CSB Update Details Missed Warnings Before Fatal H2S Release at Maine Pulp Mill
The U.S. Chemical Safety and Hazard Investigation Board has released new findings on the January 27, 2026, hydrogen sulfide release that killed two workers at the Woodland Pulp mill in Baileyville, Maine, ISHN reports.
The release killed a 20-year-old co-op chemical engineering student and a 26-year-old chemical engineer who had recently joined the company. Ten other employees were exposed to the gas. Both victims collapsed on the second floor of the Kraft Mill building and were not discovered for more than six hours, according to the CSB update.
Investigation Findings
CSB investigators traced the release to a shutdown sequence that began the night before the incident, when Woodland Pulp decided to idle most of the mill due to a spike in natural gas prices. As Bleach Plant equipment was drained, high-pH process fluids containing sulfur compounds flowed into a 1,000-foot acid sewer pipe. An automated pH control system kept adding sulfuric acid to the line, which reacted with the sulfur compounds to generate hydrogen sulfide gas. When the Bleach Plant’s scrubber fan was shut off around 11:40 a.m. as part of the shutdown, the toxic gas had no path for removal and escaped into the Kraft Mill through holes and openings in nearby equipment.
CSB Chairperson Steve Owens said the tragedy “should never have happened,” noting that the two victims had no personal hydrogen sulfide monitors and the building had no installed detectors. CSB Board Member Sylvia Johnson said Woodland Pulp knew hydrogen sulfide could form in the acid sewer piping but lacked systems to monitor or mitigate the hazard. The CSB update also found the facility had no system for tracking personnel locations during the shutdown and no building ventilation system during normal operations or shutdowns. The agency’s final report, including formal recommendations, has not yet been issued.
What It Means for Subcontractors
- Crews performing maintenance, drawing, or inspection work in pulp, paper, or chemical processing buildings during shutdowns should confirm personal H2S monitors are issued and functioning before entering areas near acid sewers, scrubbers, or process vessels, not just confined spaces.
- Facilities without stationary H2S detectors or building ventilation systems in process areas represent a real exposure risk for subcontracted E&I, mechanical, and instrumentation crews working near sewer lines, scrubbers, or pH control equipment during unit shutdowns.
- Contractors should require a documented personnel tracking or check-in system before working inside Kraft Mill-type buildings during shutdown operations, since Woodland Pulp had no method for accounting for who was in the building or where.
- Field service firms bidding process safety, gas detection, or scrubber maintenance work at pulp and chemical facilities should watch for CSB’s final report, which will include specific recommendations on hydrogen sulfide detection, alarms, and management-of-change practices that could shape future contract specifications.
