The OSHA Laboratory Standard defines an explosive as a chemical that causes a sudden, almost instantaneous release of pressure, gas, and heat when subjected to sudden shock, pressure, or high temperature. There are many laboratory chemicals that can become unstable or potentially explosive over time when the chemical becomes desiccated or contaminated with other materials, air, or water. Explosives can result in damage to surrounding materials, generation of toxic gases, fire, and injury to personnel. Before undertaking any procedures with a potential for explosion, researchers should determine whether a safer chemical can be substituted in the experiment. Lab personnel must gain prior approval from the PI/Laboratory Supervisor for use of these materials, have documented training on safe use, and a written SOP maintained in the lab specific Chemical Hygiene Plan. For assistance with lab‐specific SOP development for the use of the materials in this section of the UK institutional Chemical Hygiene Plan, please contact labsafety@uky.edu .
Explosives and Reactive Chemicals
Explosive and Potentially Explosive Chemicals
Examples of explosive and potentially explosive chemicals include:
- Compounds containing the functional groups azide, acetylide, diazo, nitroso, haloamine, peroxide, and ozonide
- Nitrocellulose
- Di‐ and Tri‐nitro compounds
- Peroxide forming compounds
- Picric acid (dry)
- 2,4‐Dinitrophenylhydrazine (dry)
- Benzoyl peroxide (dry)
Containers of these types of chemicals shall be marked with the receive date, opened date, and expiration, if applicable. Containers shall be routinely checked for signs of deterioration or degradation, crystalline growth, and discoloration of the chemical. Containers exhibiting these signs shall be immediately reported to the UK Environmental Quality Management Department at (859) 323‐6280. Lab personal shall not attempt to move the container.
Lab personnel using these materials are never to work in the lab alone. Use of these materials must be indicated on door signage and signs in the work area. A safety shower and suitable extinguisher is absolutely required for any area working with these materials. Please consult the UK Fire Marshal to ensure an appropriate extinguisher is available for use in the laboratory.
Additional work practices for utilization of potentiallyexplosive or reactivechemicals:
- Provide a mechanism for adequate temperature control and dissipation of excess heat and pressure.
- Use shielding as appropriate to minimize personnel exposure and injury, and facility damage.
- Minimize the quantity of reactive chemicals used or synthesized to the smallest amount needed.
- Utilize shields and barricades, and personal protective equipment (such as face shields with throat protectors and heavy gloves)
- Review any proposed changes to laboratory procedures, especially any plans for scaling up the reaction with the PI or other designated knowledgeable person before performing them.
- Consider performing a “dry run” of new procedures involving pyrophoric chemicals to help identify overlooked handling issues or hazards, and to increase users’ proficiency.
- Remove any and all unnecessary chemicals from the CFH, glovebox, or working area before commencing procedures with these types of chemicals.
Pyrophoric Chemicals
OSHA defines a chemical as pyrophoric if a small quantity of the chemical will ignite within 5 minutes after coming into contact with air. Liquid or gaseous pyrophorics are of enhanced concern. Water vapor can also cause some pyrophorics to ignite. The ability of pyrophoric chemicals to spontaneously ignite on contact with air and/or water usually requires that they be handled under an inert atmosphere through use of a glove box and/or special handling techniques.
Examples of some phyrophorics include:
- Grignard Reagents: RMgX (R=alkyl, X=halogen)
- Metal alkyls and aryls: Alkyl lithium compounds; tert‐butyl lithium
- Metal carbonyls: Lithium carbonyl, nickeltetracarbonyl
- Metal powders (finely divided): Cobalt, iron, zinc, zirconium
- Metal hydrides: Sodium hydride
- Nonmetal hydrides:Diethylarsine, diethylphosphine
- Non‐metalalkyls: R3B, R3P, R3As; tetramethyl silane, tributyl phosphine
- Phosphorus
- Potassium
- Sodium
- Gases: Silane, dichlorosilane, diborane, phosphine, arsine)
A commonly discussed pyrophoric lab chemical in terms of lab safety practices and potential injury is tert‐butyllithium under hexanes. In 2008, a UCLA lab technician lost her life in a highly publicized lab accident. This incident led to the first instance in the USA of an academic institution and the principal investigator being prosecuted as liable in a court of law. Use of pyrophoric chemicals call for specialized engineering controls and procedures to prevent incident. Use of these chemicals requires prior approval from the PI/Laboratory Supervisor, documented training on safe their safe use, and a written SOP maintained in the lab specific Chemical Hygiene Plan. Contact labsafety@uky.edu for more information.
When using pyrophoric chemicals:
- Store in the original manufacturer container (e. g., Sure Seal bottles) unless experimental work requires transfer to other containers.
- Septum tops may leak after perforation. These shall be inspected on a regular basis.
- Pyrophoric chemicals that require refrigeration must be only stored in a refrigerator that is designed and constructed for storing flammable liquids, no exceptions. Pyrophorics should be stored in a dedicated refrigerator, not in a refrigerator that also contains flammable liquids.
- Routinely check pyrophorics stored in a protective solvent to ensure that there is sufficient liquid.
- Do not return pyrophoric chemicals to their original storage container as small quantities of impurities can cause fire or explosion.
Moisture‐Sensitive Chemicals
Some laboratory chemical compounds react violently with water to form toxic vapors and/or flammable gases that can ignite and cause a fire. If the lab is using or storing moisture sensitive compounds and the lab does not have a Class D fire extinguisher present, then please contact the UK Fire Marshall at (859) 257‐6326.