NATURAL GAS PURGE EXPLOSION — CONTRACTOR SAFETY — 4 FATALITIES — 67 HOSPITALIZED
ConAgra Foods Slim Jim Facility Natural Gas Explosion
ConAgra Foods, Inc.
📍 Garner, NC
Incident: June 9, 2009  •  CSB Report: February 2010
4
Fatalities
Natural Gas (Methane — Indoor Piping Purge Operation)
Chemical Involved
8
CSB Recommendations
📋 Incident Summary

On June 9, 2009, a natural gas explosion ripped through the 425,000-square-foot ConAgra Foods Slim Jim processing facility in Garner, North Carolina, killing four workers and injuring 67 others who required hospital treatment. The explosion occurred during the installation of a new industrial water heater by a contractor.

The CSB found that an Energy Systems Analysts (ESA) contractor attempted to purge air from a three-inch natural gas supply pipe by venting natural gas directly into an enclosed pump room inside the building. The natural gas accumulated inside the pump room and then spread through the building until it reached an ignition source and exploded.

The explosion caused significant structural damage to the facility — the sole production site for ConAgra's Slim Jim brand — and resulted in major economic disruption, including loss of the facility and displacement of hundreds of workers. The CSB issued recommendations to the National Fire Protection Association (NFPA), the American Gas Association (AGA), and the NFPA 54 committee to update natural gas code requirements to prohibit indoor gas purging.

