Procedures for Safe Use of Pyrophoric/Water Reactive Reagents
Pyrophoric and water reactive materials can ignite spontaneously or react violently on contact with air, moisture in the air, oxygen, or water. Failure to follow proper handling procedures can result in fire or explosion, leading to serious injuries, death, and/or significant damage to facilities. This SafetyNet describes the hazards, proper handling, disposal and emergency procedures for working with pyrophoric and water reactive materials.
Any handling of a pyrophor/water reactive material is high risk and must be controlled with adequate system design, direct supervision and training. These tasks are two person tasks and workers must not work alone.
Examples of Pyrophoric/Water Reactive Materials
- Grignard Reagents: RMgX (R=alkyl, X=halogen)
- Metal alkyls and aryls: Alkyl lithium compounds; tert-butyl lithium
- Metal carbonyls: Lithium carbonyl, nickel tetracarbonyl
- Metal powders (finely divided): Cobalt, iron, zinc, zirconium
- Metal hydrides: Sodium hydride, lithium aluminum hydride
- Nonmetal hydrides: Diethylarsine, diethylphosphine
- Non-metal alkyls: R3B, R3P, R3As; tetramethyl silane, tributyl phosphine
- White and red phosphorus
- Group I (Alkali) metals: Lithium, potassium, sodium, sodium-potassium alloy (NaK), rubidium, cesium
- Gases: Silane, dichlorosilane, diborane, phosphine, arsine
Because these reagents ignite/react violently on contact with air and/or water, they must be handled under an inert atmosphere and in such a way that rigorously excludes air/moisture. Some are toxic and many come dissolved or immersed in a flammable solvent. Other common hazards include corrosivity, teratogenicity, water reactivity, or peroxide formation, and may damage to the liver, kidneys, and central nervous system.
Controlling the Hazards
BEFORE working with pyrophoric or water reactive reagents, read the relevant Safety Data Sheets (SDS), technical bulletins, and guidance documents to understand how to mitigate the risks. The SDS must be reviewed before using an unfamiliar chemical and periodically as a reminder. Users of reactive materials must be trained in the laboratory-specific standard operating procedure and be able to demonstrate proficiency. Do not work alone or during off hours, when there are few people around to help. ALWAYS wear the appropriate personal protective equipment.
Remove all excess and nonessential chemicals and equipment from the fume hood or glove box where pyrophoric or water reactive chemicals will be used. This will minimize the risk if a fire should occur. Keep combustible materials, including paper towels and Kimwipes, away from reactive reagents.
Keep the amount of pyrophoric or water reactive material present in your lab to the smallest amount practical. Use and handle the smallest quantity practical. It is better to do multiple transfers of small volumes than attempt to handle larger quantities (greater than 15 mL). Alternatively, an appropriately engineered system, capable of safely handling the larger quantity must be designed, tested, and properly used.
Personal Protective Equipment (PPE)
- Indirectly vented chemical splash goggles are required when working with air/water reactive liquids. Prescription eye glasses and safety glasses will NOT provide adequate protection. A face shield that meets ANSIZ.87.1 1989, worn over splash goggles, is required any time there is a risk of explosion, splash hazard, or a highly exothermic reaction.
- All manipulations of pyrophoric chemicals which pose these risks must be carried out in a fume hood with the sash in the lowest feasible position or in a glove box.
- Gloves must be worn when handling pyrophoric chemicals. Nitrile gloves should be adequate for handling most of these reagents in general laboratory settings but they are combustible. Use adequate protection to prevent skin exposures. Heavy gloves are required for work with larger quantities. A Nomex flight glove (used by pilots to protect from heat and flash), worn over disposable nitrile gloves, may be an option for work with larger quantities.
- A fire retardant laboratory coat must be worn. Special fire-resistant lab coats made from Nomex or other fire resistant materials are required. Laboratory coats must be buttoned and fit properly to cover as much skin as possible. Clothing, shirt and long pants, should be cotton or wool. Synthetic clothing is strongly discouraged.
- Appropriate shoes that cover the entire foot (closed toe, closed heel, no holes in the top) must be worn.
Researchers working with reactive materials must have the proper safety equipment and the emergency phone number (9-1-1) readily available for any emergencies, prior to starting research activities. Acceptable extinguishing media include soda ash, lime, Met-L-X, or dry sand to respond to fires. DO NOT use water to attempt to extinguish a pyrophoric/reactive material fire as it can actually enhance the combustion of some of these materials, e.g. metal compounds. A small beaker of Met-L-X, dry sand, lime, or soda ash in the work area is useful to extinguish any small fire that occurs at the syringe tip and to receive any last drops of reagent from the syringe. Review the SDS for the proper fire extinguisher to use with the given material.
- A combination eyewash/safety shower should be within 10 seconds travel time where reactive chemicals are used. Inside the laboratory is optimum.
