TOXIC CHEMICAL RELEASE — METHYL MERCAPTAN FATALITIES
DuPont La Porte Facility Toxic Chemical Release
DuPont La Porte Facility
📍 La Porte, TX
Incident: November 15, 2014  •  CSB Report: June 25, 2019
4
Fatalities
Methyl Mercaptan (Highly Toxic — Insecticide/Fungicide Manufacturing)
Chemical Involved
9
CSB Recommendations
📋 Incident Summary

On November 15, 2014, four workers were killed and one was injured at DuPont's La Porte, Texas facility when methyl mercaptan -- a highly toxic chemical used in the manufacture of insecticides and fungicides -- was released inside an enclosed manufacturing building. Workers who entered the building to locate missing coworkers were exposed to lethal concentrations of methyl mercaptan.

The CSB investigation found that the enclosed manufacturing building configuration directed the released gas toward workers rather than allowing dispersion, that pressure relief systems discharged methyl mercaptan to locations accessible by workers rather than to a destruction system, and that the emergency response team was poorly equipped and unprepared to respond to a toxic release in a confined building.

The final report, released June 25, 2019, issued 9 recommendations addressing inherently safer building design, pressure relief system routing to destruction devices, robust process hazard analysis, workforce participation in safety improvements, and a comprehensive overhaul of the emergency response plan. All recommendations were ultimately closed as no longer applicable after DuPont permanently closed the IBU manufacturing operations.

