ALOHA Software Research Articles

Gas Leakage Risk Management Of Biogas Powerplant Using Aloha Gas Dispersion Modelling And Bowtie Analysis

Biogas, a fuel derived from organic waste, has gained popularity as a sustainable energy source. The adaptability of biogas allows its utilization for electricity and heating. This study aims to evaluate the risk of biogas leakage using ALOHA gas dispersion modeling and Bowtie analysis to identify hazard zones and evaluate the effectiveness of preventive and mitigation measures. The research method using Gas dispersion modeling in ALOHA software can simulate the spread of leaked biogas, identify potential hazard zones, and inform emergency response planning. The results show that gas dispersion reaches up to 296 meters from the leak source in a worst-case scenario without ignition, with significant implications for safety. The ignition scenario produces high thermal radiation, further exacerbating the risk. In conclusion, these findings highlight the intolerable risk of biogas leakage, requiring comprehensive risk mitigation measures. This study recommends the implementation of a robust control system, routine maintenance, and emergency response plan to ensure the safety and sustainability of biogas facility operations

Quantitative Fire Risk Assessment of Crude Oil Tank at Company A

The oil and gas industry has a high risk of losses due to fire. There have been several fire incidents in the oil industry involving fires in crude oil tanks. The objective of this research is to assess the level of fire risk in Crude Oil Tank T32 at Company. The research method used is to analyze the frequency of fire occurrences using event tree analysis and modeling the consequences of fires using ALOHA software. After conducting frequency analysis and consequence modeling, individual risk and social risk are calculated. Results: Based on the results of consequence modeling, the furthest distance for heat radiation with a 100% risk of death is 84 meters. The largest risk calculation result is in the leaky tank scenario with a hole size of 100 mm with an individual risk value of 1,84 x 10-8 and a social risk value of 3,13 x 10-7. The results of the T32 tank fire risk assessment at Company A's oil collection tank facility show that individual and social risks are still within the acceptable risk category according to the UK HSE Risk Acceptance Criteria. Even though the risk of a fire incident is still within acceptable limits, risk control efforts still need to be carried out so that the risk remains within acceptable tolerance limits

Comparison of numerical calculations and ALOHA modeling in consequence assessment of chlorine gas emissions from ethylene dichloride reactors.

Incidents involving chemical storage tanks in the petrochemical industry are significant events with severe consequences. Within the petrochemical industry, EDC is a sector that produces ethylene dichloride through the reaction of chlorine and ethylene. The present research was conducted to evaluate the consequences of chlorine gas released from the EDC reactor in a petrochemical industry in southern Iran. Data regarding reactor specifications were obtained from the factory's technical office, while climatic data was acquired from the Meteorological Organization. The consequences of chlorine gas release from the reactor were assessed in four predefined scenarios using numerical calculation methods and modeling with the ALOHA software. The numerical calculation method involved thermodynamic fluid path analysis, discharge coefficient calculations, and wind speed impact analysis. The hazard radius was determined based on the ERPG1-2-3 index. Results showed that in the scenario of chlorine gas release from EDC reactors, according to the ALOHA model, an increase in wind speed from 3 to 7m/h led to an expanded dispersion radius. At a radius of 700m from the reactor, the maximum outdoor concentration reached 3.12ppm, decreasing to 2.27ppm at 800m and further to 1.53ppm at 1000m. The comparison of numerical calculations and modeling using the ALOHA software indicates the desirable conformity of the results with each other. The R2 coefficient for evaluating the conformity of the results was 0.9964, indicating the desired efficiency of the model in evaluating the consequences of the release of toxic gasses from the EDC tank. The results of this research can be useful in designing the site and emergency response plan.

An integrated risk assessment method for urban areas due to chemical leakage accidents

Chemical parks which hold large inventories of hazardous materials have become one important type of urban critical infrastructure. The hazardous chemical leakage such as toxic gas leakage has emerged in recent years, resulting in not only serious environmental pollution but also catastrophic consequences to certain urban areas. It is critical to make scientific risk assessment for such events to reduce negative effects. To address this issue, an integrated urban risk assessment (IURA) method coupling consequences of chemical leakage accidents and the vulnerability of local population is proposed in this work. The threat zones and hazard maps of toxic gas dispersion are present by using the ALOHA software. The population vulnerability is decided by three indicators including exposure, sensitivity, and adaptive capacity of residents in affected areas, the Grey Correlation-TOPSIS (GC-TOPSIS) method is used to rank the vulnerability of different regions. The ArcGIS software is applied to generate an integrated risk map through superimposing the hazard map and the population vulnerability map. The original risk matrix evaluation results were subdivided using the Borda count method. A case about an industrial city in Hubei, China is analyzed to test the method. Result shows the new integrated risk assessment method is more accurate and effective, which is beneficial for the government to develop emergency plans and enhance the safety of people.

