The performance of a low‐cost fan filter unit (FFU) in mitigating hazardous particulate matter (PM) levels in a naturally ventilated school classroom is presented. The FFU can be considered as a simplified mechanical ventilation and air‐conditioning system without heating and cooling functions. The FFU improves indoor air quality through introduction of cleaned outdoor air to flush out internally generated heat and moisture and reducing infiltration by maintaining indoor pressurization. Indoor particle number concentrations were reduced between 85% and 95%. The particle removal performance (PRF_FFU) of the FFU is determined and incorporated into the augmented façade penetration factor (P_aug). A case‐specific recursive dynamic mass balance model is used to characterize the infiltration factor (F_INF), deposition rate (K), and the penetration efficiency (P_aug) from continuously monitored indoor and outdoor mass concentration levels. Computed “P_aug” (0.07, 0.09, and 0.13) and “F_INF” (0.06, 0.08, and 0.11), respectively, for PM10, PM2.5, and PM1 suggest that exposure to PM was significantly reduced indoors. The effectiveness of the FFU for reduced “F_INF” and “P_aug” may be attributed to its superior filtration, dilution, and exfiltration mechanisms. In comparison with alternative PM mitigation solutions, the FFU is effective, affordable, and sustainable.

中文翻译：

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雾霾条件下自然通风教室中风扇过滤装置 (FFU) 降低颗粒物水平的性能特征

介绍了低成本风扇过滤器单元 (FFU) 在降低自然通风学校教室中有害颗粒物 (PM) 水平方面的性能。FFU 可以被认为是一种简化的机械通风和空调系统，没有加热和冷却功能。FFU 通过引入清洁的室外空气以排出内部产生的热量和水分并通过保持室内加压减少渗透来改善室内空气质量。室内粒子数浓度降低了 85% 到 95%。确定_FFU的颗粒去除性能 (PRF _FFU ) 并将其纳入增强的外墙穿透系数 ( P _aug）。特定情况的递归动态质量平衡模型用于从连续监测的室内和室外质量浓度水平表征渗透因子 ( F _INF )、沉积速率 ( K ) 和渗透效率 ( P _aug )。PM10、PM2.5 和 PM1 分别计算的“ P _aug ”（0.07、0.09 和 0.13）和“ F _INF ”（0.06、0.08 和 0.11）表明，室内 PM 暴露显着减少。所述FFU的减少为“有效性˚F _INF ”和“ P_八月”可能归功于其卓越的过滤、稀释和滤出机制。与替代 PM 缓解解决方案相比，FFU 有效、负担得起且可持续。