The system uses odour sensors on the outside of the car. When the sensors detect an unpleasant aroma, the system automatically closes the intake vents to stop the air getting in.
It can then release a leafy 'forest' smell, created using essential oils, into the car to combat any whiffs that manage to get through.
— From The astonishing new air-con that blocks unpleasant smells from even entering into your car at the Daily Mail. The car in question is the Nissan Fuga saloon.