What specific emergency procedure must be implemented immediately upon detection of a hydrogen sulfide (H2S) leak in a tidal barrage powerhouse?

Upon detection of a hydrogen sulfide (H2S) leak in a tidal barrage powerhouse, the immediately implemented emergency procedure must be to activate the alarm system, initiate immediate evacuation of all personnel from the affected area to a designated safe zone upwind of the powerhouse, and contact emergency services, followed by an assessment of the situation by trained responders wearing self-contained breathing apparatus (SCBA). Hydrogen sulfide (H2S) is a toxic and flammable gas that can be produced by the decomposition of organic matter in seawater or sewage. It is heavier than air and can accumulate in low-lying areas. Exposure to H2S can cause a range of health effects, from eye and throat irritation to unconsciousness and death. Because H2S is especially dangerous, an immediate response is necessary. Upon detection with H2S sensors, the alarm system must be activated to notify everyone in the powerhouse. All personnel must immediately evacuate to a designated safe zone upwind to avoid inhaling the gas. Calling emergency services ensures a trained team is available with the appropriate equipment to handle the leak. Trained responders equipped with SCBA can enter the affected area to assess the source and severity of the leak and to take steps to mitigate the hazard. The powerhouse must not be re-entered until the H2S levels have been confirmed to be within safe limits by qualified personnel using appropriate monitoring equipment. Therefore, immediate alarm activation, evacuation, emergency service notification, and assessment by trained responders are critical to protecting the health and safety of personnel in the event of an H2S leak.