Protecting Personnel and Plant with Facility Siting

Process industry history is sprinkled with catastrophic incidents that acted as drivers of regulatory change, such as the 1974 Flixborough explosion, the 1984 Bhopal toxic release disaster, and the 2005 Texas City Refinery flammable material release and explosion. Lack of process safety management, damage, and deaths were the commonalities among these incidents. The OSHA Process Safety Management (PSM) Standard and EPA Risk Management Plan (RMP) regulations were promulgated in response to these types of devastating accidents. These regulations were supplemented in the US by industry standards such as the American Petroleum Institute (API) Recommended Practices 752, 753, and 756, and with guidance developed by the Center for Chemical Process Safety (CCPS). These standards and guidance documents became the consensus industry practices for performing facility siting (FS) studies.

Refinery with facility siting

FS studies analyze potential toxic, fire, and explosion hazards to personnel from releases of hazardous chemicals. From a regulatory perspective, facility siting is required in the US by OSHA PSM and EPA RMP for facilities that meet the qualifying definition. A checklist is often utilized during Process Hazard Analyses (PHAs) to meet the regulatory requirements for facility siting; however, a FS study provides a more detailed analysis of specific facility siting concerns and should be referenced during PHA scenario development.


Irrespective of regulation, it is best practice to conduct a FS study to understand the implications of a release of hazardous materials at your facility. While PHAs develop hazard scenarios that could potentially result in loss of containment, a FS study assumes a release has occurred and evaluates the outcomes accordingly.


aeSolutions utilizes the following general approach to performing a FS study:

  1. Identify chemicals of concern

  2. Collect information on site-specific conditions (e.g., equipment and process data, building construction and occupancy data, equipment and building locations on the facility)

  3. Identify potential hazard event scenarios from a review of PHAs, incident investigation reports, discussions with experienced personnel, and other pertinent sources of information

  4. Identify and classify occupied buildings

  5. Perform the hazardous material release consequence analysis

  6. Perform the risk analysis if a risk-based approach is used

  7. Package the results in a way that the results can be understood and review the results with the client

  8. Discuss with the client options to reduce risk

For the consequence analysis, software can be used to model the discharge, dispersion, and impacts of an accidental release of flammable or toxic material. Limiting the analysis to the consequence analysis, the FS results are consequence-based, which provides a measure of the severity of the hazard. Taking the assessment, a further step, a Quantitative Risk Assessment (QRA) can apply release event frequencies and appropriate probabilities, such as probability of ignition and vulnerability of people to the various effects, to quantify the risk associated with a release scenario.


A consequence-based FS study is simpler and requires less resources to perform, but the results of a consequence-based FS study may set a higher bar to address and necessitate additional action or protection at a facility. A risk-based QRA requires more expertise and resources to perform the study, but the benefit gained is that the study often finds that the event likelihood of many scenarios is so low that the hazard meets the company risk criteria and additional means of protection that a consequence-based study concludes is needed are not required after all (i.e., less resources spent on addressing FS study results).


Conducting a facility siting with a practical approach to study methodology and risk mitigation can balance the cost and course of action to protect personnel and facility assets. This enables company leaders to better make reasonable decisions on how to protect their employees. For instance, relocating all personnel to blast resistant modules can become expensive and may not be necessary in all cases; an alternative combination of innovative solutions may accomplish the risk reduction. Protection can come in different forms, such as increasing airflow through a building for preventing flammable vapor or gas accumulation or utilizing shelter-in-place for toxic concerns. Facility siting requires a pragmatic evaluation of the nature and level of hazard and what would be best for personnel and the plant.


Facility siting regulations and standards have improved significantly since the Flixborough, Bhopal, and Texas City Refinery catastrophic incidents and continue to evolve to ensure toxic, fire, and explosion hazards are appropriately mitigated in the future. Ultimately, a detailed facility siting study can help you understand the hazards of potential releases, how those hazards can impact occupied buildings, and most importantly, determine effective solutions to protect your valued workforce.