JOURNAL OF OCCUPATIONAL HYGIENE ENGINEERING
Year:2018 | Volume:5 | Issue:2 |Papers Count:8

Background and Objective: Sound absorption coefficient determination is an important factor in selecting the proper materials to control indoor noise. Therefore, this study aimed to compare the results of sound absorption coefficient of different materials by standing wave ratio and transfer function method, as well as developing a regression model in adjusting the provided results. Materials and Methods: The current study was conducted on 46 acoustic materials. In order to measure the absorption coefficient of different materials, two instruments called the impedance tube (model 9410, AvaSina, Iran) and the impedance tube (model SW 260, BSWA, USA) in compliance with ISO 10534-2 in the frequency range of 125 to 2000 Hz were utilized. Results: The obtained results from the regression model revealed that frequency of 500 Hz has the highest correlation (r=0. 968, R2=0. 936), and the lowest correlation coefficient was found at 125 Hz (r=0. 368, R2=0. 136). In addition, the correlation coefficient of NRC was 0. 829. Conclusion: The results showed that the two methods were consistant at the frequencies of 250, 500, 1000 and 2000 Hz. It can be concluded that the standing wave ratio method is a reliable approach in determining sound absorption coefficient of acoustic materials.

Background and Objective: The most important goal of modeling is to acquire knowledge about the actual behavior of the system. Toxic leakage is a likely issue in process and chemical industries and one of the threatening factors for the personnel and residents involving in the mentioned industries. In this regard, the present study aimed to model the effect of ammonia leakage from the ammonia reservoirs. Materials and Methods: In the present study, the ammonia liquid release from the reservoir was modeled using ALOHA software version 5. 4. 7 in one of the southern refineries. This study was modeled based on the three scenarios, including the formation of the toxic vapor clouds, flammable environment, and toxic explosive atmosphere. Results: Based on the results of the present modeling, the concentration of ammonia was 1, 100 ppm, 5 km around the reservoir (red range). In addition, from this area to about 160 miles (about 10 km) around the reservoir (orange range) the concentration of ammonia was 160 ppm. In the event of full leakage of ammonia from the reservoir up to 500 m, the ammonia concentration was reported to be about 90, 000 ppm, which was approximately 60% of the minimum flammable concentration of ammonia gas. Furthermore, the ammonia concentration up to about 1. 7 km of the tank was 15000 ppm, which was about 10% of the minimum of the flammable ammonia concentration. It should be considered that in the event of vapor cloud explosion, the explosive wave pressure is approximately 700 m from the reservoir equivalent to Psi 8 that can cause serious damage to the buildings. Conclusion: According to the results of modeling, ammonia intoxication is the most important threat to personnel. Therefore, the inspections in accordance with the manufacturer company's proposal on ammonia repositories and emergency response plans will have an effective role in the limitation of the harmful effects of toxic and dangerous emissions.

Background and Objective: Despite continuous efforts to reduce risks in different systems, unsafe mistakes and behaviors are the main causes of incidents at the workplace. The safety of laboratories is important because of the variety of chemicals, electrical equipment, high costs of some pieces of equipment, as well as the large number of students, professors, and staff who use labs. For this reason, it is necessary to identify, assess, and control their hazards by appropriate methods. Materials and Methods: In this study, the assessment and classification of hazards in laboratories (ACHiL) method was used. The ACHiL approach was based on a platform in which 28 risks were classified into three levels based on their limitations. Limit values were edited by United Nations Organization, The International Agency for Research on Cancer, and other global requirements. Results: The results of this study showed that chemical agents were identified as the most important risk factor in the studied laboratories. Environmental agents were also identified as the second most effective factor in the occurrence of accidents. Biological agents and then physical agents had the least important roles in the occurrence of accidents in the studied laboratories. Furthermore, the level and the location of hazards were defined based on their severity. Conclusion: The ACHiL platform is a simple yet highly efficient tool for health and safety professionals. This allows them to get a full and deep view of the existing hazards, as well as dangerous samples in the lab in order to take appropriate safety measures.

Background and Objective: Offshore emergency operations are one of the most potentially hazardous incidents. Considering the major role of human factors in this operation, human error assessment is necessary in this section. The aim of this study was to evaluate human error levels in emergency evacuation conditions using Human Error Probability Index method (HEPI). Materials and Methods: This research was conducted on 17th and 18th alpha platforms in South Pars region. To collect data, the ranked aggregation questionnaire was used for the HEPI index with regard to event factors, stress, complexity, climate conditions, training, and individuals' experiences. Results: The results showed that the risk of returning process to the safe mode, the activity of immunizing the environment, moving the way to the emergency exits, the identification of emergency exits and registering the names in Temporary Safe Refuge (TSR) were unacceptable. The corrective actions, such as training, repairing, using safety signs, preparing and delivering emergency response plans, and training the personnel, were carried out and confirmed within an acceptable range. Conclusion: According to the results of this study, conducting more maneuvers with respect to their feedback can be effective in reducing the risk of reaction in emergency evacuation. In addition, a tool such as HEPI can also provide a better understanding of the concept of human error.