Simulation analysis of hazardous chemicals released from the furniture plant using ALOHA software.

The manufacturing of wooden furniture is extensive in Thailand's east. Hazardous chemicals were used in the wooden furniture industry's manufacturing process. Hazardous substances released into the surrounding atmosphere appear to have an impact on the environment and individuals. The ALOHA model is frequently used to assess hazardous chemicals released into the environment; this simulation model is an effective tool for modeling chemical compounds and detecting chemical disasters. It has a tremendous potential for preventing mishaps in potentially hazardous or emergency situations. Acetone and butyl acetate were extracted from the hardwood furniture business to identify accidents such as leaking, spillage, and evaporation. It is described as a highly poisonous, combustible, and explosive material. Toxic accident releases have negative implications for the surrounding areas. The goal of this work was to examine each accident using ALOHA software, and the computation of acetone and butyl acetate accidents was shown in this study. This project provides critical data for the furniture plant's chemical emergency rescue strategy as well as recommendations for emergency evacuation site decision-making.

Consequences analysis of a natural gas pipeline: The case of the trans‐Anatolian natural gas pipeline

AbstractIndustrial accidents include fire, explosion, and toxic substance spread involving hazardous substances. They threaten the health of many people, cause permanent or long‐term pollution of the natural environment, cause a high degree of property damage, and require a large‐scale emergency response. Pipelines that transfer hazardous chemicals over a large area are risky for industrial accidents. In this study, we aimed to analyze the consequences of a possible industrial accident at the Edirne Ipsala compressor station in the trans‐Anatolian natural gas pipeline (TANAP). Analyses were carried out with the ALOHA software on two hypothetical scenarios: In Scenario 1, the chemical escapes from the pipe without the gas burning; and in Scenario 2, the chemical escapes from the pipe with the gas burning (jet fire). In the analysis of overpressure effects, TNT EM and TNO MEM were used besides the software. The largest effect distance (≈5000 m) was determined in the flammable area as a result of Scenario 1, and the prominent hazard property of the chemical was supported. The overpressure effects obtained with TNO MEM and the software were compatible with each other, but the values obtained with TNT EM were less severe and quite different. In the analysis of overpressure effects, it is shown that the ALOHA software provided more conservative results and that buildings would collapse and lethal effects might occur at a distance of 1000 m from the source. ALOHA produced outputs integrated with GIS by providing thermal radiation and toxic effect threat zones as well as overpressure effects. ALOHA turns out to be a more convenient and practical tool for risk assessment studies and emergency plans.

A quantitative model to assess the human consequences of a natural gas pipeline rupture in urban distribution networks

Natural gas is known as a hazardous fuel that could cause human casualties, especially in urban areas. For this reason, assessing the consequences of natural gas pipeline ruptures is settled as an important element in determining the potential effects of such ruptures on human health and developing risk management programs for natural gas networks. Several efforts have been made in the literature to establish potential consequence areas; however, there are many limitations on the methodologies proposed so far; or alternatively, consequence analyses have been performed in specific cases using a defined location, but not along a natural gas distribution network. The model proposed in this research consists of two main components: (i) a spatial assessment of gas dispersion through the ALOHA software to obtain the potential impact areas, and (ii), the count of the number of individual people located within the potential impact areas through a geographic information system (GIS) model, which proves to be a valuable tool for assessing the consequences of natural gas distribution networks. The proposed model has been applied on a case study to validate the ability to quantify the number of people exposed per linear meter of pipeline, and provide the opportunity to relatively assess the level of consequences of the pipeline network.

