Abstract: An auxiliary device is tended and adapted to be accommodated in an air conduit forming part of an air conditioning device, to which air conduit first flow components, such as a fan, are connected for the purpose of bringing about a main airflow through the air conduit such that the whole main airflow flows through the auxiliary device. The auxiliary device has an arrangement of a number of air conditioning modules which in an active state of the relevant air conditioning module, each allow passage of a partial flow of the airflow and together allow passage of the whole main flow. Control components adjust each of the air conditioning modules between an active state, in which passage of the relevant partial flow is allowed, and a passive state in which a partial flow substantially amounts to zero or flows in opposite direction.