What happened?

In a fume hood, a researcher used 5 grams of LAH to conduct a reduction reaction of a synthetic compound dissolved in 100 mL of tetrahydrofuran (THF). The remaining LAH stock of 95 grams, in its original non-resealable plastic bag, was placed in the hood next to the reaction apparatus after the necessary material had been weighed. In the same hood, adjacent to the reduction reaction was an unrelated experiment involving pentane, a flammable solvent.

Minutes after start of the reaction, the reaction flask over-pressurized causing the flask septum to pop off, initiating a fire in the hood. Nearby researchers initially used a CO₂ fire extinguisher, which spread the fire igniting the adjacent setup containing pentane. Other researchers then used Met-L-X®dry powder fire extinguishers to put out the hydride portion of the fire. Finally, a CO₂ extinguisher was deployed to extinguish the remaining other fuel sources.

Smoke from the fire triggered the building smoke detectors and a full-building evacuation. As a result of the incident, several researchers reported smoke inhalation and laboratory damage was limited to one fume hood.

What was the cause of the incident?

The primary cause of the fire was the researcher’s incorrect determination of the LAH:THF ratio. This incorrect LAH:THF ratio led to a significant exotherm and the rapid release of gas (H₂) and solvent from the reaction flask, initiating the fire.  Prior to the experiment, a thorough review of the experimental design had not been conducted.

What should have been done differently?

Contributing factors that intensified the fire event included:

• Additional fuel (open container of LAH, adjacent pentane experiment) was present in the hood.
• The incorrect fire extinguisher (CO₂) was initially used to attempt to extinguish the LAH fire. This action may have contributed to the spreading of the fire to an adjacent pentane setup, possibly adding to the initial fire danger

How can incidents like this be prevented?

Review of Standard Operating Procedure (SOP)
Prior to beginning work with LAH and other metal hydrides, ensure an SOP is written and reviewed. The PI is to assure that SOP review accounts for details including but not limited to:

• Experimental details (i.e., material selection, reaction concentration, scale of reaction, etc.)
• Identification and control of potential hazards (i.e., fume hood use, PPE, etc.)
• Special emergency procedures (i.e., response for metal fires)

For SOP guidance and an SOP template, refer to:  https://ehs.stanford.edu/sop-guidance

See the general use SOP on highly reactive/unstable materials.

General Handling and Storage of Lithium Aluminum Hydride

• Handle LAH and other pyrophorics under an inert atmosphere, within a glove box, fume hood, or equivalent.
• Keep and store away from heat/flame, oxidizers, acids, and moisture/water sources.  For storing LAH, keep sealed under an inert atmosphere.
• Learn more by reading about Stanford Storage Groups.

Relocating/Removing of Adjacent Research Experiments
Where LAH and other pyrophorics are used, keep the immediate work area clear of un-related experiments containing combustible/flammable materials as well as unused LAH and solvents, lab notebooks, and other non-essential combustible/flammable items.

Appropriate Fire Extinguisher Use
For use of LAH and other metal hydrides, ensure Met-L-X® dry powder fire extinguishers are identified as the extinguishers for metal hydride fires, and clarify this detail in each associated SOP.For assistance with selection and provision of fire extinguishers, contact the Stanford University Fire Marshal’s Office at .

To assure adequate awareness exists on proper fire extinguisher use:

• EH&S will review existing training materials for additional opportunity to emphasize above items.
• Groups using LAH or other pyrophoric materials are recommended to obtain periodic refresher training on proper use of fire extinguishers.

Appropriate PPE
When working with LAH or other pyrophoric materials, at minimum, a flame-resistant laboratory coat is required, along with protective eyewear, and gloves.NOTE: Nomex and related aramid fiber products are flame-resistant materials, but pose dexterity concerns when used as hand protection.Where hand protection from flammability hazards is required, flame-resistant gloves such as Nomex flight gloves are to be worn on top of gloves providing adequate chemical protection.

Emergency Response
In case of a fire emergency, ensure prompt reporting by completing the following actions:

• Pull the nearest fire alarm pull station to activate the building-wide fire alarm system.
• Call 9-911 to report and describe the incident so emergency responders can be updated regarding current conditions while en route