Hazmat Survival Tips: Dealing with a Spill of Sodium Hydrosulfite

Beyond the Rule of Thumb
Survival Tip 51

By Steven De Lisi

On a rainy morning in December, first responders were dispatched to a report of a motor vehicle accident involving an overturned tractor-trailer on a narrow two-lane road in a rural area. On arrival, they discovered a van trailer that had rolled over into an empty field after failing to negotiate a right-hand curve. The force of the impact completely destroyed the trailer and severely damaged its contents of 10 large metal totes, each containing approximately 4,000 pounds of a powdered mixture whose primary component was sodium hydrosulfite.

The driver suffered only minor injuries and was able to escape from the tractor. However, a large amount of the sodium hydrosulfite had been released and, because of its chemical nature, began to react with the humidity in the atmosphere. This presented first responders with wisps of white smoke along with hydrogen sulfide and sulfur dioxide. As a result of their previous hazardous materials training and proper execution of initial response procedures, they were alert for placards and were able to detect what remained of a “spontaneously combustible” placard on one of the totes. They immediately knew that the “smoke” they observed was not from any fire that needed extinguishment and, thus, resisted the urge to “put the wet stuff on the red stuff.” Due diligence on the part of the first-arriving officer paid off and allowed him to hold back, isolate the immediate area, and call for help. In this instance, aggressive actions most likely would have had catastrophic results.

The driver was unable to access the shipping papers prior to fleeing the tractor, and it was deemed too dangerous to have first responders attempt to retrieve these documents. However, the driver was able to provide a telephone number for the shipper; contact with this office yielded additional information along with a copy of the product’s material safety data sheet (MSDS) prepared by the manufacturer. 

Once first responders learned of the material’s products of decomposition, they evacuated the few homes nearby and recommended in-place protection for an industrial facility downwind of the incident site. They also requested assistance from the state’s regional hazardous materials response team and environmental quality agency. Working together, these groups performed continuous air monitoring in the affected areas and obtained air samples that were later analyzed by a state laboratory to determine exact exposure levels. Soon after initial air testing was conducted, weather conditions improved: the humidity decreased, subsequently reducing the production of toxic vapors.

Representatives of the shipper and manufacturer of the product agreed to respond to the scene to assist first responders in developing a strategy for dealing with this incident. They determined that the best means of disposal would be to allow the product to react with a solution of water and sodium hydroxide. This caustic solution, with a pH of 11 – 12, was necessary to neutralize the product following its reaction with the solution.

A contractor hired by the shipper conducted all cleanup operations on-site. The shipper was responsible because it had control of the material at the time of the release.

(1) Conditions found on arrival by first responders. A “Spontaneously Combustible” placard is visible on one of the totes. Photo by author.

Initial plans called for conducting the disposal process in a retention area dug on-site. However, first responders had earlier taken the initiative to contact the region’s utility locating service and soon learned that various underground utilities were present in the area. The presence of these utilities, along with concerns expressed by representatives from the state environmental agency, led them to abandon any plans to dig a retention basin. Instead, two large open-top tanks, each with a capacity of 21,000 gallons, were brought to the site and filled with the sodium hydroxide solution. 

To place the spilled sodium hydrosulfite into the sodium-hydroxide solution, a 40-yard dumpster was brought to the site along with an excavator provided by the cleanup contractor. This machine had a closed cab, and the operator was provided with Level B personal protective clothing. The cylinder for the self-contained breathing apparatus (SCBA) had a 60-minute capacity and was firmly secured to the rear of the operator’s seat. A representative from the state’s Department of Labor and Industry was onsite and ensured that the equipment operator met all requirements for operations at a hazardous materials waste site and the use of SCBA.

Once cleanup operations began, the operator used the excavator to carry individual totes to the dumpster. Once placed inside the dumpster, the excavator blade was used to break open the tote and pour out the contents. The operator then scooped up the material from the dumpster floor, traveled a short distance to one of the two open-top tanks, and slowly poured in the sodium hydrosulfite. The act of adding the powder to the solution resulted in a significant, but momentary, reaction and the release of hydrogen sulfide and sulfur dioxide. This procedure, which began at approximately 10 p.m., was repeated throughout the night. It took more than six hours to completely dispose of the contents of the 10 damaged totes. 

During the disposal process, local firefighters and EMS stood by with ongoing shift changes. Shift rotations for the equipment operator occurred approximately every 45 minutes, which allowed for an exchange of the SCBA cylinder. During these shift rotations, the pH of the sodium hydroxide solution was checked and adjusted as necessary.

Air monitoring of the site and downwind locations continued throughout the night. Crews found that during the momentary reaction immediately following the addition of sodium hydrosulfite to the sodium hydroxide solution, readings for sulfur dioxide spiked to 150 parts per million. No significant readings for hydrogen sulfide were detected. 

By 2 p.m. the following day, all of the totes and their contents had been disposed of, and efforts were then concentrated on removing the damaged tractor-trailer. The contents of the two open-top tanks were pumped into tank trucks provided by the cleanup contractor. The contractor was also responsible for removing any contaminated soil from the area.

Most importantly, this incident demonstrated the need for first responders to be alert and pay attention to hazardous materials “clues” when responding to any incident. Despite the large number of state, federal, and private resources brought in to stabilize an event of this magnitude, always remember that local firefighters, EMS, and law enforcement will be the first to arrive and their actions will set the stage for success or failure. During this incident, the fact that we were able to clear the scene with no injuries or fatalities was not the result of the hazardous materials team that arrived three hours later, but of the engine company that arrived three minutes into the incident.

I’m sure that some firefighters who were on standby duty at midnight may have thought the incident was boring. Quite frankly, during a hazardous materials incident, I have always considered a claim of “boring” to be a good thing. Of course, if it’s excitement you want, just play the game of “rush-in roulette” at your next tractor-trailer accident. You won’t be disappointed. 

Questions or comments on this or any other monthly Hazardous Materials Survival Tip may be directed to Steven De Lisi at HazMatSurvivalTip@comcast.net.

Click here for more info on Steven De Lisi’s book, Hazardous Materials Incidents: Surviving the Initial Response.