Proposal for preventing fatal nitrogen gas inhalation while working: an autopsy case and review of the literature.

BACKGROUND: Nitrogen is a colorless, odorless, and generally inert gas that acts as a simple asphyxiant by displacing oxygen. While accidental nitrogen gas inhalation typically occurs in confined spaces, fatalities resulting from mask misconnections during industrial work are extremely rare. Inhaling excess nitrogen can rapidly cause disorientation, rendering victims unable to escape critical situations. Therefore, developing preventive measures is an urgent priority.

CASE PRESENTATION: A Japanese factory worker in his 40s was found in cardiopulmonary arrest inside a pot he was cleaning alone and subsequently died. The company's standard protocol requires a two-person team. In poor ventilation, workers typically use face masks connected to an atmospheric fresh air line or an oxygen source to meet physical demands. The victim was discovered wearing a mask mistakenly connected to a nitrogen gas line located adjacent to the oxygen line. Although both gas sources were color-coded and labeled, this misconnection occurred. After a forensic autopsy, his cause of death was diagnosed as nitrogen poisoning.

DISCUSSION: A literature review spanning PubMed data up to 2024 identified only 17 unintentional nitrogen-related deaths, with only 5 involving mask misconnections, mostly due to poor labeling. Japanese labor statistics from 1993 to 2022 recorded 30 nitrogen-related fatalities, including 4 mask-related cases, although detailed medical data were absent. To our knowledge, this case represents the first detailed forensic autopsy report in the English literature of a worker dying from nitrogen poisoning due to a mask misconnection. Our findings suggest that relying solely on the single person's visual information is insufficient to prevent fatal human error.

CONCLUSION: To diminish work-related nitrogen fatalities, we propose two potential preventive measures. First, to actively prevent human errors, we propose several technical approaches for fail-safe designs, such as incompatible or dedicated connectors, separation of supply systems, and equipping masks with oxygen monitoring devices that automatically shut off the gas supply when the oxygen concentration falls below a safe threshold. Secondary, a strict "double-check" system must be implemented. Workers should never connect air lines alone. The other worker must verify the connection and remain available to remove the mask and perform immediate resuscitation if an accident occurs.