CONYERS, Ga. — The U.S. Chemical Safety and Hazard Investigation Board (CSB) provided an update on Friday on its investigation into the Conyers chemical plume disaster.
On Sept. 29, a massive fire sparked at a BioLab facility in Rockdale County, which filled the air with toxic chemicals and smoke for weeks. The catastrophic incident led to significant community impacts, including widespread evacuations and shelter-in-place orders.
According to the CSB, the incident began with a chemical reaction involving trichloroisocyanuric acid (TCCA), sodium dichloroisocyanurate (DCCA), and bromochloro-5,5-dimethylimidazolidine-2,4-dione (BCDMH) stored in a warehouse at the facility.
The CSB's investigation revealed that the chemicals decomposed, releasing heat and toxic vapors and eventually igniting. The resulting blaze and plume of hazardous smoke, including chlorine and other toxic substances, caused widespread alarm.
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Conyers BioLab chemical plume from fire in Rockdale County
The CSB said it has been reported that approximately 17,000 residents evacuated, while nearly 90,000 people in metropolitan Atlanta were advised to shelter in place. I-20, next to the Bio-Lab facility, was closed for 18 hours, and the surrounding roads were also affected. Nightly shelter-in-place advisories continued for weeks as air quality concerns persisted. The warehouse involved in the incident was destroyed.
"This incident and the substantial potential risk that it posed to the surrounding community was completely unacceptable. Reactive chemical incidents can have severe environmental and public safety impacts due to the combination of fire, toxic gas emissions, and hazardous materials involved, and Bio-Lab and any other facility that has reactive chemicals onsite must manage those materials safely," CSB Chairperson Steve Owens said in the release.
The CSB provided the following outline of the events surrounding the chemical plume:
Timeline of events | Conyers chemical plume disaster
5:00 a.m.: A Bio-Lab employee conducting a fire watch at the Plant 12 storage warehouse reported hearing a popping sound, which they attributed to wet product. No flames were visible at the time.
5:10 a.m.: After failing to isolate the reacting materials, the employee called 911 when they saw large plumes of toxic vapors inside the building.
6:30 a.m.: Visible flames emerged from the reaction site and were extinguished within two hours.
12:30 p.m.: Emergency responders initiated evacuations after a second, larger fire broke out at Plant 12.
4:00 p.m.: The second fire was extinguished.
During the days following the incident, air monitoring by the Environmental Protection Agency (EPA) detected elevated levels of chlorine and hydrogen chloride, particularly during nighttime hours from September 30 to October 2.
Ongoing investigation into Conyers chemical plume
The CSB is analyzing several critical factors, including:
The cause of the chemical decomposition, toxic vapor release, and subsequent fires.
Proper storage and handling practices for oxidizers and chemical compatibility.
Emergency response best practices for bulk solid oxidizer reactions.
Regulatory and industry guidance on fire protection systems for such chemicals.
The CSB said its investigation remains ongoing and will provide complete findings, analyses, and recommendations in its final report.
For additional updates and more information about the CSB, click here.