Journal of Health and Safety at Work
Year:2020 | Volume:9 | Issue:4|Papers Count:8

Introduction: The safety of CNG stations is important because of their location in urban areas, as well as to prevent accidents and to protect the safety of personnel, property, and environment. An event occurrence analysis with probability updating is the key to dynamic safety analysis. Material and Methods: In this study, the Failure Modes and Effects Analysis (FMEA) technique was used to determine the hazards of the study unit, the method of analyzing. After determining the hazards with high risk, the Bayesian fault tree analysis (BFTA) method was used to determine the effective causes of events occurrence and the type of possible relationships among them. Results: First, the phase of hazards identification, 16 Hazardous equipment were identified. Then the Risk Priority Number for the identified equipment was calculated. The results showed that the dispenser system had the highest risk priority number and was identified as the most critical equipment. According to this, the dispenser gas leakage (as the top event) was selected in this study. Then, the analysis of the dispenser gas leakage, using BFTA method identified 56 main causes, including 17 intermediate events and 39 basic events. Finally, cracking and corrosion of the dispenser hose were determined the most effective factor in the occurrence of the top event. The probability of occurrence of the top event based on FTA and BFTA analysis was calculated 9. 67×10-2 and 9. 11 × 10-2, respectively. Conclusion: The result of the study that by employing the Bayesian Network, can create a useful guideline to determine the relationship between the occurrence causes of the top event. This provides an assessment of the effectiveness of preventive measures before using them.

Introduction: Many studies, especially in recent years, have evaluated and controlled the occupational heat stress in Iran using environmental indices. However, so far, no comprehensive study has been conducted to review and classify these studies. Therefore, this study aimed to review and investigate the occupational studies performed by environmental heat stress indices in Iran. Material and method: In the present study, the published articles from 2000 to 2016 were searched using Persian and English keywords including heat stress, heat strain, hot condition, warm condition, occupational health, thermal environment and Iran in databases such as Web of Science, Google Scholar, PubMed, Scopus, Science Direct, SID, Magiran, Civilica, Iran Medex, Barakatkns and Irandoc. Finally, 134 articles were included in this study. Results: Based on the results, most studies have been carried out in the indoor industrial environments of Isfahan, Tehran, and Assaluyeh between years of 2010 to 2016. As well as, WBGT index with 76 percent and the UTCI and PHS indices with 0. 6 percent had the highest and lowest usage in all environments and industries, respectively. In addition, the industries of the refinery, steel, glasswork, melting and casting, mines, and ship repairs have the highest mean values of WBGT index, respectively. Conclusion: The results showed the need to more attention of researchers for conducting studies in outdoor environments, in different cities of Iran, on development and validation of novel heat stress indices, and on implementation and evaluation of control measures in the environments with high heat stress.

Introduction: Occupational exposure to sevoflurane as an anesthetic gases in hospitals, dental clinics and veterinary clinics has been reported in various studies. Considering the harmful effects of sevoflurane anesthetic gas on the health of exposed personnel such as reproductive, preterm delivery and fetal abnormalities and increased spontaneous abortion, it is necessary to remove them from the air of the work environment, especially the treatment centers, with inexpensive and optimal methods. This study was aimed to compare two oxide-titanium based on Activated Carbon/ Graphene Oxide Nanosheets in nano and non-nano scales. Material and Methods: Titanium oxide particles and nanoparticles were coated on actived carbon/ Graphene Oxide Nanosheets adsorbents. The prepared sorbents were characterized by instrumental techniques such as BET, SEM, XRD, FTIR and SEM-EDS to determine their properties. After characterization, the breakthrough and adsorption capacity of sevoflurane on both adsorbents were determined using the modified wheeler equation. Finally, the software of Microsoft Office Excel 2016 and SPSS Statistic version 21 IBM were used for statistical analysis of data. Results: the results of XRD, SEM-EDAX analysis were confirmed the stabilization of titanium oxide particles and nanoparticles on the sorbents. Furthermore, the FTIR results determined the functional groups on the sorbents. The BET results also were showed the coating of titanium oxide nanoparticles on composite decreased the specific surface area of adsorption in comparison to adsorption containing titanium oxide particles. The adsorption capacity of the activated carbon/ Graphene Oxide Nanosheets coated with titanium oxide nanoparticles and titanium oxide particles were 240. 7 and 210. 5 mg sevoflurane per gram of sorbent, respectively (p-value<0. 001). Conclusion: The results were concluded that composite of activated carbon/nano oxide graphene coated with titanium oxide nanoparticles has a higher adsorption capacity of sevoflurane than other composite coated with titanium oxide particle, under the same conditions. This increase can be as a result of changes in surface chemistry (increase of the functional groups) in composite.

Introduction: The causal analysis of occupational accidents’ severity in the chemical industries may improve safety design programs in these industries. This comprehensive study was implemented to analyze the factors affecting occupational accidents’ severity in the chemical industries. Material and Methods: An analytical study was conducted in 22 chemical industries during 2016-2017. The study data included 41 independent factors and 872 accidents in a ten-year period (2006-2015) as a dependent variable. Feature selection algorithm and multiplied linear regression techniques were used to analyze this study. Results: Accident severity rate mean was calculated 214. 63 ± 145. 12. The results of feature selection showed that 30 factors had high impacts on the severity of accidents. In addition, based on regression analysis, the severity of accidents in the chemical industries was affected by 22 individuals, organizational, HSE training, risk management, unsafe conditions and unsafe acts, as well as accident types (p<0. 05). Conclusion: The findings of this study confirmed that accidents’ severity in the chemical industry followed the multi-factorial theory. In addition, the main finding of this study indicated that the combination of features selection algorithm and multiple linear regression methods can be useful and applicable for comprehensive analysis of accidents and other HSE data.