Background and Objective: Xylene is a volatile organic compound that is widely used in various industries. Xylene is hazardous not only for the environment but also for human health even in its low-risk concentrations. Today, photocatalytic removal methods has received a great deal of attention in comparison with other methods of removing pollutants. Therefore, the present study aimed to determine the efficiency of removal of xylene vapor from airflow using photocatalytic property of titanium dioxide on ZSM-5 zeolite. Materials and Methods: In this experimental study, the characteristics of the catalysts were determined using Brunauer– Emmett– Teller, X-ray diffraction (XRD), and scanning electron microscopy scanning (FESEM). Xylene vapors were produced using a dynamical condenser system and the efficiency of xylene vapor depletion was investigated using UV / ZSM-5 / TiO2. Results: The obtained results of the images and spectra from XRD, EDS, and FESEM showed good signs of immobilization. The findings revealed that the removal efficiency was decreased by increasing the concentration from 50 ppm to 150 ppm and increasing the flow rate from 0. 3 to 0. 5. The removal efficiency at concentrations of 50, 100, and 150 was 35. 46%, 22. 70%, and 17. 37%, respectively. Conclusion: The results showed that the use of composite substrates increases the efficiency of photocatalytic removal, and it is suggested that these adsorption and photocatalytic combination systems can be used to remove other volatile organic compounds in the gas phase.

Background and Objective: Petrochemical industries are known as one of the most important sources of organic pollutants which endanger the workers' health. The aim of this study was to evaluate the relationship between inhaled Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) concentrations and some urine metabolites of people working at a petrochemical complex. Materials and Methods: This cross-sectional study was an analytical type with 60 inhalation air samples and biological samples. Sampling and decomposition of pollutants were carried out in accordance with 1501 and 2549 methods of National Institute for Occupational Safety and Health (NIOSH). The results then were compared with the Occupational Exposure Scale (OEL) and the proposed National Occupational Exposure Indicators (BEI) in Iran. Statistical analysis was performed in SPSS software (version 17). Results: The results of the study showed that the mean concentration of Trans, Trans-muconic acid (TTMA) was 137μ g/g Creatinine. The concentrations of Hyporic acid, Phenylglyoxalic acid, and Methyl-hyporic acid were obtained as 0. 577, 0. 066, and 0. 404 g/g Creatinine, respectively. In addition, the mean concentration of benzene, toluene, ethylbenzene, o-, mxylene, and p-xylene were 3. 818, 4. 004, 3. 357, 0. 132, and 2. 0159 ppm, respectively. The results also showed that toluene and benzene concentrations in 5 inhalable samples and Hyporic acid and TTMA in 10 urine samples were higher than the proposed limit. Conclusion: The mean total concentration of inhaled BTEXs and the urine metabolites were lower than the acceptable range recommended by the country. There is a high correlation between measured pollutants in respiratory air and the concentration of urine metabolites. Therefore, it can be concluded that the chronic exposure to these pollutants leads to an increase in the excretion of urine metabolites. As well, the working conditions have detrimental effects on the health of people encountering with these organic compounds.

Background and Objective: Incidental events due to human error in the maintenance activities of molecular sieve replacement in the dehydration unit of gas refineries indicate the inadequate effectiveness of the techniques available to identify human errors. This study aimed to identify and analyze human errors in this maintenance activity using the predictive human error analysis (PHEA) technique and provide appropriate control strategies to prevent or reduce the consequences of identified errors. Materials and Methods: In this study, all activities and tasks performed to achieve the main goals were identified using hierarchical task analysis (HTA) technique. Subsequently, possible types of human errors in each phase of the above processes were predicted and identified using the PHEA method and a series of guidance keywords. After determining the consequences of each error, appropriate control methods were also provided. Results: Out of 11 operations and 111 sub task occupations analyzed in the PHEA worksheets, a total of 337 errors were identified, of which 246, 13, 28, 33, and 17cases were regarded as action, checking, retrieval, information transfering and planning errors, respectively. The most significant identified errors were forgetting the task, doing the task incorrectly, incompletely, at the wrong time, making the right decision on the wrong option, and doing the task more or less than necessary. Conclusion: According to the obtained results, it can be concluded that functional errors were the most prevalent type of errors. Theses results emphasize the necessity of using control strategies in terms of adequate and effective training for personnel, the preparation and modification of instructions, the monitoring of implementation of work and hardware changes.

Background and Objective: Nowadays, the saliency of workload has become more apparent in ergonomic studies. Workload can cause incident since it is directly related to unsafe situations at work. Therefore, it is important to measure workload in different occupations. This study was conducted to evaluate the validity and reliability of driver activity load index questionnaire for assessing the mental load of drivers. Materials and Methods: This cross-sectional and descriptive-analytic study was conducted on 100 bus drivers operating in one of the manufacturing companies. The validity of the questionnaire was evaluated by academic and queue experts (lay experts). Additionally the reliability of this index was measured through employing Cronbach's alpha and intra-cluster correlation test on the data obtained from 10 participants. Data were analyzed using SPSS (version 18) software. Results: The mean age of participants was 50. 8 years with the standard deviation of 8. 29. Furthermore, the mean of work experience among drivers was 22. 18 years. The outcome of the Cronbach’ s alpha coefficient revealed that the reliability of the questionnaire was higher than 0. 7. Furthermore, intra-cluster correlation coefficient of the questionnaire was estimated higher than 0. 7 in all factors affecting the interference factor. The obtained results were indicative of moderate and optimum level of reliability. Conclusion: According to the results of validity and reliability indices, the driver activity load index questionnaire can be used as a valid and reliable questionnaire in Iran to examine and measure the mental load of drivers.