Browsing by Author "Shih, TS"

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Characteristics of lead aerosols in different work environments
(1997-09-01)
Tsai, CJ
;
Shih, TS
;
Sheu, RN
;
環境工程研究所
;
Institute of Environmental Engineering
Air samples were collected to examine physical and chemical characteristics of lead aerosols in different work environments in the airborne lead concentration range from 28-783 mu g/m(3). Size distribution of aerosols was measured using a Marple personal cascade impactor,and lead analysis was conducted using graphite atomic absorption spectrometry. Lead aerosol size distribution was found to be different from that of total particles. Such differences are not negligible and must be taken into account when estimating aerosol deposition within the human respiratory tract. Variation of MMAD (mass median aerodynamic diameter) and GSD (geometric standard deviation) of lead aerosols in the coarse mode with total airborne concentration was found to be small, and the assumption that lead aerosol distribution is constant is reasonable for establishing the relationship between airborne lead and blood lead concentrations. Respirable lead concentration is shown to be well correlated with the total airborne lead concentration in all work areas of the three plants except the charging area of the capacitor plant. Therefore, it is expected that either total airborne lead or respirable airborne lead concentration can be used to correlate blood lead concentration.
Characteristics of lead aerosols in different work environments
(1997-09-01)
Tsai, CJ
;
Shih, TS
;
Sheu, RN
;
環境工程研究所
;
Institute of Environmental Engineering
Air samples were collected to examine physical and chemical characteristics of lead aerosols in different work environments in the airborne lead concentration range from 28-783 mu g/m(3). Size distribution of aerosols was measured using a Marple personal cascade impactor,and lead analysis was conducted using graphite atomic absorption spectrometry. Lead aerosol size distribution was found to be different from that of total particles. Such differences are not negligible and must be taken into account when estimating aerosol deposition within the human respiratory tract. Variation of MMAD (mass median aerodynamic diameter) and GSD (geometric standard deviation) of lead aerosols in the coarse mode with total airborne concentration was found to be small, and the assumption that lead aerosol distribution is constant is reasonable for establishing the relationship between airborne lead and blood lead concentrations. Respirable lead concentration is shown to be well correlated with the total airborne lead concentration in all work areas of the three plants except the charging area of the capacitor plant. Therefore, it is expected that either total airborne lead or respirable airborne lead concentration can be used to correlate blood lead concentration.
Design and testing of a personal porous-metal denuder
(2001-07-01)
Tsai, CJ
;
Huang, CH
;
Wang, SH
;
Shih, TS
;
環境工程研究所
A personal denuder made of porous-metal disc has been designed and tested. The entire casing and substrate support are made of Teflon, and the sampling flow rate is 2 L/min. The sampler consists of a two-stage cascade impactor (having cut-off aerodynamic diameters of 9.5 and 2.0 mum, respectively) to collect liquid particles and two porous-metal discs (diameter: 2.54 cm; pore size: 100 mum; thickness: 0.317 cm) to collect basic and acidic gases, respectively. The denuder was tested for gas collection efficiency and capacity at a gas concentration of two times the permissible exposure limit (PEL, promulgated by Taiwan Institute of Occupational Safety and Health (IOSH)), with relative humidity (RH) of 80 +/- 5% and temperature of 30 +/- 3 degrees C. The test data indicate that the gas collection efficiency is high, and the capacity is sufficient for the acidic/basic gas sampling in the workplace. Using 5% (w/v, g/mL) sodium carbonate/1% (w/v) glycerol coating on the porous-metal disc, the collection efficiency is 91.2 +/- 0.26% (average +/- standard deviation), 95.08 +/- 0.06% and 100 +/- 0.04%, and the capacity is 4.47, 7.2, and 2.5 mg for HNO3, HCl and HF, respectively. The collection efficiency for NH3 for the porous-metal disc with 4% (w/v) citric acid coating is 96.39 +/- 0.13%, and the capacity is 33.6 mg.
