A device for collecting aerosol particles in an exhaled airflow, the device comprising: - a housing having a length in an extension direction between a first end with an inlet arranged to receive an exhaled airflow, and a second end with an outlet arranged to transmit the exhaled airflow, an inner cross section defined by one or more inner walls of the housing, wherein the cross section is circular or rectangular with a transverse width (d), and wherein the housing has an elongated shape; and - at least four first type partition walls, arranged at a distance (x) from each other and extending in a direction essentially perpendicular to the one or more inner walls, partly covering the inner cross section of the housing, wherein the first type partition walls protrude from opposite sides of the one or more inner walls of the housing creating opposite openings (4a, 4b) with an opening area between the first type partition walls and the respective opposite inner wall of the housing, whereby the first type partition walls are arranged to create a labyrinth-shaped flow path having a cross-sectional flow area from the inlet to the outlet, the first type partition walls being arranged to divert the exhaled airflow from the inlet towards the outlet in a direction parallel to the first type partition walls towards the opposite inner wall of the housing, such that aerosol particles in the exhaled airflow collide with the first type partition walls and/or the inner walls and attach on the device, wherein the distance (x) between two opposite first type partition walls is smaller than the transverse width (d) of the cross section of the housing, characterised in that the distance (x 1,..., x n) between opposite first type partition walls increases in the extension direction of the housing from the inlet. - a housing having a length in an extension direction between a first end with an inlet arranged to receive an exhaled airflow, and a second end with an outlet arranged to transmit the exhaled airflow, an inner cross section defined by one or more inner walls of the housing, wherein the cross section is circular or rectangular with a transverse width (d), and wherein the housing has an elongated shape; and - at least four first type partition walls, arranged at a distance (x) from each other and extending in a direction essentially perpendicular to the one or more inner walls, partly covering the inner cross section of the housing, wherein the first type partition walls protrude from opposite sides of the one or more inner walls of the housing creating opposite openings (4a, 4b) with an opening area between the first type partition walls and the respective opposite inner wall of the housing, whereby the first type partition walls are arranged to create a labyrinth-shaped flow path having a cross-sectional flow area from the inlet to the outlet, the first type partition walls being arranged to divert the exhaled airflow from the inlet towards the outlet in a direction parallel to the first type partition walls towards the opposite inner wall of the housing, such that aerosol particles in the exhaled airflow collide with the first type partition walls and/or the inner walls and attach on the device, wherein the distance (x) between two opposite first type partition walls is smaller than the transverse width (d) of the cross section of the housing, characterised in that the distance (x 1,..., x n) between opposite first type partition walls increases in the extension direction of the housing from the inlet.