CO₂, fine dust, nitrogen oxides – every day, cars, trucks, and buses emit pollu­tants into the air that harm people and the envi­ron­ment. In congested urban areas, high nitrogen dioxide levels are partic­u­larly dangerous, as they can cause respi­ra­tory and cardio­vas­cular diseases over the long term. When cities exceed the permis­sible limit for nitrogen dioxide, diesel driving bans are there­fore a frequent conse­quence.

The indi­vidual city air puri­fiers can clean up to 60,000 cubic meters of air in one hour. (Photo | Purevento)

In Kiel, there was a risk of these being imposed on the Theodor-Heuss Ring highway, where the EU limit of 40 micro­grams per cubic meter was signif­i­cantly exceeded in 2019. The measuring stations reported an average of 56 micro­grams of nitrogen oxides per cubic meter of air. At peak times, values even exceeded 120 micro­grams.

The mayor of Kiel’s concern was that if only the main road were closed for diesel vehi­cles, this could result in traffic jams and traffic taking alter­na­tive routes through other resi­den­tial districts. So the problem would only be displaced rather than fixed. So he looked for an alter­na­tive – and found it with Purevento. Six mobile air puri­fiers from the company have been cleaning the air on the road since October 2020.

Air puri­fiers for cleaner air to breathe

Robert Krüger, Managing Director and founder of Purevento, explains how the system works: “Our modular air filtra­tion system stands on the side of the road and sucks in the polluted air on one side. In the devices, four-stage filter units remove fine dust parti­cles and nitrogen oxides from the intake air and retain them in the system. The puri­fied air is blown out again on the other side. As a result, resi­dents, passers-by and cyclists in the vicinity of the city air puri­fiers are supplied with signif­i­cantly cleaner air to breathe.” Up to 90 percent of the fine dust and 85 percent of the nitrogen oxides and ozone remain in the city air puri­fier. As soon as the satu­ra­tion limit of the filter media is reached, they are replaced and disposed of together with the pollu­tants in an envi­ron­men­tally friendly way.

The indi­vidual city air puri­fiers can clean up to 60,000 cubic meters of air in one hour. Assis­tance is provided by two powerful centrifugal fans from ebm-papst, which are located in each of the two cleaning cham­bers. Krüger explains why ebm-papst was chosen: “It was impor­tant for us that the fans’ air flows remained large and stable, even if the filter media increas­ingly absorbed pollu­tants and the pres­sure through the filter system dropped as a result. Effi­ciency, volume, and control options were also deci­sive factors for us. Across all these para­me­ters, ebm-papst won us over with the perfor­mance of its fans.”

“It was impor­tant for us that the fans’ air flows remained large and stable, even if the filter media increas­ingly absorbed pollu­tants”

Robert Krüger, Managing Director and founder of Purevento

After trials with various models, the choice finally fell on RadiCal fans because they offered the best combi­na­tion of air perfor­mance and oper­ating noise. Thanks to indi­vidual control, Purevento can also always adjust the air flow to suit require­ments, as the amount of air purifi­ca­tion required depends on the volume of traffic as well as wind and weather condi­tions.

In discus­sions with other cities

For Purevento, which was founded in 2017 and is based in Trittau, the project in Kiel is the first time their devices have been used in series. But Robert Krüger is confi­dent that this is just the begin­ning: “We are already in talks with several cities in Germany, Europe and Asia where compli­ance with the limits is not guar­an­teed. It would be nice if we could prevent driving bans in those places too, and provide healthy air for resi­dents.”