Effect of deposited particles and particle charge on the penetration of small sampling cyclones
(1999-03-01)
Tsai, CJ
;
Shiau, HG
;
Lin, KC
;
Shih, TS
;
環境工程研究所
Effects of particle mass deposited in the cyclone and particle electrostatic charge on the particle penetration of the commonly used 10mm nylon cyclone have been experimentally investigated in this study. The solid particle penetration of the cyclone has been found to decrease with an increase in particle mass deposited in the cyclone. This effect is most significant for particles near the cutoff aerodynamic diameter and when the deposited particle mass is low. The penetration of the cyclone has also been found to be influenced by particle electrostatic charge. This effect is also significant for particles near the cutoff aerodynamic diameter and when the number of elementary units of charge is greater than several thousands. To overcome these problems, a new cyclone made of conductive aluminum and with inner diameter nearly twice that of the 10 mm nylon cyclone has been designed and tested. Experimental results indicate that effects of both deposited particle mass as well as electrostatic charge on the penetration are reduced substantially in this cyclone. (C) 1999 Elsevier Science Ltd. All rights reserved.
Exposure assessment of organic solvents for aircraft paint stripping and spraying workers
(2006-03-01)
Uang, SN
;
Shih, TS
;
Chang, CH
;
Chang, SM
;
Tsai, CJ
The main objective of this study is to investigate the personal or area exposure of organic solvents during paint stripping and paint spraying. Three aircraft paint stripping/spraying workplaces in Taiwan were selected, and the Council of Labor Affairs and NIOSH recommended sampling/analytical methods used in this study. Activated charcoal tubes were used to investigate the personal and area exposure concentration of organic solvents in paint stripping and paint spraying operations. During aircraft paint stripping, experiment results show that methylene chloride personal exposure concentration at the ground area, 42.01 +/- 31.86 ppm, is higher than that at the working platform 4 M high above the ground, 20.41 +/- 11.43 ppm. Exposure concentration of methylene chloride in the initial paint stripping operation stage of every workplace is over the PEL (50 ppm) set by the Taiwan Council of Labor Affairs. Corrective actions are needed. During paint spraying, concentrations of all organic solvents were found to be below the PEL of OSHA. (c) 2005 Elsevier B.V. All rights reserved.
Field study of the accuracy of two respirable sampling cyclones
(1999-12-01)
Tsai, CJ
;
Shiau, HG
;
Shih, TS
;
環境工程研究所
;
Institute of Environmental Engineering
This study is to evaluate the sampling bias of a new cyclone (Tsai et al. 1999) and a 10 mm nylon cyclone under field sampling conditions. Both cyclones were operated at the optimum flow rate of 1.7 L/min. The Marple personal cascade impactor was used to measure the particle size distributions, which were used to calculate the reference RPM (Respirable Particulate Matter) concentrations according to the new ACGIH criteria. A wind tunnel was used in the field to ensure uniform particle concentration and wind speed across the tested cyclones and impactors in the working section. The wind speed, which was varied from 0.8 to 2.3 m/s, was kept constant in the wind tunnel. Near the packaging area of a glazing-making factory (mass median aerodynamic diameter, or MMAD: 11.1 mu m), the average ratio of the RPM concentrations measured by the cyclones to the standard RPM concentrations was found to be 1.20 and 1.10 for the 10 mm nylon and the new cyclone, respectively. Near the packaging area of a lead powder factory (MMAD: 4.82 mu m), the average ratio of the RPM measured by the cyclones to the reference RPM was found to be 1.13 and 1.02 for the 10 mm nylon and the new cyclone, respectively. Wind speed and total airborne particle concentration were found to have little effect on the accuracy of the two respirable cyclones. This field study showed that the new cyclone is more accurate than the 10 mm nylon cyclone based on the reference RPM.
