CSB Investigation — Reactive Chemical Explosion
First Chemical Corp. Reactive Chemical Explosion
First Chemical Corporation
📍 Pascagoula, MS
Incident Date: October 13, 2002  |  CSB Report Released: November 2002
0
Fatalities
Several
Injuries
4
CSB Recommendations
MNT
Reactive Chemical
📋 Incident Summary

On October 13, 2002, a reactive chemical explosion occurred inside a 145-foot distillation column at the First Chemical Corporation facility in Pascagoula, Mississippi. Mononitrotoluene (MNT) — a hazardous nitroaromatic compound — underwent an uncontrolled thermal decomposition reaction, generating pressure sufficient to blow the top section off the distillation tower. Debris was ejected onto adjacent industrial facilities.

The incident occurred during a process upset when MNT reached temperatures that triggered self-accelerating decomposition inside the column. Critically, operators were unaware the process was running in an active state at the time of the event. The runaway thermal decomposition of MNT generated gas and pressure that catastrophically failed the column — a consequence that would have been predictable if the decomposition hazard had been formally characterized.

The CSB found that First Chemical's process safety information on MNT decomposition characteristics was inadequate, and that no engineering interlocks existed to prevent MNT from reaching temperatures capable of initiating uncontrolled decomposition. For nitroaromatic compounds, calorimetry testing is essential to define the self-accelerating decomposition temperature (SADT) and design operating limits and interlocks that keep the process safely away from the hazard.

