SOP: Explosive Compounds

Definition from Prudent Practices in the Laboratory:  Handling and Management of Chemical Hazards (section 4.D.3.1 Explosive Hazards) The National Academies Press:  Washington, DC, 2011.

“An explosive is any chemical compound or mechanical mixture that, when subjected to heat, impact, friction, detonation, or other suitable initiation, undergoes rapid chemical change, evolving large volumes of highly heated gases—typically nitrogen or CO2—that exert pressure on the surrounding medium.  The term applies to materials that either detonate or deflagrate.”

Hazard Description

The Principal Investigator must alert students and lab staff to the presence of potentially explosive compounds used in the laboratory and any time it is possible they may produce explosive compounds during their work.

Explosive compounds are part of the broad hazard class “Reactive Chemicals”.  See the following SOPs and Fact Sheets in the Chemical Hygiene Plan for other reactive chemical hazards, some of which also have explosion risks.

• Strong Oxidizers
• Pyrophorics
• Reactive Chemicals
• Hazardous and Highly Toxic Gases
• Water-Reactive Chemicals
• Peroxide-Forming Chemicals
• Perchloric Acid

Commercial Chemicals

Examples of laboratory chemicals with explosive potential are included at the end of this SOP in "List of Explosive Chemicals"

Commercial chemicals with explosive properties can be identified by the manufacturer’s container label and Safety Data Sheet.

Section 2 (Hazard Identification) of the Safety Data Sheet will list hazard statements that will indicate whether a compound is potentially explosive.  The physical hazard statements that relate to explosives are listed in the table below.

Take note of the following “red flag” chemical nomenclature that may alert you that a potentially explosive functional group is present:

More information about perchlorates can be found in Fact Sheet:  Perchloric Acid.

Chemicals Synthesized in the Lab

It is also possible to intentionally or unintentionally synthesize or isolate explosive compounds in the lab.  Some synthetic pathways may proceed via a potentially explosive intermediate.  Explosive compounds can form as a result certain decomposition reactions such as when commercial chemicals or chemical samples are stored improperly, kept past their expiration date, or heated (e.g. Peroxide-Forming Chemicals)  Mixing incompatible chemicals, especially in a tightly sealed container can also result in explosions (e.g. mixtures of acetone and concentrated nitric acid).  See section 10 of a compound’s SDS for information on reactivity, stability and chemical incompatibilities.

Potentially Explosive Classes of Compounds

Explosive Salts

More information about perchlorates can be found in Fact Sheet:  Perchloric Acid.

All compounds with bonds between electronegative atoms should be considered to be highly reactive, but the following functional groups should alert you to danger:

• peroxides (-O-O-, -O-O-O-)
• nitro compounds (O-NO2, N-NO2, and C-NO2)
• nitroso compounds (O-NO, N-NO)
• azo and related compounds (C=N2, R-N2+, -N=N-, -N3, -N=N-S-N=N-)
• hypohalites and haloamines (RCOO-X, N-X)
• oxyhalide salts (ClO4-, ClO3-, BrO3-, IO3-, ClO2, ClO-)
• and related metal salts (M-N3, M-CC-M, M-N=C=O, M-OClO3, picrates, dinitrophenolates)

Compressed and Condensed Gases

Compressed gases pose a risk of explosion if their containers rupture or otherwise fail.  Refer to SOP: Compressed Gases and SOP: Hazardous and Highly Toxic Gases for more information on safe handling of compressed gases. 

Condensed gases, such as liquid nitrogen, pose a risk of explosion if cooling does not occur or pressure relief is impeded.  For more information on safe handling of liquid nitrogen, see SOP: Cryogens and Dry Ice. 

Approvals

A Hazard Control Plan is required for this class of hazardous chemicals

All work with explosive and potentially explosive compound classes requires the approval of the P.I. The P.I. must ensure that the person or team who will be working with the explosive compound writes a task-specific Hazard Control Plan (HCP). The HCP must be sent to EHRS for review.  EHRS will upload the HCP to the “documents” section of the lab’s BioRAFT page.  

The P.I. must also ensure that the the person or team who will be working with the explosive chemicals understands the hazards and has received adequate training and supervision for the procedure. 

EHRS approval is required for any work involving commercially-available compounds that are known to be explosive.  EHRS approval is required regardless of whether the compounds are purchased new, are already available in your lab’s inventory, are acquired from another Penn lab, or are synthesized in your lab.

Some explosive materials are federally regulated.  See the Bureau of Alcohol, Tobacco, and Firearms List of Explosive Materials (updated annually) to see if the compound you wish to work with is listed.  You must contact EHRS for assistance if the compound you wish to work with is listed.