Field test of a porous-metal denuder sampler
(2003-12-01)
Tsai, CJ
;
Huang, CH
;
Lin, YC
;
Shih, TS
;
Shih, BH
In this study, acidic/basic gas and particle concentrations determined with a porous-metal denuder and other samplers, that is, silica gel tube, impinger, honeycomb denuder system (HDS), Marple personal cascade impactor, and filter cassette, were compared in the ambient environment and different industrial sites in Taiwan. Results show that the concentrations determined by the denuder are very close to those of other samplers, with excellent correlation. The denuder also was tested successfully to determine H2SO4 size distribution in a lead-acid factory. One-way ANOVA shows no significant differences (P > 0.05) between the porous-metal denuder (PDS) and other samplers. The denuder is compact in size and suitable for sampling in the workplace and ambient environment.
Laboratory testing of three direct reading dust monitors
(1996-06-01)
Tsai, CJ
;
Shih, TS
;
Lin, JD
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機械工程學系
;
環境工程研究所
This study used a dust chamber to test the response of three direct reading dust monitors, GCA MINIRAM PDM-3, Sibata PCD-1, and TSI 8510, to different dust materials having similar size distributions. Total dust concentrations obtained by open-face filters were used as standards for comparing total dust concentration readings, while respirable dust concentrations calculated from particle size distribution measured by the MOUDI cascade impactor were used as standards for comparing respirable dust concentration readings. It was found that the GCA MINIRAM PDM-3 was accurate within +10-16% in regard to total dust concentration, independent of dust material. The calibration constant k of the Sibata PCD-1 was close to 6.0 for both quartz and SAE fine dusts and was independent of dust concentrations. However, for carbon particles, k remains nearly constant from 13-16 only when the total dust concentration is greater than 3.0 mg/m(3). The TSI 8510 seriously underestimates the concentration of SAE fine dust, and is more accurate for quartz and carbon dusts when respirable dust concentration is less than 6.0 mg/m(3). When respirable dust concentration is greater than 6.0 mg/m(3), it will also underestimate quartz dust concentration substantially, while it remains accurate for carbon dust.
Particle collection efficiency of an inertial impactor with porous metal substrates
(2001-09-01)
Huang, CH
;
Tsai, CJ
;
Shih, TS
;
環境工程研究所
;
Institute of Environmental Engineering
This study has investigated numerically the particle collection efficiency of an impactor with porous metal substrates. Two-dimensional flow field in the inertial impactor was simulated by solving the Navier-Stokes equations with the control volume method. Particle trajectories were then calculated to obtain the collection efficiency at different Reynolds numbers, which are based on nozzle diameter, and at different K, which is the resistance factor of the porous metal substrate. This study shows that some air may penetrate into the porous metal substrate resulting in different particle collection efficiency than that predicted by the traditional theory. The particle collection efficiency for the impactor with the porous metal substrate is higher than that with the flat plate substrate below the cutpoint, and numerical results are in good agreement with the experimental data. The dimensionless parameter phi = (rhoU(0)/2K mut)(D-c/W)(0.9) has been introduced to determine the excess particle collection efficiency, eta (e), by the porous metal substrate in the limit of root St --> infinity. The theory explains the experimental data of the excess collection efficiency very well. (C) 2001 Elsevier Science Ltd. All rights reserved.
Sampling time effect on 2,4-Toluene diisocyanate concentration by using different samplers
(2006)
Tsai, CJ
;
Lin, HC
;
Lin, KY
;
Shih, TS
;
Chang, KC
In order to understand the sampling time effect on the 2,4-TDI (Toluene diisocyanate) concentrations, laboratory and field tests were conducted in this study. An ADS (annular denuder sampler) and two OFFCs (open face filter holders) with different filters were tested for 1 to 120 minutes in the laboratory using 2,4-TDI gas. In the field study, the standard sampling method, the dual filter the triple filter and annular denuder systems were used at two workplaces to study the change of 2,4-TDI concentrations with sampling time from 15 to 60 minutes. The test results in both laboratory and field studies show that the sampling time influences the sampled TDI concentration considerably which may be due to reaction of TDI with water vapor and polyo in the sampling process. It is evident that as sampling time increases the TDI concentration decreases very significantly.
