When Waste Becomes a Process Hazard: EHS Lessons from a Fatal Hydrogen Sulfide Release

Waste Handling Is Still Chemical Processing

Waste disposal, equipment cleaning, shutdowns, and decommissioning can sometimes be viewed as lower-risk activities because normal production has stopped. In reality, these activities can introduce chemical combinations and operating conditions that do not occur during routine manufacturing.

A fatal hydrogen sulfide release at a West Virginia industrial facility illustrates the danger.

On April 22, 2026, two employees were killed and four others were seriously injured at the Catalyst Refiners facility in Institute, West Virginia. According to the U.S. Chemical Safety and Hazard Investigation Board, or CSB, a chemical reaction occurred while employees were transferring chemicals into a wastewater receiving tank during facility decommissioning. The reaction produced highly toxic hydrogen sulfide gas.

For manufacturing and pharmaceutical EHS teams, the incident provides an important reminder: chemicals do not become less hazardous simply because they have been classified as waste.

What Happened at Catalyst Refiners

Catalyst Refiners had conducted silver and ethylene oxide catalyst refining operations, including recovering silver from spent catalyst and manufacturing silver oxide. Production had stopped, and the facility was being decommissioned, although its wastewater pretreatment system remained operational.

Employees were disposing of chemicals remaining at the facility through that wastewater system. According to the CSB's investigation update, workers transferred approximately 80 gallons of a calcium chloride solution and 275 gallons of a sodium trithiocarbonate solution into a wastewater receiving tank. They then began pumping diluted nitric acid into the same tank.

Workers observed a reaction and fog forming above the tank. The nitric acid transfer was stopped, but employees subsequently became unconscious or were overcome by vapors while entering or approaching the area.

Two employees died, and four sustained serious injuries. Emergency responders later detected hydrogen sulfide.

The CSB investigation remains open, so its final findings and recommendations have not yet been issued. However, the agency has identified chemical incompatibilities, decommissioning hazard analysis, chemical disposal procedures, personal protective equipment, atmospheric monitoring, and corporate oversight as areas under examination.

Why This Matters for Manufacturing and Pharma

The circumstances are relevant well beyond catalyst refining.

Manufacturing and pharmaceutical facilities routinely generate chemical waste from production, laboratory operations, cleaning, maintenance, formulation, synthesis, wastewater treatment, and equipment decontamination. These streams can contain acids, bases, solvents, active pharmaceutical ingredients, cleaning agents, oxidizers, reducing agents, and process residues.

During normal operations, chemicals may be separated by equipment, procedures, piping systems, or production schedules. During shutdown or disposal activities, those same materials can suddenly come together in totes, tanks, drains, or wastewater systems.

That creates a different process chemistry.

A container labeled "waste" may still contain reactive material. A wastewater tank may effectively become a reaction vessel when incompatible chemicals are introduced. Changes in pH can also trigger unexpected reactions and potentially release toxic gases.

The risk can increase during shutdowns and decommissioning because established production procedures may no longer fit the work being performed. Knowledge may also be lost as operations wind down and experienced personnel leave.

That makes nonroutine chemical disposal a process-safety issue, not simply a housekeeping task.

Four EHS Lessons for Chemical Handling

1. Confirm Chemical Compatibility Before Transfer

Chemical compatibility should be evaluated before waste streams are combined.

The review needs to go further than checking whether individual substances are hazardous. EHS and operations teams should evaluate what can happen when those substances interact under the conditions expected in the receiving vessel.

Important considerations include concentration, pH, temperature, contaminants, decomposition products, and the possibility of generating toxic or flammable gases.

Waste characterization is particularly important when material composition may have changed during processing or storage.

2. Treat Waste Characterization as Hazard Characterization

Waste labels often focus on disposal requirements, but personnel performing transfers need information about chemical hazards as well.

Before consolidation or disposal, facilities should be able to answer basic questions: What exactly is in the container? What chemicals have previously entered the receiving tank? Are residues present? Could the transfer change the pH? Could an incompatible reaction generate heat, pressure, toxic gas, or other hazardous products?

For pharmaceutical operations, similar questions can apply to API residues, solvent mixtures, cleaning solutions, intermediates, laboratory chemicals, and wastewater streams.

Unknown composition should be treated as uncertainty requiring additional evaluation, not as permission to proceed.

3. Apply Management of Change Thinking to Nonroutine Work

Formal management of change programs are often associated with production processes and equipment modifications. The same mindset is valuable during shutdowns, temporary operations, chemical disposal, and decommissioning.

Changes in operating status can introduce new hazards.

A wastewater system designed for routine production may behave differently when concentrated chemicals are disposed of in batches. Ventilation, monitoring, staffing, PPE, and emergency response arrangements may also change once normal production ends.

The CSB reported that Catalyst Refiners did not have a written procedure for disposing of the chemicals involved through the wastewater treatment system. Investigators also reported that workers said respiratory protection was no longer required after the facility moved from production to decommissioning.

Nonroutine work deserves a defined hazard review before the activity begins.

4. Do Not Rely on Human Senses for Toxic Gas Hazards

Hydrogen sulfide is especially dangerous because exposure can rapidly incapacitate workers.

The CSB reported that employees and contractors at the facility were not provided or required to use personal gas monitors. Investigators also found full-face respirators onsite, but not all were equipped with filters capable of protecting against hazardous gases such as hydrogen sulfide.

Where chemical reactions could generate a toxic atmosphere, facilities should evaluate appropriate atmospheric monitoring, alarms, ventilation, respiratory protection, access controls, and emergency response arrangements.

Rescue planning matters as well. Workers attempting to help an incapacitated colleague can become additional victims if they enter a contaminated atmosphere without appropriate protection.

Questions EHS Teams Should Ask Before the Next Transfer

The Catalyst Refiners incident offers a useful reason to examine chemical disposal practices before the next drum, tote, or tank transfer occurs.

Key questions include:

• Is the composition of each material known and documented?

• Has compatibility with the receiving vessel and its contents been evaluated?

• Could changes in pH or concentration generate toxic gases, heat, or pressure?

• Are written procedures available for the specific disposal activity?

• Have nonroutine or temporary conditions been included in the hazard assessment?

• Is atmospheric monitoring needed before or during the transfer?

• Are PPE and respiratory protection appropriate for credible worst-case exposures?

• Do employees know what to do if an unexpected reaction, odor, vapor cloud, or alarm occurs?

• Could someone attempting a rescue become exposed to the same hazard?

A brief review of these questions can expose assumptions that might otherwise remain hidden until a transfer begins.

Treat Nonroutine Work Like a Process Hazard

Production may stop, but chemistry does not.

Shutdowns, chemical disposal, wastewater operations, and decommissioning deserve the same disciplined hazard recognition applied to active manufacturing processes. For pharmaceutical and manufacturing EHS teams, that means understanding what is being transferred, where it is going, what it may contact, and what could happen next.

The most important lesson is simple: before chemicals are mixed, transferred, neutralized, or discarded, understand the reaction that may follow.