Evaluation of Respirator Filters for Asbestos Fibers

Cheng, Yung‐Sung; Holmes, Thomas; Fan, Bijian

doi:10.1080/15459620500444046

Cited by 17 publications

(16 citation statements)

References 18 publications

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“…Previous filtration studies on CNTs (Seto et al 2010;Wang et al 2011a,b;Vo and Zhuang 2013) or asbestos fiber (Cheng et al 2006) indicated that the major difference between fiber and sphere-like particles was caused by the interception mechanism, for which the CNT length played a significant role. Conversely, the filtration method can be used to determine the CNT length (Bahk et al 2013).…”

Section: Introductionmentioning

confidence: 97%

Carbon Nanotube Penetration Through Fiberglass and Electret Respirator Filter and Nuclepore Filter Media: Experiments and Models

Chen

Wang

Bahk

et al. 2014

Aerosol Science and Technology

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Three different respirator filter media (two electrets and one fiberglass) were challenged with monodisperse multi-walled carbon nanotubes (MWCNTs) of mobility diameters 20-500 nm at 5.3 and 10.6 cm s ¡1 face velocities. The penetration data were compared with that of sphere-like NaCl particles. The MWCNT penetrations were generally lower than those of NaCl at both face velocities in all three filters. However, the MWCNTs had a slightly higher penetration than the NaCl in the fiberglass filter at 10.6 cm s ¡1 face velocity when their mobility diameters were lower than 50 nm and the alignment effect was expected to occur. Results from the scanning electron microscopic (SEM) analysis supported the hypothesis of the alignment effect, which showed that the MWCNTs tend to be straighter or with higher aspectratios at the mobility sizes less than 100 nm, leading them more readily to align with the flow. Therefore, caution should be exercised when respirators are used against the MWCNTs with the mobility diameters less than 100 nm. The single fiber theory predicted the penetration of both particles in the fiberglass filters well for the particles with below 100 nm mobility diameters but discrepancies occurred beyond 100 nm. The theory still predicted the NaCl penetration through the electret filters well for the sizes below 100 nm but only predicted the MWCNT penetration well for »20-30 nm. The Nuclepore filter and the corresponding capillary tube model were adopted to study the mechanical deposition mechanisms of MWCNTs. The model was found to predict MWCNT penetration very well when the effective length of the MWCNT was taken into account.

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Section: Introductionmentioning

confidence: 97%

Carbon Nanotube Penetration Through Fiberglass and Electret Respirator Filter and Nuclepore Filter Media: Experiments and Models

Chen

Wang

Bahk

et al. 2014

Aerosol Science and Technology

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“…Values for filter penetration of the fibers in this study were similar to ranges reported previously. (4)(5)(6) Figure 5 shows the comparison of faceseal penetration between fibers and PSI at different breathing rates. Geometric means of faceseal penetration of fibers were 0.40, 0.14, and 0.09% at MIF of 15, 30, and 85 L/min, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Only high efficiency particulate air (HEPA) filters had similar penetration levels between DHES particles and the three types of asbestos fibers. (6) Filter penetration of asbestos fibers and DEHS particles through the other respirators ranged from below 0.01 to 8.63% and below 0.01 to 15.37%, respectively. Penetrations of amosite and crocidolite through the non-HEPA respirators were lower than those of the DEHS.…”

Section: Introductionmentioning

confidence: 92%

“…They found lower penetration for asbestos (0-3%) compared with DEHS (0-30%). Cheng et al (6) also compared filter penetration of the DEHS with a mass median aerodynamic diameter of 0.30 μm and three types of asbestos fibers through four different types of respirators: disposable face mask, dust/mist mask, powered respirator, and HEPA filter. The three asbestos types were amosite, crocidolite, and chrysotile, with CMDs 0.18, 0.08, and 0.03 μm, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Penetration of Fiber Versus Spherical Particles Through Filter Media and Faceseal Leakage of N95 Filtering Facepiece Respirators with Cyclic Flow

