On July 2, 2021, at approximately 9:15 p.m., approximately 700 pounds of a mixture of vapors, including chlorodifluoromethane (“R22”) and perfluoroisobutene (“PFIB”), were released a facility in Alabama . Exposure to the toxic mixture of vapors fatally injured two operators and seriously injured another Daikin operator.
A drying tower was being returned to service after it had been offline for maintenance. After the maintenance activity, this equipment contained air, and the procedure included steps to remove this air and replace it with R22. To accomplish this, the company used a two-step purge process. First, nitrogen was added to sweep out the air, and second, R22 was added to sweep out the nitrogen. The displaced vapors were released into the ambient air from an open valve about six feet above the ground for each step. The valve was aimed vertically downward, resulting in the vapors being released in a downward direction toward the area where the operators were working.
The procedure did not specify the source of the R22 material used in this purging operation. The R22 was taken from another process vessel that contained other chemicals, including PFIB. As operators performed this purging, PFIB was released into the ambient air from the open valve, exposing three operators to this toxic vapor. The operators did not immediately report any adverse effects from the exposure and went home at the end of their shift. Approximately two days later, two of the operators became ill and were admitted to the hospital. The next day, the third operator was hospitalized. Two of the operators later succumbed to their respiratory injuries. One operator died on August 10, 2021, and the second operator passed away on September 28, 2021.
After the incident, the comapny updated its procedure to warn that toxic vapors may be present and to require that its operators use supplied air respirators. In addition, the company now directs the purge vapors to an incinerator. The procedures were also updated to specify that only high-purity (non-toxic) R22 can be used in the purging procedure.
Probable Cause
Based on the company's investigation and an investigation by the federal Occupational Safety and Health Administration (OSHA), the CSB determined that the toxic PFIB vapors were likely released with R22, which was purged from equipment into the ambient air to remove nitrogen. The safety management systems, which allowed the discharging of R22, PFIB, and other byproducts into a work area, contributed to the severity of the incident. Had the company ensured that the release of these hazardous vapors was avoided or discharged to a safe location, the incident could have been prevented.
Source:CSB.gov
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