A portable pneumotachograph for determining components in an exhalation volume. The problem of extreme sensitivity of sensors to temperature and moisture content of the gases, and cross-sensitivities to other potential components of the exhalation gas, is solved by providing a climate control chamber wherein a defined gas atmosphere can be set such that by means of the climate control chamber the relative humidity and/or temperature and/or composition of a sample and/or calibration gas can be set to predefined parameters.
