Update on investigation in Didion Milling explosion

The U.S. Chemical Safety and Hazard Investigation Board (CSB) held a news conference on Monday, giving a "factual investigative update" on their investigation in to the explosion.

The explosion happened at the plant in May 2017, killing five workers and injuring 14 others. According to the OSHA, the explosion likely occurred from Didion’s failure to correct the leakage and accumulation of highly combustible grain dust throughout the facility.

The company received 19 citations and was placed in OSHA's Severe Violator Enforcement Program.

The CSB gave a “factual investigative update” on Monday. They said it is still too early in the investigation to make any conclusions but they have interviewed ten of the 14 survivors to better understand what may have happened.

The U.S. Chemical Safety and Hazard Investigation Board (CSB) is investigating how to prevent these types of explosions and there goal is to find ways to avoid them in the future.

"Our goal is to take the lessons learned at Didion and share them to bring about meaningful safety change," CSB Chairperson Vanessa Allen Sutherland said.

CSB said at the news conference on Monday that the explosion happened in the “dry corn” portion of the mill. Workers at Didion Milling told investigators the mill was operating normally the night of the explosion. Workers reported seeing and smelling smoke coming from the facility. Some workers started trying to find the source of the smoke.

CSB reports that 15 to 30 minutes before the explosions, workers focused on the piece of equipment called the “gap mill" (pictured below). Worker said they saw an air filter “blow off” of the gap mill’s air intake line. That resulted in corn dust filling the air and three to four foot flames shooting from the intake line.

During the press conference, CSB explained that the filter on the machine (pictured below) blew off, causing a cloud of corn dust. In this case, the cloud was confined and “combustion gases” caused an explosion.

Lead investigator Dr. Mary Beth Mulcahy said Didion Milling has fully cooperated with the investigation.

Combustible dust was the first issue the CSB listed as a critical driver of safety change in 2006. That year the board conducted a study on combustible dust. They identified 281 combustible dust explosions between 1980 and 2005 that killed about 120 workers and injured 718. They happened across 44 states in different industries and involved a variety of materials.

Between 2006 and 2017 the CSB has confirmed that 111 additional combustible dust incidents have occurred. The CSB investigated five of them including the one at Didion. Chairperson Sutherland calls dust an "insidious hazard."

CSB is an independent, non-regulatory agency. The board can not administer sanctions or punishments but often makes recommendations to agencies like OSHA on how they should set standards.

Didion released this statement on Monday following the update from CSB stating:

"Didion is reviewing the Chemical Safety Board (the CSB) report released today and will continue to assist in efforts to learn what happened at our corn milling facility last May. We have been working cooperatively with the CSB as well as industry experts, on ongoing investigations into the incident to determine its cause. Throughout this process, Didion has reiterated our commitment to the safety of our employees. Our teams have worked diligently to ensure that industry safety practices and protocols are in place. Didion pledges to continue to work cooperatively with the CSB and other agencies to maintain and enhance the safety of our team, which is our highest priority. We are also working with industry experts on construction of a new state-of-the-art corn mill, which will feature the latest technology and most effective and safe operational systems available today."