Pistochini Theresa, Jaeger Graham, Cappa Christopher D, Corsi Richard L
Department of Civil and Environmental Engineering, University of California Davis, 1 Shields Avenue, Davis, CA, USA.
Western Cooling Efficiency Center, University of California Davis, 215 Sage Street, Suite 100, Davis, CA, USA.
Environ Sci Process Impacts. 2025 Jun 18;27(6):1629-1639. doi: 10.1039/d4em00406j.
Filtration performance of do-it-yourself (DIY) box fan filters deployed across a university campus was assessed over an academic year. Four DIY air filters were constructed from box fans and air filters with a minimum efficiency reporting value (MERV) of 13 and deployed in four spaces (two laboratories that include sources of particles and two offices). They were operated 9 hours daily with a programmable timer and were continuously monitored with power meters. Particle concentrations in the spaces were continuously monitored with low-cost nephelometers. The particle size dependent clean air delivery rate (CADR) and single pass filtration efficiency for each box was measured in a laboratory before deployment and every 10 weeks, for a total of five measurements over 40 weeks. We find that these DIY box fan filters maintain robust performance over time, with each air filter maintaining at least 60% of its initial CADR at the end of the 40 week study even with daily operation in environments with modest particle concentrations. CADR values for particles of 1.0-3.0 μm optical diameter averaged 34% higher than CADR values for 0.35-1.0 μm particles, aligning with MERV 13 filter size-dependent filtration expectations. Reductions in CADR over time were attributed to a reduction in filtration efficiency, likely due to a loss of filter electrostatic charge over time. There was no strong indication that increased resistance due to particle accumulation on filters appreciably decreased flow rates over time for any of the fans. The long-term robustness of DIY box fan air filters demonstrates their validity as a cost-effective, high performance, alternative to portable high efficiency particulate air (HEPA) filters.
在一学年的时间里，对部署在大学校园各处的自制盒式风扇过滤器的过滤性能进行了评估。用盒式风扇和最低效率报告值（MERV）为13的空气过滤器制作了四个自制空气过滤器，并部署在四个空间（两个有颗粒物源的实验室和两个办公室）。它们每天用可编程定时器运行9小时，并用功率计进行连续监测。用低成本的浊度仪对这些空间内的颗粒物浓度进行连续监测。在部署前以及每10周在实验室中测量每个盒子的粒径相关清洁空气输送率（CADR）和单次通过过滤效率，在40周内共进行了五次测量。我们发现，这些自制盒式风扇过滤器随着时间推移保持了强劲的性能，即使在颗粒物浓度适中的环境中每日运行，在40周研究结束时，每个空气过滤器仍保持其初始CADR的至少60%。光学直径为1.0 - 3.0μm的颗粒物的CADR值平均比0.35 - 1.0μm颗粒物的CADR值高34%，这与MERV 13过滤器的粒径相关过滤预期相符。CADR随时间的降低归因于过滤效率的降低，这可能是由于过滤器静电荷随时间流失所致。没有明显迹象表明，对于任何一个风扇，由于颗粒物在过滤器上积累导致的阻力增加会随着时间显著降低流速。自制盒式风扇空气过滤器的长期耐用性证明了它们作为便携式高效空气过滤器（HEPA）的一种经济高效、高性能替代品的有效性。