Impact of Filling Stations: Assessing the Risks and Consequences of the Release of Hazardous Substances

In today’s world, where environmental protection and sustainability are increasingly important, it is essential to pay attention to the environmental impact of different industries. One of these industries with a potentially significant impact on life, human health, the environment, and property is gas stations, which are essential links in the fuel supply chain. This article focuses on the topic of assessing the impact of gas stations on surrounding environments and will examine the potential negative impacts that these operations can have on society and the environment. The aim of the paper is to analyze how gas stations affect their surroundings in the event of an incident involving a spill of hazardous substances. The scope of the paper is to assess the impacts of a spill of hazardous substances from a gas station, with an emphasis on assessing the risks and consequences on the life and health of the people in the immediate vicinity of the gas station. The selected gas station’s location in the High Tatras National Park enhances the study’s significance due to the unique environmental context, heightened environmental sensitivity, and potential legislative implications. ALOHA software version 5.4.7 was chosen for simulating the release of hazardous substance due to its extensive substance database, mathematical models, support for various release sources, internet availability, and graphical result representation. This manuscript argues for risk assessment beyond current legislation, addressing unclassified sources of risk. This research contributes by utilizing predictive modeling, recognizing environmental contexts, and emphasizing legislative attention. It discusses the consequences of emergency scenarios involving gasoline and LPG, addresses potential limitations and uncertainties, and advocates for accident prevention and risk assessment, especially in environmentally sensitive areas. The conclusion suggests improvements in predictive modeling, legislative adaptation, collaboration, and an expanded scope of analysis for future research. The aim of the paper is also to discuss measures that can be taken to minimize these impacts and ensure sustainable and safe operation. Assessing the risks arising from the operation of gas stations contributes to the development of measures to protect and preserve our environment for future generations.

Implementation guide for process safety management

AbstractA general guide how to implement process safety management (PSM) is missing in the literature. This article provides general procedure to implement PSM which any industry in underdeveloped, developing and developed countries can adopt to start PSM implementation. PSM implementation can be initiated through the proposed framework consisting of four steps: (1) PSM introduction, (2) Assigning departmental wise PSM duties, (3) Trainings and (4) Audits and improvements. Trainings include process hazard analysis (PHA) using Integrated What‐If/HAZOP analysis, quantitative risk assessments using ALOHA or equivalent software, PSM forms developments and other trainings. In a case study, ammonia release is estimated and quantified using ALOHA. Nine various forms for PSM are required to be developed for industry implementing PSM. Various trainings should be arranged including specific learning outcomes and few examples are discussed in this article. An audit scheme is proposed for any new industry implementing PSM. PSM elements implementation sequence is discussed. New established industries can adopt this procedure to implement PSM following suggested forms and sequences, which can help engineers in understanding PSM implementation. This PSM implementation proposed framework is being implemented in the fertilizer industry and caustic industry.

Investigation and simulation of non-adaptive psychology of crowd evacuation under toxic gas leakage accident in chemical park

Chemical parks promote economic development, but accidents have caused casualties. Non-adaptive crowd psychology during evacuations can lead to panic, which can result in irrational behavior. Exploring ways to control panic and improve evacuation efficiency is crucial. In this paper, we conduct a questionnaire survey to grasp the psychological rules of evacuating people in the context of toxic gas leakage accidents in chemical parks, and define the weight of panic influence factor accordingly. Combined with a specific chemical park scenario, ALOHA software was used to simulate and analyze the consequences of toxic gas (liquid ammonia as an example) leakage, and the evacuation available time was obtained as 720s. The simulation experiments of personnel evacuation in the accident context were conducted by using Anylogic software based on the social force model, and the required evacuation time was 663.9s, 706.3s, 725.4s and 744.5s respectively under different panic influence factors. Drawing on the idea of building fire performance assessment, the safety criteria for evacuation under toxic gas leakage considering evacuation panic is proposed, namely RSET < ASET, to determine the safety status of personnel evacuation under different panic impact factors, which is hoped to provide some effective guidance for emergency evacuation in chemical parks.

Potential Threat Assessment and Degree of Exposure in the event of an Explosion by Sudden Expansion of Boiling Liquid Vapor in the LPG Ground Storage Terminal in Monteverde, coastal Ecuador

