Showing papers by "Congrong He published in 2007"

Particle emission characteristics of office printers.

Abstract: In modern society, printers are widely used in the office environment This study investigated particle number and PM25 emissions from printers using the TSI SMPS, TSI CPC 3022 and 3025A TSI P-Trak and DustTrak The monitoring of particle characteristics in a large open plan office, conducted continuously for over 48 hours, showed that particles generated by printers can significantly (p = 001) affect the submicrometer particle number concentration levels in the office An investigation of the submicrometer particle emissions produced by each of the 62 printers used in the office building was also conducted In terms of emission levels, the printers were divided into four classes of non-emitters, low, medium and high emitters, based on the particle concentrations in the immediate vicinity of the printers, after a short printing job It was found that about 60% of the investigated printers did not emit submicrometer particles and of the 40% that did emit particles, 27% were high particle emitters Particle emission characteristics from three different laser printers were also studied in an experimental chamber, which showed that particle emission rates are printer type–specific and are affected by toner coverage and cartridge age The average particle number emission rates from a printer in the class “low emitter‿ were 004×109 particle min-1 (new cartridge with 5% toner coverage); 421×109 particle min-1 and 954×109 particle min-1 for a “medium emitter‿ (old cartridge with 5% and 50% toner coverage, respectively); and 411×109 particle min-1 (old cartridge, 5% toner coverage), 928×109 particle min-1 (old cartridge, 50% toner coverage), 763×109 particle min-1 (new cartridge, 5% toner coverage) and 159×109 particle min-1 (new cartridge, 50% toner coverage) for a “high emitter‿ Particle size distributions indicated that the higher emitters tended to generate more ultrafine particles (< 01 µm) than the lower emitters whilst the trend in PM25 emissions was different, with the “low emitter‿ in having a PM25 emission rate of (029 ±007 µg min-1) and the “high emitter‿ showing nearly zero mass emissions While a more comprehensive study is still required to provide a better database of printer emission rates, as well as their chemical characteristics, the results from this study imply that submicrometer particle concentration levels in an office can be reduced by a proper choice of the printers

Rapid Identification of High Particle Number Emitting On-Road Vehicles and Its Application to a Large Fleet of Diesel Buses

Abstract: Pollutant concentrations measured in the exhaust plume of a vehicle may be related to the pollutant emission factor using the CO2 concentration as a measure of the dilution factor. We have used this method for the rapid identification of high particle number (PN) emitting on-road vehicles. The method was validated for PN using a medium-duty vehicle and successfully applied to measurements of PN emissions from a large fleet of on-road diesel buses. The ratio of PN concentration to CO2 concentration, Z, in the exhaust plume was estimated for individual buses. On the average, a bus emitted about 1.5 × 109 particles per mg of CO2 emitted. A histogram of the number of buses as a function of Z showed, for the first time, that the PN emissions from diesel buses followed a gamma distribution, with most of the values within a narrow range and a few buses exhibiting relatively large values. It was estimated that roughly 10% and 50% of the PN emissions came from just 2% and 25% of the buses, respectively. A regressi...

The rapid identification of high particle number emitting on-road vehicles and its application to a large fleet of diesel buses

Abstract: Pollutant concentrations measured in the exhaust plume of a vehicle may be related to the pollutant emission factor using the CO2 concentration as a measure of the dilution factor. We have used this method for the rapid identification of high particle number (PN) emitting on-road vehicles. The method was validated for PN using a medium-duty vehicle and successfully applied to measurements of PN emissions from a large fleet of on-road diesel buses. The ratio of PN concentration to CO2 concentration, Z, in the exhaust plume was estimated for individual buses. On the average, a bus emitted about 1.5 x 109 particles per mg of CO2 emitted. A histogram of the number of buses as a function of Z showed, for the first time, that the PN emissions from diesel buses followed a gamma distribution, with most of the values within a narrow range and a few buses exhibiting relatively large values. It was estimated that roughly 10% and 50% of the PN emissions came from just 2% and 25% of the buses, respectively. A regression analysis showed that there was a positive correlation between Z and age of buses, with the slope of the best line being significantly different from zero. The mean Z value for the pre-Euro buses was significantly greater than each of the values for the Euro I and II buses.