Carbon monoxide (CO) is an odorless, tasteless, colorless, and non-irritating gas formed by the incomplete combustion of various fuels. Carbon dioxide (CO₂) arc welding also produces significant amounts of CO.1 Particularly, the concentration of CO in the air may increase to dangerous levels when CO₂ arc welding is performed in poorly ventilated areas.2 In this technique, the CO₂ gas used as an inert gas shield or as carbonates of flux cored wire can decompose into high concentrations of CO gas. Therefore, proper ventilation conditions are required to prevent CO exposure.

The shipbuilding industry is the most common industry using CO₂ arc welding in an enclosed space, and hence welders are prone to the risk of CO exposure. The value of CO concentration generated during welding in a Korean shipyard was 23.9 ppm in the department of block erection and outfitting installation, both of which involved working in closed spaces. Among the different types of welding, CO₂ arc welding showed the highest average concentration of CO (21.4 ppm). As for CO concentration according to the characteristics of the workspace, the severe sealing degree was associated with the high CO level.3

The clinical symptoms of CO poisoning are diverse, depending upon the level and duration of exposure. Patients with mild or moderate acute CO poisoning present constitutional symptoms, including headache, nausea, dizziness, drowsiness, vomiting. Severe CO poisoning can produce symptoms such as seizure, chest pain, syncope, or coma.4

Even minor cases of CO poisoning can cause serious complications including brain damage.5 Delayed encephalopathy after acute CO poisoning is defined by the recurrence of neurological or psychiatric signs after a transient symptom-free period following the acute phase.6 The latency period is usually 2 to 40 days.7, 8 This clinical syndrome manifests as neurological or psychiatric symptoms, including memory loss, urinary and fecal incontinence, disorientation, confusion, parkinsonism, and other motor disturbances.9, 10, 11

Although the risk of CO exposure in CO₂ arc welding is well-known, to the best of our knowledge, no studies have yet reported an encephalopathy case attributed to CO poisoning among CO₂ arc welders. Herein, we present a case of CO poisoning-induced encephalopathy in a CO₂ arc welder in the Korea.