Per-Person and Whole-Building VOC Emission Factors in an Occupied School with Gas-Phase Air Cleaning

Using real-time measurements of CO2 and volatile organic compounds (VOCs) in the air handler of an occupied middle school, we quantified source strengths for 249 VOCs and apportioned the source to the building, occupants and their activities, outdoor air, or recirculation air. For VOCs quantified in this study, there is a source to the outdoors of 8.6 ± 1.8 g/h in building exhaust air, of which 5.9 ± 1.7 g/h can be attributed to indoor sources (the building and occupants and their activities). The corresponding whole-building area emission factor from indoor sources is 1020 ± 300 μg/(m2 h), including reactive VOCs like isoprene and monoterpenes (33 ± 5.1 and 29 ± 5.7 μg/(m2 h), respectively). Per-person emission factors are calculated for compounds associated with occupants and their activities, e.g., monoterpenes are emitted at a rate of 280 ± 80 μg/(person h). The air handler included carbon scrubbing, reducing supply air concentrations of 125 compounds by 38 ± 19% (mean ± std. dev.) with a net removal of 2.4 ± 0.4 g/h of organic compounds from the building. This carbon scrubber reduces steady-state indoor concentrations of organics by 65 μg/m3 and the contribution of indoor sources of VOCs to the outdoor environment by ∼40%. These data inform the design and operation of buildings to reduce human exposure to VOCs inside buildings. These data indicate the potential for gas-phase air cleaning to improve both indoor air quality and reduce VOC emissions from buildings to the outdoor environment.

本研究针对一所正在使用中的中学的空气处理机组内的二氧化碳与挥发性有机化合物（Volatile Organic Compounds, VOCs）开展实时监测，量化了249种VOCs的源强，并完成污染源解析，将其归因于建筑、人员及其活动、室外空气或循环空气四大类。针对本研究中量化的VOCs，建筑排风系统向室外排放的VOCs总源强为8.6 ± 1.8 g/h，其中5.9 ± 1.7 g/h可归因为室内源（涵盖建筑、人员及其活动）。室内源对应的整建筑面积排放因子为1020 ± 300 μg/(m²·h)，包含异戊二烯、单萜类等反应性VOCs，二者的排放因子分别为33 ± 5.1 μg/(m²·h)与29 ± 5.7 μg/(m²·h)。针对与人员及其活动相关的化合物，研究计算了人均排放因子：例如单萜类的人均排放速率为280 ± 80 μg/(人·h)。该空气处理机组搭载碳净化装置，可使125种化合物的送风浓度降低38 ± 19%（均值±标准差），并从建筑中净移除2.4 ± 0.4 g/h的有机污染物。该碳净化装置可将有机污染物的稳态室内浓度降低65 μg/m³，同时将室内VOC源向室外环境的贡献降低约40%。本数据集可为建筑的设计与运行提供数据支撑，以降低室内人员的VOC暴露水平。研究结果表明，气相空气净化技术兼具改善室内空气质量与降低建筑向室外排放VOCs的双重潜力。