Cho

Turkevich

Miller

et al. 2013

Journal of Occupational and Environmental Hygiene

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This study investigated differences in penetration between fibers and spherical particles through faceseal leakage of an N95 filtering facepiece respirator. Three cyclic breathing flows were generated corresponding to mean inspiratory flow rates (MIF) of 15, 30, and 85 L/min. Fibers had a mean diameter of 1 μm and a median length of 4.9 μm (calculated aerodynamic diameter, d ae = 1.73 μm). Monodisperse polystyrene spheres with a mean physical diameter of 1.01 μm (PSI) and 1.54 μm (PSII) were used for comparison (calculated d ae = 1.05 and 1.58 μm, respectively). Two optical particle counters simultaneously determined concentrations inside and outside the respirator. Geometric means (GMs) for filter penetration of the fibers were 0.06, 0.09, and 0.08% at MIF of 15, 30, and 85 L/min, respectively. Corresponding values for PSI were 0.07, 0.12, and 0.12%. GMs for faceseal penetration of fibers were 0.40, 0.14, and 0.09% at MIF of 15, 30, and 85 L/min, respectively. Corresponding values for PSI were 0.96, 0.41, and 0.17%. Faceseal penetration decreased with increased breathing rate for both types of particles (p ≤ 0.001). GMs of filter and faceseal penetration of PSII at an MIF of 30 L/min were 0.14% and 0.36%, respectively. Filter penetration and faceseal penetration of fibers were significantly lower than those of PSI (p < 0.001) and PSII (p < 0.003). This confirmed that higher penetration of PSI was not due to slightly smaller aerodynamic diameter, indicating that the shape of fibers rather than their calculated mean aerodynamic diameter is a prevailing factor on deposition mechanisms through the tested respirator. In conclusion, faceseal penetration of fibers and spherical particles decreased with increasing breathing rate, which can be explained by increased capture by impaction. Spherical particles had 2.0-2.8 times higher penetration through faceseal leaks and 1.1-1.5 higher penetration through filter media than fibers, which can be attributed to differences in interception losses.

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“…Filtration technology for those particles has been used as one of the primary technologies for nanoparticle control. Especially, among fibrous particles, filtration of CNT particles (Seto et al 2010;Wang et al 2011a,b;Bahk et al 2013;Wang and Pui 2013), and asbestos (Cheng et al 2006;Vallero et al 2008) have been mainly studied.…”

Section: Introductionmentioning

confidence: 99%

Silver Nanowire Penetration Through Screen Filter

Son

Park

et al. 2014

Aerosol Science and Technology

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Understanding the filtration characteristics of fibrous particles is important since those particles have caused health and environmental concerns. Due to the straight morphology of metal nanowires, unlike carbon nanotube (CNT) particles nanowires can be considered as appropriate test material to evaluate existing filtration theory for cylindrical particles. We measured the penetration of silver nanowires in the size range of d m = 200 to 400 nm through screen mesh filter. By using Li et al. (2012)'s theory, we determined the orientation status of silver nanowires inside differential mobility analyzer (DMA) and calculated the dynamic shape factor of nanowires. Theoretical penetration was obtained by using single fiber theory with modified interception parameter including orientation angle between a filter wire and a particle. The orientation angle obtained by fitting experimental data into single fiber theory for the 1 layer of screen mesh filter is found to be close to 40• indicating random orientation of nanowires near filter. However, in the experiments with multi-layers of screen mesh, any tendency related to the orientation angle was not found. We performed numerical simulations for the filtration processes such as impaction, diffusion, interception, and interception of diffusing particles by introducing modified slip correction factor. Overall, when interception of diffusing particles is considered in addition to diffusion and interception, numerically simulation results and theoretical prediction agree better with experimental data regarding the penetration of silver nanowires through the 1 layer of screen mesh filter.

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Evaluation of Respirator Filters for Asbestos Fibers

Cited by 17 publications

References 18 publications

Carbon Nanotube Penetration Through Fiberglass and Electret Respirator Filter and Nuclepore Filter Media: Experiments and Models

Carbon Nanotube Penetration Through Fiberglass and Electret Respirator Filter and Nuclepore Filter Media: Experiments and Models

Penetration of Fiber Versus Spherical Particles Through Filter Media and Faceseal Leakage of N95 Filtering Facepiece Respirators with Cyclic Flow

Silver Nanowire Penetration Through Screen Filter

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