Journal of Health and Safety at Work

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Introduction: The acoustic performance of natural fiber adsorbents has been investigated in numerous studies. A part of these materials show a poor adsorption within the frequency range of less than 1000 Hz. In the present study, attempts were made to investigate the effect of layout sequence of double-layered composites consisting of natural and synthetic fibers on improving the acoustic adsorption coefficient of natural fiber in the low-frequency range (63 to 1000 Hz) using the numerical finite element method.
Material and Methods: In this study, the finite element method and the Johnson-Champoux-Allard model in COMSOL software version 5.3a were used to investigate the acoustic performance of the double-layered composites consisting of natural and synthetic adsorbents. The acoustic absorbers under study included date palm fiber, polyurethane foam and cellular rubber. Each double-layered composite included a date palm fiber with 10mm in thickness and a synthetic adsorbent (polyurethane foam or cellular rubber) with 10mm in thickness. In sum, four double-layered composite structures with different layouts of adsorbents in each structure were studied.
Results: The location of natural fiber can play a critical role in the acoustic performance of the double-layered composite structures such that comparing the studied double-layered composites revealed that when the natural fiber was the first layer exposed to the normal sound in the double-layered composites with 20mm in thickness, the trend of acoustic performance was approximately the same as the single-layered composite of natural fiber with 20mm in thickness; but in the composite structures, when the synthetic adsorbent was the first layer exposed to the sound, the trend of acoustic absorption was improved.
Conclusion: On the basis of the results, the double-layered composite structure with a higher-density and lower-porosity upper layer showed a better acoustic absorption trend than the single-layered composite including the natural adsorbent.

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Introduction: The aim of this study was to investigate the effect of particle size (mesh) on the sound absorption coefficient of the absorbers made from Arundo Donax reed and to determine the optimal mesh for sound absorption.
Material and Methods: After crushing the reed stems in 10, 30, 20, 16, and 40 mesh sizes, they were washed with 5% NaOH. To make the samples 3 and 10 cm in diameter, 10% PVA was used as a binder, and the impedance of the two-channel tube was used according to ISO 10534-2 standard to determine the absorption coefficient. 22 samples of meshes 16 and 20 were made to achieve the optimal mesh based on the optimized RSM method, and the SAA index was used to compare the samples and determine the optimal mesh.
Results: The highest absorption peak was related to meshes 16 and 20 at the frequency of 2500 Hz, which is 0.94 and 0.98 ,respectively. The effect of increasing the thickness and density on the absorption coefficient is evident. The results have shown the effect of increasing the thickness and density on the absorption coefficient in mesh 20 in such a way that by increasing the density from 150 to 250 and the thickness from 10 to 30 mm, the absorption coefficient has increased from 35 to 63.5%. The optimal sample was mesh 20 with a thickness of 30 and a density of 250 kg/m3, which had the highest average absorption (SAA=0.57). The greater distance between the real and imaginary parts of the impedance shows the reactivity of the sample. In mesh 16 this distance is greater, as a result, mesh 16 has more reactivity and correspondingly less absorption.
Conclusion: The role of particle mesh as one of the important and influencing parameters on absorption coefficient has been investigated in this study.

 

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Introduction: In recent years, exposure to nanomaterials has been known as a challenge among occupational health experts. In this line, personal protective equipment has been considered as a solution to reduce the worker’s exposure. Since respiratory and skin tracts represent the most common workplace exposure routes, knowledge of the efficiency of respiratory and skin protection equipment is particularly important. So, the aim of this study is the assessment of the efficiency of respiratory and skin protection equipment toward controlling nanoparticles in the workplace with a scoping review approach.
Material and Methods: This study was conducted in 2022 with a scoping review approach. Arksey and O’Malley’s five-step framework was chosen as the research method. The search strategy was followed in the databases necessary to access the research data, including PubMed, Google Scholar, Science Direct, Web of Science, and Scopus. Also, EndNote X9® and Microsoft Excel software were used to collect and analyze studies, respectively.
Results: In the first step, 1014 articles were identified. Finally, 38 articles were included in the study to examine quantitative and qualitative information about the efficiency of respiratory and skin protective equipment. Twenty-five articles were related to breathing masks, and six studies were about protective gloves, and seven other articles were devoted to protective clothing. According to the studies of breathing masks, the mean total penetration of nanoparticles was estimated at 2.27%. Also, based on the studies of protective clothing, the maximum penetration of nanoparticles was 30nm for protective clothing made of polypropylene and polyethylene with different layers.
Conclusion: Although the efficiency of existing personal protective equipment showed a good result for controlling nanoparticles, the size of nanoparticles is one of the essential parameters in determining the efficiency of the equipment, which should be considered the workplaces. So, it is recommended that more studies be considered to improve their efficiency, and standard tests should be developed to evaluate them.