Two fatal cases due to inadvertent discharge of carbon dioxide fire suppressant: Intoxication or asphyxiation?

Carbon dioxide (CO2) is widely used for fire protection and is lethal when inhaled at the minimum design concentration. Two workers were performing periodic maintenance of isolated stored CO2 cylinders of a fire extinguishing system, and during the maintenance, CO2 was accidently discharged into the storage room. The workers were found unconscious beside the cylinders and were confirmed dead in the hospital soon after. Arterial blood gas analysis revealed severe acute hypercapnia accompanied by respiratory acidosis. Combined with the scene investigation and autopsy findings, the cause of their death was determined to be CO2 intoxication and possible involvement of asphyxiation. Considering the repeated occurrences of unfortunate deaths involving CO2 fire extinguishing systems, this report will be useful for forensic pathologists when dealing with similar cases.