How many patrons in the university library ? CO2 sensors as tools to determine the occupancy of a whole building

摘要

The Lilliad learning center of the University of Lille is a multi-use facility including the science library, a food court, a conference hall, and a technological showcase. It is located in an architecturally complex building from the 1960', renovated in 2017. It consists mostly of an open hall from the ground to the third floor, with one large reading room at each level, and about 40 small working spaces. The conference hall and technological showcase are separated from the main hall, but share the same entrance, which is equipped with electronic people counters, however with very limited reliability. The library receives daily a maximum of ～4000 patrons. Sensor nodes developed at the University of Lille were installed in December 2018 in 4 different places of the Lilliad learning center, one in the food court, one in a 4-person working space, and two in the main hall, on the second and third floors. These nodes contain sensors for CO, C02, VOC, NOx, 03, for size-resolved number concentrations of particles (0.3-10 urn), as well as comfort and physical parameters: temperature, relative humidity, pressure, light, sound, motion. The aim was to investigate indoor air quality inside the different environments of the building, and to estimate the real occupancy. To our knowledge this is the first time that C02 sensing is used for a whole building. We show that in most part of the buildings the air quality is within the recommendation levels, except in the food court where the ventilation is not sufficient. From the C02 sensors located in the main hall, we were able to determine retrospectively the total occupancy of the building of any day, with a ～10% error. Further analysis is underway to assess the occupancy in real time.