The industrial complexes that handle dangerous products with flammable characteristics have been the cause of great misfortunes when sudden explosions are generated, either due to mechanical failures or human negligence. The Monteverde Gas Complex (MGC), located in the province of Santa Elena in Ecuador, represents a potential risk by housing close to 105,000 m3 of precursor gases such as Propane (PPN), Butane (BTN), and LPG finished product. Therefore, an analysis of the potential threat to which the population is exposed in case of the explosion of one of the tanks with the different products they contain has been carried out, considering the closest communes to the MGC, which are Monteverde and Jambelí. Tools such as the Probit method proposed by TNO (The Netherlands Organization for Scientific Research), and the ALOHA software of the EPA (Environmental Protection Agency, USA) were used, whose combinations allowed estimating the radius of influence, which were divided into zones according to the degree of impact on the community. The results demonstrated that the community of Monteverde, despite being more than 1 km away from the CGM, is within the red zone or high influence radius that corresponds to 2000 meters for propane and butane tanks. Whitin this area, a person could have fatal third-degree burns. The calculations have been performed under ideal conditions, so it is recommended to review the attenuations generated by natural elevations of the terrain or the direction of the wind in further studies

Dynamic risk assessment of storage tank using consequence modeling and fuzzy Bayesian network

Accidents in process industries cause irreparable economic, human, financial and environmental losses annually. Accident assessment and analysis using modern risk assessment methods is a necessity for preventing these accidents. This study was conducted with the aim of Dynamic risk assessment of tank storage using modern methods and comparing them with traditional method. In this study, bow tie (BT) method was used to analyze the Leakage event and its consequences and model the cause of the outcome, and the Bayesian network method was used to update the probability rate of the consequences. Then, four release scenarios were used. Possible selection and release outcome were modeled using version 5.4 of ALOHA software. Finally, according to the degree of reproducibility of possible consequences and risk number modeling for the four scenarios were estimated. The results of modeling the cause and effect showed that 50 Basic events are effective in chemical leakage and Pool fire is the most probable consequence due to chemical leakage in both BT and Bayesian network (BN) models. Also, the modeling results showed that Leakage 50 mm diameter has the highest Emission rate (80 kg/min) and Leakage of 1 mm have the lowest emission rate. The results of risk assessment showed that the estimated risk number in both models is in the unacceptable range. In this study, an integrated approach including BT, Fuzzy Bayesian networks and consequence modeling was used to estimate the risk in tank storage. The use of these three approaches makes the results of risk assessment more objective than conventional methods. The results of outcome modeling can be used as a guide in adopting accident prevention and emergency preparedness approaches.

Dynamic risk analysis of flammable liquid road tanker based on fuzzy Bayesian network

AbstractDue to environmental variability of combustible liquid road transportation, it is difficult to analyze risk accurately. This article proposes a method for real‐time analysis of the risk of flammable liquid road transportation using a fuzzy Bayesian network. This method combines the binary logistic regression model with the bow‐tie model to analyze the influencing factors and accident evolution. Then, a Bayesian network framework is established based on the fault tree model. In the case of limited historical accident statistics, the fuzzy set theory and Leaky Noisy‐OR theory are used to determine the prior probability and conditional probability of Bayesian network nodes, and ALOHA software is used to simulate the dangerous area of the accident to define further the safe evacuation range and emergency rescue material demand. Taking the road transportation of a tanker in Beijing as an example, the accident probability is updated in real time by monitoring the data of transportation nodes, and the change rule of risk level with internal and external conditions at different times is analyzed. The research shows that this method can dynamically describe the road transportation accidents of hazardous chemicals with the GPS data of vehicles.

Consequence analysis in industrial organizations containing H2S gas through accident scenarios based on chemical source selection

AbstractH2S gas emissions occur in various processes, especially in the purification of polluted waters, mining, and petroleum refining processes and this extremely dangerous chemical has serious toxic emission, explosion, and fire effects. These physical effects vary considerably depending on the source strength. Therefore, consequence analyzes based on source strength models are critical components in the process of assessing hazards. In this study, a consequence analysis was performed with accident scenarios related to different sources of H2S gas. ALOHA 5.4.7 and EFFECTS 8.0.1 Software were used for physical effects modeling. Modeling studies were conducted on direct source (continuous release:100 m3/s, 5 m3/s), puddle source (100 m3, 5 m3), tank source (vertical‐horizontal cylindrical, spherical, 1.57 m3), and gas pipeline source with ALOHA Software. Possible Gas LOC (Levels of Concern) scenario Leak (G3) and Gas LOC scenario release in 10 min (G2) scenarios were studied with EFFECTS Software. When the results of both software were compared with each other, it was seen that the effects of thermal radiation and explosion were of similar order and value, and the toxic effect values were very different from each other. Both software allow for a release above ground level for gases that behave as neutrally buoyant. The main difference between the dispersion models used in the software is that the gas is assumed to behave as non‐interacting ideal gas in ALOHA, but in EFFECTS deviations from ideal gas are considered. And, ALOHA dispersion models use surface roughness lengths in a limited fashion and only include 60‐min AEGLs. ALOHA does not account for topographic steering or winds that vary with time in EFFECTS. It can be said that the results of the ALOHA Software are more conservative than the EFFECTS Software.

