On Friday at roughly 9:05 a.m., an incident at a demolition site in Hakodate City, Hokkaido, led to ten workers being transported to hospitals after developing headaches and nausea, with local fire authorities suspecting carbon monoxide poisoning.
The site, where interior demolition work was underway, saw the affected men and women—aged between their teens and 60s—complain of symptoms that, after an emergency report was received, were consistent with exposure to a toxic gas. While some could not move without assistance, all participants remained conscious, the Hakodate Fire Department reported.
Investigators identified an engine‑powered high‑pressure washer as the probable source of the chemical. High‑pressure washers, devices that use an engine and a hose to blast water at pressures in the thousands of pounds per square inch, can emit carbon dioxide and, under certain conditions, carbon monoxide from engine exhaust when operating in confined spaces. Carbon monoxide is a colorless, odorless gas that binds to hemoglobin in the blood, reducing its capacity to transport oxygen and potentially causing neurological symptoms such as headaches, nausea, and, in severe cases, unconsciousness.
The workers had been engaged in interior work when the first signs of distress emerged. The cause of the gas exposure remains unclear, but the presence of the high‑pressure washer in a confined demolition area provides a plausible link. According to the department, the smoke‑filled environment typical of demolition—combined with the exhaust plume of the washer—may have elevated local carbon monoxide concentrations beyond the safety threshold, which is generally set at 50 parts per million over an eight‑hour exposure.
Given the age range of the affected staff, the symptoms pose a varied clinical risk. Younger workers may experience more acute neurological effects, while older workers are potentially at greater risk for cardiovascular complications from hypoxia. However, the fact that all ten remained conscious and received prompt medical attention is indicative of a relatively mild exposure, before severe hypoxic injury could occur.
The Hakodate Fire Department’s rapid response to the emergency call illustrates the importance of first‑response protocols in industrial demolition. Firefighters have been trained to recognize the early signs of gaseous exposure—headache, shaking, dizziness—and to deploy portable air‑sampling equipment. They also carry hand‑held carbon monoxide monitors, critical for confirming hazardous levels in real time, though such instruments were not referenced in the initial report.
Investigations are ongoing to confirm the source and extent of the gas release. The department has requested a review of the equipment’s maintenance log and the ventilation status of the demolition room. No official statement has yet been issued by the site operators or the machinery manufacturer.
Safety experts point out that high‑pressure washers cannot be used in poorly ventilated spaces unless operators employ carbon monoxide detectors or enforce strict time limits. The Occupational Safety and Health Administration in the United States recommends that any diesel‑powered device be operated only with proper exhaust ventilation, a standard that appears to align with best practice guidelines in Japan. If the findings confirm the suspected link, it may prompt revisions to local demolition safety regulations and trigger stricter enforcement of ventilation and gas‑monitoring requirements.
Meanwhile, the medical responders focus on supportive care—air replacement, monitoring for delayed neurologic symptoms, and ensuring proper oxygenation. The fact that no worker lost consciousness or required intensive care underscores the importance of timely evacuation and decontamination.