🔎 Key Findings
Finding 1
MNT Decomposition Hazard Insufficiently Characterized
The thermal decomposition characteristics of MNT under process conditions were not adequately documented. The onset decomposition temperature and self-accelerating decomposition temperature (SADT) were not used to define safe operating limits.
Finding 2
Operators Unaware Process Was Active
At the time of the decomposition, operators had no situational awareness that the distillation process was running in an active state, eliminating the last human safeguard.
Finding 3
No Temperature Interlock
No engineering interlock existed to automatically shut down the process or reduce heat input when column temperatures approached the MNT decomposition threshold.
Finding 4
Inadequate PHA for Reactive Hazards
The PHA for the MNT distillation process did not adequately evaluate the runaway thermal decomposition scenario — a known hazard class for all nitroaromatic compounds.
Finding 5
Debris Impact on Adjacent Facilities
The ejected column top section landed on adjacent industrial facilities, demonstrating the community and neighbor hazard of reactive chemical distillation in shared industrial complexes.
Finding 6
Nitroaromatic Decomposition is a Well-Known Hazard
Thermal decomposition of nitroaromatic compounds at elevated temperatures is an extensively documented industrial hazard. The hazard class was known — the specific characterization for MNT was not performed.
🔍 Root Causes
1
Inadequate Reactive Hazard Characterization
The SADT and decomposition kinetics of MNT under process conditions were not characterized and incorporated into process design, safe operating limits, or interlock setpoints.
2
Absent Temperature Interlock for Decomposition Prevention
Without an engineering interlock to prevent temperature excursion into the MNT decomposition range, the process depended entirely on operational awareness — which failed when operators lost situational awareness.
3
PHA Did Not Evaluate Reactive Decomposition Scenario
The process hazard analysis did not identify MNT runaway decomposition as a credible scenario, so no safeguards were designed for this high-consequence event.
4
Operator Situational Awareness Failure
Deficient monitoring and control room communication left operators without real-time awareness that the column was in an active state, removing the last human safeguard.
☑ CSB Recommendations
→ First Chemical Corporation
Conduct comprehensive reactive hazard analysis for all MNT and nitroaromatic processes, including calorimetry testing to determine SADT, decomposition onset temperature, and gas generation rates.
→ First Chemical Corporation
Install temperature high-high interlocks that automatically shut down heat sources and initiate safe process shutdown if column temperatures approach MNT decomposition thresholds.
→ First Chemical Corporation
Revise control room monitoring and operator communication systems to ensure operators have real-time awareness of the operating state of all reactive chemical units at all times.
→ AIChE / CCPS
Expand reactive hazard characterization guidelines to make calorimetry testing requirements explicit for all nitroaromatic compound processing operations.
💡 Lessons Learned
⚠ Reactive chemicals — especially nitroaromatics — can undergo runaway decomposition above a critical temperature. Process Safety Information must include thermal decomposition data derived from calorimetry testing.
⚠ Operating limits derived from reactive hazard characterization (SADT, onset temperature) must be enforced by engineering interlocks, not just operational procedures subject to human awareness lapses.
⚠ Process hazard analysis for reactive chemical operations must specifically evaluate runaway reaction and decomposition scenarios — these cannot be assumed low-probability without specific characterization.
⚠ Operator situational awareness is a safety-critical function. Systems must ensure operators always know the active state of reactive chemical processes, especially during unattended periods.
⚠ Reactive chemical decomposition in distillation columns can generate catastrophic pressures that far exceed vessel design limits. Relief systems sized for normal upsets are completely inadequate for decomposition scenarios.
PSM Elements: PSI · PHA · SOP · MI · TRN
🔨 Safety Meeting Toolbox Talk
Topic: Reactive Chemical Hazards in Distillation Operations
💬Does our process involve reactive chemicals — nitroaromatics, peroxides, unstable isomers — with documented self-accelerating decomposition temperatures?
💬Have we conducted calorimetry testing or reactive hazard screening to define safe temperature operating limits for all reactive chemical processes?
💬Are temperature operating limits for reactive processes enforced by engineering interlocks, or are they procedural controls relying solely on operator vigilance?
💬Does our PHA specifically address runaway reaction and thermal decomposition scenarios for reactive chemicals in our process units?
💬Do operators always have real-time visibility into the operating state of reactive chemical units, including knowing when a distillation column is actively processing reactive materials?
💬Are emergency shutdown procedures for reactive processes tested regularly to verify they interrupt temperature excursions within the required response time?
✎ Team Action Items
✓Review Process Safety Information for any reactive chemicals in your process — confirm SADT data, decomposition onset temperatures, and gas generation data are documented and current
✓Identify temperature high-high interlocks for reactive chemical process units and verify they are functional with setpoints that provide adequate safety margin below the SADT
✓Pull the PHA for reactive chemical processes in your unit and confirm runaway reaction and thermal decomposition scenarios were specifically evaluated and safeguards identified
✓Verify operator monitoring tools provide real-time visibility into all active reactive chemical processes, including unattended distillation columns
🔗 PSM Failures Behind This Incident

This incident traced to breakdowns across 5 PSM elements (PSI · PHA · SOP · MI · TRN). Each represents a documented gap that process safety documentation and consulting can close before a similar event occurs at your facility.

Process Safety Information (PSI)
Accurate, complete Process Safety Information is the foundation every other PSM element depends on. When PSI is missing or wrong — chemistry data, equipment specs, P&IDs — the entire hazard analysis is built on a flawed base.
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Process Hazard Analysis (PHA)
A structured PHA or HAZOP study exists to identify exactly these scenarios before they occur. When PHA is absent, superficial, or overdue for revalidation, hazards operate unseen until they kill someone.
Supporting documents in our library →
Operating Procedures (SOPs)
Operators cannot reliably hold safe operating limits without clear, current, enforced procedures. Deviation from acceptable operating conditions — a root cause here — is a direct consequence of SOP failure.
Supporting documents in our library →
Mechanical Integrity (MI)
Equipment must be designed, inspected, and maintained to operate safely in its intended service. Mechanical integrity failures — degraded equipment, missed inspections, deferred repairs — contributed to loss of containment here.
Supporting documents in our library →
Training & Operator Competency
Workers must understand process hazards — not just the steps on the page. Training records, refresher frequency, and verified competency are all OSHA PSM requirements that gaps here violated.
Supporting documents in our library →
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