- If a combination eyewash/safety shower is not available within the laboratory, an eyewash must be available (within 10 seconds travel distance) for immediate emergency use within the lab. Bottle type eyewash stations are not acceptable. A combination eyewash/shower must be available in the hallway or similar, within 10 seconds travel distance and accessible through only one door.
- Ensure that lab personnel know the locations of eyewashes and safety showers and the most direct route to access them.
- Many reactive chemicals release noxious or flammable gases upon decomposition and should be handled in a laboratory hood. In addition, some pyrophoric materials are stored under kerosene (or other flammable solvent), therefore the use of a fume hood (or glove box) is required to prevent the release of flammable vapors into the laboratory.
Glove (dry) box
- Inert atmosphere glove boxes are an excellent device for the safe handling of reactive materials. Glove boxes used for this purpose should be in good working order and the moisture and oxygen levels of the atmosphere should be confirmed prior to introduction of reactive compounds into the box. Continuous monitoring of oxygen and moisture is highly recommended. Also, take into account interactions between items in the glovebox (e.g., nitrogen is not an inert gas for lithium metal as the lithium is reduced violently to lithium nitride).
- Storage of pyrophoric gases is described in the California Fire Code, Chapter 41. Gas cabinets, with appropriate remote sensors and fire suppression equipment, are required.
- Gas flow, purge, and exhaust systems should have redundant controls to prevent pyrophoric gas from igniting or exploding.
- Emergency back-up power should be provided for all electrical controls, alarms, and safeguards associated with the pyrophoric gas storage and process systems.
Important Steps to Follow
Reactive reagents can be handled and stored safely as long as all exposure to atmospheric oxygen and moisture or other incompatible chemicals is avoided. Finely divided solids must be transferred under an inert atmosphere in a glove box. Liquids may be safely transferred without the use of a glove box by employing techniques and equipment discussed in the Aldrich Technical Information Bulletin AL-134 and described below. Pyrophoric gases must be handled in compliance with the California Fire Code, Chapter 41. Another good reference is “Manipulation of Air-sensitive Compounds” by Shriver and Drezdzon
Handling Pyrophoric Liquids
- Users must read, understand, and follow manufacturer's recommendations, the Aldrich Technical Information Bulletin No. AL-134, and this Safety Net. The PI should also have in place laboratory-specific standard operating procedures for handling, storage, and disposal. The standard operating procedures must be included in the laboratory's Chemical Hygiene Plan. Videos developed by University California, San Diego (links here and here), and Yale University, may be used as part of lab-specific training.
- By using proper syringe techniques, these reagents can be handled safely in the laboratory. The Aldrich Sure/Seal™ Packaging System provides a convenient method for storing and dispensing air-sensitive reagents.
- Many of these reagents are stored at reduced temperatures. Before accomplishing any transfer, let the reagent bottle warm to room temperature in the fume hood or glove box. Water vapor could condense on the needle surface which can initiate ignition. Be sure to wipe any moisture off the bottle and septum.
- Luer-lock disposable Teflon syringes are recommended, rather than glass syringes, as they have a better seal.
- Non-disposable syringes and needles should be cleaned, dried in an oven and left to cool in a desiccator to avoid absorption of water upon cooling. Be sure to cool all equipment to room temperature before attempting transfer.
- Clamp reagent bottle firmly before beginning transfer. Attach a balloon of inert gas or an inert gas line through the septum to keep positive pressure in the reagent bottle during the transfer, keeping the needle tip out of the liquid.
- Flush the syringe and needle three times with inert gas. In the last flush, fill the headspace of the reagent bottle with some inert gas, then quickly insert the needle into the reagent bottle.
- Firmly hold the syringe plunger and very slowly fill the syringe by gently pulling the plunger up. NEVER fill a syringe to more than 3/4 capacity.
- By bending the long needle and holding the needle in the septum, tip the syringe upside down and slowly force any excess reagent and bubbles back into the reagent bottle. Pull the needle tip up out of the liquid and draw a plug of inert gas from the reagent bottle headspace into the needle.
- Holding the syringe barrel in place, slowly pull the needle out of the septum. Quickly insert the needle into a septum-sealed receiver flask. Slowly deliver the measure volume into the receiver flask – dropwise if there's evolution of gas or increase in reaction behavior. Be sure the pressure inside the receiver flask is equalized.
Double-Tipped Needle (Canula) Transfer
Larger quantities of the reagent (> 15 ml) can be dispensed using a double-tipped needle (canula) (16, 18, or 20 gauge) inserted through the hole in the metal cap, as shown in fig. 2 below. Aldrich Technical Bulletin No. AL-134 details the technique. It is recommended that the plastic cap be replaced after each use and in particular for long-term storage.
Fig. 2 Double-tipped needle transfer of liquid reagent
Important note: If bubbler is water filled, it is important to locate the bubbler low enough that an inadvertent vacuum condition in the flask cannot draw the water into the reaction flask, or use oil instead.
- For extended storage of unused reagents, use the solid plastic cap, or equip the bottle with an Oxford Sure/Seal valve cap, or transfer the reagent to a suitable storage vessel, as described below.
