State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou, 310027, China; Center for Green Buildings and Cities, Harvard University, Cambridge, MA, 02138, USA; School of Mechanical Engineering, Zhejiang University, Hangzhou, 310027, China.
State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou, 310027, China; School of Mechanical Engineering, Zhejiang University, Hangzhou, 310027, China.
Environ Pollut. 2020 Nov;266(Pt 2):115107. doi: 10.1016/j.envpol.2020.115107. Epub 2020 Jun 25.
The air quality in classrooms is a critical factor that affects students' daily exposure. Although air filtration units (AFUs) are often used to reduce exposure to air pollution in China, the effectiveness of installing AFUs in Chinese classrooms have not been quantitatively studied. Hence, we carried out concurrent air quality experiments in two identical classrooms where one room was equipped with commercial AFUs and the other one relied on the natural introduction of outside air. Measurements were taken during regular school days in the winter at a primary school in Hangzhou, China. Three AFU ventilation modes, i.e., fresh air, mixed air and recirculation mode were evaluated, respectively. We found that classrooms equipped with AFU showed significant PM reductions, but this was accompanied by CO build-ups. In classroom with AFUs on internal recirculation, nearly 70% of the PM concentration at the beginning of the class was reduced by the end of a 40-min class. However, the CO concentration was observed to reach levels that were six times greater than that of the ambient due to inadequate air change rate (<1 h). To mitigate the issue of excessive in-classroom CO accumulation when using AFUs, filtered outside air must be brought in during their operation. In comparison with the internal recirculation mode, we demonstrated that the fresh air mode that draws the supply air from outdoor can considerably lower CO build-ups in the classroom with a moderate increase in PM concentration of 15 ± 10 μg/m. The findings from this study helps policy makers especially in developing countries with serious air pollution issues to determine whether or not to install AFU in primary schools and what ventilation mode is effective in reducing negative health effects.
教室空气质量是影响学生日常暴露的关键因素。尽管空气过滤设备（AFU）常用于降低中国的空气污染暴露，但在中国教室中安装 AFU 的有效性尚未进行定量研究。因此，我们在两所相同的教室里进行了同步空气质量实验，其中一间配备了商用 AFU，另一间则依靠外部空气的自然引入。测量是在中国杭州的一所小学在冬季的正常上学日进行的。分别评估了三种 AFU 通风模式，即新鲜空气、混合空气和再循环模式。我们发现，配备 AFU 的教室显示出显著的 PM 减少，但这伴随着 CO 的积聚。在 AFU 处于内部再循环的教室里，在 40 分钟的课程结束时，将近 70%的 PM 浓度在课程开始时就降低了。然而，由于空气交换率不足（<1 h），CO 浓度被观察到达到了环境水平的六倍。为了减轻使用 AFU 时教室内 CO 积聚过多的问题，在操作过程中必须引入过滤后的外部空气。与内部再循环模式相比，我们证明，从室外抽取供应空气的新鲜空气模式可以大大降低教室中 CO 的积聚，同时适度增加 15±10μg/m 的 PM 浓度。本研究的结果有助于决策者，特别是空气污染严重的发展中国家，确定是否在小学安装 AFU，以及哪种通风模式在降低负面健康影响方面更有效。
