Accurate occupancy information helps to improve building energy efficiency and occupant comfort. Occupancy detection methods based on CO2 sensors have received attention due to their low cost and low intrusiveness. In naturally ventilated buildings, the accuracy of CO2-based occupancy detection is generally low in related studies due to the complex ventilation behavior and the difficulty in measuring the actual air exchange through windows. In this study, we present two novel features for occupancy detection based on the spatial distribution of the CO2 concentration. After a quantitative analysis with Support Vector Machine (SVM) as classifier, it was found that the accuracy of occupancy state detection in naturally ventilated rooms could be improved by up to 14.8 percentage points compared to the baseline, reaching 83.2 % (F1 score 0.84) without any ventilation information. With ventilation information, the accuracy reached 87.6 % (F1 score 0.89). The performance of occupancy quantity detection was significantly improved by up to 25.3 percentage points versus baseline, reaching 56 %, with root mean square error (RMSE) of 11.44 occupants, using only CO2-related features. Additional ventilation information further enhanced the performance to 61.8 % (RMSE 9.02 occupants). By incorporating spatial features, the model using only CO2-related features revealed similar performance as the model containing additional ventilation information, resulting in a better low-cost occupancy detection method for naturally ventilated buildings.

翻译：准确的 occupancy 信息有助于提升建筑能效与 occupant 舒适度。基于 CO₂传感器的 occupancy 检测方法因低成本、低干扰性而受到关注。在自然通风建筑中，由于通风行为复杂且难以测量窗户实际空气交换量，相关研究中基于 CO₂的 occupancy 检测准确率普遍较低。本研究提出两种基于 CO₂浓度空间分布的 occupancy 检测新特征。以支持向量机（SVM）作为分类器进行定量分析后发现，在不依赖任何通风信息的情况下，自然通风房间的 occupancy 状态检测准确率相比基线提升最高达14.8个百分点，达到83.2%（F1分数0.84）；引入通风信息后，准确率提升至87.6%（F1分数0.89）。occupancy 数量检测性能相比基线显著提升最高达25.3个百分点，达到56%，均方根误差（RMSE）为11.44人，仅使用 CO₂相关特征即可实现。额外引入通风信息后，性能进一步提升至61.8%（RMSE 9.02人）。通过引入空间特征，仅使用 CO₂相关特征的模型展现出与包含额外通风信息的模型相似的性能，从而为自然通风建筑提供了一种更优的低成本 occupancy 检测方法。