After the launch to the International Space Station with The Space Shuttle flight STS 118 13A.1 on August 9th 2007 and the accommodation in the US lab Destiny, the air quality monitor ANITA (Analyzing Interferometer for Ambient Air) has been successfully put into operation. ANITA is a technology demonstrator flight experiment being able to continuously monitor with high time resolution the air conditions within the crewed cabins of the ISS (International Space Station). The system has its origin in a long term ESA (European Space Agency) technology development program. The ANITA mission itself is an ESA-NASA cooperative project. ESA is responsible for the provision of the HW (Hardware), the data acquisition and data evaluation. NASA's responsibilities are launch, accommodation in the US Lab Destiny, operation and data download. The ANITA air analyser is designed to detect and quantify online and with high time resolution 30 trace gases simultaneously with down to sub-ppm (parts per million) detection limits in addition to the always present background gases carbon dioxide and water vapour. The air analyser thus monitors the trace gas dynamics of the spacecraft's atmosphere in providing continuous air monitoring as well as crew warning capability in case of malfunctions. Beside continuous measurements in the vicinity of the gas monitor, air samples from remote places in the International Space Station can be analyzed using gas bags and a hand pump. However, considering the experimental character of ANITA, the measurements are not on-line visible to the Crew. ANITA is an on-orbit test experiment and a precursor for a permanent continuous trace gas monitoring system on the ISS – ANITA II. It further represents a precursor system for future air monitoring in crewed vehicles being developed for the Human Space Exploration program. This is the first paper of two describing the measurement principle, the HW and the mission on the ISS. Finally, an outlook into the future highlights the potential of the ANITA technology for the Exploration program. The work described has been performed under contract of the European Space Agency.