Characteristics and influencing factors of particulate matters released from printers

Background Printing and copying equipment in operation will likely release a large amount of particulate matters, thereby endangering human health. However, at present, there is insufficient research on the concentration and size distribution of fine particles in domestic print shops and the factors affecting the level of particles released by printers.

Objective This study is designed to analyze the characteristics of particle concentration and particle size distribution in print shops, and explore the influencing factors of particle emission during printer operation.

Methods The number concentration and mass concentration of particles with multiple particle sizes (0.25-32.00μm) were dynamically monitored using a portable aerosol spectrometer for more than 12h in three print shops (A, B, and C) in a school in Beijing. Besides, experiments were carried out indoor to explore effects of indoor temperature, indoor relative humidity, paper grammage, and toner cartridge types on the peak concentrations of particles ≤ 1μm (PM₁) released by the printers.

Results The particle number size distributions in the three print shops were basically identical, and more than 96% of the particles were ≤ 0.50 μm (PM_0.5). The number concentration increased as the particle size became smaller, and the PM_0.5 number concentration was as high as 11.36×10⁵ P·cm^-3. The particle size distributions in the three print shops were largely between 0.25-0.65μm and 1.30-7.50μm. The particulate matters released by printers were the main source of indoor particulate matter pollution in the print shops, and the number of printers in operation and outdoor PM_2.5 concentration affected the level of particles in the print shops. The experiments showed that when the indoor temperature was 15, 23, and 27℃, the peak value of PM₁ number concentration during printing was (1.76±1.33)×10⁴, (1.95±0.64)×10⁴, and (3.20±3.00)×10⁴P·cm^-3, respectively, and the difference among them was not statistically significant (F=0.58, P>0.05); when the indoor relative humidity was 30%, 45%, 60%, the peak value of PM₁ number concentration during printing was (1.95±0.64)×10⁴, (0.96±0.26)×10⁴, and (0.79±0.11)×10⁴ P·cm^-3, respectively, and the difference among them was statistically significant (F=9.65, P < 0.05); when using standard A4 printing paper weighted 70 and 80 g·m^-2, the peak value of PM₁ number concentration during printing was (1.95±0.64)×10⁴ and (5.25±1.07)×10⁴ P·cm^-3, respectively, and the difference between them was statistically significant (t=-4.59, P < 0.05); when using domestic compatible toner cartridges, domestic refillable toner cartridges, and imported original toner cartridges, the peak value of PM₁ number concentration during printing was (1.95±0.64)×10⁴, (1.90±1.22)×10⁴, and (9.85±4.70)×10⁴ P·cm^-3, respectively, and the difference among them was statistically significant (F=7.44, P < 0.05).

Conclusion The size of particles in the selected print shops is mainly ≤ 0.50 μm, and the particle number concentration and instantaneous particle mass concentration are high. Indoor relative humidity, paper grammage, and toner cartridge type are the factors that affect the number concentration of PM₁ emitted by printers.