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Glossary · PSI

What is Process Safety Information (PSI)?

Process Safety Information (PSI) is the documentation package that OSHA's Process Safety Management regulation requires every covered facility to maintain on every covered process. PSI is the factual foundation that every other Process Safety Management element builds on — Process Hazard Analysis, Operating Procedures, Management of Change, Mechanical Integrity, and Pre-Startup Safety Review all depend on PSI being complete, accurate, and current.
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The PSI requirement is codified in OSHA 29 CFR 1910.119(d).

What PSI must contain

Paragraph (d) organizes the required information into three categories:

  1. 011910.119(d)(1) — Information on the hazards of the highly hazardous chemicals in the process. This covers toxicity, permissible exposure limits, physical data, reactivity data, corrosivity data, thermal and chemical stability data, and hazardous effects of inadvertent mixing of different materials.
  2. 021910.119(d)(2) — Information on the technology of the process. This covers the block flow diagram or simplified process flow diagram, process chemistry, maximum intended inventory, safe upper and lower limits for temperature, pressure, flow, composition, and an evaluation of the consequences of deviations.
  3. 031910.119(d)(3) — Information on the equipment in the process. This is the largest PSI category and includes:
  • Materials of construction
  • Piping and instrument diagrams (P&IDs)
  • Electrical classification
  • Relief system design and design basis
  • Ventilation system design
  • Design codes and standards employed
  • Material and energy balances for processes built after May 26, 1992
  • Safety systems

Why P&IDs are the central PSI element

The P&ID appears explicitly in OSHA 1910.119(d)(3) and is in practice the most-used PSI document in a facility's compliance program. Every HAZOP session works from it. Every Management of Change that affects physical equipment updates it. Every Pre-Startup Safety Review confirms against it. Every LDAR survey traces components back to it.

This centrality is also the PSI element most prone to drift. Because P&IDs are commonly maintained as PDF files with ad-hoc revision control, undocumented field modifications accumulate over time. OSHA inspections frequently identify PSI deficiencies where the governing P&IDs do not match the actual field installation.

PSI update requirements

PSI must be updated whenever a Management of Change under 1910.119(l) affects the covered process. The MOC procedure explicitly requires that “the process safety information required by paragraph (d) of this section shall be updated accordingly” when a change is made.

The practical consequence is that PSI completeness is a moving target. Every physical change that is not a replacement in kind triggers a PSI update requirement, and the accuracy of PSI at any given moment depends on the discipline of the MOC program over the preceding months and years.

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