Dangerous chemical reactions led to explosions that killed three people in two separate incidents at a West Virginia facility for decontaminating obsolete odorizer vessels, a U.S. Chemical Safety Board report issued Tuesday states.

“One possibility is that the equipment contained methanol, which can react with sodium hypochlorite (bleach) to form highly explosive methyl hypochlorite,” a CSB press release says.

The company involved, Midland Resource Recovery (MRR) in Philippi, WV, provides many services related to natural gas odorants known as mercaptans, which are chemicals used to give natural gas a distinct unpleasant odor.

One of those related services is to decommission and remove obsolete odorizer equipment from sites in the U.S. and Canada. MRR transports this equipment to its Philippi facility for chemical treatment to remove the mercaptan odor from the steel equipment before it is scrapped.

The process involves filling the equipment with diluted bleach and sealing it shut for a period of time.

On May 24, 2017, two MRR workers and the company owner attempted to unseal and drain one of the decommissioned odorizer vessels when a violent explosion occurred, fatally injuring the owner and one worker while severely injuring the second worker.

Later, on June 20, 2017, a contract worker hired to investigate and drain the remaining odorizers on site was killed when a second odorizer exploded shortly after it was unsealed.

In its final report, the CSB stated that there is no way to know exactly what chemicals were present in the two odorizers before they were decommissioned and treated. The report goes on to state that “given that the odorizers were filled with unknown chemicals and sealed tight, along with the potential for dangerous reactive chemistry such as what occurs when soldium hypochlorite mixes with methanol, MRR’s equipment deodorizing process created the possibility that each treated odorizer was essentially a bomb.”

MRR lacked an effective safety management system to identify and control hazards from reactive chemicals, the CSB report states. Among other things, MRR had no formal hazard identification process in place to analyze or characterize what chemicals were inside the odorizer vessels – and in what quantity – before decommissioning and chemically treating the equipment with bleach.

“MRR did not have, and federal regulations did not require, a comprehensive safety management system to identify and control hazards from reactive chemicals,” CSB interim executive authority Kristen Kulinowski said. “As a result, two serious explosions occurred.” The company also lacked effective safeguards to prevent unexpected or uncontrolled chemical reactions, the report states.