How often should you clean air ducts?

Duct cleaning frequency per building type in one table

The table combines advice from government, manufacturers, insurers and standards. Where a figure comes from a secondary source, this is stated.

For bakeries and the food industry the sources give no fixed interval. There, the contamination found at inspection decides the moment.

Why standards give no fixed interval for duct cleaning

The European standard EN 15780:2025, which replaces the 2011 version, does not work with a calendar but with cleanliness. You place the system in a cleanliness class, inspect at fixed intervals and clean as soon as an acceptable level has been exceeded. Informative Annex A contains tables with cleanliness classes, inspection intervals per class in months and acceptable levels.

According to trade publications, the dust limits per quality class are 0.6 g/m² (high), 3.0 g/m² (medium) and 4.5 g/m² (low). Those figures come from secondary sources; we have not seen the standard itself. The practical message: a clean system in a quiet office can last longer than a system next to a busy road or a building site.

Exactly which standards apply and how they relate to each other is explained under Rules for clean ductwork.

Ventilation duct cleaning: how often in homes and residential buildings?

For homes the advice is the most concrete. For mechanical ventilation cleaning, Milieu Centraal advises outsourcing the extract ducts at least once every 8 years, having the fan unit serviced once every 2 years and cleaning grilles yourself at least once a year.

For ducts of balanced ventilation filter maintenance is added: replace twice a year, more often if you live next to a busy road. The manual of an Itho Daalderop heat recovery unit calls duct cleaning a task for the installer, every 8 years.

For housing associations and owners' associations (VvE) with many homes this is relevant: an 8 year cycle means you can schedule roughly one eighth of the portfolio each year.

Inspection intervals in care, offices and schools

In non-residential buildings, the responsibility lies with the employer or building owner. Article 6.2 of the Working Conditions Decree (Arbobesluit) requires sufficient uncontaminated air and installations that are always ready for use. How often you clean follows from your own inspections.

• Care: the German VDI 6022 mentions a hygiene inspection every 2 years for installations with humidification and every 3 years without. For operating theatres, an air management plan with periodic checks is part of the guideline. More under air duct cleaning in hospitals.
• Schools: Frisse Scholen (the Dutch fresh schools programme) calls for periodic technical and hygienic maintenance. RVO (Netherlands Enterprise Agency) reports that ducts in newly completed schools are sometimes full of construction dust, so plan an inspection at handover. See also fresh air in classrooms.
• Humidification: for humidification installations, legionella measures apply under article 4.87b of the Working Conditions Decree, with a risk analysis and a management plan.

Interval for kitchen extraction based on operating hours

In commercial kitchens the frequency depends heavily on how much cooking is done. A British supplier of kitchen extract cleaning uses this breakdown:

Dutch sources are in line with this: KHN mentions at least once a year in practice and more often with grilling, deep frying or wok cooking. The NVRL certification scheme, drawn up with TNO, uses an intervention value of 500 µm of grease and a performance value after cleaning of no more than 200 µm; the certificate is valid for 1 year. How to tackle this in practice is covered under cleaning a cooker hood duct.

Signs that you need to clean sooner than planned

A schedule is a starting point. These signs are a reason not to wait:

• visible mould, vermin or excessive dust in or near the ducts (EPA);
• less airflow at the valves: in a lab test, heavily contaminated filters gave 37% less supply air;
• CO2 meters in classrooms that more often exceed the target level;
• a renovation or new build in which construction dust can get into the system;
• in kitchens: grease at grilles or filters, because according to KHN serious contamination is often not visible to the naked eye.

To look inside ducts with tight bends you need a camera. Air nozzle duct cleaning combines compressed air with a built in camera with LED lighting, so you inspect and clean in one pass.

How to build your own ductwork cleaning schedule for your buildings

With these six steps you turn loose pieces of advice into a schedule you can justify:

1. Make an inventory of the systems per building: extract, balanced, air handling unit, kitchen extraction, humidification.
2. Inspect a representative part with a camera and record the contamination.
3. Choose a class per system, for example high for care and medium for offices.
4. Set an interval and link it to inspection moments, not only to cleaning.
5. Record every cleaning with photos and measurements.
6. Evaluate every year: if the system was still clean at inspection, the interval can be longer.

Anyone managing many buildings will notice that the frequency feeds straight into the budget. For that, look at the air duct cleaning cost and at which ventilation duct cleaning tools fit your ducts. For ducts of 100 to 600 mm and lengths of up to 30 m, DC4 duct cleaning machine for cleaning contractors is a logical first choice.

A practical tip for the schedule itself: put inspection and cleaning in separate columns. An inspection that finds a clean system is not wasted time but evidence that your interval works, and it gives you the basis to stretch the next interval with confidence.