How often should ventilation ductwork be inspected and cleaned?
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Inspect general ventilation systems at least once a year and clean them when inspection shows it is needed. The law requires ventilation systems to be kept clean but sets no interval: BESA's TR19 Air and BS EN 15780 set the inspection rhythm according to how the building is used.
BESA's public summaries give two different inspection figures, and the BS EN 15780 class table (updated in 2025) could not be checked.
What to do, and how often
| Task | How often | Who | Basis |
|---|---|---|---|
| Inspect the ventilation system for cleanliness (visual assessment, deposit measurement and photographs) | Every year | Competent ventilation hygiene specialist | Guidance BESA says TR19 recommends that inspections should not exceed 12 month intervals for any system, and advises a baseline inspection every 12 months. SourcesS3S5 |
| Risk assessment survey of ductwork cleanliness to BS EN 15780 | Every 2 yearsAt least every 2 years in most facilities; annually in higher-risk environments. Range given by the source: every 1 to 2 years | Competent ventilation hygiene specialist | British Standard BESA summarises BS EN 15780 as requiring inspections at least every two years in most facilities, and annually in higher-risk environments such as healthcare, laboratories and cleanrooms. SourcesS4 |
| Clean ductwork and air handling plant when inspection shows deposits above the limit | No fixed intervalCondition-based: when inspection results require it | Competent ventilation hygiene contractor | Guidance BESA says cleaning is carried out as needed based on deposit levels or system condition. TR19 does not impose a fixed cleaning interval for general ventilation. SourcesS5 |
| Visual inspection of every ventilation system Applies to: Healthcare premises | Every year | Competent person under the healthcare ventilation regime | Guidance Health Technical Memorandum 03-01 Part B says all ventilation systems must have at least a simple visual inspection annually. SourcesS6 |
Where a row says who or what it applies to, the task is for that case only.
The law
Regulation 5 of the Workplace (Health, Safety and Welfare) Regulations 1992 requires mechanical ventilation systems provided in workplaces to be maintained, including cleaned as appropriate, in efficient working order. HSE's Approved Code of Practice says they should be regularly and adequately cleaned, tested and maintained. No interval is set in law.
The standard
BS EN 15780 (cleanliness of ventilation systems), which BESA says was updated in 2025, and BESA's TR19 Air specification, which aligns with it.
Records to keep
- Inspection report with deposit thickness measurements and photographs
- Post-clean verification report where cleaning was done
- Record of access panels and any sections that could not be reached
- Entry in the planned maintenance schedule
Notes
There is no single statutory figure. BS EN 15780 assigns each area a cleanliness quality class according to its use and sets inspection intervals by class; the class-by-class table is in the paywalled standard and is not reproduced here.
BESA's published summaries give two figures (no more than 12 months under TR19; at least every two years under BS EN 15780 for most facilities), and both are shown. Kitchen extract systems follow the separate TR19 Grease intervals.
Who delivers this in the group
Clean Ducts
Delivered by Clean Ducts, Gemini AMPM's ventilation hygiene brand. One number reaches every company in the group, day or night: 0330 043 0080.
Questions people ask
Ventilation hygiene (ductwork inspection and cleaning): is the interval set in law?
No task on this page has an interval set in legislation. Each one is recommended by a British Standard or by guidance. Regulation 5 of the Workplace (Health, Safety and Welfare) Regulations 1992 requires mechanical ventilation systems provided in workplaces to be maintained, including cleaned as appropriate, in efficient working order. HSE's Approved Code of Practice says they should be regularly and adequately cleaned, tested and maintained. No interval is set in law.
Ventilation hygiene (ductwork inspection and cleaning): who should carry out each task?
Competent ventilation hygiene specialist: inspect the ventilation system for cleanliness (visual assessment, deposit measurement and photographs); risk assessment survey of ductwork cleanliness to BS EN 15780. Competent ventilation hygiene contractor: clean ductwork and air handling plant when inspection shows deposits above the limit. Competent person under the healthcare ventilation regime: visual inspection of every ventilation system.
Ventilation hygiene (ductwork inspection and cleaning): what records should you keep?
Keep these records: inspection report with deposit thickness measurements and photographs; post-clean verification report where cleaning was done; record of access panels and any sections that could not be reached; entry in the planned maintenance schedule.
Ventilation hygiene (ductwork inspection and cleaning): which tasks have no fixed interval?
Clean ductwork and air handling plant when inspection shows deposits above the limit: condition-based: when inspection results require it.
Sources
Every task and legal statement is supported by at least one source fetched over HTTPS and read on the date shown. Quotes are verbatim and 25 words or fewer. A second, independent verification pass re-fetched every source and re-read the legislation on 5 October 2026. Intervals taken from British Standards were checked against published summaries of those standards by trade bodies and government guidance, because the standards themselves are paid publications.
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legislation.gov.uk (The National Archives) · Revised text as shown on 5 October 2026 · read on
“shall be maintained (including cleaned as appropriate) in an efficient state, in efficient working order and in good repair”
Supports: Legal duty to maintain and clean mechanical ventilation systems
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Workplace health, safety and welfare: Approved Code of Practice and guidance (L24) ↗
Health and Safety Executive · Second edition, 2013 · read on
“Mechanical ventilation systems (including air-conditioning systems) should be regularly and adequately cleaned.”
Supports: HSE's Approved Code of Practice on cleaning ventilation systems
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TR 19 Indoor Air Quality Standards For HVAC And Ventilation Systems ↗
Building Engineering Services Association (BESA) · Published 2 December 2025 · read on
“recommends that inspections should not exceed 12-month intervals for any system”
Supports: BESA: TR19 inspections should not exceed 12 month intervals
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TR 19 Indoor Air Quality Standards For HVAC And Ventilation Systems ↗
Building Engineering Services Association (BESA) · Published 2 December 2025 · read on
“most facilities requiring inspections every two years minimum”
Supports: BESA summary of BS EN 15780 survey frequencies
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Duct Cleaning Best Practice For Meeting TR 19 Standards In HVAC ↗
Building Engineering Services Association (BESA) · Published 18 December 2025 · read on
“A baseline inspection is typically advised every 12 months, with cleaning carried out as needed based on deposit levels or system condition.”
Supports: BESA: baseline annual inspection, cleaning as needed
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Health Technical Memorandum 03-01: Specialised ventilation for healthcare premises, Part B ↗
NHS England · 2021 · read on
“all ventilation systems must be subject to at least a simple visual inspection annually”
Supports: NHS guidance: annual visual inspection of all ventilation systems in healthcare premises