The use of a mixed gas sensor in the study of indoor air quality and its application to demand based ventilation.

Demand Based Ventilation systems are potentially valuable in terms of energy saving in building with fluctuating occupation patterns. Most demand based ventilation systems are controlled by C02 measurement. However this approach cannot take account of other polluting elements found in indoor air. This paper will describe the results of a study of the indoor air quality in a recently built university library with continuous ventilation. The literature relating to typical levels of naturally occurring gases, volatile organic compounds and microbes, in indoor air is considered. The range of pollutants in indoor air is discussed and various methods of measuring them are tested and compared. In particular a mixed gas air quality sensor is used to monitor air quality in an attempt to measure the efficacy of the instrument as controller for a demand based ventilation system. A questionnaire based on the BRE Office Environment Survey is used to establish the building users perception of indoor air quality. The questionnaire analysis and the performance of the mixed gas sensor are compared to assess the suitability of the sensor as a controller for a ventilation system. Results indicate that mixed gas sensor control for demand based ventilation systems may well be the way forward for better air quality and optimum energy conservation.