Tier 1 / Tier 2 PSE Rate Calculator

Calculate Tier 1 and Tier 2 Process Safety Event (PSE) rates in line with API RP 754 methodology — standardizing your loss of primary containment (LOPC) event counts against total work hours, using either the 200,000 or 1,000,000-hour convention.

Reporting Standard / Base Hours API RP 754 allows either a 200,000 or 1,000,000 man-hour multiplier — the choice should match your company's occupational injury rate convention.

Tier 1 PSE Count LOPC events with the greatest consequence (e.g. injury/fatality, ≥$100k fire/explosion damage, community impact, release ≥ Table 1 threshold).

Tier 2 PSE Count LOPC events with lesser consequence (e.g. recordable injury, ≥$2,500 fire/explosion damage, release ≥ Table 2 threshold).

Total Work Hours Total hours worked by all employees and contractors in the same reporting period.

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Tier 1 PSE Rate

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Tier 2 PSE Rate

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Combined Tier 1+2 Rate

Formula Reference (API RP 754)

PSE Rate = (Total PSE Count ÷ Total Work Hours) × Base Hours — calculated separately for Tier 1 and Tier 2.

200,000-hour base	Matches standard OSHA TRIR convention
1,000,000-hour base	Per-million-hours convention
Basis for choice	Should match your company's occupational injury rate convention

Tier 1 vs Tier 2 — Quick Reference

Both tiers begin with an unplanned or uncontrolled loss of primary containment (LOPC). Tier 1 covers the most severe outcomes — injury/fatality, hospital admission of a third party, fire/explosion damage ≥ $100,000, community impact (e.g. evacuation), or a release at or above the Table 1 threshold quantity. Tier 2 covers lesser-consequence LOPCs not already counted in Tier 1 — a recordable injury, fire/explosion damage ≥ $2,500, or a release at or above the (lower) Table 2 threshold quantity.

Calculations follow the PSE Rate methodology set out in API RP 754 (Process Safety Performance Indicators for the Refining and Petrochemical Industries, 3rd Edition, 2021). Tier 1/Tier 2 event classification depends on detailed threshold quantity tables (Annex A of RP 754) not captured in this simplified calculator — always confirm classification against the full standard before official reporting. For customized calculators tailored to your organization, please contact Impact Tech Solutions.