🔎 Key Findings
Finding 01
Four Workers Killed by Methyl Mercaptan Exposure
Workers entered the enclosed manufacturing building to locate missing coworkers and were exposed to lethal methyl mercaptan concentrations. The building design and gas release characteristics prevented safe entry and rapid rescue.
Finding 02
Enclosed Building Concentrated Toxic Gas
The enclosed manufacturing building structure allowed methyl mercaptan to accumulate and concentrate rather than disperse. An open or partially open building design could have significantly reduced the lethal concentration workers encountered.
Finding 03
Pressure Relief Systems Discharged to Unsafe Locations
Pressure relief devices in the Insecticide Business Unit discharged methyl mercaptan to locations accessible to workers rather than routing releases to a destruction system such as a scrubber -- a fundamental design gap.
Finding 04
Emergency Response Team Was Unprepared
The ERT mini-pumper truck was inoperable, responders lacked equipment to monitor for toxic and oxygen-deficient atmospheres, the hot zone was not properly established, and personnel lacked familiarity with the building layout.
Finding 05
No Real-Time Process Data Analysis During Incident
No one analyzed process control data during the emergency to identify the source, scope, or magnitude of the release -- leaving responders without critical information needed to safely direct rescue operations.
🔍 Root Causes
1
Building Design Created Toxic Trap
The enclosed manufacturing building was not designed using inherently safer design principles. No evaluation had been conducted of whether an open structure would reduce consequences, and ventilation did not effectively protect workers from an internal release.
2
PSV Discharge Systems Routed to Occupied Locations
The facility's pressure relief systems discharged to accessible work areas without routing toxic releases to safe destruction systems -- a fundamental process safety design deficiency that PHAs had not adequately evaluated.
3
PHA Failed to Identify Toxic Release Consequences
The facility's process hazard analysis did not adequately evaluate the consequences of a toxic chemical release within the enclosed manufacturing building or identify the need for inherently safer design alternatives.
☑ CSB Recommendations
→ DuPont La Porte Facility
Conduct comprehensive engineering analysis of manufacturing building and PSV discharge systems; evaluate inherently safer design options including open building structure and routing toxic relief discharges to destruction systems.
→ DuPont La Porte Facility
Conduct robust engineering evaluation of building ventilation system to define a documented design basis protecting all workers from toxic, asphyxiation, and flammability hazards during normal and emergency operations.
→ DuPont La Porte Facility
Commission a pressure relief device analysis per API Standard 521 and ASME Code to ensure all relief systems discharge to safe locations protecting workers and the public from toxic chemical exposure.
→ DuPont La Porte Facility
Perform more robust PHAs across all Insecticides Business Unit areas, prioritized by risk, using the hierarchy of controls to ensure highest-risk areas receive priority corrective action.
→ DuPont La Porte Facility
Develop and implement a plan ensuring active participation of workers and union representatives in the implementation of engineering and PHA safety recommendations.
→ DuPont La Porte Facility
Publish a publicly available summary of the incident investigation, integrated restart plan, and actions taken to implement all safety recommendations.
→ DuPont / ERT Member Companies
Update the emergency response plan to address: unit expert pre-identification, emergency alerting protocols, ERT vehicle maintenance, hazardous atmosphere characterization equipment, hot zone control, and release source identification via process data.
→ ICWUC/UFCW Local 900C
Work with DuPont to develop and implement a workforce participation plan ensuring workers and representatives are actively involved in safety recommendation implementation.
→ ICWUC/UFCW Local 900C
Work with DuPont to develop and implement the updated emergency response plan addressing all key lessons from the November 15, 2014 incident.
💡 Lessons Learned
Methyl mercaptan and other highly toxic chemicals can kill at very low concentrations. Manufacturing buildings handling such chemicals must be designed with this reality as a core engineering constraint -- enclosed structures with inadequate ventilation become death traps when toxic gases are released.
Pressure relief systems protect equipment -- but where they discharge determines whether workers are protected or endangered. Routing toxic PSV discharges to destruction systems (scrubbers, flares) is not optional; it is a fundamental process safety design requirement.
Emergency response to a toxic release inside a building requires specific, practiced procedures. Responders who enter a building without confirmed atmospheric characterization and functional equipment face the same hazards that killed the original victims.
PHAs must evaluate the consequences of toxic releases within occupied process buildings -- not just release scenarios that reach the fence line. The building itself can create a confined-space exposure hazard that amplifies the lethality of even a moderate release.
Worker participation is not a compliance checkbox. Involving workers and their representatives in PHA and corrective action implementation strengthens the quality of safety decisions and ensures those closest to the hazards have meaningful input.
PSI: Process Safety InformationPHA: Process Hazard AnalysisMI: Mechanical IntegrityEAP: Emergency Planning & Response
🔨 Safety Meeting Toolbox Talk
►If a toxic chemical were released inside one of our process buildings right now, would our ventilation system protect workers -- or concentrate the gas to dangerous levels?
►Where do our pressure relief devices discharge? Could a PSV activation expose workers to toxic, flammable, or high-pressure materials in any accessible area?
►Is our emergency response team equipped and trained to characterize the atmosphere before entering a building with a suspected toxic release?
►When did our process hazard analysis last specifically evaluate a toxic chemical release inside an occupied process building as a distinct hazard scenario?
►What would our ERT do in the first 10 minutes of a toxic gas release in an enclosed building -- and has that procedure been drilled recently?
Immediate Action Items
✓Review all pressure relief valve discharge locations and confirm that toxic or flammable relief streams are routed to destruction systems, not to open areas accessible by workers.
✓Walk down your highest-risk process building and assess whether an internal toxic or flammable release could rapidly reach dangerous concentrations for workers inside.
✓Pull your last PHA for a process handling highly toxic chemicals and verify that toxic release inside the building was specifically evaluated as a hazard scenario.
✓Verify that your ERT has functional, calibrated atmospheric monitoring equipment and that all team members know how to operate it before entering a potential toxic environment.
✓Review your emergency response plan for toxic chemical releases and confirm it includes steps for hot zone establishment, atmospheric characterization, and source identification using process data.
🔗 PSM Failures Behind This Incident

This incident traced to breakdowns across 4 PSM elements (PSI · PHA · MI · EAP). 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.
Supporting documents in our library →
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 →
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 →
Emergency Planning & Response
When process safety barriers fail, emergency response capability determines whether the outcome is controlled or catastrophic. Gaps in emergency preparedness amplified the consequences here.
Supporting documents in our library →
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