Usage of printing equipment in college teachers' offices and influencing factors of released particulate matter
除1台打印机置于地面，其他30台打印机放置在距地面高（0.71±0.16）m桌面上，20台（65%）打印机与教师的水平距离小于1 m。23位（74%）老师打印频率在每周1~5次之间，每次打印的页数为（7.03±4.07）页。打印设备工作时的教师办公室PM10、PM2.5、PM1质量浓度峰值为（21.96±12.96）、（7.92±5.54）、（5.77±5.00）μg·m−3，PM0.25~0.28数量浓度峰值为（40941±36926）个·L−1。模拟实验表明，当位于打印机的正面、侧面和后面时，打印过程释放的0.25~0.28 μm颗粒物数量浓度峰值分别为（24257±551）、（12588±1354）、（11192±249）个·L−1，差异有统计学意义（
F=214.9， P<0.01）；当检测点与打印机的距离为0.1、0.2、0.3 m时，打印过程释放的0.25~0.28 μm颗粒物数量浓度峰值分别为（24257±551）、（19847±1426）、（16480±878）个·L−1，差异有统计学意义（ F=44.66， P<0.01）；当通风与不通风时，打印过程释放的0.25~0.28 μm颗粒物数量浓度峰值分别为（18595±488）、（24257±511）个·L−1，差异有统计学意义（ F=192.6， P<0.01）；当打印机与窗口相距1、2、3 m时，打印过程释放的0.25~0.28 μm颗粒物数量浓度峰值分别为（16780±823）、（18347±348）、（18595±488）个·L−1，差异有统计学意义（ F=8.407， P<0.05）。 结论
Printing and copying equipment is likely to release a large amount of particulate matter, thereby endangering human health. However, there is insufficient research on the level of particulate matter released by printers in offices and its influencing factors.
This study is designed to investigate the usage of printing equipment in college teachers' offices and the level of indoor particulate matter during printing, and to explore the influence of printer location and indoor ventilation on the particulate matter pollution level released during printer operation.
From 9:00 to 16:00 on January 4 to 6, 2021, 20 faculty offices in a university in Beijing were selected by convenient sampling to measure the indoor particulate matter level during printing, and to investigate the printing equipment usage of 31 users in the offices. Besides, experiments were designed to explore the influence of position and distance from a printer, ventilation, and the distance between a printer and a nearby window during ventilation on the number concentration of particulate matter released by the printers.
Except one printer being placed on the ground, the other 30 printers were placed on office desks (0.71±0.16) m above the ground. Among them, 65% of the printers (
n=20) were less than 1 m away from the users horizontally, and 74% of the users ( n=23) accessed the printers 1-5 times a week, printing (7.03±4.07) pages per time. The peak mass concentrations in users' offices during printing of PM10, PM2.5, and PM1 were (21.96±12.96), (7.92±5.54), and (5.77±5.00) μg·m−3, respectively, and the peak number concentration of PM0.25−0.28 was (40941±36926) P·L−1. The experiments showed that when the particle sizer was located in the front, side, and back of the printers, the peak values of PM0.25−0.28 number concentration during printing were (24257±551), (12588±1354), and (11192±249) P·L−1, respectively, and the difference among them was statistically significant ( F=214.9, P<0.01); when the particle sizer was placed 0.1, 0.2, and 0.3 m away from the printers, the peak values of PM0.25−0.28 number concentration during printing were (24257±551), (19847±1426), and (16480±878) P·L−1, respectively, and the difference among them was statistically significant ( F=44.66, P<0.01); when the experiment room was ventilated or not, the peak values of PM0.25−0.28 number concentration during printing were (18595±488) and (24257±551) P·L−1, respectively, and the difference between them was statistically significant ( F=192.6, P<0.01); when the distance between the printer and the window was 1, 2, 3 m, the peak values of PM0.25-0.28 number concentration during printing were (16780±823), (18347±348), and (18595±488) P·L−1, respectively, and the difference among them was statistically significant ( F=8.407, P<0.05). Conclusion
The overall printer workload is small and the concentration of particulate matter in the faculty offices is low when the printers are working. Printer position, distance, ventilation, and the distance from a nearby window under ventilation conditions are factors affecting the concentration of particulate matter released by the printers.