Simultaneous sampling of gas- and aerosol-phase TDI with a triple filter system
(2003-10-01)
Tsai, CJ
;
Cheng, KC
;
Aggarwal, SG
;
Shih, TS
;
Hung, IF
A new triple filter system sampler/model is proposed for the precise and accurate simultaneous sampling and determination of gas- and aerosol-phase 2,4-toluene diisocyanate (TDI). The system consists of two front Teflon filters for sampling aerosol-phase TDI and a final coated glass fiber filter to collect gas-phase TDI. The aerosol-phase TDI is collected on the first Teflon filter, while the second Teflon filter is used to estimate gaseous TDI adsorbed by the first. According to the gas adsorption test of two Teflon filters in series, the TDI gas adsorption fraction of the two filters is almost the same. Results of the evaporation test using pure TDI aerosols collected on the Teflon filter show that significant evaporation of the compound does not occur during sampling. These two findings allow the use of a model to estimate accurate gas- and aerosol-phase TDI, concentrations. The comparison test with an annular denuder shows that the triple filter system can minimize the TDI sampling bias between the dual filter and the annular denuder systems.
Single-longitudinal-mode semiconductor laser with digital and mode-hop-free fine-tuning mechanisms
(2004-12-27)
Shih, TS
;
Lan, YP
;
Lin, YF
;
Pan, RP
;
Pan, CL
We report a novel external cavity laser diode (lambda = 1.5 mum). An intra-cavity liquid crystal pixel mirror allows digitally tuning of the laser wavelength to more than 40 wavelength channels of 100 GHz spacing according to the International Telecommunication Union (ITU) grid. Laser wavelength can further be fine-tuned by varying the driving voltages applied to an intra-cavity planar nematic liquid crystal phase plate. With a cell 52.3 mum in thickness, the output frequency can be continuously tuned over 1.89 GHz. The root-mean-square voltage required for driving the phase plate was from 1.00 to 4.56 volts. (C) 2004 Optical Society of America.
The effect of environmental conditions and electrical charge on the weighing accuracy of different filter materials
(2002-07-03)
Tsai, CJ
;
Chang, CT
;
Shih, BH
;
Aggarwal, SG
;
Li, SN
Different filter materials and electrical charge elimination methods were used to investigate the weighing accuracy of filter papers under different environmental conditions. The results show that the standard deviations (S.D.) of weight data for glass fiber and MCE filters were substantial without environmental control, whether or not the electrical charge eliminators were used. Values of 0.157 and 0.349 mg were determined for glass and NICE filters, respectively. The accuracy of weighing was substantially improved and the S.D. was reduced to 0.01 and 0.09 mg for glass fiber and MCE filters, respectively, after applying the environmental control conditions. For PVC and Teflon filters, the accuracy of weighing was good, even in the uncontrolled environmental conditions, whether or not the electrical charge eliminators were used. The S.D. values of weighing data of PVC and Teflon filters were 0.007 and 0.011 mg, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.
Use of porous foam as the substrate of an impactor for respirable aerosol sampling
(2005-11-01)
Huang, CH
;
Chang, CS
;
Chang, SH
;
Tsai, CJ
;
Shih, TS
The effect of a porous foam substrate on the penetration characteristics of an impactor with a single round nozzle was investigated experimentally, with liquid and solid particles in the size range of 1-10 mu m. The experimental results show that the cut-off aerodynamic diameter of the impactor with porous foam substrate is lower than that with porous metal substrate due to more air penetration into the porous foam; in addition, the impactor penetration curve is less sharp. A numerical simulation of the penetration curve for the impactor with porous foam substrate was in good agreement with the experimental data. The numerical method was then used to find the best sampling flow rate for respirable aerosol sampling. Results show that when the nozzle diameter is 0.36 cm and the sampling rate is 1.91/min, the penetration curve of the impactor with the porous foam is very close to the criteria for respirable aerosol sampling. (C) 2005 Elsevier Ltd. All rights reserved.