By David J. Peters, CSHM, CHMM, CMQ/OE

Most operating facilities perform some form of job hazard analysis (JHA), activity hazard analysis (AHA), or pre-job briefing before work begins. These tools are indispensable for identifying hazards and communicating controls to the workforce.

Yet one question is often left unasked:

Is the worker performing this task operating within the assumptions under which the facility was designed to be safe?

That distinction matters.

Facilities are designed around normal operating conditions. Operators follow established routes, occupy designated work areas, and interact with equipment in predictable ways. Engineering controls, administrative controls, and operating procedures are developed with these routine interfaces in mind.

Maintenance, inspection, construction, and testing are fundamentally different. These activities intentionally place workers where operators seldom (or never) go. The process may remain unchanged, but the worker’s relationship to the process changes dramatically.

Consider an elevated vent stack. Its purpose may be to discharge gases high enough into the atmosphere to promote dispersion and reduce exposure to personnel at ground level. Under normal operations, that engineering control works as intended. However, if work must be done on the stack using a scaffold, the maintenance crew is intentionally positioned within or adjacent to the area the engineering analysis assumed would remain unoccupied. The vent has not become unsafe. The assumptions behind its safe operation have changed.

One example illustrates this well:

Workers were replacing a pressure safety valve on a boiler system at elevation. Access to boiler areas is exceedingly common, but the pressure safety valves release steam and are therefore at an elevated position, requiring a scaffold for access, which is not a common area to access. The hazards analysis walkdown was performed before the scaffold was built and was therefore conducted at ground level. The hazards associated with that pressure safety valve were identified, but proximity to nearby pressure safety valves were not. When the workers returned from lunch later in the day, they recognized that significant amounts of steam were in the area, as well as pools of water on and near the scaffold. Following investigation, it was identified that a nearby pressure safety valve had activated and discharged to their working area, and if they had been present, the workers would have been subjected to hazardous energy.

Traditional job hazard analyses often focus on the task itself, such as:

  • What tools are being used?
  • Is fall protection required?
  • Are pinch points identified?
  • Has energy isolation been verified?

These are all critical questions. However, they do not always evaluate whether the planned work invalidates assumptions embedded within the facility’s design or hazard analysis.

A more comprehensive review asks additional questions:

  • Are engineering controls being relied upon outside their intended application?
  • Does this work introduce ignition sources into environments where none normally exist?
  • Does this activity introduce chemicals which may react with process chemicals or systems?
  • Does the activity defeat, bypass, or temporarily remove existing protective features?
  • Does the worker become a new receptor for hazards that were previously controlled through distance, elevation, shielding, or restricted access?

These questions move beyond occupational hazards and begin examining how the work interfaces with the process itself. The same principle applies across many industries and activities:

  • Grinding adjacent to combustible dust accumulations that operators never disturb.
  • Welding near pressure relief valve discharge locations.
  • Personnel working within radiant heat zones surrounding flare systems.
  • Tank roof inspections where vapor concentrations differ significantly from ground level.
  • Temporary occupancy of areas affected by nitrogen purges or ventilation exhausts.
  • Removal of guarding, shielding, insulation, or barriers that normally separate personnel from hazards.
  • Does the work require operating systems to be placed in an abnormal lineup or configuration which may not have been analyzed?

This is not an argument that traditional job hazard analyses are ineffective. Rather, it is an argument that they should explicitly account for how maintenance and non-routine work alter the assumptions that underpin safe operation. This doesn’t require a separate process hazards analysis.  When that occurs, simply evaluating the hazards of the task may not be enough.

Perhaps one additional question that belongs in every job hazard analysis is:

“What assumptions about normal operations become invalid because we are performing this work today?”

This expands the job hazard analysis to deliberately evaluate whether planned work changes the assumptions that existing engineering and administrative controls depend upon, rather than creating additional processes and more paperwork for safety professionals.

This single question may also reveal hazards that would otherwise remain hidden—not because they were poorly analyzed, but because they were never relevant until the work began.

Resources for More Information*:

*Depending on your industry, regulatory rules and case studies may vary. This article is not intended to serve as an authoritative source for all industries and locations.

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Disclaimer: This article was authored by an IHMM certificant and is published for informational and educational purposes only. The views, opinions, conclusions, and recommendations expressed are solely those of the author and do not necessarily reflect the official position, policies, or views of the Institute of Hazardous Materials Management (IHMM), its Board of Directors, officers, employees, committees, or affiliates. Publication by IHMM Today does not constitute IHMM’s endorsement of the author’s statements, any referenced organization, product, service, or practice. Readers are responsible for independently evaluating the information presented and should obtain appropriate legal, regulatory, technical, or professional advice before relying upon or acting on the article’s contents.