Introduction: Nowadays multiple techniques have been developed to noise control. One the most important way is the control based on sound absorption and insulation. The purpose of current study was to improve the acoustic properties of soft polyurethane foam regarding combined sound absorption and insulation characteristics. Materials and Methods: Polyacrylonitrile and polyvinylidine fluoride nanofibers are fabricated using solution electrospinning technique. Nano-clay particles (montmorillonite, 1-2 nm in diameter) were purchased from Sigma-Aldrich, Inc. Experimental design was prepared using Design-Expert ver. 7 software. The 50 samples of nanocomposites were fabricated on the basis of experimental run. The measurement of sound transmission loss and the absorption coefficient was conducted using BSWA SW477 550005 Impedance Tubes according to the standard ASTM E2611-09 and ISO10534-2, techniques. Response surface methodology (RSM) with central composite design (CCD) was applied to optimize the conditions to produce nanocomposites for each frequency range. Results: The polymer nanocomposites had the higher combined sound transmission loss and the absorption coefficient than pure polyurethane foam. Their combined transmission loss and the absorption coefficient in the low, middle and high frequency range was 02. 02, 1. 91 and 2. 53 times higher than the pure polymer. The combined transmission loss and the absorption coefficient in all frequency ranges have been increased by increasing the thickness of the composites and air gap. At a thickness of 2 cm, the combined composites, sound transmission loss and the absorption coefficient increased with the increase of content of both nanofibers. The highest combined transmission loss and the absorption coefficient was observed when mass fraction of nanofibers was in at its maximum level. Conclusion: This study showed that the adding nano-clay particles, polyacrylonitrile and polyvinylidine fluoride nanofibers to polyurethane foam can lead to increased sound transmission loss and the absorption coefficient. The obtained optimized nanocomposite can be applied to noise control where requiring the absorption as well as reduction of sound transmission.

Introduction: Hydrogen sulfide is one of the most important impurities in natural gas. Since this gas is hazardous, toxic, corrosive and volatile, therefore, the removal of hydrogen sulfide has been studied using several methods. In the present study, activated carbon and activated carbon-based composite scaffolds (MOF-5) were used as a cartridge mask to remove hydrogen sulfide from respiratory air. Material and Methods: Activated carbon (AC) was converted to powder form by ball mill, and AC / MOF-5 composite with 10%, 25%, and 40% MOF-5 / AC was synthesized from the MOF-5 metal-organic scaffold. The rates of adsorption and breakthrough time were then tested using a designed setup. The Aeroqual S500 Direct-reading sensor with 0. 01 ppm accuracy was applied to measure the exact amount of hydrogen sulfide gas. Results: The AC/MOF-5 composite showed higher adsorption and breakthrough time compare to the other adsorbents. The maximum adsorption (mg/gS) and breakthrough time (min) were related to AC/MOF-5(40 Wt. %) adsorbent with 60. 41 mg/gS and 56. 26 min. By adding more than 25% MOF-5 metal-metal scaffold to activated carbon, the amount of adsorption, breakthrough time, and pressure drop were increased. Conclusion: AC / MOF-5 composite adsorbent due to its porous structure, high specific surface area, and most importantly, having Zn-O-C groups increased the adsorption rate as well as the pollutant breakthrough time. However, it showed a relatively higher pressure drop than commercial activated carbon (AC).

Introduction: In toxicological studies of particulate matter (PM), inhalation exposure chambers (IEC) are usually used for distributing the test atmosphere uniformly and stability in the respiratory zone of laboratory animals. This study was aimed to design, evaluate and optimize a whole-body IEC, to expose small laboratory animals with PM. Material and Methods: The initial design of the chamber was determined based on the advantages and disadvantages of the existing chambers. To create a uniform distribution of particles, metal guide plates were used in the upper cone. ANSYS Fluent software was used for numerical simulation and optimize the initial design. The used particles had a mean aerodynamic diameter of 10 microns. Particle concentration was measured along the cylindrical radius at 10 cm intervals on the x-axis. Then the percentage of variation coefficient (CV%) of the particle concentration for each line was calculated. The design with the lowest CV% was selected as the best chamber design. Results: The optimized design has a cylinder section with two upper and lower cones, and two guide plates and its CV equal to 4. 08%. Conclusion: The optimized design was provided with a uniform and stable distribution of the particles to expose small laboratory animals.

Introduction: Industrial incidents are one of the major problems the most societies. Different studies in this field showed that the main and most important cause of error occurrence is human factor. Therefore, the aim of this study was to identify and asses the risk of human error in the activities related to the operation of electrical installations in Tehran Province Electricity Distribution Company. Material and Methods: This study is a qualitative and cross-sectional research was conducted through direct observation of the tasks, surveying documents, and interview. A task analysis was done using Hierarchical task Analysis, (HTA), the results were presented in the form of HTA. Finally, according to the instructions of SHERPA, the relevant worksheet was completed. Results: The analysis of SHERPA worksheets showed that a total of 3399 errors were detected for 759 tasks as 39. 57% of them were action errors, 32. 4% check, 7. 32% retried type, 19. 64% communication and 1. 80% were selective errors. According to the results of risk assessment, 12. 47% of the errors were in unacceptable risks level, 59. 57% were undesirable, and 20. 2% were acceptable risks but need to be revised and the rest, 7. 93% acceptable with no need for revision or remedy action. Conclusion: According to the results, the most common type of error was action error. Adopting corrective measures such as proper selection of people for occupations, training, monitoring, using smart machines, tag outs and periodical checking and updating the instructions would be useful and effective countermeasures.