Abstract: Valve device intended for use in an apparatus for examining human metabolism processes through analysis of the breathing air, provided with a connection for a patient mouth-piece and a connection for the hose to the apparatus, an inhalation valve which opens as a result of inhalation and an exhalation valve which opens as a result of exhalation wherein the two connections are disposed in line with each other on a substantially cylindrical housing, and wherein the inhalation valve is formed by several valves in the cylinder wall of the housing distributed substantially along the entire periphery thereof. Preferably the valves are formed in a valve ring on the basis of a regular polygon which is made separately and which, in its entirety, is placed in the internal space of the housing.