The object of the present invention is to reduce the exposure of polluted air to a baby, and in particular to minimize the pollutions inhaled by a baby when strolling, walking or transporting a baby in an exterior environment. The object is attained by providing a portable device for filtering air, said device being adapted to be arranged in association with a top end of a baby-transporting device. With such an air-filtering device, air from outside of the baby-transporting device may be filtered and purified before being provided in a well-distributed manner to the area of the baby-transporting device where a baby is positioned.