Ventilation hygiene maintenance: a practical guide for facilities managers

Before scheduling any cleaning, establish the current condition. A baseline ventilation system inspection walks the ductwork, AHUs and extract systems, opens existing access panels, photographs internal conditions and produces a graded condition report. The output is a clear picture of where the system is today and where access provision needs improving.

A baseline inspection is also the document new FM contracts should reference. It defines what was inherited, what is in scope and what was already deferred at hand-over.

The common mistake is to clean every system annually because that is the easiest line in a PPM schedule. In practice, some systems need more frequent attention (heavy-use kitchen extract, AHUs in high-occupancy offices) and some can safely stretch further between cleans (low-use back-of-house, lightly loaded supply runs). Inspection-led frequency is both cheaper over a three-year cycle and easier to defend if challenged. See our ventilation risk assessment for the grading approach.

Supply and return ductwork is cleaned mechanically with negative-air extraction. Frequency is driven by the contamination type and rate — fibrous office dust in lightly loaded ductwork may justify a multi-year interval, while ductwork serving busy high-occupancy spaces needs closer monitoring. Ensure access panels are specified at sensible intervals so the full length can be inspected and cleaned.

AHUs are usually the most cost-effective hygiene win in a building. A planned AHU visit covers filter condition, coil cleaning, drain pan cleaning and disinfection, fan section hygiene and a check of seals and door condition. Recurring "musty AC" complaints are almost always resolved here. This is covered under AHU cleaning.

Kitchen extract systems are managed against TR19 Grease (see grease build-up in extract systems) and typically operate on a quarterly to annual cycle depending on use. General extract systems serving toilets, changing rooms and back-of-house should be visited as part of the wider hygiene programme so they do not silently fall off the schedule.

The single biggest gap in most maintenance regimes is documentation. A visit that is not documented effectively did not happen for the purposes of an FM audit, an insurance renewal or a tenant request. Every hygiene visit should produce a report: system covered, methods used, access worked from, before-and-after photography, items deferred and recommended next visit. Keep these centrally so they can be shared on request.

The forward plan is what turns reactive hygiene into a programme. Set inspections at predictable points in the year, batch cleaning visits to minimise mobilisation cost, and align with tenant calendars so disruptive work happens out of hours. A simple annual plan with the inspection date, cleaning dates and document hand-over dates is enough to keep the programme defensible.

• Cleaning only the visible duct sections because access is poor — fix the access.
• Treating AHUs as mechanical-only assets and ignoring hygiene.
• Letting kitchen extract slip when the kitchen "doesn't seem that busy".
• Cleaning without producing a written, photographed record.
• Using a flat annual frequency for every asset regardless of condition.

The most useful next step is almost always an inspection. From there, a condition-based programme can be sized to the actual building and added to the PPM schedule. We can scope the inspection, deliver the cleaning and produce the records to support it.