Training Requirements

No researcher may work independently with the hazardous material described in this SOP until the Principal Investigator (or their designee) has ensured that the researcher:

• Has completed all required EHRS laboratory safety training programs
• Understands the hazards of the materials and risks of the processes involved
• Has read and understands the contents of this SOP and the lab's task-specific Hazard Control Plan
• Demonstrates the ability to execute their work according to the requirements in this SOP and the lab's task-specific Hazard Control Plan

Facility Requirements

General Ventilation

Explosive chemicals may not be handled or stored in a room or facility with recirculating exhaust.

Chemical Fume Hood

All work with explosive chemicals in open or closed systems must be done in a designated area of a laboratory inside of a properly functioning chemical fume hood.

Emergency Irrigation

Emergency irrigation (safety shower, eyewash) must be accessible within a 10-second travel distance of the area where the work is performed.

Signage and Labeling

A legible manufacturer’s label including hazard information must be present on all commercial containers of explosive chemicals.

If commercially purchased explosive chemicals are transferred to another container for storage or to make stock solutions for later use, special labeling requirements apply.  See the “Researcher-Created Labels” section in Section IV:  Chemical Container Labeling in this CHP for a complete list of requirements.

Date Containers

Write on the container label the date that an explosive commercial material was received and the date the container was opened. 

Labeling Potentially Explosive Compounds Synthesized in the Lab

Clearly label samples with the following information.  If necessary, securely attach a tag to the container.

Storage and Transport

The Hazard Control Plan for your lab's procedures involving explosive compounds will detail any specific storage conditions and restrictions that apply to your materials.

Proper storage and transport of explosive chemicals must be determined by assessing all of the hazards and physical properties of the chemical. 

See Section VI:  Chemical Storage and Transportation in this CHP for a complete list of requirements.

Special Considerations for Explosive Compounds

Commercial Chemicals

• Follow the manufacturer's recommendations for storage of commercial chemicals with explosion hazards.
• Unless an inhibitor was added by the manufacturer, unopened containers of potentially explosive and shock-sensitive materials must be discarded within 6 months of opening.
• See the "Signage and Labeling" section of this SOP for guidance on labeling and dating containers.

Chemicals Synthesized in the Lab

• Some explosive compounds must not be isolated or stored at any concentration.
• If possible, avoid storing samples of potentially explosive material.
• When it is necessary to store samples of potentially explosive materials, do so in solution at concentrations below 1 M. (Your HCP may specify a lower concentration)
• Do not store more than 5 grams of any lab-synthesized explosive materials no matter how dilute. (Your HCP may specify a lower maximum quantity)
• Many explosive compounds must be stored at reduced temperature (refrigerator or freezer).
• Re-assess your continued need for any stored samples of potentially explosive materials every 6-months.  Properly dispose of any unneeded samples.  (See the "Waste and Decontamination" section of this SOP)
• See the "Signage and Labeling" section of this SOP for guidance on labeling and dating containers.

Hazard Controls

The Hazard Control Plan for your lab's procedures involving explosive compounds will detail specific engineering controls, work practices, or personal protective equipment that is required.

Some general guidance is given below.

Engineering Controls

Chemical Fume Hood

All work with explosive chemicals in open or closed systems must be done in a designated area of a laboratory inside of a properly functioning chemical fume hood.

The fume hood is designed to capture chemical vapor and the hood sash acts as a shield in case of chemical splash.  The sash must be kept closed as much as feasible.

Blast Shield

A portable blast shield may be placed in front of a vessel containing explosive material.  This provides additional protection in the case of an explosion.  Your lab's task-specific Hazard Control Plan will specify whether a blast shield is required for your process.

Vacuum Protection

Mechanical vacuum pumps must be protected using cold traps and, where appropriate, must include a filter to prevent particulate release.  The pump exhaust must be vented into an approved exhaust duct or chemical fume hood.

Glove Box

Certain explosive chemicals must be handled in a glove box rather than a fume hood. The Office of Environmental Health and Radiation Safety (8-4453) or the Principal Investigator will determine if this is required.

If a chemical fume hood or glove box is not available, contact EHRS to determine whether the risks can be adequately controlled using alternative controls.

Work Practices

A list of recommended work practices for hazardous chemical handling is included in Section V: Chemical Handling in this CHP. Of particular relevance to explosive chemical use:

Considerations for purchase

• Do not use explosive chemicals if less-hazardous alternatives are possible.
• Purchase, dispense, and use the smallest quantity of explosive chemicals possible. 
• Purchase the lowest concentration of explosive chemicals that will meet your research needs.

