A challenge device for use with a measuring unit for testing steam sterilization efficiency, the challenge device comprising a measuring chamber, a first opening for insertion of a first temperature sensor of the measuring unit in the measuring chamber, and a second opening allowing air exchange between surroundings and the measuring chamber, where said air exchange is achieved by a hollow air flow passage. The measuring chamber is closed except for the first and second openings, and the air flow passage includes an outlet, which is located at a distance from the second opening in the direction of the length axis. The invention further relates to a method of manufacture of a challenge device.