🔎 Key Findings
Finding 01
Contractor Purged Natural Gas Supply Pipe Directly Into Enclosed Building
An ESA contractor, during water heater installation, attempted to purge air from a natural gas supply pipe by opening the valve and venting the gas directly into the enclosed pump room — an interior location with no direct path for gas to escape to the outdoors.
Finding 02
Natural Gas Accumulated in Pump Room and Spread to Larger Building
The natural gas released during the purge operation accumulated in the pump room and then — driven by the building's ventilation system — spread to other areas of the large 425,000-square-foot production facility until the gas cloud reached an ignition source and detonated.
Finding 03
No Applicable Code or Standard Prohibited Indoor Gas Purging
At the time of the ConAgra explosion, NFPA 54 (National Fuel Gas Code) and other applicable standards did not explicitly prohibit purging natural gas to the interior of a building — the same regulatory gap that existed with the Kleen Energy gas blow procedure.
Finding 04
Contractor Was Working Without Adequate Oversight or Written Procedure
The ESA contractor performing the water heater installation was not working under a specific written procedure for the gas purging step. There was no ConAgra permit or oversight requirement that would have required the contractor to purge gas to the outdoors rather than into the building.
Finding 05
Facility Was Sole Slim Jim Production Site — Explosion Caused Major Economic Disruption
The ConAgra Garner facility was the sole production site for Slim Jim snack foods. The explosion's destruction of the facility caused a significant supply disruption and economic impact beyond the immediate casualties, including displacement of hundreds of production workers.
🔍 Root Causes
1
Indoor Natural Gas Purging Procedure Created Accumulation of Flammable Gas in Occupied Building
The contractor's decision to purge the gas pipe directly into the enclosed pump room — rather than outdoors — allowed natural gas to accumulate in the building interior. No standard, code, or contract requirement prohibited this practice or required outdoor purging.
2
Contractor Management Program Did Not Control Gas Purging Method
ConAgra's contractor management program did not require contractors performing gas work to follow specific procedures specifying that natural gas must be purged to the outdoors rather than into building interiors. The absence of this requirement allowed the dangerous indoor purging to proceed.
3
NFPA 54 Did Not Explicitly Prohibit Indoor Gas Purging
The NFPA National Fuel Gas Code did not explicitly prohibit purging natural gas supply piping to the interior of a building — the same code gap that allowed indoor gas blow procedures to persist without regulatory prohibition in the power generation industry.
☑ CSB Recommendations
→ NFPA / American Gas Association (AGA)
Amend NFPA 54 (National Fuel Gas Code) and related standards to explicitly prohibit purging natural gas piping systems to the interior of any occupied building; require that natural gas purging be conducted only to a safe outdoor location or through an inert gas displacement method.
→ ConAgra Foods / Industry
Require that all contractors performing gas piping work develop and follow written procedures specifying that natural gas purging must be conducted to a safe outdoor location; incorporate this requirement into contractor qualification and on-site permit requirements.
→ OSHA
Develop and issue guidance addressing the hazards of indoor natural gas purging by contractors at food processing and other facilities; consider rulemaking to require safe gas purging methods when contractor gas work is performed in occupied facilities.
→ Construction Contractors / ESA and Industry
Prohibit indoor venting of natural gas during piping purging operations; require all gas piping contractors to use outdoor purging or nitrogen displacement; include gas purging method in pre-task job safety analysis requirements.
💡 Lessons Learned
The ConAgra and Kleen Energy explosions occurred within months of each other and had the same root cause: natural gas being vented to an indoor or occupied-area location without anyone recognizing that the procedure created an immediately dangerous flammable atmosphere. Both involved a contractor performing a routine gas-work task using a technique that was standard in the industry — and both resulted in mass-casualty events. Routine does not mean safe.
Contractor management programs that do not specify hazardous work methods create a gap between what the contractor does and what the facility owner assumes the contractor does. ConAgra's contractor management program qualified contractors and managed their on-site safety performance — but did not specify how gas piping work must be executed. Requiring specific safe methods for high-hazard contractor tasks is as important as checking safety records.
The NFPA National Fuel Gas Code is the primary code governing natural gas installations in most jurisdictions. When the code does not prohibit an inherently hazardous practice — such as indoor gas purging — facilities cannot rely on code compliance alone as evidence that their gas work practices are safe. Facilities must independently evaluate whether code-compliant practices are also safe for their specific building configuration and occupancy.
Gas purging procedures are management-of-change and pre-startup safety review items. Installing a new water heater, modifying a gas supply line, or extending a gas distribution system are changes to a natural gas process that should trigger MOC and PSSR review — including a review of how the gas line will be purged during and after installation. The specific gas purging method used by the contractor should be a reviewed and approved element of the work plan, not an uncontrolled contractor decision.
Four fatalities and 67 hospitalizations from a contractor gas purging procedure demonstrate that construction and maintenance work involving flammable materials carries the same magnitude of process safety risk as operating process upsets. Life safety depends on treating high-hazard maintenance and construction work with the same rigor as process operations.
CON: Contractor SafetySOP: Operating ProceduresMOC: Management of ChangePSSR: Pre-Startup Safety ReviewEP: Emergency Planning
🔨 Safety Meeting Toolbox Talk
►Does your facility's contractor management program specify the methods that must be used for high-hazard work activities — including natural gas purging procedures? Or does your program focus on contractor safety records and orientation without specifying work methods?
►When contractors perform natural gas work at your facility, do you require a written work plan specifying how gas will be purged from new or modified piping — and confirming that purging will be conducted to a safe outdoor location?
►Has your facility applied MOC and pre-startup safety review requirements to installation of new gas-fired equipment, modification of gas supply lines, or extension of natural gas distribution systems? Is gas purging method included in the PSSR checklist?
►Do your hot work and general work permits include a requirement for contractors to identify and address gas purging method when their work involves connections to or modifications of natural gas piping?
Immediate Action Items
✓Review your contractor management program and add a specific requirement that all natural gas purging must be conducted to a safe outdoor location or using inert gas displacement; communicate this requirement to all gas-work contractors and include it in contractor orientation.
✓Add natural gas purging method to your pre-startup safety review and management of change checklists for any project involving installation, modification, or reconnection of natural gas supply or distribution piping.
✓Require written, site-approved work procedures for any contractor activity involving connection to, modification of, or purging of natural gas piping; confirm that the procedure specifies outdoor or inert-gas purging before work begins.
✓Brief your EHS and maintenance supervision on the ConAgra and Kleen Energy incidents; review current contractor oversight practices for gas work and confirm that field supervision verifies that gas purging is being conducted safely before the work proceeds.
🔗 PSM Failures Behind This Incident

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

Contractor Safety Management
Contractor workers must be held to the same PSM standard as employees. When contractor safety oversight fails, knowledge and compliance gaps follow contract workers onto your site.
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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.
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Management of Change (MOC)
Changes to equipment, chemistry, operating limits, or procedures that bypass formal review create new hazard pathways your PHA never evaluated. MOC failures open the door to incidents like this one.
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Pre-Startup Safety Review (PSSR)
PSSR is the final checkpoint before hazardous chemicals are introduced into a new or modified system. When PSSR fails or is bypassed, unresolved hazards go live with the process.
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Employee Participation
OSHA PSM requires workers to be meaningfully involved in hazard analyses and procedure development — not just trained on the finished product. Active participation catches gaps that management alone misses.
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