Hydrogen sulfide (H ₂ S) is a highly toxic gas produced by the anaerobic decomposition of organic matter. Acute exposure in confined environments can cause rapid respiratory arrest and death through histotoxic asphyxia. Although collective poisonings have been described worldwide, such events remain exceptional in North Africa and seldom documented in medico-legal literature.

A retrospective medico-legal case series was conducted following a collective fatal intoxication involving eight workers exposed to H ₂ S in a public wastewater pumping station in Algeria, on March 31st, 2021. Full medico-legal autopsies, histopathological examinations, and toxicological analyses were performed.

All victims showed classical signs of toxic asphyxia, including cyanosis, bright red hemorrhagic discharge, and pulmonary edema. Histology revealed acute hemorrhagic pulmonary edema with siderophages, consistent with histotoxic hypoxia. The integration of contextual and pathological findings confirmed massive H ₂ S exposure as the cause of death.

This collective fatal intoxication illustrates the fulminant lethality of hydrogen sulfide in confined spaces and the cascade pattern of deaths among unprotected rescuers. The combined medico-legal, histopathological, and toxicological analysis provides a comprehensive understanding of the fatal mechanism and underscores the need for strict preventive measures, including gas detection, respiratory protection, and controlled rescue protocols to prevent recurrence in occupational environments.