Risk assessment of vapor cloud explosions in a hydrogen production facility with consequence modeling

New technologies using hazardous materials usually have certain risks. It is more serious when the technology is supposed to be applied in a large scale and become widely used by many people. The objective of this paper was to evaluate the risk of vapor cloud explosion in a hydrogen production process. Potential hazards were identified using the conventional hazard identification method [HAZID]. The frequency of the proposed scenarios was estimated from statistical data and existing records. The PHAST professional software was applied for consequence modeling. Both individual and societal risks were evaluated. This cross-sectional study was conducted from June 2010 to December 2011 in a Hydrogen Production Plant in Tehran. The full bore rupture in heat exchanger had the highest harm effect distance. The full bore rupture in desulphurization reactor had the highest [57% of total] individual risk. Full bore rupture in heat exchanger was the highest contributor to social risk. It carried 64% and 66.7% of total risk in day and night respectively. For the sake of safety, mitigation measures should be implemented on heat exchanger, reformer and hydrogen purification absorbers. The main proposed risk reductive measures included; the increasing of installed equipment elevation, the application of smaller vessels and pipes

Cardiac strain between normal weight and overweight workers in hot/humid weather in the persian gulf

In hot weather, overweight and obesity are considered as significant risk factors for the incidence of cardiac strain in workers. This study was aimed to compare cardiac strain among overweight and normal weight workers in hot, humid conditions in the south of Iran. This cross sectional study was conducted on 71 workers in the south of Iran in summer 2010. The heart rate was measured at rest and at actual work. Cardiac strain based on working heart rate [WHR], the relative cardiac cost [RCC], the net cardiac cost [NCC], load relative cardiovascular [CVL], and heart rate reduction was analyzed in 35 normal weight people [body mass index [BMI] <25 kg/m[2]] and 36 overweight people [BMI >25 kg/m[2]] using descriptive statistics. In 42% of the total workers, BMI was >25 kg/m[2]. The average of Wet Bulb Globe Temperature Index [WBGT Index] in the two groups was not significantly different. The mean WHR in the two groups was 101 +/- 20.3 and 112 +/- 18.9, respectively [P = 0.026]. Percentages exceeded the acceptable limits in the parameters NCC, RCC, WHR, CVL, and Brouha index, which were significantly higher in overweight people than in those with normal weight. Based on the study results, it is concluded that the severity of cardiac strain was higher in overweight workers compared with that in normal weight workers. Hence, in order to decrease the cardiac strain, selecting overweight individuals for these jobs should be avoided and also some vital intervention for losing weight should be implemented such as nutrition education and encouraging them regarding physical activity

Occupational exposure of a medical school staff to formaldehyde in Tehran

Cadavers are preserved in a fixing solution containing formalin. Formaldehyde [FA] released from formalin is inhaled by the personnel in the anatomy laboratory. Exposed personnel have reported respiratory problems and various symptoms. Due to the toxicity of FA as a strong irritant and carcinogen and also lack of a national study assessing occupational exposure to FA in gross anatomy labs in Iran, the present study aimed at occupational monitoring of personnel exposed to FA and evaluating relevant symptoms in them. A total of 20 subjects [all the staff] working in a gross anatomy lab and 20 library personnel were considered for occupational monitoring of exposure to FA during three months with various climatic conditions. They were also monitored for respiratory symptoms. Air sampling and analysis of its FA content were conducted according to the NIOSH method No.2016. Symptoms of cases and controls [library personnel] with active and passive exposure to formaldehyde were also studied by a self-report questionnaire. In the first stage of monitoring with ventilation [supply-exhaust] system on, the exposure of personnel [Mean +/- SE] was 306 +/- 21ppb. In the second stage of monitoring the personnel's exposure was 317 +/- 26ppb with only the ventilation supply system on and in the final monitoring stage this rate was 698 +/- 34ppb with the ventilation system [supply and exhaust] off. In this study, personal's exposure level to FA was higher than the indoor concentration, and the individual exposure levels of instructors were higher than those of the students. Exposure of library personnel in the adjacent department [central library] was about 50ppb. Most important complaints reported by actively exposed staff members and library personnel were the unpleasant odor [68%], cough [64%], throat irritation and runny nose [56%], burning and itching of nose [52%] and irritating eyes [48%]. Considering the level of exposure of all subjects in this study and existence of clinical symptoms, better control of the exhaust system in the gross anatomy lab and use of a more efficient ventilation system are recommended to protect the staff and instructors of the Anatomy Department

Extrapolation of experimental field study to a national occupational noise exposure standard

Proposing a Noise Standards should be considered seriously by the governmental authorities because of the prevalence of hazardous noise exposure and the seriousness of the effects. In a survey founded by World Health Organization's regional office in Iran, the existing as well as gathered data from field were applied to propose a National Occupational Noise Exposure Limit. The collected data plus the existing data were processed to: propose a national occupational noise exposure limit and depict the major restrictions in application of existing field data in proposing a national occupational noise exposure limit. Results obtained from the present study shows that the occupational noise levels of 90 to 95 dBA can lead to hearing losses greater than 25 dBA. It was shown that occupational noise levels of 85 to 90 dBA would not lead to hearing losses greater than 20 dBA. The comparison of hearing losses shows that the noise levels of less than 80 dBA will not lead to any significant hearing loss. It was deduced that 85 dBA can be recommended for a national occupational noise limit in Iran. The study also showed that the application of existing field data to recommend a national occupational noise standard may have some restrictions

Risk assessment of workers exposed to crystalline silica aerosols in the East Zone of Tehran

The term "crystalline silica" refers to crystallized form of SiO2 and quartz, as the most abundant compound on earth crust, is capable of causing silicosis and lung cancer upon inhaling large doses in course of occupational exposure. In this study, airborne respirable dust samples were collected on mixed cellulose filters [25 mm diameter, 0.8 mm pore size], by using a cyclone separator at the flow rate of 2.2 l/min for a maximum volume of 800 liters. Infrared absorption spectrometry was used according to the "National Institute of Occupational Safety and Health" [NIOSH] method No. 7602 for analysis of samples. Risk assessment techniques predictive of silicosis and lung cancer were employed. The geometric mean of workers' exposure to crystalline silica in ten industrial fields [stone milling and cutting, foundry work, glass manufacturing, asphalt, construction, sand and gravel mining, sand blast, ceramics, bricks and cement manufacturing] was in the range of 0.132 to 0.343 mg/m[3]. Mortality rate of silicosis was predicted to be in range of 1 to 52 per one thousand exposed individuals. Risk of lung cancer mortality in exposed workers in the east zone of Tehran based on geometric mean exposure of industrial activity and 45 years of exposure was in range of 50 to 129 per one thousand. In terms of risk assessment of silicosis mortality, cumulative exposure of 21 percent of population complied with the notion of acceptable risk. In regard to lung cancer mortality, 100 percent of the population were expected to have an unacceptable risk after 45 years of active work experience. This study is the first of its kind in Iran demonstrating a profile of exposure in different groups of workers in the east zone of Tehran's greater city, covering 5.5 million populations. Considering the total population of one hundred thousand workers exposed to quartz in east zone of Tehran and aging of the current young workforce, numerous cases of silicosis and lung cancer are forecasted in near future