Hydrogen Sulfide Exposure — LOTO Failure and Missing Detection
Aghorn Operating Inc. H2S Release Fatalities
Aghorn Operating, Inc.
📍 Odessa, TX
Incident: October 26, 2019  •  CSB Report: May 21, 2021
2
Fatalities
Hydrogen Sulfide (H2S) in Oilfield Produced Water
Chemical Involved
9
CSB Recommendations
📋 Incident Summary

On October 26, 2019, two people were killed by hydrogen sulfide (H2S) exposure at an Aghorn Operating waterflood pump station near Odessa, Texas. An Aghorn employee started a pump without locking out / tagging out (LOTO) the equipment, causing H2S-laden produced water to be released inside an enclosed pump house. H2S accumulated and the worker was fatally overcome. Subsequently, a member of the public entered the unlocked facility and was also fatally exposed.

The CSB found that Aghorn had no formal LOTO program, no personal H2S detection required for workers entering the pump house, and a fixed H2S detection and alarm system that was non-functional at the time of the incident. The facility was not covered by OSHA PSM because oil and gas field operations are excluded from the standard.

The May 2021 CSB report issued 9 recommendations (7 to Aghorn, 1 to OSHA, 1 to the Texas Railroad Commission), all closed, addressing LOTO programs, personal H2S monitors, fixed detection systems, and site security.

🔎 Key Findings
Finding 01
Pump Started Without LOTO — H2S Released in Pump House
An Aghorn worker started a pump without performing LOTO, causing H2S-laden produced water to be released inside the enclosed pump house — no formal LOTO program meant no systematic barrier to inadvertent pump start-up.
Finding 02
No Personal H2S Detection Required for Workers
Aghorn did not require workers entering the pump house to wear personal H2S gas detectors — workers had no early warning of H2S accumulation before becoming incapacitated.
Finding 03
Fixed H2S Detection System Non-Functional
The pump house had a fixed H2S detection and alarm system, but it was non-functional at the time of the incident — no alarm was triggered as H2S accumulated.
Finding 04
Member of Public Entered Unlocked Facility and Was Fatally Exposed
After the worker's initial exposure, a member of the public entered the unlocked, unsecured facility and was also fatally overcome — security failures extended the fatality count beyond the workforce.
Finding 05
Oil and Gas Field Operations Excluded from OSHA PSM
Aghorn's waterflood station was not subject to OSHA PSM due to the oil and gas field operations exemption — a regulatory gap leaving a facility with significant H2S hazards outside the formal process safety management framework.
🔍 Root Causes
1
No Formal LOTO Program — No Barrier to Inadvertent Equipment Start-Up
The absence of a lockout/tagout program meant no systematic physical barrier existed to prevent pump start-up while workers were in the pump house — the most basic energy control safeguard was absent.
2
H2S Detection System Failure and No Personal Monitor Requirement
Both layers of H2S detection protection were absent or non-functional. Workers had no warning of accumulating H2S before becoming incapacitated, and no alarm triggered emergency response.
3
Site Security Failure — Unlocked Facility Accessible to Public
No site security (locked gates, fencing, signage) prevented a member of the public from entering an H2S-hazardous facility after the initial incident.
☑ CSB Recommendations
→ Aghorn Operating (7, all closed)
Develop and implement a formal lockout/tagout program meeting 29 CFR 1910.147 requirements for all energy control procedures at waterflood pump stations and other oil and gas field operations.
→ Aghorn Operating
Require all workers entering pump houses or enclosed spaces where H2S may be present to wear functioning personal H2S gas detectors, with defined alarm setpoints and mandatory evacuation procedures.
→ Aghorn Operating
Repair, test, and maintain the fixed H2S detection and alarm system at all pump houses and enclosed facilities where H2S-bearing produced water is handled.
→ Aghorn Operating
Implement site security measures (locked gates, perimeter fencing, hazard signage) at all pump stations to prevent unauthorized public access to H2S-hazardous areas.
→ Aghorn Operating
Develop written emergency response procedures for H2S releases at pump stations, including evacuation routes, rescue procedures not requiring entry without SCBA, and notification protocols.
→ Aghorn Operating
Train all workers on H2S hazards, LOTO procedures, personal monitor use, and emergency response procedures before they work at any facility where H2S may be present.
→ Aghorn Operating
Establish written safe work practices for pump station operations, including written procedures for all routine tasks that could create H2S exposure.
→ OSHA (1, closed)
Evaluate the oil and gas field operations exemption from 29 CFR 1910.119 and consider issuing guidance requiring PSM elements for oil and gas operations with significant H2S hazards.
→ Texas Railroad Commission (1, closed)
Develop H2S safety requirements for oil and gas waterflood operations, including LOTO programs, personal H2S monitors, fixed detection systems, and site security.
💡 Lessons Learned
Lockout/tagout is not optional — it is the barrier that prevents inadvertent energy release from killing workers. A facility with no LOTO program has no systematic protection against the most common mechanism for operational fatalities.
Personal H2S monitors are essential for any worker entering a space where H2S may be present. Fixed detection systems can fail. Personal monitors give workers the last-resort warning they need to self-rescue before incapacitation.
Fixed detection systems not maintained and verified as functional provide false assurance — they are worse than no system because they create the belief that a safeguard is in place when it is not.
Oil and gas field operations — even small waterflood stations — can contain lethal quantities of H2S. The PSM exemption does not eliminate the hazard; it eliminates the regulatory requirement. Voluntary application of process safety principles is essential.
Site security at H2S-hazardous facilities is a life-safety requirement. When a worker is incapacitated inside an H2S-filled pump house, an unlocked door is an invitation for bystanders to enter and become additional victims.
PSI: Process Safety InformationSOP: Operating ProceduresTRN: TrainingEAP: Emergency Planning & Response
🔨 Safety Meeting Toolbox Talk
►Does every worker who enters a space where H2S could be present wear a personal H2S monitor? When were those monitors last calibrated?
►Before starting any pump or equipment that could release H2S, what LOTO steps are required? Can you walk through the specific procedure for your most frequently used equipment?
►When did you last test and verify the function of your fixed H2S detection and alarm system? What happens if it goes into alarm — and who responds?
►Are all H2S-hazardous areas at your facility secured against unauthorized access? What would prevent a member of the public from entering if a worker were incapacitated inside?
►If H2S accumulated to dangerous levels in a pump house at your facility right now, what is the rescue procedure — and does it require anyone to enter without SCBA?
Immediate Action Items
✓Verify that every worker who enters any enclosed space where H2S may be present is required to wear a calibrated personal H2S monitor — audit compliance with this requirement.
✓Pull your LOTO procedures for pump and equipment operations in H2S service and verify they are current, specific, and understood by all affected employees through documented training.
✓Test your fixed H2S detection system — all detectors, alarms, and control panel indicators — and document the results. If any component is non-functional, initiate immediate repair.
✓Walk the perimeter of your most H2S-hazardous facility location and identify any access point that could allow unauthorized public entry — verify all gates are secured.
✓Review your emergency response plan for H2S incidents and confirm it specifies no-entry rescue without SCBA, notification of 911, and defined evacuation procedures for enclosed space H2S releases.
🔗 PSM Failures Behind This Incident

This incident traced to breakdowns across 4 PSM elements (PSI · SOP · TRN · 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 →
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 →
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 →
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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