From natural disasters to equipment failures and on-site accidents, industrial plants face a multitude of unpredictable events. When dealing with materials that can potentially release hazardous vapor into the air, being prepared for the worst-case scenario could mean the difference between continued operations or costly mitigation efforts.

Understanding and characterizing hazardous vapor risk starts by analyzing certain parameters using dispersion modeling tools. Projects, processes and assets are assessed for potential risk, considering a range of possible situations to provide steps for minimizing a project’s risk of generating hazardous atmospheric conditions. While certain regulations can drive dispersion modeling, safety is the most important and overarching driver behind successful hazardous vapor dispersion modeling, offering owners and operators a cost-effective means to mitigate risk and increase peace of mind.

Organizations that include hazardous vapor dispersion modeling and risk analyses in the development of new projects — or perform such assessments on existing plants — stand to gain a number of benefits.

Impacts to New Plant Design and Existing Plants

Understanding the proper placement of equipment, such as valves and vents, to mitigate risk is important to keeping processes, workers and the local community safe. That’s why implementing hazardous vapor dispersion modeling at the outset of a project is key. There are a variety of regulations that plants must comply with to meet safety standards, such as National Fire Protection Association rules and Occupational Safety and Health Administration standards. Hazardous vapor dispersion modeling not only determines the risk of harm to the environment, but also to workers and equipment on-site.

Applying hazardous vapor dispersion modeling at the start of a project has the potential to decrease the chance of incurring additional costs of necessary changes down the line. Hazardous vapor dispersion modeling can be performed at an existing plant, should it be found that the site needs to adjust the placement of assets and equipment to meet certain safety guidelines. Such adjustments are necessary to meet safety regulations and protect workers and equipment; they also can result in costly redevelopment of equipment layouts and interruptions to processes.

Worst-Case Scenario Planning

Worst-case scenarios do, unfortunately, happen. Hazardous vapor dispersion modeling helps organizations characterize their risk by taking into account an enormous number of variables to determine proper mitigation actions. These assessments ask, “What’s the worst thing that could possibly happen?” and then seeks the answer and work backward to mitigate for it.

The worst-case scenario can be identified by modeling different projected operational situations, such as during typical ambient conditions or during upsets due to extreme meteorological events.

For existing sites, hazardous vapor dispersion modeling provides an assessment of existing equipment layouts to locate flaws and offer solutions to increase safety.

Implementing Value

By providing a characterization of existing risk, dispersion models offer the basis for a mitigation plan for the emission of hazardous vapors. With the worst-case scenario in mind, organizations have an understanding of what events are possible on a site, allowing them to develop plans designed specifically to preempt those events.

The results of hazardous vapor dispersion modeling also provide organizations the information needed to inform local emergency response departments of potential hazards on-site.

Understanding Risk

Faced with a multitude of risks, organizations must find ways to characterize and mitigate certain scenarios that may put their communities, employees and equipment in danger. Understanding such risks helps organizations position themselves as good corporate citizens and strengthen community ties.

Hazardous vapor dispersion modeling demonstrates the potential impact of vapor releases on-site, presenting possible risks through the development of various scenarios. By applying this method during the early phases of the project, organizations give themselves a leg up for future success should conditions conducive to a release event occur.


Comprehensive investigation and analyses provide a full overview of potential risks to your site.


Jon Hill specializes in air quality permitting and hazardous air dispersion modeling at Burns & McDonnell. Jon helps industrial and utility clients acquire operating and construction air permits for projects. He also conducts regulatory interpretations, emission calculations and air dispersion modeling.