The invention relates to a device for collecting aerosol particles in an exhaled air flow. Said particles may be aerosol particles such as biomarkers or particles related to drugs or other substances formed or found in the alveoli of the lungs. Said device comprises a housing having an extension direction between a first end with an inlet arranged to receive an exhaled air flow and a second end with an outlet arranged to transmit the exhaled air flow and an inner cross section defined by inner walls of the housing and at least four first type partition walls, arranged in a direction essentially perpendicular to the walls, partly covering the inner cross section of the housing. Said first type partition walls protrude from opposite sides of the inner wall of the housing creating opposite openings between the first type partition walls and the housing inner wall, whereby said first type partition walls are arranged to create a labyrinth shaped flow path from said inlet to said outlet which is arranged to divert the air flowing from the inlet towards the outlet in a direction towards opposite inner wall of the housing so that said particles separate from the air flow and attach on the device and wherein the distance between two opposite first type partition walls is smaller than the distance between the inner walls of the housing.