January 25, 2024

CSB Determines Faulty "Bubbler" Tube Cause of Fatal Liquid Nitrogen Release

The U.S. Chemical Safety and Hazard Investigation Board (CSB) has released its final report (PDF) on a deadly liquid nitrogen release that occurred on Jan. 28, 2021, at a poultry processing plant in Gainesville, Georgia. Investigation by CSB determined that a damaged “bubbler” tube, a device used to measure liquid nitrogen levels inside industrial freezers, was among the equipment and process failures that led to the incident. The release caused the deaths of six poultry plant workers by asphyxiation. Three other plant workers and one firefighter responding to the incident were seriously injured, also by asphyxiation.

The report states that the bubbler tube likely became bent on the morning of the incident, during maintenance on a freezer used to prepare chicken product. The damaged tube was unable to measure and control liquid nitrogen levels inside the freezer, allowing liquid nitrogen to overflow into the freezer room. The nitrogen vaporized into a cloud that displaced the room’s oxygen up to five feet above the floor. The two maintenance workers who had been troubleshooting the malfunctioning freezer were then the first to succumb to asphyxiation. The remaining fatalities and serious injuries among plant employees occurred during their attempts to rescue their coworkers.

Firefighters equipped with self-contained breathing apparatuses later arrived on site in response to a 911 call by a plant director. The firefighters entered the freezer room, pulled out the unresponsive workers, and deactivated the freezer.

CSB determined that the bent bubbler tube represented a “single point of failure” in the design of the freezer, as there were no other safeguards to prevent the release of liquid nitrogen. The report also states that Messer LLC, the freezer manufacturer and owner, had practiced improper product stewardship. Messer had identified deficient safety practices by Foundation Food Group (FFG), the company that owned the Gainesville plant at the time of the incident, but continued to supply the plant with liquid nitrogen.

FFG had not installed atmospheric monitoring and alarm systems that could have detected the oxygen-deficient atmosphere, automatically shut off the liquid nitrogen supply, and alerted workers to evacuate, CSB found. FFG had neglected to prepare employees for the possibility of a liquid nitrogen release, so they were unaware of the hazards of nitrogen, unable to recognize the oxygen-deficient atmosphere, and lacked personal protective equipment that would have allowed them to safely enter the freezer room. No process safety management system had been implemented by FFG, and the company had allowed the job position responsible for safety management to remain vacant for more than a year leading up to the incident, CSB’s report states.

Following the incident, OSHA proposed nearly $1 million in total penalties to be paid by FFG, Messer, and two contractors not directly involved in the incident. FFG sued its insurer for roughly $1.7 million in damages and sold the facility to Gold Creek Foods.

CSB’s report makes a total of 12 recommendations directed toward Gold Creek Foods, the facility’s current owner, as well as Messer, the Compressed Gas Association, the National Fire Protection Association, and OSHA. The recommendations to OSHA include updates to the Poultry Processing Facilities Regional Emphasis Programs for Regions 4, 5, and 6, as well as to promulgate a standard specific to cryogenic asphyxiates and publish a guidance document on process safety management for compressed gasses and cryogenic asphyxiates.

More information about the incident and CSB’s findings and recommendations may be found in the board’s press release.