OSHA Hazard Information Bulletins¹
Water-Reactive Chemicals, Hazardous Materials Not Covered Under 29 CFR 1910.119

July 3, 1996

This HIB highlights a potentially serious hazard regarding materials not covered by the Process Safety Management Standard, 29 CFR 1910.119. Recently, the Hasbrouck Heights Area Office investigated an explosion and fire which occurred at a custom chemical blending ("toll blending") facility, resulting in the deaths of five employees and the destruction of the facility. The employees were in the process of making "Gold Precipitating Agent" by blending 5,400 lbs. of sodium hydrosulfite, 1,800 lbs. of aluminum powder, 900 lbs. of potassium carbonate, and 8 liters of benzaldehyde. Sodium hydrosulfite and aluminum powder are highly water reactive and aluminum powder in this quantity has catastrophic potential. Neither of these materials are covered by 29 CFR 1910.119.

The employer's representatives stated that they relied on the information in the material safety data sheets (MSDSs) to perform a brief hazard review. This review failed to identify the hazards of that mixture. The mixing was done in a 125 cubic foot blender that had a water-cooled mechanical seal. It is very likely that water inadvertently entered the blend. Mechanical seals are known throughout the industry to be prone to this type of failure. Symptoms of a leak were noted and reported, but only to employees who did not know that water reactive chemicals were to be blended. A mechanical problem developed with the liquid feed system, which had not been checked prior to the addition of the dry ingredients. This caused a deviation from the standard operating procedures and the dry ingredients remained in the blender for a much longer period than originally anticipated. Water entering the subsurface caused the sodium hydrosulfite and possibly the aluminum powder to react, slowly at first. The large volume of powder did not conduct heat readily and the exothermic reaction intensified. In response to noxious gases being released, the employer decided to unload the blender, based upon the information in the MSDS for the finished blend. During the unloading process, an ignition and explosion occurred, propelling the vessel and its concrete supports approximately 48 feet. The pressure wave destroyed part of the facility and caused four of the five deaths; the fifth employee was killed by the ensuing fire, which destroyed most of the plant.

As a result of this accident, the following recommendations are made:

• A process safety analysis should be done for all materials with a catastrophic potential, even if they are not covered by the Process Safety Standard. This should include a careful review of chemical hazards, incompatibilities, and a thorough check of all mechanical equipment. Standard operating procedures should be developed and the consequences of deviation should be identified.
• Employers that rely on MSDSs created by other entities must be aware that the MSDSs for raw materials may not identify all hazards which may be encountered when mixing or blending them with other materials. This may be true even if there is no reaction anticipated or apparent. MSDSs for the final mixture may specifically address the hazards of shipping container quantities, but may not apply to the hazards of the larger quantities necessary to make the mixture.
• Many types of industrial vessels use mechanical seals to permit external drive of internal equipment such as agitators. In certain applications, mechanical seals must be liquid cooled. While regular maintenance may help to prevent failure and leakage, the possibility of a malfunction always exists. Employers should assure that materials processed in these vessels are not incompatible with liquids used to cool the seals.

Please distribute this bulletin to all Area Offices, State Plan States, Consultation Projects and appropriate local labor and industry associations. Copies of this HIB may be used for outreach purposes.