers, landlords or auditors
Limitations and what this assessment cannot tell you
Duct cleanliness testing describes surface condition at the time of the survey.
- It covers accessible sections only
- It does not by itself identify microbial contamination — microbiological sampling can be added where needed
- It does not measure ventilation performance
- It does not on its own diagnose an indoor air quality complaint — we combine it with IAQ testing where needed
What your report includes
- Systems surveyed and access points used
- Test method and results at each location
- Photographs linked to locations
- Condition classification against TR19 Air
- Inaccessible areas and limitations
- Recommended actions, if any, and re-test advice
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Frequently Asked Questions
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Need Indoor Air Quality Testing?
Get a no-obligation quote. We provide IAQ testing, ventilation assessment and environmental monitoring across London and the South East.