Investigating the Challenges of Ammonia Emission in Firuzabad Sodium Carbonate Factory Incident: A Case Study

Background: An ammonia gas explosion poses immediate health hazards such as respiratory tract burns, skin and eye irritation, and potential death within seconds. It also causes long-term negative impacts on biodiversity, affecting aquatic life and vegetation. An explosion in the Firuzabad sodium carbonate factory in Iran led to massive ammonia gas leakage and the poisoning of several employees. This study evaluates the risks of ammonia gas release caused by the explosion and the rescue team’s response in the same factory. Materials and Methods: This study was conducted in 2020 in Firuzabad City, Iran. The investigation was based on case reports and data analysis obtained via field observations, document reviews, interviews, and experiments. Technical and specialized information on explosion were analyzed by ALOHA software. Results: Based on data analysis, red, orange, and yellow zones around the explosion area were identified. The red zone had an ammonia emission range of 1.2 km with an explosive power of 10 kW, causing potential death in 60 seconds. Orange zone had a range of about 1.7 km, an explosive power of 5 kW, and the potential for second-degree burns and respiratory damage within 60 seconds of release. The yellow zone covered an area of about 3.3 km. Interviews and field observations provided information on the risk-based response process, response equipment, medical treatment, hazardous materials, handling and response equipment, personal protective equipment, mutual aid, and resource typing. Conclusion: The results of this study show that the immediate evacuation of the area, employment of the rapid warning system, the triage of the injured, the presence of an emergency operation plan to control hazardous and toxic materials disasters, the performance of the rapid response team and multi-specialty teams were among the existing challenges of the operation team. Background of this study confirms the potential hazards associated with ammonia gas emissions from explosions in sodium carbonate plants.

Risk analysis of gas dispersion, fire and explosion due to gas pipeline leak at Onshore Receiving Facility of PT XYZ in Muara Karang using Aloha Software 5.4

This research identifies hazards, assesses risks, and recommends mitigations for the risk of gas pipeline leaks at Onshore Receiving Facility (ORF). The objectives of this study are to determine the probability of gas pipeline leaks at ORF and the level of risk of gas pipeline leaks at ORF using a risk matrix, to model gas dispersion, fire, and explosion using ALOHA software to assess the consequences of gas pipeline leaks at ORF, and to provide risk mitigation recommendations to the company if the risk level is unacceptable and the existing risk mitigation measures are not effective. This study is qualitative research in which the author develops a model from theoretical framework to conceptual framework, and then describes the results of the analysis descriptively. The hazard identification approach used historical data from the Hazard Operability’s Study (HAZOP) data, which found that the highest risk level was gas pipeline leaks in pipelines with a pressure of 350 psi. The probability of pipeline leaks was obtained from the Generic Failure Frequency (GFF) table from the existing Risk-Based Inspection (RBI) study. Consequence analysis was performed using modeling software ALOHA and MARPLOT with gas dispersion, fire, and explosion scenarios. The analysis showed that the risk level of gas dispersion, fire, and explosion scenarios were all still acceptable, referring to the criteria of NFPA 59A. Therefore, it can be concluded that the risk level of gas pipeline leaks at ORF is still acceptable, and the existing risk mitigation measures are sufficient.

A systematic review of consequence modeling studies of the process accidents in Iran from 2006 to 2022

Analytical models and the prediction of accidents and their consequences are important tools for preventing accidents in the industry. Therefore, the present study was conducted to review process accident consequence modeling in Iran (2006–2022), helping improve incident modeling, and creating a context for preventing these accidents. In this study, the articles of 5 international Embase Medline/PubMed databases, ProQuest, Scopus, Google Scholar, and Web of Science, and four Iranian databases SID, MagIran, IranMedex, and IranDoc were examined using the PRISMA checklist. After reviewing the studies, 40 articles were included in the final analysis. The results showed that 25 studies used PHAST software, 11 studies used ALOHA software and 4 studies used ALOHA and PHAST software together. The highest number of studies was conducted in Imam Khomeini Port and Asaluyeh city, respectively. In addition, the number of studies published in Persian was more than in other studies. There was no similar agreement between the results of the two software in providing correct results at low concentrations. PHAST software also provided more accurate results than ALOHA over longer distances in stable and relatively stable weather conditions. The study and identification of hazards and scenarios in the studies that used PHAST software were more, more accurate and more coherent than in the studies that used ALOHA software. It is suggested that in future studies the same scenario can be compared with PHAST, ALOHA, and newer modeling software such as Fire Dynamics Simulator (FDS).