Considerations for work space

• Work with explosive compounds in areas that you've designated especially for this work. 
• Post a sign on the fumehood when a process involving potentially explosive compounds is unoccupied.  A template is available for download:  Unattended Operations Sign Template
• Remove all other chemicals and hazardous materials from the work area.
• Be aware of nearby processes and other conditions that may effect the stability of the explosive chemicals.  Examples are adjacent sources of heat or light, which may increase the likelihood of uncontrolled chemical reactions.

Considerations for handling

• Do not handle explosive chemicals when working alone.
• Notify other lab occupants when you work with potentially explosive compounds is in progress.
• Immediately close all containers of explosive chemicals after use and return them to their designated storage location. 
• Dilution decreases the potential for explosive chain reactions.
• Avoid the use of metal spatulas and needles when working with compounds for which metal ions may catalyze explosive decomposition reactions.
• Avoid the use of ground-glass joints when working with compounds for which friction or mechanical shock may trigger explosion.
• Explosive reactions are often triggered by one of the following conditions or events:  Heat, Impact, Friction, Catalysts, or Light.  Avoid any of these conditions that may trigger the class of compound you are working with.

Additional work practices for reducing the risks of any lab procedure involving explosive chemicals must be described in a written Hazard Control Plan.

Personal Protective Equipment

Consider the potential routes of exposure and health consequences when selecting personal protective equipment (PPE) for tasks involving explosive chemicals. 

In addition to the minimum lab apparel and PPE requirements, other protective equipment may be necessary to reduce risks.  When additional equipment (such as tight-fitting chemical splash goggles, chemical-resistant gloves, or disposable lab coats) are required, a Hazard Control Plan must be written to document the risk assessment and controls.

Contact EHRS for assistance with risk assessments, glove compatibility, and other PPE selection.

The minimum PPE requirements for all chemical handling tasks, and information about specialty PPE can be found in the "Personal Protective Equipment" section of Section V:  Chemical Handling in this CHP.

Waste and Decontamination

The Hazard Control Plan for your lab's procedures involving explosive compounds will detail specific procedures for spills, decontamination of surfaces, and collection of hazardous waste.

Some general guidance is given below.

• Wash hands thoroughly with soap and water after handling any chemical and whenever you leave the lab.
• Use good housekeeping practices to avoid contamination of surfaces, garments, personal belongings, and self.
• Decontaminate all surfaces that have come in contact with explosive chemicals and clean-up small spills promptly.  See the chemical Safety Data Sheet or contact EHRS for assistance with determining an appropriate decontamination method.  See “Spills” below for instruction on what to do in the event of a large or hazardous spill of an explosive chemical.

For complete hazardous waste guidelines, see the waste section of the EHRS website: Laboratory Chemical Waste Management Guidelines

Emergencies

Emergency Contacts

General emergency response information can be found at Emergency Info

Spills

General procedures for chemicals spill response can be found in Section X: Chemical Spills in this CHP.

Do not hesitate to call EHRS for assistance with spill cleanup for Explosive materials.

24 hours: 215-898-4453

Contact Penn Police (511) only if the spill involves a fire, imminent risk of fire, an injury requiring an ambulance, or if there is a hazard that may affect others in the building.

List of Explosive Compounds

The following examples of commonly used explosive chemicals was taken from the UC Center for Laboratory Safety SOP for Potentially Explosive Compounds, 2013.

If you are interested in finding out whether your ChemTracker inventory contains any explosive chemicals, see the EHRS Tip Sheet: Completing a Hazard List Analysis. 

Potentially Explosive Lab Chemicals

Related SOPs and Fact Sheets

Reactive Chemicals

Strong Oxidizers

Pyrophorics

Water-Reactive Chemicals

Peroxide-Forming Chemicals

Perchloric Acid

Compressed Gases

Hazardous and Highly Toxic Gases

Cryogens and Dry Ice

References

This SOP was based on the previous version of “EHRS SOP for Explosive Chemicals” and the following additional resources:

1. UC Center for Laboratory Safety SOP for Potentially Explosive Compounds, 2013.
2. Prudent Practices in the Laboratory:  Handling and Management of Chemical Hazards (section 4.D.3.1 Explosive Hazards) The National Academies Press:  Washington, DC, 2011.
3. Standford University's EH&S page "Information on Azide Compounds"
4. University of California Santa Barbara. “Laboratory Safety Fact Sheet #26: Synthesizing, Purifying, and Handling Organic Azides”
5. CAS. (2020). Ammonium Nitrate Explosions: Lessons Learned. [White paper]. Retrieved November 26, 2020 from CAS: www.cas.org/resources/whitepapers/ammonium-nitrate