The measurement of CO₂ concentration is a relevant indicator for defining the occupation of indoor spaces. The real-time knowledge of occupation of such spaces is relevant both for maintaining indoor air quality standards and for energy efficiency purposes connected with the operation of heating, ventilation, and air-conditioning (HVAC) systems. The exact knowledge of occupation allows for rapid feedback from and the regulation of an HVAC system and the ventilation rate. Interesting applications include educational buildings and other buildings of the civil sector (e.g., shopping centres and hospitals).

This paper provides the results of an experimental analysis in different classrooms of a university campus under real operating conditions, in different periods of the year, and with different kinds of activities. The correlation between the CO₂ concentration and occupancy profiles of the spaces is then analysed. Some graphical trends of the CO₂ concentrations in these indoor spaces are provided to determine the most important variables affecting such concentrations. The basic elements of the mathematical models for estimating the occupation of classrooms in relation to increases in CO₂ concentration are also discussed and analysed.

CO ₂浓度的测量是定义室内空间占用的重要指标。实时了解此类空间的占用情况对于保持室内空气质量标准以及与供暖，通风和空调（HVAC）系统的运行相关的能源效率目的均具有重要意义。确切的职业知识允许HVAC系统和通风率的快速反馈和调节。有趣的应用包括教育建筑和民用建筑的其他建筑（例如购物中心和医院）。

本文提供了在实际操作条件下，一年中的不同时期以及在不同类型的活动下，在大学校园的不同教室中进行实验分析的结果。然后分析该空间中CO ₂浓度与占用率分布之间的相关性。提供这些室内空间中CO ₂浓度的一些图形趋势，以确定影响此类浓度的最重要变量。还讨论和分析了用于估计教室占用与CO ₂浓度增加相关的数学模型的基本元素。