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Three-dimensional (3D) printing is an emerging and booming industry in Taiwan. Compared to traditional manufacturing, 3D printing has various advantages, such as advanced customization, additive manufacturing, reduced mold opening time, and reduced consumption of precursors. In this study, the real-time monitoring of particulate matter (PM) and total volatile organic compound (TVOC) emissions from various filaments is investigated using fused deposition modeling with material extrusion technology, a liquid-crystal display, a stereolithography apparatus based on vat photopolymerization technology, and binder jetting for occupational settings. An exposure assessment for nearby workers using the 3D printing process was performed, and improvement measures were recommended. Nine 3D printing fields were measured. The generation rate of ultrafine particles ranged from 1.19 × 1010 to 4.90 × 1012 #/min, and the geometric mean particle size ranged from 30.91 to 55.50 nm. The average concentration of ultrafine particles ranged from 2.31 × 103 to 7.36 × 104 #/cm3, and the PM2.5 and PM10 concentrations in each field ranged from 0.74 ± 0.27 to 12.46 ± 5.61 μg/m3 and from 2.39 ± 0.60 to 30.65 ± 21.26 μg/m3, respectively. The TVOC concentration ranged from 0.127 ± 0.012 to 1.567 ± 0.172 ppm. The respiratory deposition (RDUFPs) dose ranged from 2.02 × 1013 to 5.54 × 1014 nm2/day. Depending on the operating conditions, appropriate control and protective measures should be employed to protect workers' health. [ABSTRACT FROM AUTHOR]

Size-segregated sampling of particulate matter (PM) using impactor suffers from D50 cutoff shift due to particle loading and re-entrainment problems. Cyclonic separation is a viable option to overcome the above problem. However, conventional reverse flow cyclone design having a single inlet and upward-facing outlet also presents a common issue of sample (particle) loss during sampling and requires several arrangements to convert it into an efficient PM sampler. Therefore, here we present a high-volume (HV) PM10 multi-inlet cyclone (MIC) design with a downward-facing outlet, which overcomes existing problems and has additional advantages, such as omnidirectional sampling where a filter collector is placed in a straight line below the cyclone outlet to minimize sample loss. Moreover, like the existing USEPA reference low-volume PM2.5 sampler inlet design, which consists of 2-impactor stages (PM10 followed by PM2.5) in a straight path, this developed HV PM10 MIC sampler can accommodate a second size fractionator (e.g., PM2.5 impactor) to sample finer-size PM on a filter. D50 cutoff of developed PM10 MIC is numerically and experimentally investigated. Since the study regarding cutoff size of another type PM10 cyclone, called respirable dust sampler (RDS) is not available in the public domain and is widely used for PM10 monitoring in India, we investigated its cutoff size empirically and experimentally, and also performed field comparisons. Collocating field evaluation of PM10 MIC and PM10 RDS cyclone was done under a wide range of particle mass loading, and results were compared with USEPA-approved high-volume PM10 impactor sampler and with a real-time particle sizer. The D50 cutoff of PM10 MIC is experimentally achieved to be 9.89 ± 0.3 µm, which is close to 9.94 µm predicted numerically and lies in the range of 9.5–10.5 µm size measured by others for PM10 impactor sampler (USEPA). The D50 cutoff of the PM10 RDS cyclone is experimentally determined to be 3.56 ± 0.1 µm, which is surprisingly lower than its claimed cutoff of 10 µm mentioned in numerous articles, where it has been used for air quality reporting and studies related to aerosol science. The field comparison correlation of PM10 MIC for PM10-2.5 levels with PM10 sampler (USEPA) (R = 0.99) and particle sizer (R = 0.94) correlated well, and the mean deviations are found to be 6.2% and 3%, respectively. While PM10 (RDS) cyclone poorly correlates (R = 0.67), and the mean deviation is 68%. Overall, the developed PM10 MIC overcomes issues associated with existing impactor and conventional cyclone sampler, and can be a better option for high-volume PM10 sampling, especially under a wide range of ambient conditions particularly where the particle mass loading is consistantly high. [ABSTRACT FROM AUTHOR]

Low-cost sensors (LCS) have been increasingly deployed to monitor PM2.5 concentrations. More than 1500 LCS have been installed in Thailand to increase public awareness of air quality. However, performance of these sensors has not been systematically investigated. In this study, PM2.5 LCS were co-located next to a PM2.5 federal equivalent method (FEM) reference instrument at three Thai locations—in the north, center and northeast. We evaluated the performance of a PM2.5 LCS (PMS7003, Plantower) to understand the key factors affecting performance, including emission sources, relative humidity, temperature and PM2.5 concentration. Low PM concentration and high humidity levels had a significant impact on performance. Sensors in a high traffic emission area showed low correlation. The unadjusted PM2.5 LCS performance varied with locations. Errors were mainly observed at low concentrations. They significantly underestimated concentrations in congested urban environments. After calibration, accuracy was improved with multiple regression models. The performance of sensors only at Chiang Mai (CM) during the dry season and Ubon Ratchathani (URT) during the dry and wet seasons were acceptable with coefficient of variation: 5.8 ± 4.7–6.8 ± 5.0%, slope: 0.829–0.945, intercept: 1.12–5.49 µg/m3, R2: 0.880–0.934 and RMSE: 4.3–5.1 µg/m3. In the congested area in Bangkok (BKK), they underestimated concentrations of small particles. [ABSTRACT FROM AUTHOR]

ABSTRACT The hydride gas of phosphine ([PH.sub.3]) is commonly used for semiconductor and optoelctronic industries. The local scrubbers must immediately abate it because of its high toxicity. In this study, [...]