On May 4, 2023, approximately 790 pounds (358 kg) of a hydrocarbon mixture containing hydrogen sulfide (H2S) was accidentally released at a refinery in California. Exposure to the toxic H2S gas seriously injured one employee.
Before the gas release, four operators were sent to the field to replace a broken pressure gauge (Figure 1a). Because the lower valve (Figure 1b) was visibly broken, the operators closed the valve closest to the pressure gauge. They were not aware that an internal obstruction prevented the valve from fully closing. One operator began removing the pressure gauge; there was no indication of residual pressure while unscrewing the gauge. After the gauge was removed, the process pressure likely dislodged debris in the piping and released a flammable hydrocarbon mixture containing toxic H2S. None of the operators were wearing a respirator to protect themselves. Three operators regained consciousness and evacuated. The fourth operator, still unconscious, was rescued by emergency responders and received medical treatment at a hospital.
▲Figure 1. In 2023, four operators who were sent to replace (a) a pressure gauge were exposed to hazardous hydrogen sulfide gas due to an unknown internal obstruction that prevented (b) the safety valve (denoted by the blue rectangle) from closing. The lower valve, which is denoted by the blue oval, was visibly broken and, therefore, not used to prevent flow to the gauge. The effects of the exposure were worsened by the operators not wearing the appropriate personal protective equipment (PPE).
The investigation determined that the release was caused by failure to effectively isolate the piping before removing the pressure gauge. The plugged gauge gave a false sense of safety. The severity of the incident was exacerbated by the operators’ failure to wear appropriate personal protective equipment (PPE).
Did You Know?
- PPE is an administrative safeguard, but in order for it to be used effectively, personnel must know what PPE is required for the job and how to wear it correctly. Proper PPE protects against bodily and respiratory exposure.
- Operating and maintenance procedures should specify the PPE required to safely perform a task.
- Safety data sheets (SDSs) have a section on recommended PPE.
- There are several instances when PPE might not be effective, such as if it is not used or not used properly; if the user is not properly trained on how to use the PPE; the specified PPE is not correct for the task or the nature of the task has changed; or if the PPE is in poor condition.
- PPE cannot prevent the release of hazardous materials, but it is a critical line of defense when a loss of containment occurs.
What Can You Do?
- Before starting a task, consult the procedure to know what PPE is required. The SDS for the materials can also provide guidance on what PPE is appropriate.
- Inspect your PPE before use to ensure it is in good condition.
- Wear the required PPE until the task is completed and the hazards are contained.
- Inspect your PPE regularly to ensure that it is in good condition and key parts such as respirator cartridges are not expired.
Take care of your PPE, and it will take care of you.
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