H2S release incidents

During a well service operation, a workover rig encountered unexpected fluid and gas flow from plugged tubing, triggering multiple H₂S alarms that were ignored as work continued.

One worker was briefly overcome by H₂S, evacuated by colleagues without using self-contained breathing apparatus (SCBA), taken to hospital, and later released with normal vital signs.

In a separate incident, two workers dismantling a pressure safety valve were exposed to H₂S without wearing the required SCBA; one lost consciousness and the other became dizzy while attempting a rescue.

Both workers collapsed, prompting activation of the Emergency Response Team and immediate on‑site medical attention.

A plant‑wide evacuation alarm and Level 2 EMT response were initiated due to the H₂S exposure.

The affected workers were transported to a clinic and then medically evacuated to a regional hospital for further evaluation.

The first incident showed the crew had normalized exposure to wellbore fluids and gases, continuing work despite repeated H₂S alarms and the absence of a required fixed detector on the rig floor.

• Procedures lacked contingencies for plugged tubing, and the completion design provided no safe method to remove trapped wellbore fluids.
• Workers underestimated the seriousness of toxic exposure, continued operations against well‑control and H₂S protocols, and did not use Stop Work Authority.

The second incident reinforced that when zero‑energy verification isn’t possible due to design limits, enhanced PPE and additional safeguards are essential.

• Piping configuration and procedures did not support reliable zero‑energy verification during pressure safety valve (PSV) calibrations.
• Permit‑to‑work planning underestimated the time and risk involved in high‑hazard PSV tasks, relying on generic rather than task‑specific estimates.

Respond to alarms immediately: Any H₂S alarm — personal or fixed — requires instant action; even brief exposure can be life‑threatening.

Strengthen PPE and SCBA use: Ensure workers use the correct respiratory protection, including SCBA, whenever required by conditions or permits.

Improve emergency response: Train teams to evacuate and rescue using proper equipment, including SCBA, and follow site‑specific emergency procedures.

Reinforce Stop Work Authority (SWA): Build a culture where speaking up is expected, concerns are acted on, and workers feel safe to halt work when something is wrong.

Improve monitoring systems: Ensure fixed H₂S detectors are correctly installed, maintained, and positioned; establish clear reporting protocols for personal monitor activations.

Strengthen isolation and permitting: Verify zero‑energy states, use compliant isolation methods, and ensure permit to work (PTW) steps — including site checks — are completed before work begins.

How are people responding to the activation of personal monitors?

Is your team reinforcing SWA on a regular basis?

Are stop-work triggering scenarios built into the planning?

Are the safeguards installed and functioning as per the design of the equipment? When and what frequency is the equipment functionality verified?

Does the team know their individual roles in an emergency, and are they able to execute them?

Are team members aware of the high risk of trying to rescue others overcome by H₂S/other gases?

Have all task-related hazards been identified and the corresponding safeguards verified?

Have the PTW conditions been verified on-site to ensure the worksite's safety before approval?

How do you verify zero energy before breaking containment?

Do you have all the necessary tools and PPE to execute the task safely, and are you prepared for changing conditions?

Have clear communication channels been established for emergency procedures activation?