The medicine still requires new, more advanced tools for better human body diagnoses. The great developments in electronics let to construct more and more sophisticated instruments for both human tissues examination and tests of human body functionality as well. The system described in the paper belongs to the last one and lets to check functionality of one of human body subsystems - the breathing system. It can measure dynamic changes of temperature and dew point temperature (humidity) of inspired and expired air. Some example results of dew point hygrometer and temperature measurements during respiration are presented. New factors describing condition and capability of human breathing system are proposed. © 2005 IEEE.