Free guide for facilities teams
Choosing an Independent Ventilation Hygiene Assessor
Use this checklist when you commission a ventilation hygiene survey, compare quotes, or review a cleaning contractor's proposal. The more boxes a provider ticks, the more confident you can be that you will only pay for the work your systems actually need.
1. Independence
- Does the assessor provide cleaning services? If yes, how is the conflict of interest managed?
- Will the same company inspect, clean and sign off the work?
- Will you receive a cleaning scope you can take to any contractor for competitive quotes?
2. Standards and method
- Do they assess against the current edition — BESA TR19® Air Version 2 (2026), and TR19® Grease for kitchen extract?
- Do they explain which test method they will use — DTT, vacuum test (EVT) or WFTT — and why?
- Do they recognise where DTT is not suitable, such as spiral, lined or greasy ductwork?
- Will they test at enough representative locations — at least three per system, more for larger systems?
- Will test locations be marked on a plan so they can be re-tested after cleaning?
3. The report
- Individual results for every test location, not just a summary.
- Photographs linked to each location.
- Classification by system against TR19 criteria.
- A record of inaccessible areas and limitations.
- Prioritised recommendations — including which systems do NOT need cleaning.
- A re-inspection date and verification plan.
- Ask to see a redacted sample report before you commission the work.
4. Post-clean verification
- Will cleaning be verified independently at the same locations as the pre-clean tests?
- Will the contractor's Post-Work Verification Report be checked, including before-and-after photos and test results?
- Will each system be given a TR19 v2 outcome: Full Clean, Partial Clean, Inspection (Clean) or Inspection (Not Clean)?
5. Competence and assurance
- Health and safety pre-qualification (for example SafeContractor).
- Professional memberships relevant to occupational and indoor air hygiene (for example BOHS).
- Appropriate insurance for work in your buildings.
- Safe working arrangements for access, isolation and working at height, agreed with your team.
6. Programme management (multi-site clients)
- A system register for every site.
- Risk-based inspection intervals rather than one fixed frequency.
- Exception reporting and close-out tracking.
- Consistent methods and report format across all sites.
- An annual summary suitable for client or board reporting.
7. Reviewing a cleaning quote? Ask these first
| Question | Why it matters |
|---|---|
| What evidence shows cleaning is needed? | A quote should follow measured results, not a fixed interval alone. |
| Which systems and sections are included? | Vague scopes lead to disputes and partial cleans. |
| How will the result be verified — and by whom? | Self-certification is not independent evidence. |
| Will access panels be needed? | Missing access limits both cleaning and verification. |
| What will the Post-Work Verification Report contain? | TR19 Air v2 sets out what post-clean reporting should include. |
How Green Air Monitoring measures up
Independent — we do not clean. We assess to BESA TR19® Air Version 2 and TR19® Grease, select DTT, EVT or WFTT to suit each surface, report every result with photographs and limitations, and verify cleaning independently. SafeContractor approved · BOHS Affiliate Member · established 1999 · London and the South East.
This guide is general information and does not replace BESA TR19® or professional advice for your building. TR19® is a registered trademark of the Building Engineering Services Association.