Storage and Disposal
- Use and store minimal amounts of reactive chemicals. Do not store reactive chemicals with flammable materials or in a flammable liquids storage cabinet. Secondary containers carrying reactive materials must be clearly labeled with the correct chemical name, in English, and hazard warning.
- Store reactive materials as recommended in the SDS. An inert gas-filled desiccator or glove box are suitable storage locations for most materials.
- If pyrophoric or water reactive reagents are received in a specially designed shipping, storage or dispensing container (such as the Aldrich Sure/Seal packaging system) ensure the integrity of that container is maintained.
- Ensure that sufficient protective solvent, oil, kerosene, or inert gas remains in the container while the material is stored.
- NEVER return excess chemical to the original container. Small amounts of impurities introduced into the container may cause a fire or explosion.
- For storage of excess chemical, prepare a storage vessel in the following manner:
- Dry any new empty containers thoroughly
- Insert the septum into the neck in a way that prevents atmosphere from entering the clean dry (or reagent filled) flask.
- Insert a needle to vent the flask and quickly inject inert gas through a second needle to maintain a blanket of dry inert gas above the reactive reagent.
- Once the vessel is fully purged with inert gas, remove the vent needle then the gas line. To introduce the excess chemical, use the procedure described in the handling section, below.
- For long-term storage, the septum should be secured with a copper wire (figure 1A).
- For extra protection a second same-sized septa (sans holes) can be placed over the first (figure 1b).
- Use parafilm around the outer septa and remove the parafilm and outer septum before accessing the reagent through the primary septum.
Disposal of Pyrophoric Reagents
- Any container with a residue of reactive materials should never be left open to the atmosphere.
- Any unused or unwanted reactive materials must be destroyed by transferring the materials to an appropriate reaction flask for hydrolysis and/or neutralization with adequate cooling.
- The empty container should be rinsed three times with an inert dry COMPATIBLE solvent; this rinse solvent must also be neutralized or hydrolyzed. The rinse solvent must be added to and removed from the container under an inert atmosphere.
- After the container is triple-rinsed, it should be left open in back of a hood or ambient atmosphere at a safe location for at least a week.
- The empty container, solvent rinses and water rinse should be disposed as hazardous waste and must not be mixed with incompatible waste streams.
Disposal of Pyrophoric or Water Reactive Contaminated Materials
- All materials – disposable gloves, wipers, bench paper, etc. - that are contaminated with pyrophoric chemicals must be disposed as hazardous waste. Proper and complete hazardous waste labeling of containers is vital. See SafetyNet #110 for more information on labeling hazardous wastes.
- The contaminated waste should not be left overnight in the open laboratory but must be properly contained to prevent fires.
- DO NOT use water to attempt to extinguish a reactive material fire as it can actually enhance the combustion of some reactive materials, e.g. metal compounds.
- Do not use combustible materials (paper towels) to clean up a spill, as these may increase the risk of igniting the reactive compound. Met-L-X, soda ash, lime, or dry sand should be used to completely smother and cover any small spill that occurs.
- A container of Met-L-X, soda ash, lime, or dry sand should be kept within arm’s length when working with a reactive material.
- If anyone is exposed, or on fire, wash with copious amounts of water, preferably under a safety shower.
- If metal compounds are involved, smothering the fire is a better course of action.
- The recommended fire extinguisher is a standard dry powder (ABC) type. Class D extinguishers are recommended for combustible solid metal fires (e.g, sodium, potatssium), but not for organolithium reagents. Contact the Fire Department and review the SDS for the appropriate fire extinguisher.
- Call 9-1-1 for emergency assistance and for assistance with all fires, even if extinguished.
- Pyrophoric gas releases and associated fires, should be extinguished by remotely stopping the gas flow. NEVER ATTEMPT TO PUT OUT A GAS FIRE IF THE GAS IS FLOWING.
Sources and Acknowledgements:
Created from a variety of sources including: Brandeis University, Standard Operating Procedure for Pyorphoric Chemicals; University of Nebraska, Lincoln, Pyrophoric Chemicals Standard Operating Procedure; University of Pittsburgh Safety Manual, Flammable and Pyrophoric Gas; Rochester University, SOP for Pyrophoric Chemicals. Images from Sigma-Aldrich Technical Bulletins AL-134 and AL-164.
Personal communication with (and grateful acknowledgement to) Dr. Russell Vernon, Environmental Health and Safety, UC, Riverside; Dr. Joseph Pickel, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory; Dr. Neal Langerman, Principal, Advanced Chemical Safety, Inc.; Dr. Mark Kurth and Dr. Frank Osterloh, Professors of Chemistry, UC Davis.
Note: The California Fire Code prohibits the storage or use of pyrophorics in buildings not fully protected by an automatic sprinkler system. If you are using a pyrophoric in an unsprinkled building, contact the Fire Department/Prevention at 752-1236 or EH&S at 752-1493 immediately.