Mechanical ventilation cleaning: ducts, unit and valves

Which components are part of mechanical ventilation cleaning?

With mechanical extract ventilation (MEV), a ventilation unit draws air out through valves in the kitchen, bathroom and toilet; fresh air enters through grilles. Each component gets dirty in its own way and has its own maintenance rhythm.

The difference with balanced ventilation is that it also has supply ducts and a heat exchanger. We cover that separately under cleaning a heat recovery system.

Why MEV ducts get dirty and when to step in

Exhaust air from kitchens and bathrooms contains dust, moisture and grease particles. Part of it settles on the duct wall. The US EPA points out that a lot of dust stays stuck to the wall, so it does not disappear on its own. The Dutch National Institute for Public Health and the Environment (RIVM) calls maintenance of the system and regular cleaning of filters and grilles important, because sufficient ventilation prevents substances from building up indoors.

Clear signals to have the ducts cleaned, according to the EPA:

• visible mould in or near the ducts;
• vermin in the duct system;
• excessive dust coming out of the valves.

It is also sensible to include the ducts straight away when a ventilation unit is replaced or after a renovation. Milieu Centraal reports that almost one in five homes has damp or mould problems and that there is often more fine dust indoors than outdoors. A well functioning exhaust helps against this.

Mechanical ventilation in offices, hotels and schools

In non residential buildings, mechanical extraction often runs all day, with many more valves and longer ducts. The responsibility then lies with the employer or building owner. Article 6.2 of the Working Conditions Decree requires sufficient unpolluted air, an installation that is always ready for operation and signalling of faults where this is needed for health.

For cleanliness itself, a trade article on EN 15780 names a dust limit below 3.0 g/m² for medium risk buildings such as offices, hotels and schools, with a maximum of 4.5 g/m² in secondary ducts. The standard itself was not consulted in that source; see EN 15780 duct cleanliness for the background.

• Hotels: every room has its own extract point, so the number of valves adds up fast. See bathroom extraction in hotels.
• Offices: extraction in toilet blocks, pantries and archives. See cleaning office ductwork.
• Schools: the Dutch Frisse Scholen (Fresh Schools) programme asks for periodic technical and hygienic maintenance of climate installations.

For a facilities team this means a larger inventory: count the valves per floor, note which ones serve toilets or pantries, and plan the duct cleaning floor by floor so the building stays in use.

Mechanical ventilation cleaning cost according to price sources

Prices for cleaning mechanical ventilation differ widely between a home and a commercial building. The amounts below come from Dutch price comparison sites and a cleaning company; they are indicative and concern outsourcing.

Fictitious worked example. An installer maintains a complex of 40 homes with mechanical extract ventilation for a housing manager. At the Werkspot indication of 150 to 250 euros per home, an outsourced cleaning round costs 6,000 to 10,000 euros. If that round returns every eight years in several complexes, owning equipment becomes a serious option. A broader overview is available under prices for ductwork cleaning.

Which equipment suits MEV ducts?

Mechanical ventilation ducts vary widely in diameter, material and number of bends. So always measure the diameter and the length of the longest run first. Then choose the machine.

For domestic ducts, PD4 duct cleaning tool is often the first step. With many bends you work with air lance with camera, and for main ducts with the electric DC4 brushing machine for cleaning contractors. Choose the brush to suit the duct material; the EPA advises soft brushes for sheet metal and duct board. Compare all options under duct cleaning equipment for cleaning contractors, and the brushes themselves under duct brush.

How to approach cleaning an MEV system

A fixed sequence prevents you from blowing dust back into a clean section. This approach works for a home as well as an office wing.

1. Switch off the ventilation unit and record the setting of each valve per room.
2. Remove the valves and clean them separately.
3. Inspect the ducts with a camera, so you know where the dirt is and how the run goes.
4. Seal open end points with foam caps and put the duct under negative pressure, via the unit connection or an extraction unit with HEPA.
5. Brush or blow each duct from the valve point towards the extraction.
6. Check with the camera, put the valves back in their old setting and switch the unit back on.
7. Record what you have done, with before and after photos.

The general guide to how to clean air ducts describes each step in more detail. For sealing you need negative pressure HEPA extraction.

A short checklist before you leave the site: all valves back in their recorded setting, unit running, no foam caps left in the ducts, before and after photos saved and the next inspection date noted for the client.

DIY or an installer: where is the line for MEV?

For the occupant of a home the line is clear: grilles and valves yourself, unit and ducts by a professional. Milieu Centraal describes cleaning the ducts as work to outsource. For a facilities team or installation company the line is different, because they have the knowledge and can purchase equipment.

For homeowners and housing managers there is the Dutch quality mark Ventilatiekeur, under which maintenance, operation and performance of mechanical extract and balanced ventilation are checked and recorded. That helps when choosing a specialist company. More on the trade off under cleaning ventilation ducts yourself, and on how often it is needed under air duct cleaning interval. Are you an installer who wants to know which kit suits your work? Then contact Lamers.