Cars are a big reason city air is so grimy, and not just because of what comes out of the tailpipe. Researchers in South Korea now want to turn them into massive Roombas for city air, with a grille that scrubs roadside air as the car drives and a catcher that grabs brake dust where it's made.
The timing isn't accidental. From November 29, Europe's Euro 7 rules start applying to newly type-approved cars and vans, and for the first time they cap brake dust. Passenger cars with combustion engines, hybrid powertrains or fuel cells will be limited to 7 mg/km of PM10 (particulate matter of 10 μm), and battery electric vehicles (EV) to 3 mg/km. Europe may soon have company. India's draft BS-VII rules, published October 13, would copy the same limits from 2031 if adopted, and a UN regulation adopted in March offers a ready-made test that governments can write into law.
That's the gap the Korea Institute of Machinery and Materials (KIMM) wants to fill. Its researchers have fitted their system to two production models, a Kia Carnival minivan and a Hyundai Sonata sedan, and rather than designing a car from scratch, it builds on parts that are already there – the grille, the brakes and the radiator fan.
The grille works as an electrostatic precipitator, the same technology found in many home air purifiers and power-plant smokestacks. Carbon fibers thinner than a human hair give an electric charge to particles in the air flowing through the front of the car, and oppositely charged plates pull them out of the stream. Because the fibers need very little current, KIMM says ozone (a classic by-product of these devices) is kept to a minimum.
On the road, the grille doesn't need a fan of its own, since the car's movement shoves the air through unaided. And when it's parked over a wireless power pad, it can hijack the radiator fan and keep scrubbing the air around it.
According to KIMM, the grille removes at least 95% of PM2.5 particles (2.5 microns or smaller, small enough to get deep into the lungs) and 99% of coarser ones between 2.5 and 10 microns, in tests at 30 and 50 km/h (19 and 31 mph). Each car would process about 1,800 cubic meters (63,600 cubic feet) of air per hour, while fuel efficiency changed by no more than 1%.
The team already described the grille in a 2025 paper, reporting about 99% capture of 0.3-micron particles in typical Seoul traffic. By its math, one car could in theory clean enough air for 2,900 adults to breathe for an hour, based on average daily driving time.
A second device sits behind the brake caliper. Friction between pad and disc already leaves the wear particles electrically charged, so the collector doesn't need its own charger or a suction pump. Electrically charged plates do the grabbing. Over the WLTC test cycle, KIMM says it captured 22.2 mg of dust per kilometer, or roughly 10 g (0.35 oz) every 450 km (280 miles). A peer-reviewed study puts its average capture rate at about 61%.
"A key feature of this technology is that vehicles can remove fine particulate matter from roadside air while also reducing brake wear particles directly at the source," says project lead Bangwoo Han.
KIMM isn't the only one going after traffic pollution beyond the tailpipe. Carmakers are rethinking the brake itself. Mercedes-Benz is testing "in-drive brakes" for EVs, which move the braking hardware off the wheels and into the drivetrain, inside a sealed unit that keeps the dust in a small compartment. Researchers are also turning the road itself into a filter. Another Korean institute, KICT, coated a traffic tunnel in Seoul with light-activated concrete and cut nitrogen oxide levels by about 18% over 24 hours.
The closest relative to KIMM's idea is Ventra, a concept EV unveiled a few weeks ago by Dutch student team TU/ecomotive, which uses static charge to trap tire and brake dust at the wheels. The team's simulations suggest it can catch 42% of tire particles in city driving. The difference is that Ventra is a purpose-built two-seater, while KIMM's hardware is built into production cars.
There are caveats. The 95% figure refers to air passing through the grille, not to how much cleaner a busy street would get – nobody has measured that yet. KIMM hasn't said how often the plates need cleaning or what the kit would cost, and hasn't announced carmaker partners.
"Having verified the technology through vehicle testing, we plan to further validate its performance and long-term durability under real-world driving conditions," says senior researcher Gun Hee Lee.
Source: KIMM