Safety assessment: predicting fatality rates in methanol plant incidents

In this article, the prediction of fatality accident rate at methanol (MeOH) plant was studied using different assessment methods. The prediction method was performed and simulated using HYSYS, ALOHA, MARPLOT, and MATLAB software. Recent studies for pressure variation up to 442 bar in MeOH synthesis by carbon dioxide (CO2) hydrogenation showed that three times more MeOH was produced than in conventional plants, with 90% CO2 conversion and 95% MeOH selectivity. However, safety concerns were noted when MeOH production was operated at pressures above 76–500 bar. Therefore, a safety assessment of the pressures between 76 and 500 bar was performed to predict the fatality rate at the MeOH plant. Adaptive Neuro-Fuzzy Inference System (ANFIS) was compared with a conventional analysis by using the consequence method to predict the fatality rate. First, 26 input parameters were simulated in HYSYS, ALOHA, and MARPLOT software by using the consequence method. Then, the input parameters were reduced to six, namely, pressure, mass, volume, leakage size, wind speed, and wind direction, for prediction using ANFIS tool in MATLAB. This study aimed to highlight the accuracy of the fatality rate prediction by using the ANFIS method. In this manner, accurate prediction of fatality rate for MeOH plant incidents was achieved. The prediction values for the ANFIS method was validated using the standard error of the regression. The percent error measurement obtained the lowest regression of 0.0088 and the lowest percent error of 0.02% for Hydrogen (H2) Vapor Cloud Explosion (VCE) ident. Therefore, the ANFIS method was found to be a simpler and alternative prediction method for the fatality rate than the conventional consequence method.

Human vulnerability modeling and risk analysis of railway transportation of hazardous materials

People who live in densely populated regions could be at risk of mishaps that occur during hazardous materials (hazmat) transportation. Population vulnerability assessment is an essential parameter for developing risk mitigation strategies to prevent negative consequences of hazmat transportation incidents. In this study, a procedure is developed to estimate the risk of hazmat railway incidents, focused on two parts. First, the most probable and the most dangerous meteorological variables (e.g., stability class, wind speed, solar radiation, etc.) are processed to simulate threat zones and prepare hazard maps using the ALOHA software. Second, sociodemographic characteristics (e.g., age, sex, education, household, income, employment, etc.) of the affected population are used to create vulnerability maps along with their weights. As risk is a function of hazard and vulnerability, risk maps are generated by superimposing the hazard and vulnerability maps using ArcGIS software. This procedure is tested in a city in Canada and confirms the significance of integrating population vulnerability in risk assessment by revealing that the areas with high hazards indicated on the hazard maps are not necessarily considered as the areas with high risk indicated on the risk maps. The risk maps generated in this study can be used to provide recommendations to improve land-use planning, enhance the safety of the people, living in higher-risk areas, and prioritize emergency response decisions. The procedure developed in this study can also be applied to different types of railway incidents and other potential incidents in the transportation industry when all the necessary information is available, such as regional meteorological conditions and the characteristics of the affected population.

Risk Analysis Related to the Possibility of Using CNG in Trans Jogja Buses

&lt;p class="E-JOURNALAbstractBodyEnglish"&gt;One of the issues in urban areas such as DI Yogyakarta province is air pollution. The pollution level is high, as shown by the quality index value of about 85.25 in 2019. Vehicle emissions are the most significant source of this pollution in urban areas and can be decreased by using fuel with minimum carbon emission. Compressed Natural Gas (CNG) is an environmentally friendly fuel. However, a safety study is required because CNG is stored under high pressure. Therefore, this research aims to analyze the risk of using CNG in the Trans Jogja bus. The research method collects secondary data and then processes them using FTA, ETA, ALOHA software, and a risk matrix. The result shows that the risk value for CNG usage in the Trans Jogja bus is low to a moderate level or acceptable.&lt;/p&gt;