An uncommon source of carbon monoxide poisoning—industrial gas-burning fryers—caused carbon monoxide poisoning among a large group of workers at an industrial kitchen, according to an investigation published in the CDC’s Morbidity and Mortality Weekly Report (MMWR).

Carbon monoxide is a colorless, odorless, and potentially deadly gas. When carbon monoxide is inhaled, a substance called carboxyhemoglobin forms in the blood. This substance prevents the blood from carrying oxygen to tissues and vital organs in the body. Annually, carbon monoxide poisoning kills approximately 400 people in the United States.

In September 2017, 40 workers from an industrial kitchen presented to several Wisconsin hospitals for treatment after a suspected carbon monoxide leak led to a workplace evacuation. Emergency room staff in two of the hospitals consulted the Wisconsin Poison Center for guidance on evaluation and treatment of these patients. The center alerted the NIOSH-funded Wisconsin Division of Public Health, Occupational Health Surveillance Program, which launched an investigation that included interviewing emergency responders and reviewing workers’ medical records.

Carbon monoxide poisoning is defined as carboxyhemoglobin blood levels of more than 5% for nonsmokers and more than 10% for smokers or those whose smoking status is unknown. Most of the patients had carboxyhemoglobin blood levels higher than the cutoff for carbon monoxide poisoning—in some cases, more than twice as high. The most common symptoms included headaches (93%), dizziness (40%), and nausea (38%). There were no deaths.

In the facility, carbon monoxide levels were as high as 313 ppm (parts per million) near the gas-burning fryers, which is well above the NIOSH recommended exposure limit of 200 ppm. Gas burners were the carbon monoxide source. The carbon monoxide gas built up in the plant due to inadequate ventilation, according to the Occupational Safety and Health Administration, which also investigated. Although gas-burning appliances are not a common cause of work-related deaths due to carbon monoxide poisoning, it is important to maintain and ventilate them properly, and install carbon monoxide detectors to prevent exposure among workers.

More information is available: