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Air purification in parking garages could reduce PM10 by up to half in areas in downtown Eindhoven

Eliminating particulate matter (PM10) from underground car parks in the city center of Eindhoven could result in local reductions in the concentration of these particles of up to 50%, according to a study by researchers from Eindhoven University of Technology (TU/e). The team based its fingings on air flow models and computer simulations of the city center.

The simulations, reported in a paper in Journal of Wind Engineering and Industrial Aerodynamics, suggest the potential effectiveness of an initiative by the environmental innovation company ENS Technology to use underground car parks as air purification sites, or “lungs of the city”.

Under the supervision of Professor of Building Physics Bert Blocken, the Eindhoven researchers made a very detailed computational grid of the city center of Eindhoven. This grid covered an area of 5.1 square kilometers and included 16 underground car parks.

The researchers used computational fluid dynamics (CFD) based on the 3D steady RANS equations and an Eulerian advection-diffusion equation. First, an extensive CFD validation study was performed with gas dispersion wind-tunnel measurements. Next, the case study for Eindhoven city center was conducted on the high-resolution grid.

Traffic intensities on the streets and in the garages were converted to PM10 source terms. The garages were ventilated with outdoor air. Simulations were performed with and without removal units in the garages.

The reduction of particulate matter concentrations in the city center with the use of 594 air purification units. The darkness of the blue represents the amount of the reduction. In certain locations the reduction peaked clearly to 50%. The influence of the wind is very clear from this picture. Click to enlarge.

The placing of 99 air purification systems inside the car parks generally decreases particulate matter concentrations outside the car parks locally by up to 10%. But with the use of 594 air purification units, a substantially larger area—up to a kilometer from the underground car parks—is affected where at least 10% reduction in particulate matter is observed.

In certain locations this reduction even peaked to 40 or 50% less. While the simulations have their limitations compared to practice—the force and direction of the wind, for example, can be particularly influential—the researchers conclude that this approach is an effective way of improving the air quality in a city center.

ENS (Environmental Nano Solution) Technology devised the idea of capturing particulate matter in underground car parks. The company has developed an innovative technology that turns fine dust into coarse dust, says ENS director Lia Van de Vorle. This is achieved by efficiently charging airborne fine dust particles and capturing them on a grounded collection plate.

Since the ventilation systems of the underground car parks are in contact with the streets and shopping zones above, these garages have a considerable influence on the air quality in the city center. By eliminating the particulate matter in these places and by ventilating clean air into the city, underground car parks act as cleansing lungs of the city.

—ENS director Lia van de Vorle

The Eindhoven researches used the specifics of the air purification systems of ENS Technology in their simulations.

A pilot project in an underground car park has generated a perceptible improvement in the air quality around the car park over the past two years.


  • Bert Blocken, Rob Vervoort, Twan van Hooff (2016) “Reduction of outdoor particulate matter concentrations by local removal in semi-enclosed parking garages: A preliminary case study for Eindhoven city center” Journal of Wind Engineering and Industrial Aerodynamics, Volume 159, Pages 80-98, doi: 10.1016/j.jweia.2016.10.008


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