Showing papers by "Congrong He published in 2016"

Application of multi-metric approach to characterization of particle emissions from nanotechnology and non-nanotechnology processes

Abstract: We assessed particle emission, using a three-tiered assessment process, to identify points of particle emission, temporal and spatial size and number concentration and to validate engineering controls in relation to selected nanotechnology processes and during the operation of laser printers.

Unexpected increase in indoor pollutants after the introduction of a smoke-free policy in a correctional center.

Abstract: Correctional centers (prisons) are one of the few non-residential indoor environments where smoking is still permitted. However, few studies have investigated indoor air quality (IAQ) in these locations. We quantified the level of inmate and staff exposure to secondhand smoke, including particle number (PN) count, and we assessed the impact of the smoking ban on IAQ. We performed measurements of indoor and outdoor PM2.5 and PN concentrations, personal PN exposure levels, volatile organic compounds (VOCs), and nicotine both before and after a complete indoor smoking ban in an Australian maximum security prison. Results show that the indoor 24-h average PM2.5 concentrations ranged from 6 (±1) μg/m(3) to 17 (±3) μg/m(3) pre-ban. The post-ban levels ranged from 7 (±2) μg/m(3) to 71 (±43) μg/m(3) . While PM2.5 concentrations decreased in one unit post-ban, they increased in the other two units. Similar post-ban increases were also observed in levels of PN and VOCs. We describe an unexpected increase of indoor pollutants following a total indoor smoking ban in a prison that was reflected across multiple pollutants that are markers of smoking. We hypothesise that clandestine post-ban smoking among inmates may have been the predominant cause.

What are the driving factors influencing the size distribution of airborne synthetic clay particles emitted from a jet milling process

Abstract: In the field of workplace air quality, measuring and analyzing the size distribution of airborne particles to identify their sources and apportion their contribution has become widely accepted, however, the driving factors that influence this parameter, particularly for nanoparticles (< 100 nm), have not been thoroughly determined. Identification of driving factors, and in turn, general trends in size distribution of emitted particles would facilitate the prediction of nanoparticles’ emission behavior and significantly contribute to their exposure assessment. In this study, a comprehensive analysis of the particle number size distribution data, with a particular focus on the ultrafine size range of synthetic clay particles emitted from a jet milling machine was conducted using the multi-lognormal fitting method. The results showed relatively high contribution of nanoparticles to the emissions in many of the tested cases, and also, that both surface treatment and feed rate of the machine are significant factors influencing the size distribution of the emitted particles of this size. In particular, applying surface treatments and increasing the machine feed rate have the similar effect of reducing the size of the particles, however, no general trend was found in variations of size distribution across different surface treatments and feed rates. The findings of our study demonstrate that for this process and other activities, where no general trend is found in the size distribution of the emitted airborne particles due to dissimilar effects of the driving factors, each case must be treated separately in terms of workplace exposure assessment and regulations.